8/7/2019 Lathe Work

1/220

LATHE-WORKA PRACTICAL TREATISE

011THE TOOLS, APPLIANCES, AND PROCESSES EMPLOYED IN

THE ART OF TURNINGIIICLODIIfG

HANDTURNING, BORING AND DRILLING, THE USE OF SLIDE.RESTS AND OVERHEAD GEAR, SCREW CUTTING BY HANDAND SELFACTING MOTION, WHEEL-CUTTING,

ETC. ETC.

BY

PAUL N. HASLUCKWITH NUMEROUS ILLUSTRATIONS DRAWN BY THE AUTHOR

LONDONCROSBY LOCKWOOD AND CO.

7, STATIONERS' H A L L COURT, LUDGATE mLL1 8 8 3

[.dll ri ,Ma f'fmWIi]

8/7/2019 Lathe Work

2/220

A NEW SERIES 01'HANDBOOKS ON HANDIORAFTS.THE METAL TURNER'S HANDBOOK: A practical

Manual for Workers atthe Foot Lathe. By PAUL N. lIASLUCK.With over One Hundred IlIustratioDi. Crown 8vo, price 1/, cloth.[Now",ad,y.TM /01""" ..." ,,"' .... 1 ,. "" ,,,,, 1,,,,, , . . ,. .:t- fllliliJ 1M dtIw,

jrie. 1/6 .iJ.THE WOOD TURNER'S HANDBOOK: A . practicalManual, embracing information on Teele, Materials, Appliances,and Processes employed in Wood Turning. By PAULN. HAsLUCK.With about One Hundred Illustration THE WATCHJOBBER'S.HANDBOOK: Apractical

Manual, emhracing information on Toolst Material., Applianc8l,and Processes employed in Cleaning, Adjusting, and RePairingWatches. By PAUL N. HAILUCK. With about One HundredIllustrations.THE MODEL ENGINEER'S HANDBOOK: A prac-

tical Manual emhracing information on Tools. Material!t A"pli-ances, and Processes emJ>loyed in Constructing Model J!;n"nes.By PAULN. HAILUCK. With about One Hundred lIIusuanon THE CLOCK JOBBER'S HANDBOOK: A practicalMannal, embracing information on Tools Materials, Appliances,and Processes employed in Cleaning} Adjusting, and RePairinsClocks. By PAULN. HAsLUcx. Witll about One Hundred Ill....tratioDI.THE MECHANIC'S WORKSHOP HANDBOOK: Apractical Manual, emhrar.ing Reliable Receipts, Useful Notes,and Miscellaneous Memoranda on Mechanical Manil'lllation.By PAUL N. HASLUCK. Comprising about 1'.0 HundredSuhjects.THE CABINET WORKER'S HANDBOOK: A prac-

tical Manual, emhracing information on Tools, Material~ Appll-

f u : :~~=~i~h"::"~'(f~~y~:t.~ahbi:t!~! By AULN.THE FRET WORKER'S HANDBOOK: A practicalManual, embracin~ information on Tools, MateriaisN ACnces,wtl~~':::':)n:,,~=.,J'il~~~~~!: By PAUL. UCIt.

LoIIIDOIII: CROSBY LOCKWOOD .. CO.

8/7/2019 Lathe Work

3/220

PREFACE.WHEN first I occupied myself in mechanicalmanipulations and lathe-work engrossed myattention, the want of a handy guide-book, treat-ing the subject in a practical manner, was greatlyfelt. Though much has been done since thentowards placing technical education within thereach of all, yet I recently found, in my officialcapacity as editor of a journal largely devoted tomechanics, that beginners at the lathe still con-tinue to seek such a book, and I have thereforeprepared the following pages.In the form of desultory articles, written by me,

much of the information has already appeared invarious technical papers. The whole has beenre-written for publication in book form, and it hasbeen my endeavour to bring within the availablespace the information most useful to the beginnerat lathe-work.Though I make no claim to special literary

merit, yet I believe that the instructions are madeclear without verbiage; and as I write from per-sonal experience, the book may be accepted as

8/7/2019 Lathe Work

4/220

vi PREFACE trustworthy and practical by those who study itscontents.The illustrations have been engraved from my

own drawings, and show, at a glance, construc-tive details that could not be explained in letter-press. The drawings are from the objects theyrepresent, and will convey much useful informa-tion, and working drawings of the full size can bemade from the woodcuts; the measurements canbe filled in from the text. P. N. HA$LUCK.

LoMnON. F I " , , " , " ' , [88r. . I

NOTE.

A SECONDEDITIONhaving been called for, I havetaken the opportunity to correct a few smallmistakes .such as are apparently unavoidable inthe first edition of any book. Ihave also added aChapter on the Screw-cutting Lathe-a subject ofinterest to all who practise lathe-work.

P. N. HASLUCK.LoNDON, May. 1883

I 1

8/7/2019 Lathe Work

5/220

CONTENTS.CHAPTER I.

THE ART .OF TURNING.PAO.Its importance and. antiquity-Primitive methods of turniDg-The potter's wheel-Early Corms of the lathe-Its develop-ment-Lathes on standards-Fly-wheels-Literature of theart-Modem lathes I

CHAPTER II.THE FOOT LATHE DESCRIBED.

Its various forms and sizes-Watchmakers' lathes-Bench lathe.-Iron beds of various forms-Back-gearing-Slow motion-Screw-cutting motion-The lathe best suited for general pur-poses-The framework, bed, andfly-wheel-Mandrel headstock-Back-centre headstock-The hand-rest and collar-plate-Testing a lathe 8

CHAPTER III.HAND TURNING.

First principles of the art, commencing to practise-Wood tum-ing, the gouge and the chisel-The mode of their applicationto the cylinder and surface-Easily made objects for beginners-Making a plain wooden box-Metal tuming, the graverand triangular tool, and their 1IIe-Finishing tools, round-nosetools, & c. 29

8/7/2019 Lathe Work

6/220

viii CONTENTS.CHAPTER IV.

SCREW-CUTTING BY HAND.PARStriking the thread with outside and inside comb-screw tools-

Originating a thread-The method of cutting the thread in alathe-chuckminutely described 45

CHAPTER V.BORING AND DRILLING.

Drills, their correct form and uses-How to grind them-Half-round bits-Pin-drills-Bars with movable cutters-Rosecutters and rose bits-Lubrication necessary inboring. s.

CHAPTER VI.MOUNTING WORK FOR TURNING.

Work between centres-Method of centring-Necessity of pro-perly preparing the centres-Chucking objects of variousforms-False centres-The collar-plate-Chucking on theface-chuck 60

CHAPTER VII.FITTING CHUCKS TO THE LATHE-NOSE.

Minute details of the process-Various threads used for lathe-,noses-Making taps, &c., for fitting chucks-How the threadshould be formed-A truly cut thread necessaryon the nose 70

CHAPTER VIII.VARIOUS USEFUL CHUCKS DESCRIBED.

The point-chuck-The prong-chuck-Different forms of drill-chucks-Taperscrew-chucks-Face-chucks-Cup-c:hucks withthree and four Bcrews-Die-chucks with Bingle pairs andmovable dies-The four-law face-chuck 88

8/7/2019 Lathe Work

7/220

CONTENTS. IxCHAPTER IX.

SLIDE-RESTS.PAG.Their advantages, various forms-Fitting up slide-rests, omamentaland plain-Tool-holders-Self-acting slide-reats-The lead-ing serews and material for nuts-The bearings of the screws-Heieht of a reat-Adjusting slide-rests-Spherical rests 102

CHAPTER X.SLIDE-REST TOOLS.

Angles suited for various materials-Useful tools for general pur-poses-Cranked tools, knife tools, parting tools, spring tools-Tools for inside tumiDg, correct height and adjustmentnecessary 117

CHAPTER XI.SLIDE-REST CUTTER-BARS.

Advantages over solid tools-Some of those of most general appli-cation described-The graver used in the slide-rest-Straight-forward tool, parting tool, intemal tool-Saving effected bythe use of cutter-bars u8

CHAPTER XII.OVERHEAD GEARING.

Fixed and portable-s-Single bands and compound gearb.g-Fixedbars-Swinging bars-Revolving shafting-Serew-cutting byband-gearing-Shape of grooves for the bands 137

CHAPTER XIII.DIVIDING APPARATUS.

Its object and us_Dividing the lathe palley-Numbers most use-ful for dividing purposes-Originating and making a divisionplate--Drilling the holes-Index pegs of various kinds 147

8/7/2019 Lathe Work

8/220

CONTENTS.CHAPTER XIV.

THE DRILLING SPINDLE. 0 ~AO.Its use and how to make-Making the mandrel-Making the collars,grinding the bearings-Lead grinders-Fitting the collars, 0grinding the cones-Hardening and tempering-Putting to-

gether " 0 160CHAPTER XV.

VERTICAL CUTTER-FRAME.Its use and construction-Circular cutters for wheel teeth-Cuttersfor general purposes-Fly-cutters--Making the frame andspindle . 171

CHAPTER XVI.SCREW-CUTTING BY SELF-ACTING MOTION.

Theoretical principles-Wheels usually supplied-Preparing atable of rates that can be cut-Screw-threads, how described-Rules for calculating change-whee1s-EDDlples provingthe calculation-Multiple threads lSICHAPTER XVII.

