More Power at Your Elbow

David Haythornthwaite ex-plores the possibilities of fit-ting a powered table feed tothe popular Wabeco millingmachine.

BackgroundAbout 3 years ago I purchased aWabeco vertical mill model 1210which I find to be superb. My ex-perience is that the machine is wellbuilt and gives a good finish onmilled items. However I have al-ways been aware that a poweredtraverse to the milling machinetable would improve the finish thatis obtainable.At the time of purchase, there was(and still is) a CNC version of themachine available, but I felt thatfor my type of work, I could notjustify the extra cost of this. I en-quired about the cost of obtaininga power feed for X direction only,but felt that I couldn’t do withoutthe arm and a leg that they wereasking for!I recently set about designing andmaking a powered feed for the Xdirection using a stepper motorand controller available from ArcEuro Trade (usual disclaimer).

Design ConsiderationsThe first consideration taken intoaccount was that any motor driveshould not extend above the levelof the top of the milling table sothat long materials could still bebolted directly to the table withoutinterfering with the motor drive. Ihave the long-table version of theWabeco, model 1210, and it didnot matter to me if the motor driveextended below the end of the ta-ble as I never screw the table sofar to the left as to cause the motorto impact with the base of the ma-

chine. I did however design thedrive so that it can be rotatedabout the leadscrew and used inany position, as I believe is thecase with the factory supplieddrive. To the left of the graduateddial is a machined recess 30mmDia. and 15mm wide to whichWabeco attach their motor drivesand I decided that my fixturewould clamp to and swivel aboutthis point.I wished to retain both the originalindexed collar and the hand wheel,but to fit a belt drive to the lead-screw meant that the end of theleadscrew would be 30mm tooshort and would need extending. Idecided not to fit a clutch to themotor drive as this would addcomplication and require a furtherextension to the leadscrew. How-ever as stepper motors are“locked” in their stopped position,it is necessary to have a switch toprovide power to the “free” termi-nal on the controller which allowsthe motor to be turned by hand.You should be aware that this isnot entirely free running, but inpractice I have found the extradrag to be perfectly acceptable. I

did not wish to make drasticchanges to the actual Wabeco ma-chine, so in order to extend theleadscrew, I arranged to fix thedrive pulley onto the 10mm sec-tion of the leadscrew where themanual handle was originallyfixed, and to fix a flanged 10mmextension shaft (Part E.) to the sideof the drive pulley using fourcountersunk setscrews. The exist-ing handle is then be fitted to thisextension piece.

First PurchasesStepper Motor AC570764525Mfrom Arc Euro Trade (Usual dis-claimer)Bi Polar Stepper Motor Controllerfrom Arc Euro Trade (Usual dis-claimer)Leadscrew Pulley 30XL 037Motor Pulley 15XL 037Belt 110XL 037from local Bearing Factors shop.

ConstructionThe first task is to remove thehandwheel from the Wabeco lead-screw by gently tapping out the3mm roll pin fixing it to the shaft.If it is tight, support the leadscrew

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to eliminate any tendency to bendthe end of the leadscrew shaft.Once the handwheel is removed, itis possible (but not advisable) toslide the graduated collar from theleadscrew. I recommend that youleave it in situ, but if you reallymust remove it then remove it en-closed in a polythene bag. Thegraduated collar is friction heldonto a central bush by a 4mm ballbearing which bears on a grooveon the inside of the graduated col-lar. The ball bearing is situated ina 4mm hole in the central bush andis spring loaded. When you slidethe collar from the bush, the ballbearing and spring are expelled atgreat speed. If anyone wishes tohave a spare, they are welcome tosearch the far corners of my work-shop where lie the original parts!!Not one of my best tricks !! Evenwith help from the managementsection of the household I couldn’tlocate them. The collar and shaftare illustrated in Photo.2. The leadscrew pulley is a toothedbelt pulley bearing the code30XL037 and this, together withthe motor pulley 15XL 037 pro-vides a 2:1 step down ratio be-tween motor and leadscrew. Ofcourse a small v-belt would alsobe suitable, but I kept to a toothedbelt with a recognisable reductionratio in case I ever decided to godown the full CNC route. Fitting

the belt to the pulleys resulted in alinear distance of 80.5 mm be-tween shaft centres and this decid-ed the layout dimensions. I did notallow for any belt adjustment butdecided to fit this retrospectivelyonly if necessary. This would takethe form of a tensioning ball racerunning on the outside of the belt.Having used the device with nore-tensioning arrangement, it doesnot seem to be necessary.