THE SCREW-CUTTING LATHE.Self-acting sliding motion-Leading screws-How driven-Clasp-nuts-Forms of thread. for leading screws-Right and lefthanded leading screws- Whitworth's arrangement of clasp-nut-Self-acting surfacing motion-Suggestions for convert-ing ordinary lathes for screw-cutting-A clasp-nut arrange-ment easily fitted-How to start the slide-rest correctly foruneven pitchea 191

8/7/2019 Lathe Work

9/220

LIST OF ILLUSTRATIONS.PIG.I. Section of Back-gear Headstock2. Drill for Boring Metal3. Pin-Drill 4. Counter-sunk Centre 5. Centring Metal Rods6. Poppit Centre Point 7. Making a Dbit8. Tap for Screwing Chucks 9. Point-Chuck

10. Section of Point-Chuck[1. Prong-Chuck12. Drill-Chuck with Clamp-Screw 13. Drill-Chuck with Taper Nozzle.14. Taper Screw-Chuck .15. Four-Screw Cup-Chuck16. Section of Cup-Chuck17. Section of Die-Chuck18. Front View of Die-Chuck.19. Various Dies for Die-Chuck20. Four-Jaw Face-Chuck21. Section of Jaw .22. Diagram showing Angles of Tools23. Cranked Slide-Rest Tool

100 101 II9 IliI

8/7/2019 Lathe Work

10/220

xii LIST OF ILLUSTRATIONS.PIG. PAn240 Round-Nosed Slide-Rest Tool . 12125. Side Cranked Slide-Rest Tool 12226. Knife-Edge Slide-Rest Tool . 12327. Parting Tool for Slide-Rest 12328. Spring Tool for Slide-Rest. 12529. Inside Turning Slide-Rest Tool 12530. Cutter-Bar for holding Gravers 13031. Straightforward Cutter- Bar 13132. Cutter-Bar for Parting Tools 13233. Cutter-Bar for Inside Turning 134340 Swing-Bar Overhead Gear. 14035. Revolving Shafting Overhead Gear 14336. Template for dividing Band 15437. Temporary Division Peg . 15638. Enlarged View of Division Peg 15839. Knob for Division Peg 15840. Section of Adjustable Division Peg 15941. Drilling-Spindle I6t42. Top of Vertical Cutter-Frame 17543. Front of Vertical Cutter-Frame 17644. Locking-Nut for Cutter-Spindle. . . 178.45. Hooked Tommy 17846. Screw-Collar for Cutter-Spindle 17947. Whitworth's Clasp-Nut Arrangement. 197 II !48. Side View of Clasp-Nut 20249. Front View of Clasp-Nut Plate. 20250. Top of Clasp-Nut 2035'. Cam-Plate for Clasp-Nut . 203

8/7/2019 Lathe Work

11/220

LATHE-WORK.CHAPTER I.

THE ART OF TURNING.Its importance and antiquity-Primitive methods of turning-Thepotter's wheel-Early forms of the lathe-Its development-Lathes on standards-Fly-wheels-Literature of the art-

Modemlathes..OF all the mechanical arts none can claim a moreimportant pl~ce than that of turning, and thepractice of this branch of mechanical manipulationis capable of developing the highest skill andintelligence of the artificer. The lathe, which hasbeen dubbed the father of mechanism, has claimedthe close attention of statesmen and philosophers;even monarchs have sought recreation in thepractice of turning. Skilled artisans, who dependlargely on the lathe for the production of theirwork, enjoy to an extent a superior position intheir sphere of life, whether they be e.ngaged infashioning the rough wares made on the potter'swheel, or the highest and most refined specimensof turnery, which are probably to be found in the: 3 . . . B

8/7/2019 Lathe Work

12/220

2 LATHE-WORK.finest grades of chronometric art. We disregardthose extraordinary productions of skill and tastewhich come from the hands of the amateur turner,who uses for the production of a fragile gewgawtools and appliances that only affluence can afford.The date of the origin of turning is lost in anti-

quity. Probably longbeforehistorians began towrite,the lathe-in aprimitive form-was known and used,the potter's wheel being, perhaps, the primo~enitor.The savage's process of kindling fire by twirling astick against another piece of wood gives themotion now used for the alternating drill, and forsmall lathes driven with a drill bow; how thismotion developed into the continuous one of thepotter's wheel we can but surmise. The sym-metrical cylinder is to be found throughout nature,and art in its desire to reproduce the admirableform has developed .the turning lathe.The Bible affords a distinct reference to the

potter's wheel; we read that about five hundredyears before the Christian era Jeremiah went downto the potter's house, "and behold he was doing awork on the wheel, making a vessel of clay withhis hands." 'The use of the lathe, however, dateslong prior to this, and the manufacture of potteryware is frequently spoken of in sacred history.Amongst the relics of antiquity unearthed from theburied Egyptian cities are numerous specimensbearing unmistakable evidence of having beenwrought in the lathe.The lathe used by the Orientals for generations

8/7/2019 Lathe Work

13/220

PRIMITIVE LATHES. 3consisted of two short posts driven into the ground;a nail driven through each formed the centres onwhich the work revolved, actuated by a drill-bow.The work was thus only a few inches from theground, and the operat?r in his accustomary posi-tion-squatting on the ground-was able to usehis toes in assisting the application of the tools.The Orientals use the toes as deftly as they do thefingers in many of their handicrafts. At theParis Exhibition of 1867a gr~)Upof aborigines wereworking in this manner with the lathe just de-scribed, displaying considerable skill in usingthese primitive appliances, and producing work ofintricate and elaborate patterns, chiefly ornamental.Lathes of this primitive form it would appear are

employed at the present time by the native turnersofIndia. The skill of the Hindoos in the mechani-cal arts and in the delicate fashioning of ivory andmetal is universally appreciated; and that theyshould succeed so well with such rude tools is aproof of their natural aptitude. The turner of Indiacarries on his vocation in the style of our itineranttinker; he carries all his tools, lathe included,about with him, and when he gets a job establisheshimself near the door of his employer's house.Assisted by his boy, the turner fixes up his lathe,consisting of two posts driven into the ground, asdescribed previously. The work is mountedbetween the centres, a rope is passed twice roundit, and the boy, by pulling each end of the ropealternately, gives motion to the work, the workman

8/7/2019 Lathe Work

14/220

4 LATHE-WOl{K.guiding the edge of his tool with his toes only, thehandle being held by the hands at some distancefrom the work, both man and boy invariablysquatting on the ground, as is the national custom.Many nations in all parts of the globe employ a

lathe somewhat resembling, but still an improve-ment on, the one just mentioned. This lathe has aframe so that it is complete in itself, yet it has tobe fixed to the ground for use; it consists of twocross pieces held together by a tie-bar on whichthey slide, and may be wedged as required. Thecross pieces have iron spikes fitted to them to formcentres, the work is put between these, and they arefixed by wedging on the tie-bar. The lathe is laidon the ground and secured by means of a fewspikes, a straight bar of wood is laid across thecross pieces as near as convenient to the work, andforms a rest for the turning tools. This form oflathe is still largely used in Spain, Egypt, andother places; the pattern can be traced backto the Moors, who introduced the lathe to Spain.The Spaniards in migrating took with them thelathe and the art of turning, and thus in thoseparts of the American continent that Spain haspopulated the lathe is found made as last de-scribed.The continuous motion of the fly-wheel, which

had been employed by the potter from the earliesttimes, was not used in the 1athes of the ancients,who only had the alternating revolutionary motionderived from the bow. When introduced into the

8/7/2019 Lathe Work

15/220

EARLY LITERATURE. sworkshops of the Western nations, the lathe wasmodified to suit their customs, and whilst theOrientals kept their turning appliances low, to suittheir habitual squatting position, Europeansmounted the same contrivance on a frameworktobring it to a convenient height to work at whenstanding. This altered arrangement allowed thebow worked by hand to be replaced by a flexiblepole fixed overhead, from which a cord descended,and after passing round the work it joineda treadle, which was worked by the foot; then bothhands were at liberty to manipulate the tools.A picture published in a German book in the-

year 1568 shows a turner working a sphere in alathe; a quantity of turned objects are lying on thebench and about the workshop. This illustrationseems to be the first record of the lathe mounted onstandards, and we see by it that the pole lathe wasin use at that date. In books of about the sameperiod different kinds of lathes are me-ntioned,butthe cord up to this time appears to have been usedround the work itself, which always had to runbetween centres. It is difficult to decide preciselywhen the independent mandrel came into use.The first book devoted to the art of the turner

was published at Lyons in 1701; it was written byPlumier, and probably did much for the art byplacing before its votaries a record of the conditionthat it was then in. That there was a demand forthis ponderous book appears evident from the factof a second edition having been published in Paris

8/7/2019 Lathe Work

16/220

8/7/2019 Lathe Work

17/220

MODERN LATHES. 7majority of mechanics, a circumstance much to beregretted.The modem lathe in its various forms, from thetiny tool used by the watchmaker, worked with a

slip of whalebone for a bow and a horsehair for acord, on which he fashions with a graver pivots ofcorrect proportion and precise form on axes that arethemselves sometimes less than one-hundredth ofan inch in diameter and weigh but a grain, to theleviathan machine, itself weighing sometimes up-wards of 60 tons, and large enough to take in workof 20 to 30 feet in diameter, and double thatlength, is, therefore, the result of continuous im-provements, from at least the time of Jeremiah,nearly 2,500 years ago.The employment of cast iron as a constructive

material for lathes at once gave a great impetus tomachinery of all kinds. The planing machine usedfor iron, itself an outgrowth of the lathe, did forflat surfaces what had already been done oncylindrical work, and it is to the judicious use ofthe lathe and the application of its modified func-tions that the present degree of accuracy has beenattained in the manufacture of every grade ofmachinery

8/7/2019 Lathe Work

18/220

CHAPTER II.THE FOOT LATHE DESC.RIBED.

Its various forms and sizes-Watchmaker's lathes-Bench lathes-Iron beds of various forms-Back-gearing-Slow motion-Screw-cutting motion-The lathe best suited for general purposes-Theframework,bed, and fly-wheel-Mandrel headstock-Back-centreheadstock-The hand-rest and cOllar-plate-Testing a lathe.

THEfoot lathe is the tool to which we confine our-selves throughout this treatise, as it is by far themost generally adopted, though in factories whereheavy work is done and steam power available thefoot lathe generally is superseded by' a similartool driven by steam. The ordinary form of footlathe is too well known to need minute description.Speaking roughly, it may be said to consist of abed, supported at a convenient distance from theground, carrying the headstocks. Beneath the beda fly-wheel is fixed to revolve freely, and to thecranked axis of this wheel a treadle is attached.The motive power consists of the muscular force ofthe leg applied to the treadle each time that thisfalls on the revolution ot the fly-wheel, the weightof this wheel being sufficient to cause it to revolveby its own momentum during the time whenpower cannot be applied through the treadle.. A

8/7/2019 Lathe Work

19/220

SIZES OF LATHES. 9band from the fiy-wheel to the mandrel conveysthe motion, and in this simple contrivance are theelements of a foot lathe.The size of a lathe is described by the height ofits centres-that is, the distance from the centre ofthe mandrel to the top of the bed. In other words,the height of centre is just half the diameter of thelargest circle that will revolve in the lathe, thusthe face-plate is usually a safe guide to the size ofa lathe. The length of bed has much to do withthe bulk, and to a certain extent with the capa-bilities of a lathe; for, though increasing the lengthof bed does not increase the capacity of a givenlathe so far as diameter is concerned, yet thelength of work which may be wrought on it isincreased usually by about the amount of theadded length. The length of bed decides thelength of material that, can be turned, whilst theheight of centre governs the' diameter; thus, alathe on which discs of 40 inches diameter can beturned with ease is often incapable of receiving acylinder of even 6 inches in length, and the lathesused for turning shafting, perhaps 40, feet long, arecommonly not more than 6 inch centre.Lathes over 6 inch centre are seldom driven by

foot power, the exertion being too great for oneman who has also to manipulate the tools. Froma commercial point of view it is found to bemore economical to employ steam power ratherthan an assistant to help tread the lathe. Thislatter expedient is a common practice in small

8/7/2019 Lathe Work

20/220

10 LATHE-WORK.workshops where mechanical power is not avail-able. The heavier lathes of 6 inch centre are alsogenerally driven by steam, but some very lightones used by wood turners are driven by the foot,even though they are 7 or 8 inch centre. Thehand-driven fly-wheel is generally used as thesource of motion by those wood turners who donot employ steam power.The smallest lathe is that used by watchmakers;

motion is given to the work by means of a bow, thelathe is held in the jaws of the bench vice when inuse. The clockmakers' throw Is rather larger; it isdriven by a hand-wheel, and has always deadcentres; a small pulley on the left headstock, havinga projecting pin to catch the tail of a carrier, beingused to drive the work. The smallest of footlathes has generally a bar-bed, of triangular sec-tion, and may be from 2 to 3 inch centre, and is ingeneral arrangement similar to the throw, exceptthat it has a revolving mandrel driven by a foot-wheel, and consequently. some modifications areessential.Bench lathe, or table lathe, is the name given toall those which, complete in themselves, fix on any

bench that maybe convenient. Lathes up to 4 inchcentre having beds up to 3 feet in length areusually mounted on small standards about 3 or4 inches high, and by these they may be screweddown to any bench. The fly-wheel for driving theselathes will have to be fixed beneath quite inde-pendently of the lathe bed and headstocks. Beds

8/7/2019 Lathe Work

21/220

LATHE BEDS. IIof any sectional shape may be used for benchlathes, but the triangular bar is most in favourfor small ones and is a most suitable form ofbed. The triangle is placed with one angle upper-most, the two upper sides are wrought quitetrue and straight, the whole of the headstocks andfittings -are adjusted to these sides, the lower facebeing that on which all the clamping screws taketheir bearings. Small screw-cutting lathes havesometimes a triangular bed cast with a groovealong the lower surface, in which the leading screwlies protected from any falling dust and shavingsmade in turning. A peculiarity about triangularbar lathes is that the mandrel headstock is invari-ably made of two distinct pieces, one taking thetail-pin and the other the collar, each fixed inde-pendently on the bed. Though able to withstandconsiderable downward pressure, the triangularbar cannot resist torsion so well as the usual formof bed.Lathes of 4 inch centre and upwards have gene-

rally a cast-iron bed, the top surface of which isplaned to take the headstocks, &c. The mostusual forms of fitting are the V and flat and thedouble flat. , In the former the V-shaped bearer isthe surface which guides the movable fittings whenshifted along the bed, and in the latter the con-tinuity of the line of centres is insured by havingparallel tenons on the bottom of each piece, fittingwithout shake along the inner edges of the bed.Occasionallr the outer edges are planed true; the

8/7/2019 Lathe Work

22/220

12 LATHE-WORK.side shake of the headstocks, &c., is prevented bystrips screwed to their base and fitting the outeredges of the bed. This latter plan may offer someadvantage in being easier to fit, but is not nearlyso accurate as that of fitting the tenon to theinner sides. Some beds have a break or gap nearthe fast headstock, allowing large discs to be turned,but this is not desirable for ordinary use. Thebeds of lathes of this size are usually bolted to ironstandards which carry the centre points on whichthe crank revolves, and also those on which thetreadle oscillates. To prevent spreading at thebase a stretcher-bar connects the standards at theback, and in some cases the front feet .are similarlybraced by means of a flat bar of iron lying close tothe ground so as to be out of the way of the feetand the foot-board of the treadle.Back gear is an arrangement of wheel-work by

which a very slow motion is imparted to the man-drel; it usually consists of a wheel and pinion onthe mandrel and a wheel and pinion on a shaftrevolving parallel with the mandrel. Instead offixing the pulley on the mandrel it is allowedto run loose with its front edge close to a toothedwheel which is keyed to the mandrel; a nut pre-vents the pulley getting away from this wheel.A pinion is fixed to the small end of the pulley onthe mandrel, gearing into a wheel fixed to an axis,which also carries a pinion gearing into the wheelfixed to the mandrel. Thus on turning the pulleymotion is conveyed to the mandrel through the

8/7/2019 Lathe Work

23/220

BACK-GEARED HEADSTOCKS. 13wheel-work, and by this means the speed is usuallyreduced to one-ninth; nine revolutions of thepulley produce but one turn of the mandrel. Forordinary purposes the back shaft is thrown out ofgear; the pulley is then attached to the wheel,keyed to the mandrel, by means of a sliding bolt.The illustration, Fig. 1, shows a horizontal sec-

tion of e back-geared headstock. The mandrelruns in double bearings, and its tail-end is pro-longed to form a stud, on which change-wheels forscrew-cutting purposes are placed. Referring tothe mandrel, and commencing at the right-handend, first comes the nose, on which chucks arescrewed, immediately behind it the shoulder, andthen a conical part, forming the front bearing.Against a shoulder the wheel keyed to the man-drel is shown; the pulley and pinion solid with itrevolving loose, except when attached to the wheelby the bolt arrangement. Behind the pulley is anut, shown in section, and a washer, made of hardsteel, fitted tightly to the mandrel. This washer,bearing against the collar in the casting, takes the. back thrust in boring and such operations. Thatpart of the mandrel passing through the collar isconed to form the back bearing; a washer comesnext this, being secured by a nut, as shown. Theend-shake of the mandrel is regulated by theadjustment of the nuts on each side of the backcollar. The stud forming the tail-end has a keyfixed to it, shown white in the Illustration,The back spindle is a plain steel arbor carrying

8/7/2019 Lathe Work

24/220

14 LATHE-WORK.a wheel and pinion securely fixed together, andtight on the spindle. In the position shown inFig. 1 the wheel and pinion are out of gear withthose on the mandrel. A peg put into the hole inthe casting (see left-hand end) prevents the back

Fig. I.-Plan Section of Back-gear, Double Bearing. Screw-cutting MandrelHeadstock.

spindle shifting and getting into gear. When itis desired to put the wheels in gear the peg iswithdrawn, the spindle moved towards the lefttill the right side groove is under the hole. Thepeg is then replaced to keep the spindle in its newposition. The mandrel-wheel and pulley are at

8/7/2019 Lathe Work

25/220

OBJECTS OF BACK-GEAR. 15the same time disconnected to allow the gearingto act.Though back-gearing is undoubtedly a veryvaluable auxiliary to a lathe on which much heavy

metal turning is done, yet for most purposes anarrangement of slow-motion bands will suffice.By this means the constant noise and jarringaccompanying the use of wheel-gearing is doneaway with. Much smoother work is producedby having a strong gut band from a smallpulley on the crank shaft to a large one on themandrel. When these two pulleys are of equalsize it is possible to tum up a cast-iron face-plateof the full diameter that the lathe will take, and byputting a pulley of half the diameter on the crank-shaft such a job could be accomplished with toler-able ease. Such heavy work is, however, usuallydone by steam-power, and all the power that canbe judiciously got out of a foot lathe is usuallyobtainable with simple slow-motion bands.The slide-rest is an attachment of so much im-

portance that an entire chapter is devoted to thedescription of its varieties and merits. The chiefobject of this-all that need here be mentioned-is to form a perfectly rigid tool-holder, which, hold-ing the tool mechanically, does not allow the ine-qualities of the work to exert so much influence asis unavoidable in hand turning; moreover, guid-ing the tool mechanically, it does so with a precisionunattainable in hand-work.Screw-cutting lathes are those which, by an