PulleysBoth pulleys as supplied had a6mm bore and had two grubscrews at 900 to fix them to theshaft. Luckily the smaller pulleyfitted the 6mm shaft on the steppermotor and so needed no adjust-ment. However the larger pulleyneeded boring out to fit the 10mmsection on the end of the lead-screw.The 30 tooth pulley was mountedin the 4 jaw chuck on the lathe andset to run true by the centre holeusing a verdict. The centre hole

was then drilled to 9.5mm and fi-nally bored out to 10.1mm. Thematerial was fairly hard but ma-chined well. I held the pulley bythe fixing flange (as in Photos 3& 4) rather than risk damage tothe aluminium belt flanges. Youwill remember to remove the grubscrews before drilling and boringwon’t you?Transfer the 4 jaw chuck, com-plete with pulley to the dividinghead or rotary table, if you haveone, and set up on the Wabeco ta-ble. Centre the hole under thespindle and then move the millingtable 12mm in X direction to off-set the pulley. Centre drill, andthen drill, 4 indexed holes in theface of the pulley at this setting,4.2mm dia and 15mm deep. Thiswill give you 4 holes at 24mmpitch circle for fixing the lead-screw extender (Part E) to the pul-ley. Exchange the milling machinedrill chuck for a lathe centre anduse this to guide a 5mm tap in theholes at the same settings. Photos3 & 4 show the operation. Pay at-tention to the position of the grubscrews when carrying out this op-eration. You should drill the newfixing holes so that they do notinterfere with the existing grubscrew holes. If you don’t needyour milling machine, leave the

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Rotary Table in situ at 12mm off-set.

Leadscrew ExtensionThe leadscrew extension (Part E)was made from a piece of 41 mm(15/8”) dia. Free cutting mild steel.A length of 45 mm was sewn offon the bandsaw and chucked in the3 jaw S.C. chuck using outsidejaws. I have a 4” S.C chuck and Ifeel that this diameter is too bigfor the normal jaws as severalteeth would not be in contact withthe scroll, thus putting too muchstrain on the remaining teeth. Iclosed the jaws, and being a selftaught machinist with lots of bad(but safe) habits, I slightly slack-ened the grip of the chuck jawsand ran the back of a lathe toolagainst the side of the extendedend whilst running the lathe veryslowly (by hand) until the pieceran true on the outside end. Then Itightened the jaws fully. Puristsmay frown, but it does work ex-tremely well to true up a length ofbar on which the chuck end is notguaranteed to be EXACTLY atright angles.Centre and face the end and bringup the tailstock. Take a light skimover the outside of the bar to tidyup the outside diameter to 40mm,taking this as far as the chuck jaws

will allow. Then turn the end ofthe piece down to 10mm dia. For alength of 19mm. Use the Wabecohandle as a guide to your final fit.Whilst still in the chuck, transfer itto the milling machine face up onthe Rotary Table which in my caseI had left in situ on the Millingtable offset at 12mm after tappingthe pulley. Centre drill, Drill 5mm,and countersink the 4 holes for the5mm countersunk grub screws.Photo 5. illustrates that a fairlysmall countersink is called for.Mine was ½” dia. and worked justfine.While you have the piece in thechuck and on the Rotary Table it isa good time to drill the 3mm crosshole for the 3mm roll pin whichattaches the handle. The centre ofthe cross hole should be 6.5mmfrom the face of the flange. We allhave our own way of doing thesethings, but I set the Rotary Tablevertical and used an edge finder(wiggler) to locate the position ofthe flange face and to find the cen-tre of the shaft as shown inPhoto.6. If you locate the flangeface this way, do not forget tomove your table by half of thewidth of the edge finder (.050” inmy case) before setting your dialsor zeroing the DRO. Then move6.5mm along the shaft, centre drill

and ream or drill 3mm. Photos 6& 7 illustrate this.Some time ago I fitted a BW Elec-tronics DRO shared between myMyford Lathe and the Wabecomill. Using a DRO transforms theway you can work and almostdoes away with marking out alto-gether. It certainly helped with lo-cating the 3mm cross hole.Still in the chuck, return part E tothe lathe and part off. You need topart off at a position which willgive a flange thickness of 3mmplus a spigot length of 5mm aftercleaning up. Then reverse the itemin the lathe either centering accu-rately in the 4 jaw or as I did fit-ting the 10mm section into a colletchuck ready for turning the spigotand facing the other side of theflange, as in Photo 8. The spigotneeds to be concentric with theshaft extension on the other side ofthe flange. The leadscrew does notquite reach through to the end ofthe pulley and the spigot locates inthe recess thus formed in the pul-ley at the end of the shaft.Having taken trouble to get mycross hole truly radial, I found thatthe cross hole in the handwheelsupplied with the Wabeco wouldnot line up and it was way off cen-tre. Not what we expect from thewell made Wabeco! I decided to

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cross drill the handwheel accurate-ly at 90o to the original butcouldn’t drill right through with-out a long series 3mm drill whichwasn’t available. I thereforedrilled half through with a 3.3mmdrill and tapped it for a 4mm grub-screw to bear on my “perfectlyaligned” cross hole. A friend ofmine used to say that all quicksimple jobs are actually slow com-plicated jobs in disguise. Howtrue.

Stepper MotorHaving refitted the handwheel, wenow proceed to motorise the shaft.I actually made the power supply,pulse generator (oscillator) andwired the controller first so that Ihad a control system to try the mo-tor as I progressed. I used a 555chip for the pulse generator andwould have published the detailsexcept that Issue no 110 arrived asI typed this and I see that PeterRawlinson describes an almostidentical control system in his tail-stock power system. Unless theeditor demands it, I see no reasonto duplicate this information. Iwould however reiterate Peter’swarning about the maximum volt-age not going over 40v. My origi-nal power supply also had an offload voltage of 44v and I thereforeplayed safe and used an alternativetransformer of 26v a.c. which Iremember gave me a finishedmaximum off load d.c. voltage ofaround 34v. Well within the speci-fication of the controller.

As stated previously, the motorcomes with a 6mm shaft, front andback and this fitted the motor pul-ley which I purchased. However Idid not wish to retain the reardrive shaft and so I shortened this(more later). Electrically, the mo-tor has 8 wires coming from it andcan be wired in several configura-tions. However, as supplied it hasno terminal box and this must beaddressed to ensure that no cuttingfluid or swarf enters the motor. Ipurchased a small cast aluminiumbox from Maplin which is 48mmsq. and 30mm deep. I drilled ahole in the bottom, clearance sizefor the grommet on the cable out-let from the motor, and fitted acable exit sheath on the side of thebox. At this stage you should con-sider in which direction you wishthe cable to exit from the terminalbox. Mine goes in a downwarddirection. I then superglued thebox to the motor case, not wishingto drill the motor casing. I wouldsuggest that Araldite would proba-bly be stronger and would carryless risk of adhesive entering themotor.The motor must be configured asseries wound. On my motor, thismeant that the purple and brownwires should be connected togeth-er, as should the yellow and bluewires. This then gives you two coilcircuits across the white & greenwires and the red & black wiresrespectively. The information leaf-let supplied by Arco gives details.The two circuits should be sol-

dered to a 4 core flex leading outof the cable exit sheath. All con-nections should be insulated withtape – or preferably with shrinkwrap sleeving and the wires care-fully coiled inside the terminal boxfor closure. I did not shorten mymotor wires – you never knowwhen you may need the length.My motor does not seem to inter-fere with television or radio andthe 4 core flex is unscreened.However if you wish to remain inharmony with the neighbours and“the boss indoors” then screenedcable is to be advised. This cableis carrying considerable currentwhich is being chopped into asquare waveform at varying fre-quency depending upon the setmotor speed. It is likely to give offradio frequency interference. Isimply did not have any screenedlead to hand. Photo 10 shows thefinished motor, but please notethat the pulley is fitted to the shaftincorrectly in the photo. In realitythe pulley is fitted with the flangeagainst the motor and the fixingboss towards the shaft end.