8/7/2019 Lathe Work

26/220

16 LATHE-WORK.arrangement of wheels receiving motion from themandrel and conveying it to the leading screw,move the slide-rest along the lathe bed at auniform rate, so that a tool fixed in the rest willcut a regular spiral on the surface of a cylinderrevolving between the centres. By arranging thewheels which transmit the motion from the man-drel to the screw in relative proportions, the rateor pitch of the thread cut on the work may becoarse or fine to any degree within the com-pass of the wheels available; these are calledchange-wheels, twenty-two usually constituting theset.The leading screw itself revolves, in bearings

attached to the bed, sometimes inside but gene-rally on the ilear side of the bed; the end to-wards the mandrel projects and is made to takethe change-wheels. A slotted arm called the wheel-plate, swinging round the screw, carries one ormore studs on which the change-wheels also fit,the piece ofmandrel projecting at the tail-end beingsimilarly shaped; and thus a wheel on the leadingscrew, another on the stud, and another on themandrel make a combination producing an effectproportionate to their relative diameters. Theslide-rest is fitted with a clutch gearing into theleading screw and forming a nut, which may bedetached instantly. A screw-cutting lathe not onlyenables one to cut threads of any rate and diameterperfectly true, but it is also available for workingas a self-acting machine when turning cylinders,

8/7/2019 Lathe Work

27/220

FIVE-INCH CENTRE LATHE. 17the rate of screw then being cut amounting tonothing more than a regular feed.It is unnecessary, in this treatise, to speak of themore uncommon modifications of lathes, which fit

them for special purposes and are not of generalinterest. The next consideration will be, What is asuitable lathe for general use?Probably the requirements of each individual

reader will have certain peculiarities which it isquite impossible to take into consideration whentreating of the subject in a general manner. Forsmall work in metal a heavy 4-inch centre lathewill be useful, whilst for working in wood a light6-inch would be more appropriate. Brass workrequires quick speeds, which are best maintainedwith a light lathe; but heavy iron and steel workis wrought at a slow speed on a heavy substantialtool. The exertion required to drive a 6-inchlathe will be much more than that necessary for asmaller lathe of similar calibre, and thus it is buta waste of energy to employ a lathe unnecessarilylarge.For general purposes a 5-inch centre lathe willbe found most handy, the height of centre allowing

a wide range in diameter. Then, if the mandrel ismoderately light, without back-gear it will be strongenough to take the heaviest work that can be doneon a 4-inch lathe, with the advantage of offeringfacilities for turning wood and light material ofmuch larger size. The bed may be 3 feet 6 inchesto 4 feet long, allowing lengths of 2 feet to 2 feet

C

8/7/2019 Lathe Work

28/220

18 LATHE-WORK.6 inches between the centre points. The con-venience of the longer bed consists principally inhaving the poppit headstock or slide-rest out of theway when either of these is pushed to. the end.With short beds it is sometimes necessary to removethe slide-rest or poppit in order to get at the workconveniently, and this is some trouble.A heavy bed, bolted to substantial standards, is

most desirable; the bed for a 5-inch should measureabout 4 inches in width and depth; if a double flatthe central space may be about Iinch wide, leavingeach flat a trifle wider. A 4-feet bed should weighat least one cwt. The fly-wheel of such a latheshould have series of grooves in steps correspond-ing with those of the mandrel pulley, so that theband may be shifted to any grooves on a series, andfit taut without any readjustment of length; there .should be two series of grooves, for each a speciallength of band being necessary. The extremediameter of the wheel may be 24 to 26 inches, witha series of three or four grooves graduated from thelargest possible size. The second series would beabout half that diameter, and have but two grooves;in cases where the suggestion before made ofhaving a small pulley for slow motion is adoptedthis may be from 4 to 6 inches in diameter. Fly-wheels are generally too light; t of a cwt. is notany too heavy for one 24 inches in diameter. Thecrank shaft should be I!inch diameter, and if ,4 feet long, two cranks are advisable, as they sup-port a long treadle better than a single crank,

8/7/2019 Lathe Work

29/220

MANDREL HEADSTOCKS. 19which is,however, quite enough forone 3 feet 6incheslong. The ends should always be plugged withhardened steel, and drilled up properly before beingcountersunk; the end should then be turned downconically to meet the edge of the countersink, sothat when in position and running the oil appliedto lubricate will not be thrown away from thecentres by centrifugal force. This is an importantpoint, though constantly neglected by lathe-makers.By observing a crank-shaft with flat ends itwill beseen that the oil, applied to the centre, quicklyspreads over the face and runs away from the bear-ing-when the crank is still, by gravity, and whenrevolving, by centrifugal force. The wheel is usuallyfixed to the shaft by keying, though sometimes itis secured against a shoulder on the shaft by meansof a nut. The points on which the axis revolvesshould be so adjusted that though the bearing isquite free there is no shake whatever, and theposition of these points must be such that the crankshaft runs parallel with the lathe bed. The wheelitself must be fixed perfectlytrue, and in a verticalline under the mandrel pulley.The headstock of a plain lathe, in which the man-drel runs-called the mandrel headstock, or fastheadstock, to distinguish it from the movable orpoppit headstock, which takes the back centre-should have a deep tenon cast on the bottom, tomake the casting rigid; the upper side shouldbe hollowed out to allow freedom for a large pulley,which for a 5-inch lathe may be 8t inches in dia-

8/7/2019 Lathe Work

30/220

20 LATHE-WORK.meter, The length of the mandrel adds much tothe steadiness in turning, provided always thatonly the smallest possible amount projects fromthe collar at the nose end. A mandrel, 8 incheslong, is a good proportion, and would be spacedthus: the thread of the nose, ~ inch long, cut witha!nch Whitworth thread; cone for front bearing,I inch long, the diameter being about II inch,tapering about 1; plain part, 11 inch long, Ii dia-meter- pulley, 21 inch; washer, nut, and plain partbehind pulley 2 inches, with a small part f inch long,terminating in a cone point. The headstock for such .a mandrel would be 10 inches long at the base, witha portion of the boss which holds the tail-pinprojecting about t inch to the rear, the total lengthof the hole in which the tail-pin fits being fully2 inches; the tail-pin should be cylindrical, per-fectly true, and fit the hole tightly, being held by anut on each end. Tail-pins, which are themselvesscrewed through the casting and fixed with a locknut should be invariably avoided, as with such thecountersunk hole, bored in the centre, is sure to beeccentric when turned in the thread, and thus theaxial line of the mandrel would be continuallyaltered. That the headstock casting fits the bedproperly is most essential; in many cases it will befound that the casting gets bent on the holding-down bolt being screwed tight, thus throwing theboring of the collar-hole and the tail-pin hole outof continuity. A direct pull by one bolt, near thecentre, so often bends the casting that it is

8/7/2019 Lathe Work

31/220

FOPPIT HEADSTOCKS. 21advisable to hold it down by two bolts, one neareach end.The back centre headstock should always bebored

out quite parallel and in a direct line with the axisof the mandrel, the barrel being cylindrical, with agroove along it in which a Ti-headed cylindrical pindropped into a hole in the casting, fits and preventsthe barrel rotating. The screw which actuates thebarrel is usually made with a left-handed thread,for convenience in turning, but whether left or righthanded is perfectly immaterial, except for the con-venience. For turning the screw a hand wheel ora winch handle is used j the former is more con-venient for boring with, and the latter offers theadvantage of not being so much in the way. Anarrangement for clamping the barrel at any desiredplace always forms part of the poppit head, and if ascrew acting direct on to the cylinder is used, a discof brass or other soft metal should be interposed tosave the barrel from being dented. The point ofthe poppit cylinder is always removable j. sometimesit is fitted by screwing into the barrel; but anotherand far better plan is to fit it in conically. The conefitting is as tight as any-in fact some lathes haveconical noses, on which the chucks fit by simplypressing on, and they then jamb. A cone fitting tothe back centre offers great facility for shifting thepoint, an operation which sometimes has to be doneconstantly. The screw inside the poppit barrelshould be sufficiently long to allow the tail end of thepoint to be made long enough to touch when the

8/7/2019 Lathe Work

32/220

22 LATHE-WORK.barrel is drawn back, and thus the point is forcedout by simply winding back the cylinder. Severalpoints should be fitted to the back centre, and somepieces with flat ends for boring against; these are,however, spoken of in another chapter. The dia-meter of the barrel may be an inch, the cylindricalpart of the casting into which it fits being aboutI~ inch in diameter. The barrel is bored out fromthe front end large enough to clear the thread ofthe screw by which it is moved, to within half an inchor so of the back end; this part is tapped to fit thescrew. The lateral motion ofthe screw is confinedby having a collar on it, which on one side bearsagainst a loose washer resting against the end ofthe casting, and on the other against the capscrewed on to the casting. The handle on the endof the screw should not confine its lateral motion,and it is often merely pushed on a square or hexa-gonal fitting, though sometimes secured by a keyor a nut.The hand or T-rest needs but little comment;

the socket should be bored at right angles to thesole, which should be planed with a dovetailed slot.Ifthe lathe bed is double flat the sole of the hand-rest stands direct on it; if a V-bed it should havea cast-iron foundation plate, shaped to fit the bedon the under side and flat on the top. The screwwhich clamps the T should have a handle likethat of a bench vice fitted to it, as it so often requiresto be shifted to suit the work in hand. A" per-manent tommy" is also desirable in the screw

8/7/2019 Lathe Work

33/220

HANDRESTS. 23which clamps the back centre barrel, as it is somuch more handy to be able to fix these partswithout the trouble of finding the "tommy" oneach occasion.The T itself for general use may be about 2 inches

long on the top and should be flat and level; in useit will be continually pitted, and must be filed upsmooth again. For turning long cylinders by handa much longer T is used, measuring as much as 5or 6 inches. For still longer rods it is customaryto use a straight bar as a rest, which is supportednear its ends in twoT socket-holders; by this plana rest, reaching the entire length of the bed betweenthe centres, can easily be fitted up. In turningwork of short length the T-rest is sometimes foundto be in the way, and a 1-rest is used instead; thisis made of an angle piece, one leg fitted to the restsocket, and the other filed fiat on that surface form-ing the top. The "[-rest is often used with the pointtowards the work, thus giving a rest of about !fan inch in length, very convenient for short work.T and 1 rests are usually made of cast iron, butwrought iron is sometimes used, and this is thebetter material, especially for the latter shape.A collar-plate is an arrangement in general use

for supporting the ends of rods whilst these are .being bored up; it consists of a disc of cast ironhaving several holes bored near its edge. Theseholes are very much coned and are graduated insize; in use the largest side is put towards themandrel, and the bar being turned revolves in the