Motor Mount and GuardThe main motor mount and guardchassis is constructed from rectan-

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gular aluminium bar and as drawnit uses 80mm x 15mm bar. Thiswould clamp nicely into the 30mmdiameter clamping slot in the Wa-beco leadscrew housing which is15mm wide. Unfortunately thenearest that I could find was 3” x¾” so I purchased a length of 20”(or 500mm) from Mallard Metals(www.mallardmetals.co.uk) tomake the 4 main pieces A,B,C &D. Sorry for the mixture of metricand imperial measures but imperi-al was all I could obtain. I shall tryto describe construction from80mm x 15mm even though I ad-justed mine for the imperial bar.A clamping piece (A) clamps ontothe machined clamping recess onthe leadscrew housing and ontothe end of this clamping piece isfixed another aluminium bar (D)which lies parallel to and behindthe leadscrew. On the outer end(right hand end) of piece D isfixed a 192mm long aluminiumbar rounded off at both ends (C)which supports the motor and en-closes both pulleys and drive belt.Thus this piece acts as motor sup-port and is an integral part of theguarding arrangement. On the leftend of part D is fastened a shapedaluminium bar (B) which is situat-ed behind the motor (to the left)and acts to support the rear of themotor chip guard. I decided to ful-ly enclose the motor in this way asstepper motor casings are magnet-ic and therefore attract steel swarf.I dislike holding aluminium to-gether by tapped setscrews, but I

used ¼” Whitworth for those set-screws holding the frame togetheras the coarse thread of Whitworthis better in Aluminium than thefiner metric threads.

Marking Out andMachining Part COut of the 4 Aluminium bar parts Imade part “C” first as I like to dothe difficult bits first and once thisis made and the motor mounted onit, you can prove that the dimen-sions in the drawing are suitablefor your machine, pulleys and belt.Start by sawing off 192 mm fromthe aluminium bar and milling oneend truly square as a referenceend. Mark out a centre line downthe length 40mm from the edge –or 38.1mm if you are using 3”wide bar. Then mark points 40mm120.5mm and 151mm from thereference end for the leadscrewcentre, the motor shaft centre andthe centre of the rear curve respec-tively. Whilst doing this you mayalso mark out for the four 5mmfixing holes for attaching the mo-tor, 97 & 144mm from end, (laterto be blind drilled 4.2mm andtapped 5mm x 0.8). The specifica-tion sheet from Arc Euro Tradeshows these holes to be spaced at47.14mm centres which mustmake sense to some designersomewhere! but I drilled them at47mm centres with no problems. Ialso drew the curved ends withdividers (40mm radius for 80mmbar or 38.1mm for 3” bar) andmarked out r17.5mm and r30mm

circles for the two pulley cut-outs.You may also mark out the posi-tion of the two holes for fixing topart D. These are at points 84mmfrom the end, but I waited untilparts C,A&D were completed be-fore drilling in order to prove thelayout dimensions. Remember thatthe marking out side is the IN-SIDE side of the finished pieceand therefore DO NOT counter-sink these fixing holes, which arecountersunk on the OUTSIDEedge. Finally mark out the twolines shown at 9o to horizontalfrom pulley to pulley representingthe outside of the belt. Note thatthese are not tangential to the pul-ley cut-outs as the belt runs at asmaller diameter than the pulleyflanges. If you are using 3” barand put the setscrew holes 10mmfrom the edge BEWARE. Thecountersink holes are very close tothese 9o lines and the motor fixingscrews are also very close. Carefulmarking out and checking paysoff.The method for forming the endcurve depends upon your equip-ment, but I proceeded as follows :-Make, or find an existing, mandrelto fit into the centre of your rotarytable. I have a box of these so Iselected a 3/16” mandrel. Drillthrough part C at the point 40mmfrom the reference edge at the di-ameter of your mandrel (3/16”) forcentering on the rotary table anddrill partially through from the in-side at the 151mm mark for the

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centre point of the rear curve. Youcould drill right through if youwish but it would leave you with ahole of no apparent use on the out-side of the finished product.Insert you mandrel into your rota-ry table and mount the bar for partC on the table with one of the cen-tre holes (those at 40mm or151mm) located onto the mandrelspigot. i.e. at the centre of the ta-ble. Pack the aluminium bar upfrom the rotary table surface byclamping onto some 1/8” strips orby clamping onto some MDF.Pack so that the bar can be rotatedthrough the full 180o without thepacking or clamps interfering withthe cutter path. A 6” table is per-fectly capable of this. Round offthe end of the bar by rotating thebar against a 5/8” endmill set forthe full depth of the bar and takingshallow cuts making sure that yourotate the rotary table in the direc-tion that does not cause “climbmilling” i.e. cutter resisting therotation of the rotary table. Gradu-ally move the rotary table nearer tothe cutter until a 180o rotation ofthe table results in a smooth arcfrom one side of the bar to the op-posite side as shown in Photos11-13. Once both ends have beenrounded off, set up part C on par-allels in the machine vice with theleadscrew centre point (40mmfrom the end) directly under themilling head and take out the ma-jority of the 60 mm diameter holewith a hole saw. Then finish the

hole with a boringhead bringing itup to 60mm di-ameter. This Ifound to be aboutthe limit for theWabeco spindlebut it coped quitewell using lightcuts. Move thetable 85 mm leftin the x axis andcut the 35mm

hole for the motor pulley in thesame way. The motor has a 38mmdia. locating ring on the fixingflange so while you have the bor-ing head all lined up over the hole,bore a recessed circle of 38mm diaand 2mm deep making this a nicelocating fit on your motor.If you haven’t already drilled andtapped your motor fixing holes (12mm deep for 5mm setscrews) nowis a good time to do this.Now to take out the centre piecewhere the belt runs. Mount thepart at 9 o to the x direction usingthe swivel vice if you have one.Using a ¼” slot drill take out thefirst line of the belt , rotate by 18 o

and remove the second line asshown in Photo 12. Check yourbelt and pulleys on the bench butin my set-up the centre line ofthese cuts were tangents between a26mm radius at the leadscrew endand a 14mm radius at the motorpulley end. If you get it right firsttime, then your belt will miss allthe bolt holes and you will have anice triangular centre piece to in-sert later as part of the belt guard.Keep this seemingly waste part forrefitting later. Part C should nowlook like Photo 13. Attach the mo-tor and hold the part in positionover the leadscrew pulley with thebelt held tight to ensure that allangles and dimensions are correct.Saw off the shaft from the rear ofthe motor with a hack saw (unlessyou wish to retain it and have it

poking through part B).Parts A, B & DCut parts A B & D from the stockaluminium bar, mill square and tolength and mark out, ensuring thatyou mark right across the cen-treline of the clamping hole in partA as you will need this referencelater to saw the part into two parts.You may wish to drill and tap the¼” Whitworth fixing holes in theflat side of part A before shapingthe curve as it helps you to hold itstraight in the vice. Shape one endof parts A & B to a semicircle onthe rotary table as already de-scribed for part C. At the sametime, bore a 30mm hole in part Ato clamp to the leadscrew housing.If you are using ¾” thick bar as Iwas, the fixing recess on the Wa-beco is only 15mm wide and sothe ¾” thick bar will not fit into it.You must therefore bore a recessround the 30mm clamping hole toallow part A to clamp successfullyto the leadscrew housing. This re-cess is to be 40mm dia and 4.1mmdeep thus reducing the effectivethickness of part A at the clampingpoint to 15mm. The recess will beon the opposite side to the gradu-ated collar (left).