8/7/2019 Lathe Work

34/220

8/7/2019 Lathe Work

35/220

AXIAL CONTINUITY. 2 5imparted to the whole structure. The treadleshould be as low as possible, just to be clear ofthe floor when at its lowest point, rising to about9 or 10 inches. A narrow strip of wood nailedto the floor just in front of the foot-board of thetreadle will serve as a guard to prevent the toesfrom getting underneath.That the entire line of centres should be perfectly

parallel with the bed is always desirable, .and inmany cases absolutely essential for producing truework. The two ends of the mandrel should beexactly equidistant from the bed, as should be bothends of the poppit cylinder. The effect of havingthe axis of rotation of the mandrel at an anglewith the bed is not shown when turning betweencentres, though the carrier and the pin of thedriver-chuck will be continually rubbing againsteach other to an extent proportionate to the errorin the line of centres. The mandrel may bedifferently distanced from the bed at one end thanat the other, without affecting the work betweencentres, though when chucked without any backsupport the free end of the work will be more orless above, below, or on one side of the back centrepoint, as work unsupported will naturally take theposition of an axial continuity of the mandrelitself.In order to test the truth of the axis of rotation

with the lathe bed itself, the positions of themandrel bearings must be gauged. The paral-lelism of these bearings with the top and inside of

8/7/2019 Lathe Work

36/220

8/7/2019 Lathe Work

37/220

LATHE-NOSE.proved by screwing the tail-pin as tight as possible,so that the mfl-ndrelmay be turned by hand, and ifthere are no places where the fit is easier than atothers you may consider it accurate, providing thatthere is no side shake whatever. The mandrelmust always be kept up to its bearing by the tail-pin, and never allowed to run loose, or the bearingswill be worn unequally.The flange of the nose, against which the chucks

screw, ought to be quite flat and perfectly true, soshould the thread of the nose, though it is ratherthe exception to find that it is so. Some makerstum a groove in the mandrel at the back of thethread, reducing the diameter to that at the bottomof the thread, though with what reason is not easilyconceivable. The effect is to very materiallyweaken the mandrel at that part which is, under themost favourable circumstances, its weakest place.The bearing of the mandrel should be of steel andvery hard, and the face against which the chucksjamb should also be of steel-in fact, a continuationof the bearing, the usual plan being to shrink asteel collar on a mandrel of fagoted iron.If the boring of the poppit headstock is anythingbut absolutely true with the line of centres, theposition of the back centre point, relative to theaxial continuity of the mandrel, will be constantlyvarying as the poppit barrel is wound out. Thetruth of this boring can be tested to a certainextent by winding out the point as far as possiblewithout allowing the barrel to become loose in the

8/7/2019 Lathe Work

38/220

28 LATHE-WORK.hole, and then testing it with a point-chuck. Theoppositeness of the points cannot be tested bycontact with any degree of accuracy. The best planis to use a narrow parallel straight edge and adjustthe cones to that distance apart which just allowsthe straight edge to go between them, with itsopposite edges resting against the opposite sidesof the cones. Th- straight edge is applied on bothsides, above and below, and readily shows theoppositeness of the points. The poppit may begauged in the same way as described for testingthe mandrel bearing with a wooden temporarymandrel; using the barrel, which must fit nicely Jprojecting at both ends of the c.asting.

8/7/2019 Lathe Work

39/220

CHAPTER III.HAND TURNING.

First principles of the art, commencing to practise-Wood turning,the gouge and the chisel-The mode of their application tothe cylinder and surface-Easily made objects for beginners-Making a plain wooden box-Metal turning, the graver and tri-angular tool, and their use-Finishing tools, round nose tools, &c.

WHEN commencing to practise the art of turningit is advisable to begin by using simple tools andappliances, and with them to execute work of themost rudimentary kind, so that the learner maybecome properly acquainted with the elements oflathe-work, and he will then be able to understandthe execution of the more complicated work. Itsometimes happens that a fine collection of toolscomes into the hands of one who has never hadany previous practice in their use, but who willnevertheless boldly essay to use the most compli-cated machinery before troubling to learn the prin-ciples that govern its application, and which areonly to be studied in using the simpler tools. Aperson unacquainted with the conditions underwhich a hand-tool acts most favourably, only to belearned by practice, cannot correctly judge the bestposition in which to fix a tool in the slide-rest; and

8/7/2019 Lathe Work

40/220

30 LATHE-WORK.the art of turning, like all others, to be learnedproperly must be begun at the beginning. Thefirst lesson in turning should, therefore, be at aplain foot lathe with back-centre and T-rest only, allthe apparatus and attachments which have beendescribed as adapted for special purposes beingremoved entirely, for though the slide-rest may bevery useful to assist a beginner in roughing-downthe work, yet it would be most injudicious tomake use of such an apparatus before acquiring athorough mastership over hand-tools.A plain parallel cylinder is, perhaps, the very

best object for a beginner to try his hand at pro-ducing, for its simple form dispenses with all com-plex manipulation of the tools; yet the produc-tion of a true cylinder can only be achieved aftermuch practice, and such work demands more skill. than would be at first sight imagined. AxJ.yslightslip of the tool causing its point to dig into thework would, of course, spoil a cylinder nearlyfinished to a definite size; but for practice such amishap would be of no consequence, only necessi-tating the reduction of the entire cylinder to theaize of its smallest diameter. For wood turningthe gouge and chisel are the tools most generallyused, and they will be sufficient for our work; asimilar cylinder of metal would be turned with agraver. Soft wood will do for material, thoughhard wood is more pleasant to work, and will notrequire driving at a high speed, which is tiringto the tyro. A chuck will be wanted to carry the

8/7/2019 Lathe Work

41/220

TURNING SOFT WOOD. 31work, and the prong-chuck, described in anotherchapter, is best suited to the purpose; and we willsuppose the rough wood mounted between such achuck and the back-centre, which is screwed up totake firm bearing and the extreme point oiled.For softwood turning, place the band on the pair

of grooves giving the quickest motion-that is,from the largest on the :By-wheel to the smalleston the mandrel-and in revolving the work it willbe scarcely possible to drive it too quick. Thehand-rest is then adjusted so that the top edge ofthe T is on a level with the lathe-centres, and thework revolves just clear of it. The position forstanding at the lathe whilst turning a cylinder iswith the shoulders fairly parallel with the lathe-bed, the body upright, resting on one foot, the otherbeing on the foot-board of the treadle, the operatorusing either leg to support him, and occasionallychanging from one foot to the other as he becomestired; the foot on the ground is placed as fartowards the lathe as the treadle-board will allow.With a balanced fly-wheel, that is, one weighted sothat the crank always stands, when at rest, slightlyinclined forward from its highest point, thetreadle will be in the position to receive the pres-sure of the foot. Under ordinary circumstancesthe lathe-band is pulled down from the mandrelor the fly-wheel is revolved by the left hand, so asto bring the crank into the position described, and'then pressure is exerted on the treadle, and' thework revolves. Two or three strokes are given to

8/7/2019 Lathe Work

42/220

32 LATHE-WORK.get up the momentum before the tool is applied tothe work.The turner's gouge is used for roughing out

wood-work, and a turner should provide himselfwith several sizes, according to the work he has toexecute. For general use a gouge half-an-inch or sowide will be found most serviceable; the tool is sharp-ened differently to the carpenter's gouge, so as toleave the cutting edge rounded off instead of squarewith the shaft of the too], as in the carpenter'sgouge. The grinding is all done from the outsideof the semicircle, and forms one continuous bevel,leaving an acute angle for the cutting edge.Gouges should be fitted into long handles to enablethe operator to have complete control over the toolwhen in use. A half-inch gouge may be a foot or solong from end to end of tool and handle com-bined; larger sizes are much longer, frequentlymeasuring as much as 2 feet, and sometimes evenmore. The gouge is grasped firmly near thecutting end by the left hand, the knuckles beinguppermost, and is laid on the rest with its curvedside downwards; the right hand holds the end ofthe handle, and usually rests against the side of thebody, to afford greater steadiness. Thus held, theedge of the gouge is gradually brought sufficientlynear the revolving cylinder to touch it in the posi-tion known as at a tangent to the circle, that is, sothat aline drawnin continuation of the ground bevelwill touch but not cut into the cylinder. In this posi-tion the tool will not cut, but on raising the end of

j

8/7/2019 Lathe Work

43/220

USING THE GOUGE. 33the handle with the right hand the edge of the toolis depressed, and becomes in the position of atangent to a smaller circle, then all the materialoutside of that diameter will be shaved oft' by thetooL The pressure on the edge during the processtends to force the tool deeper into the work, and,therefore, the end held in the right hand must bekept down till the work has been reduced all roundto the new diameter, when the gouge will againcease to cut. A slight elevation of the handlewill again throw the edge into the cylinder,and so on till enough has been removed from thework.Though the elevation of the handle has been

described as an intermittant process, yet in practiceit is, of course, a continuous one, for it is by rais-ing the handle that the tool is fed into the work,the thickness of the shaving being regulated by thefeed thus given. If the theory which governs the. cutting of the gouge is properly understood itwillbe easy to carry out the principle in practice, andthus rapidly acquire proficiency in the use of thecool, By means of the gouge the rough wood isturned to a circular form, all the angles are re-moved, and the work made as straight as possible.1\. pair of callipers is used to measure or gaugethe size from end to end, and those parts foundto exceed the general diameter are reduced, so thatthe surface will be fairly straight. There will, how-ever, yet remain a series of ridges resulting fromthe use of the circular-pointed gouge, and these are