The fixing holes through theclamping line on part A are again¼” Whitworth. Start with a slotdrill, the size of the head of theset-screw, 9.5mm, and take it gen-tly as you enter the curved edge.Drill full depth with a tapping sizedrill (5.1mm although I used 5mmin aluminium) and you will openthe first section out to ¼” clear-ance once the piece is split. Mounton parallels in the vice and slitacross with a moderately fine slit-ting saw, as in Photo 14. Finallytap the holes ¼” Whitworth and fitonto the leadscrew housing.Drill the fixing and counterboreholes in part B and drill and tap¼” Whitworth on the ends of partD. I did not drill the holes in partD for fixing to part A until now,

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nor did I drill the holes in part Cfor the fixing set-screws to attachto part D. Having clamped part Ato the Wabeco, I assembled thewhole thing “loose” and made surethat the required position for thefixing holes and counterbores inparts D & C were actually wherethe drawing stated once the beltwas tight and running truly in the

middle of part C. In my case allwas in order, so the holes wereduly drilled. Please note that youcannot assemble the unit and thenfit it to the machine. Part C has tobe loosened from part D whilst theunit is fitted to the Wabeco. I re-moved the leadscrew pulley,slackened the setscrews attachingparts C&D, and jiggled the wholething onto the leadscrew housingwith the belt on the pulleys. It isfiddly but it does go . Once theunit is assembled, take the triangu-lar centre portion which you savedwhen you removed it from themiddle of the belt drive and fit it tothe end of part D using eithercheese head or, in my case, coun-tersunk set-screws (see photo 1).I must admit here to being sur-prised to find that the whole unitwould not swivel around the lead-screw housing as intended in thedesign. I had to mill a slight recessin the flat end of part D to allowthis to clear the set-screws whichattach the leadscrew housing to themilling table. This is just visible in

Photo 15. and now allows the unitto be positioned anywhere in a360o arc axially about the lead-screw.

Chip guard for the motorPhoto 1 was taken before the chipguard was fitted. The guard couldbe made from either aluminiumsheet or flexible plastic Mine wasmade from 0.5mm aluminiumsheet. I cut a rectangular shape275mm long x 110mm wide usinga hand “nibbler” type of sheet met-al cutter. This does not distort themetal sheet but cuts a long thinstrip out of the metal leaving bothsides undistorted. This guard iseither screwed or clipped to thetop edge of part D, wrapped roundthe curved ends of parts B & C,being clipped or screwed to thebottom edge of part D. Dependingon your motor wiring layout youwill need to cut a slot to allow thecable to pass through. If making inaluminium, you should bear inmind that stepper motors do gener-ate vibration when running slowly

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and I planned to slice open alength of flat, flexible, cablesheathing and to glue this roundthe outside edge of the sheet. Thiswould make a neat appearance tothe edge of the guard and make aflexible plastic “gasket” between

the aluminium sheet and partsB,C,&D to eliminate any sympa-thetic vibrations. However in prac-tice I screwed the un-edged sheetto the aluminium frame usingsmall self tapping screws and therehas been no vibration at all. The

finished item is shown inPhoto.15 complete with chipguard.I am quite happy with the finishedappearance of the drive whichlooks professional and in keepingwith the Wabeco machine.

Electronics andControl BoxAs already stated the electronicsare very similar to those describedin issue 110, but upon using thedevice I found that having thespeed and inch controls on thepower supply / control box wasvery inconvenient and I thereforepurchased another die cast alumin-ium box from Maplin (110mm x60mm x 30mm) and used it tohouse the direction switch, theinch / run switch, the free / controlswitch, the speed potentiometerand the “fast” button. All thismakes a convenient hand heldcontrol box, and I connected it tothe stepper controller and pulsegenerator by a 9 pin D connectoras used on computer serial ports,available from Maplin Electronics.This is clearly shown in Photo 15.It is important to have a “free”switch as when stepper motors areunder power they are locked solidwhen stopped and without a freeswitch you cannot use the manualleadscrew handle while the unit ispowered up.The electronics are shown in thenext article.