D

8/7/2019 Lathe Work

44/220

8/7/2019 Lathe Work

45/220

8/7/2019 Lathe Work

46/220

LATHE-WORK.and chisel it will be easy to turn rulers, and sogain experience. A roller on which to hang ajack-towel and a rolling-pin are usually to befound in every household, and capital practicewill be afforded in turning exact copies of suchthings. Cricketers' stumps and bales, tool handles,trenchers, and numerous other common articlesare made on the lathe. The production of these willafford variety to the practice and enlarge the rangeof work without very severely taxing the skill, yetalways adding to the capacity of the workman.It is well to remember that an adept at turningsuch simple objects will find it easy to proceed tothe execution of the most complicated work. Aplain wooden box affords considerable practicein the use of hand-turning tools, and the method ofmaking one is this :-Having decided on the size ofthe proposed box, select a piece of wood, almostany kind will do, but preferably use that which hasa close even grain. See that the ends are cuttolerably square, and mark a circle on each toserve as a guide forroughing out the circumferenceas nearly round as possible, first with a hatchet, andafterwards with a rasp. The length of the woodmust be :-the height ofthe box, the height ofthe rimon which the cover shuts, the height of the coveritself, enough space to allow the parting-tool to beused twice-that is, where the lid is separated fromthe body of the box, and where the box is cut fromthe superfluous piece in the chuck-and enough tochuck the wood by. All these measurements added

8/7/2019 Lathe Work

47/220

8/7/2019 Lathe Work

48/220

8/7/2019 Lathe Work

49/220

8/7/2019 Lathe Work

50/220

40 LATHE-WORK.and requires no further treatment. If it is desiredto tum the bottom face, the piece of waste woodcan be hollowed out so as to fit the rim on whichthe lid fits, and chucked by thUithe bottom may beoperated upon as required, leaving it slightly con-cave. Every time that the box or lid is re-chuckedit must run as true as it did in its former position,and to re-chuck work perfectly true is one of thefirst lessons that a turner should study. Thereare also the fittings of the lid to the box and thebox to the chuck, which will be excellent practice.It may be assumed that when a plain box, in

common wood, call be turned out-of hand in everyrespect well made, the maker has attained sufficientskill in the use of his tools to warrant his under-taking without fear of failure work of far morecomplicated design and apparently more difficultto execute. The plain box just described is scarcelya piece of work likely to attract the attention ofthose who have an extensive assortment of toolsand appliances; still the care and attention whichmust necessarily be bestowed on the various opera-tions incidental to its production afford an amountof practice in the use of hand tools on wood whichis considerable and varied, and should be prizedaccordingly.Turning metal by means of hand tools is a

process in every way similar to that just described,modified to suit the nature of the material. It isgenerally found that an inexperienced hand suc-ceeds better in turning metal than wood; there is,

8/7/2019 Lathe Work

51/220

THE GRAVER. 41however, no more difficulty in working this lattermaterial, and the circumstance named is due tothe more obvious effectproduced with wood, makingit much easier to see the effect of the tools used,but more difficult to guide them. Wood is turnedat a far greater speed than is metal, and thematerial is much softer, so that whilst the toolmore easily penetrates the work and" catches in,"this is more liable to be tom than the moretenacious metal revolving at a less velocity,The same angle is to be preserved in applying the

tool to metal, that is, it should form a tangent to thecircle being cut, f)ut consequent on the hardness ofthe material the angles of the cutting edges must bealtered to make them stronger; however, the work-man who, by practice on wood, makes himselffamiliar with the most favourable conditions underwhich the tool acts, will be best able to apply toolsto metal to the greatest advantage.The graver is the most general tool for metal

turning. It is a bar of square steel, usually aboutone-quarter to five-sixteenths of an inch in size,though smaller and larger are used. All the flatsare sometimes, but two are always, ground flatand smooth. The end is ground off diagonally,those edges formed by the sides meeting at the pointbeing used for turning. The angle made by thediagonal diamond - shaped end with the shankvaries to suit the material that it is intended to actupon, from 60 to 70 being about the usual limit.The triangular tool is also much used. It is

8/7/2019 Lathe Work

52/220

LATHE-WORK.generally made from a worn-out triangular file, ofthe dimensions named as usual for gravers, andis merely ground on the faces to take out all themarks of the file teeth, leaving sharp edges at theangles, all of which are 60. The end is groundoff obliquely, leaving a point at one angle, but thetool is generally used to cut with its side edges;and in this respect it principally differs from thegraver, which is used only at the end.With the two tools named most of the rough

turning by hand on metal is done. Tools for metalhave short handles. In use the left hand generallygrasps the T-rest and the tool, the fingers encir-cling the stem of the rest socket and the thumbclasping the tool to the T. The right hand holdsthe handle as described in holding wood-turningtools; indeed, sometimes both hands are used asthere described, only closer together, a naturalconsequence on the reduced length of the handleand tool itself. A lubricant is used with thesetools on wrought iron and steel; this is necessaryto keep the edge cool and lubricate the cutting.Water answers the purpose, but soapy water isbetter, and perhaps quite as good as oil, thoughmuch cheaper. Cast iron, brass, and gun-metal areturned dry.The way in which the graver is applied to the

work is this :-the tool is laid with one angle on theT-rest, the point being towards the back centre,and the handle at an angle with the line of centres.The lathe being set in motion and the graver

8/7/2019 Lathe Work

53/220

TURNING METAL. 43brought as near as possible to the work, it isfirmly indented on the rest, and by bringing thehandle towards the right the point is made to cutthe work; the operation is assisted by turning thegraver slightly over towards the left. This actionmakes a narrow groove on the work, and when thehandle is so far to the right that the tool is dis-engaged, the graver is shifted along the rest torecommence the same process. The work turnedby this means will consist of a series of grooves,more or less irregular, but the concentric truth willbe correct. In the same way the triangular toolmay be used to produce a like result.To further finish the cylinder, after it has been

made as straight as can be with the graver, aflat tool is used. This somewhat resembles acarpenter's chisel ground off square at the end sothat no bevel exists. This tool is applied, endon, to the cylinder, and cuts away all the ridgesreducing the surface to one level.. This flat toolmay be from about half-an-inch wide and one-eighth thick up to double these dimensions; it canoe used indifferently with either edge to cut.Cylinders with straight surfaces, whether parallelor coned, are generally finally finished by filingwhilst in rapid revolution in the lathe, a fine filebeing used. To produce an extra smooth surfaceemery paper wrapped round the file is afterwardsapplied, and by this means a very high finish canbe given to the work.Round-nosed tools, which are made of strips of

8/7/2019 Lathe Work

54/220

8/7/2019 Lathe Work

55/220

CHAPTER IV.SCREW-C,UTTING BY HAND.

Striking the thread with outside and inside comb-screwtools-Originat-ing a thread-The method of cutting the thread in a lathe chuckminutely described.CUTTINGscrews by means of comb-screw toolsguided by hand is a process only to be learnt afterconsiderable practical experience has been attainedin the use of hand tools on the ordinary cylindricalwork. The tools themselves are made in pairs, onefor use on the external the other on the internal .thread; they may be bought at all tool shopswhere turning tools are sold. One pair is ofcourse only applicable to one particular rate ofthread, though it may be cut on any diameter.The same screw tool that cuts a thread of, say, fiftyturns to the inch on a screw one-eighth of an inchin diameter is also used if the same rate of threadis required, say 2 inches in diameter as in opticalinstruments. Forholes of very small diameter it is

\ very seldom that comb-screw tools are used, and ifunder certain sizes it is impossible. Taps are gene-rally used for all inside threads that have a.thoroughfare hole excepting in optical work; the

8/7/2019 Lathe Work

56/220

LATHE- WORK.workmen in that trade always using comb tools tocut the fine threads. Holes which cannot be tapped,through having a bottom, may be cut with a combtool, and the process is explained in detail, withspecial reference to chasing the screw inside achuck, in the latter part of this chapter.The outside screw tool is very much used for

cutting the threads in bolts and all kinds of workthat can be mounted in the lathe. Frequently thethread is originated by making a spiral line withthe die stock, the work is then transferred to thelathe where the screw is cut out with the combtool, this cutting faster and better than dies, andbeing comparatively easy to keep in the spiraloriginated by the dies. If this is not quite true itis not likely to be' improved in the chasing by anybut a skilled screw-cutter. After the bulk hasbeen removed by the comb tool the dies are usedto finish with To acquire the habit of traversingthe tool at a uniform rate a beginner should practiseon a cylinder which has a thread already cut on it,such as one partially cut by dies.The way in which the screw thread is originatedby hand with the chaser will be easily understood.

It is simply necessary to move the chaser alongthe top of the T-rest exactly the same distance thatthe teeth are apart whilst the work is turned roundonce. If the tool and work have been moved at aregular speed the thread will be true; if,however,either motion has been jerky the thread will notbe regular but bent or wavy. It will be seen that

8/7/2019 Lathe Work

57/220

HAND SCREW-CUTTING. 47the rate of the screw and the diameter each governthe result, and though the difficulty of striking thetrue thread may appear very great, yet after care-ful practice and observation of the result it will bea job that can be done with ease and certainty.The thread, whether outside or in, is always first

struck on the corner of the work, and this is roundedoff for the purpose before applying the screw tool.The T-rest, which must have a smooth top, is thenplaced near to this corner, and having set thelathe going with a regular swinging motion, thecomb is brought on to the rest. By a circularmotion of the handle, the blade of the tool havinga centre of motion on the top of the T, one toothnear the centre is made to cut a spiral line, thedepth of which is greatest at its middle and dimi-nishes to nothing at the ends. When once thetrue helix. is struck it is comparatively easy tofollow it up, making it deeper and ex.tending itfurther at each application of the tool.The thread is thus struck at the end first, and

gradually deepened and lengthened till it hasreached the distance required; so that during theprocess of chasing it the thread is always cutdeeper at the end, and it is made parallel by givingthe final cuts nearer to the back end. The first spiraltraced forms a guide, and on repeating the cut thepoint of a tooth must come in the previously-madegroove, or the thread will be damaged and pro-bably spoiled. Those who have cut threads withbadly fitting dies have probably had occasion to

8/7/2019 Lathe Work

58/220

LATHE-WORK..notice the effect of another thread being originatedbetween the true one; this is what happens if thecomb tool is not always replaced in the groove firstmade.The use of the comb-screw tool for inside work

is best explained by its application to cutting thethread in' lathe chucks, after starting with thetap as described in Chapter VII.When the thread has been started in the hole

and the tap taken out, clean the. dust out of thehole and put the hand-rest, which must bequite smooth, at least at that part where thescrew tool will take its bearing, close against thehole, at such a height as may be convenient forallowing the chaser to cut. This will be with itsedge slightly above the centre, as the rake of theteeth is, in bought screw tools, the wrong way, andin consequence of the thickness of the tool itwould, if placed at the correct height-i.e. on theline of centres-have the lower points of the teethin contact with the interior of the hole. If thesepoints were to find their bearing in the spiralgroove, the upper cutting edge would not cut atthe same spiral line, but a trifle behind it. Thuswill be understood the importance of getting thetool to the correct height to let the lower edgeescape contact. When all the parts are properlyadjusted commence cutting the screw. First get aregular swinging motion to the lathe-treadle; thehabit must be acquired of keeping the same regularmotion with the foot, inderendent of the occupation

j

8/7/2019 Lathe Work

59/220

8/7/2019 Lathe Work

60/220

s o LATHE-WORK.contact with the bottom of the hole whilst theteeth are cutting the thread, or damage more orless serious according to the rigidity with whichthe tool is held must inevitably follow. The eyeand hand will soon become educated to act inunison, so that when the screw tool has gone in toa certain depth, as indicated to the eye, the muscularpower of the thumb is relaxed; the teeth of thechaser are gently drawn out of the thread, andwhen quite clear the tool is drawn outwards, sayhalf an inch or so, and the operation repeated.This is continued till the thread is nearly to size,and it is finally finished with the full tap. Thereare several points to be considered in cutting thethread. As to its size, if the chaser is too high upit will cut the thread shallower than it should be.lfthe tool is not run in parallel, the mouth of thehole will not gauge correctly, and consequently itwill be impossible to ascertain the exact size ofthe thread. These points must be studied andacted upon to the best of one's judgment, anydefinite rules being impossible.When the thread has been cut out with the chaser

to, as near as can be judged, the proper size, thefull-sized tap is inserted and screwed home exactlythe same way as was the entry tap, using the backcentre to keep it square, and working it right intill it " bottoms" in the hole.

8/7/2019 Lathe Work

61/220

8/7/2019 Lathe Work

62/220

LATHE-WORK.roughly fairly apportioned to each tool. A draw-back to the use of drills is that they are liableto run out of the straight line in which it is intenBedto bore, and the drill cutting into the solid materialis most liable to do so. Those which follow ongenerally keep fairly true to the original hole, butthey have no tendency to correct any error, andare sometimes found to increase it. Drills shouldalways be started in a fairly countersunk hole, andespecial care taken to see that they go correctly inthe spot desired till the entire point angle of thedrill is beneath the surface; the sides will thentend to guide it.Fitted to a chuck such as those described on

page 92, the drill is the most usual form ofborer, as its point will at once find its bearing in acentre punch mark and follow on fairly concentric,sufficiently so for the majority of purposes. Thusfor all the general purposes of boring where abso-lute truth and straightness are not imperative,drills are the best tools to use. It is only neces-sary to indent a conical hole with the centre punch,sufficiently large to allow the fiat end formed bythe meeting of the cutting edges across the thick-ness of the drill 'to enter well, and the hole willfollow fairly true. If a long cylinder has to bebored then a drill would be unsuitable, as it wouldbe sure to deviate from a straight line, and, thoughentered perfectly central at one end, on reaching theother it would come out more or less out of truthwith the centre. This fault is sometimes sought

8/7/2019 Lathe Work

63/220

DRILLS FOR METAL. 53to be remedied by drilling alternately from bothends and making the holes join in the middle, buthere they do so only approximately. Thoughapparently true from what may be seen at the ends,yet when looked at through the bore will be foundto be crooked. .The ordinary form of drill is shown in Fig. 2.

The shank part is turned parallel to fit a chuck,.and a flat filed to take the point of a clamp-screw.A shoulder, to prevent the drill being forced intothe chuck, should be provided as illustrated. Theentire drill should be nearly parallel; if small atthe point-end it will not bore deep through binding,

Fig. 2.-Tbe Drill for Boring Metal.and if unnecessarily small at any part behind thepoint the drill is weakened and liable to break.The blade should be flattened sufficiently far toallow borings to escape. The illustration is in-tended to convey to. the eye an idea of the bestgeneral form of a drill for ordinary purposes.Drills should have their points at an angle of

120, though they are often ground to 90, to fitan ordinary square. The extreme point must be inthe exact centre, and the flat part of the drill shouldbe nearly parallel on its sides for a short distancefrom the point; as this will materially assist inguiding; the cutting angle must be small, onlysufficient for proper clearance. On taking into

8/7/2019 Lathe Work

64/220

8/7/2019 Lathe Work

65/220

HALF-ROUND BITS. 55The description will be found on page 73. Thesebits are made of all sizes, some used for ornamentalwork being most minute. They will bore a holeinto solid metal, but are more often used to followa drill and correct any defects left by it. It is,only necessary to make a countersink to fit theD-bit correctly; it will then bore quite straight,but it must itself be straight and be revolvedstraight. The half-round part must not exceedthe semi-diameter, or the bit cannot bore a hole insolid material. An advantage which this form ofboring tool has is that it leaves the hole with aflat bottom, not a conical one as drills do. Whenof large size, these bits usually have a portionwanting to complete the semicircle on the oppo-site side of the flat. This results from their beingmade from flat bars of steel not sufficiently thickto form the entire half-round; it in noway detractsfrom their utility,Pin-drills are used to bore a larger size truly

concentric with a previously made hole; also formaking square countersinks for screw-heads, &c.Somewhat similar to a drill in their action, thesetools have a round pin at the end, and the cutting'edge is behind this. Generally they have but twocutting lips, but, when made of round steel, pin- .drills have usually four cutting edges, as illus-trated in Fig. 3- The pin fitting the hole pre-viously made effectually prevents the drill fromgoing excentrically _ In order to make one drillserviceable for different-sized holes, collars are

8/7/2019 Lathe Work

66/220

LATHE-WORK.sometimes fitted to the pin, and by this means it isadapted to larger holes. Pin-drills, often made inthe cutter bar next described, are very useful formaking a level bearing for a nut or a bolt headagainst a casting. By using this drill a circle ofany size required may be made quite fiat andsmooth, concentric with a hole bored in a roughcasting. By shaping the cutting edges to thenecessary form these tools may be used not onlyto face up but also to true the edges of bosses, &c.,that cannot be turned in the lathe, and even to puta moulding round them ..Cutters. are sometimes used fitted to a bar,which is revolved between bearings or on the lathecentres; then the cutter is at some distance fromthe end, often near the centre. When near one endof the bar it forms a kind of pin-drill. These barsare always for boring large-sized holes, and aremade from motives of economy, one shank or stockserving for a large number of cutters often havinga wide range of sizes. The cutters to such a barcan be made in so little time and at such avery small cost that the advantage is obviousfor all sizes that are not usually required. Thebar itself may be of iron, though preferably ofsteel, and after being centred and trued up, ithas a transverse mortice cut through it near theend. The end is then turned to a certain size tofollow drills or half-round bits of that size. Thecutters for the bar consist of small pieces of steelwedged into the mortice by a cotter. The cutters

8/7/2019 Lathe Work

67/220

PIN-DRILLS. 57have a groove across them, leaving nibs to fit overthe diameter of the bar and ensure their beingreplaced true. When the blank has been fitted tothe bar, it is turned true in its place to the requiredsize, the cutting edges are shaped by filing. and thecutter is hardened and tempered for use. Some-times the cutters are clamped in the mortice by aset screw.Rose-bits have several teeth on the end to cut

with; some are made quite fiat, and are used forcutting recesses of small depth that are required to

FiG'. J.-Pin Drill, with Three Cutting Lipa,'

have a fiat bottom with no hole in the centre.This form of rose-bit does the work of a pin-drillwithout requiring any thoroughfare hole to guideit. The bit is guided by clamping a piece of sheetmetal having a hole in it exactly fitting the rose-bit, and this placed in the hole bores straightaway; therefore it is only necessary to place thehole of the plate precisely over the spot that has tobe drilled. These rose-bits will not cut into thesolid metal, but for some purposes they are indis-pensable. Fig. 3 without the pin would illustrate~ rose-bit.

8/7/2019 Lathe Work

68/220

CHAPTER VI.MOUNTING WORK FOR TURNING.

Work between centres - Methods of centring - Necessity of pro-perly preparing the centres-Chucking objects of various forms-False centres-The collar-plate-Chucking on the face-chuck.WORK is mounted for treatment on the lathe invarious ways, consequent on the almost unlimitedforms which have to be chucked. There are twobroad distinctions, however, by which we may con-veniently divide the methods in general use for easein describing them. First, objects which are sup-ported by the back-centre, cone-plate, or someequivalent contrivance; and second, those whichare mounted on the mandrel independent of suchsupport. Amongst the first are generally all objectsconsiderably greater in length than diameter, suchas balusters, spindles, and rods of all kinds;the second, embracing short objects, sometimesgripped by their edges, and at others clamped bytheir surfaces, or held by cement in a similarfashion. In the chapter devoted to chucks muchinformation applicable to this subject will be found.The method of mounting work by far most gene-

rally practised is that of running it between centres.

8/7/2019 Lathe Work

69/220

CE~TRING WORK.The extreme facility of so chucking any objectcapable of such treatment is the chief cause of itsextensive use, whilst its effectiveness leaves littleto be desired. The indented, shallow, conicalrecesses to be seen at the ends of nearly all spin-dles and shafting are evidence of the work havingbeen turned between centres by the aid of such achuck as the one illustrated in Fig. 9. Work thathas been once properly centred may be removedfrom the lathe, and at any time remounted on anyother with the certainty of its running true, that is,providing the centre-points of such lathes are inproper order at the time the work is put betweenthem. Other methods of chucking do not allow ofthis being done without considerable trouble, andhence all work that has to be often removed andreplaced on the lathe should, if possible, be chuckedbetween centres.The first. consideration in preparing work for

running between the centres is. to get the exactcentre-point at each end, so that the entire objectwill run true on the lathe, and not, by being con-siderably out of centre, involve a great deal ofunnecessary labour in reducing it to a concentricform. It is curious to find that an inexperienced handseldom attempts to get an accurate centre to hiswork, and many consider the trouble involved in sodoing far outweighs the advantages. It is, however,so easy to centre work absolutely truly that theextra labour is comparatively inappreciable; infact, only 'a slovenly hand would tolerate badly-

8/7/2019 Lathe Work

70/220

LATHE-WORK.centred work, involving as it does so much extralabour to no purpose.Rod metal is, perhaps, the most usual object for

centring, and in selecting a piece for a particularobject it should be chosen just sufficiently large,both in diameter and length, for the purpose.All superfluous metal will be wasted, and not onlythat, but the labour which converts the good mate-rial into useless waste is itself all lost. The rodshould be straight and the ends cut off squarely ;these are each in tum filed fiat, and at rightanglesto the axis' of the rod. If the end-faces are ata slight angle it is more difficult to judge of thecentre of the rod. The try-square will show theinclination of the end-faces with the side of the rod,though a practised eye will, unaided, detect themost minute error appreciable in working.The actual centring is done with a fine-pointed

centre-punch usually. For work of small dia-meter the punch is placed as near the centre as canbe judged by the eye, the work being meanwhileheld vertically in the vice, and a light blow of ahammer indents the metal. The rod-end is thencarefully examined, and if the dot is found to beout of centre it is driven towards that side of therod where most metal appears; this is done byholding the punch in a slanting direction whenstriking it. When the dot is judged to be fairlycentral the rod is reversed in the vice and theother end treated similarly, the punched centresbeing only slight. The rod is then placed between

8/7/2019 Lathe Work

71/220

DRILLING IN CENTRES.the lathe-centres, and by turning it round with thethumb and finger, the amount of its eccentricity, ifany, can be noted and the high parts marked withchalk. The rod is then returned to the jaws of thevice and the centre-punch applied so as to drivethe indentations towards the centre. The work isagain tested on the lathe-centres and operationsrepeated till the rod is found to run true. Whenthis is accomplished the punch-marks are consider-ably enlarged by heavy blows, holding and drivingthe punch in a straight line with the rod, a strongerpunch being employed.Drilling in the centres is the next operation, and

an important one it is for work that has to run onits centres much, though for workthat will never be put on thelathe a second time it is some-times dispensed with. Some Fig. 4.-A properlydrilledworkmen, careless of the accu- Countersunk Centre .:racy of the work they tum out, are contentto use centre-punched centres only. In everycase when the work is liable to be run betweencentres on a future occasion, the punch-marksshould be drilled in with a small drill sufficientlydeep to ensure the centre point from bottoming; thehole should also be slightly countersunk to form adurable bearing for the centre when running. Thedepth of the hole, size of the countersink, &c., willbe dependent on the size of the work, but in allcases the countersink must bore to the angle cor-responding with the centre-point, this being, as

8/7/2019 Lathe Work

72/220

LATHE-WORK.stated in another chapter, 60. The hole bored inthe work may be very small, but must be deepenough to clear the centre and allow for a littlewear. Fig. 4 shows how a properly drilled andcountersunk centre-rod should fit the cone-point;the rod only is shown in section.Rods of large size, and those objects that have to

be centred at parts where it is difficult to judge ofthe precise centre, are usually marked with callipersor a scribing-tool to show the middle. A gaugeformed of two strips placed at an angle, and havinga straight edge bisecting the angle, can be usedfor determining the centre by putting the rod intothe angular opening and scribing on its end twodiametrical lines at somewhere about right anglesto each other, the intersection of these lines showingthe precise centre. A centre-punch sliding in abarrel at right angles with and forming a continua-tion of the apex of a hollow cone. is also employed,though not very generally. The cone is placedvertically over the. end of the rod to be centred,and on bringing down the centre-punch it willmark the centre of the object within the cone. Inpractice this form of centre-finder is confined to theworkshops of amateurs.A totally different method of centring cylindrical

rods may be adopted, and when many of likesize are to be treated it has advantages over thecentre-punching previously described. By thismethod a centre fitted into the poppit barrel, havingits end ground off to a triangular point, is employed

8/7/2019 Lathe Work

73/220

8/7/2019 Lathe Work

74/220

66 LA~-WORK.revolution. A stiff triangular point is necessary-flexibility would destroy its purpose-and the coun-tersunk hole must be drilled in, as in Fig. 4,with as small drill as has been already described.Work centred by the method last described is, ofcourse, reversed in the chucking when one end isfinished, so that the other may be operated upon.It will be understood that innumerable objects of

various forms may be chucked by simply makingsound centres in them; for these, though they mayappear but fragile bearings, are really strong enoughfor every practical requirement if they are only

Fig. 6.-Poppit Centre, with Triangular Cutting-point.

correctly made, .as Fig. 4, in the first instance.Square bars that have to be turned with cylindricalparts, as, for example, the ordinary grindstone axisof square section, with a bearing near each end, areeasily operated on when running between centres.In some cases, where work has not a suitable placefor centring in a line with the axis on which itshould be turned, a piece is put specially to afforda centre bearing. Sometimes the casting or forg-ing is so prepared, and in others a piece is fixed by .some means. As an example we may take acrank-shaft, which to be chucked, with the main-shaft excentric and the crank-pin running true,

8/7/2019 Lathe Work

75/220

8/7/2019 Lathe Work

76/220

68 tLATHE-WORK.object is ready for being bored up centrally andfor similar treatment.Work mounted for turning on a chuck, and fixedto it, independent of support from the back centre,

if of a concentric form is usually held by its edgein a recess turned in the chuck itself. When thefitting is made fairly accurate, and the work isitself tolerably true, this method will secure it firmenough for most purposes. When the work is ofangular outline it is best to have three points ofcontact, which ensure equality of grip if the pointsare equidistant. In chucking square objects bytheir angles it is necessary to see that the twodiameters across the angles are equal, or the objectwill be fixed only at two points. When there arebut three points all must be in contact, even thoughthe object be irregular, for this reason-three-jawchucks are preferable to four.The face-plate is, perhaps, the most generally

useful chuck for all objects which are capable ofbeing fixed by one side, whether the side itself besufficiently flat for the purpose, or whether thework be made level by packing. The face-platechuck is described on page 95, and work to be fixedto it is laid on it and clamped firm, using prefer-ably three points of pressure if that part of thework laid on the chuck has not already beenmade perfectly flat by turning, planing, filing, &c.Sometimes it is easier to fix work on the face-chuck when this is lying horizontally; at others,the central position of an object is maintained by

J

8/7/2019 Lathe Work

77/220

VARIOUS WAYS OF CHUCKING. 69means of the back-centre point supporting it whilstbeing fixed. Only the peculiarities of the job inhand can determine the most advantageous man-ner of placing it on the chuck; and, in short, everyparticular piece of work of an irregular form gene-rally possesses certain special features which atonce offer advantages for chucking it, or the situa-tion of the part to be operated upon makes theadoption of certain positions on the lathe essential.Even two equally competent workmen, who havebeen taught-or, perhaps, it would be more correctto say, have picked up their knowledge-in differentshops, will chuck the same object in totally differentwaY"

8/7/2019 Lathe Work

78/220

CHAPTER VII.FITTING CHUCKS TO THE LATHENOSE.

Minute details of the praces_Various threads used for Iathenoses-Making taps, &c., for fitting chucks-How the thread shouldbe formed-A truly cut thread necessaryon the Dose.

CHUCKS are those appliances which, screwed onthe nose of the lathe, are used to cause the work torevolve. The variety of work turned on the latheinvolves a corresponding variety of chucks, andthough the turner who produces only one speciesof work, as, for instance, stair balusters, only usesone single chuck, yet the amateur turner, whoprovides a lathe and attachments capable of grap-pling with work of all descriptions, will find hisstock of chucks amount to several score. Thosecomplicated apparatus which involve a lot ofmechanism in themselves, such as are used forturning excentrics, ovals, and geometric figures, willnot occupy our attention in the present treatise.They are mostly costly tools, and are seldom foundin the workshop of the general turner, though anoval chuck is the principal tool of the oval turner,and the engine-turning lathe with geometric appa-ratus is the every-day tool of watch-case engine-turners.

J

8/7/2019 Lathe Work

79/220

FITTING CHUCKS. 7 1Chucks are usually added to a lathe by the

turner as occasion occurs, because in making themthe greater part of the work as a general rule hasto be done on the identical lathe on' which thechuck will be used; consequen