Building a Butt-Welderfor Band Saw Blades

By HAROLD P. STRAND

Fig. 1. Welding a band saw blade is easy with this handy unit. The white spotbetween the electrodes is the white hot steel at the moment of the weld.

OWNERS of band saws can use a butt-weld-er to weld easily and quickly the ends ofblades varying in width from .125 to ½ in.

A welder will allow the saw to do internalcutting, when it is necessary to cut the blade soit can be passed through a center hole in thework. Blade stock can be bought in continuouscoiled lengths and cut off to the right measure,and welded. Broken blades can often be salvagedby cutting off new ends and welding, or damagedsections can be cut out and new pieces inserted.The welder can be used to join small steel rods,such as extensions to twist drill shanks up toabout .188, in. in diameter. This feature is usefulin model work for butt-welding small parts ofsimilar type.

Operation of the welder is simple. Cut offsquare the ends of the blade to be welded, grindif necessary so they will meet perfectly. Then

place them with the joint in the center of the gapof the main clamps and tighten the screws. Lineup the ends, tapping them so they butt in goodalignment. For blades of narrow width, such as.125 in., the #1 position of the selector switch willprobably be best. For those up to about .438 in.use the #2 position, with #3 taking the oth-

97

Fig. 1A. Testing the welded blade in the gage aftergrinding. The blade, less the teeth, must be able topass through the .027 gap of the gage, so it will notcatch in the saw guides. Also note the guard for thewheel and the extra toggle switch for the light below,

added later.

HOME-BUILT POWER TOOLS

MATERIALS LIST—BUTT-WELDER

1 pc. cold rolled steel plate, 8" x 10" x 1/8" (panel)1 pc. ¾" plywood, 8½ x 10½" or larger to suit parts

used (base)2 pcs. ¾" angle iron 12½" long, cut and welded to

form angle brackets (panel braces)2 5/8" stacking of E laminations or strips of silicon steel,

1¾" wide as per drawing ( t ransformer core). Angleiron as req. for side brackets

1 Struthers-Dunn or similar single pole relay, 115 voltA.C. coil

1 small receptacle and attachment plug (grinder motorsupply)

1 single pole cartridge type fuse block and 10 amperefuse

7 ft. #16 two-wire rubber cord1 attachment cap3½ lbs. (approx.) #18 Formex magnet wire, cut and

placed on two separate spools, half on each (trans-former primary)

4 pcs. about 6 ft. long, Formex rectangular magnet wire,.105 x .165 or larger (transformer secondary)

1 pc. of extra flexible insulated wire, #1 size or larger(secondary jumper)

4 100 amp. copper solder lugs (secondary terminals)1 pc. copper bus stock, 6¼" x 7/8" x 1/8" cut to make

two pieces as req. (secondary terminals)1 4-point Ohmite tap switch and indicating knob2 Micro Switches, 3/16" dia. plungers, common, O and

C terminals (control switches)1 pc. flat brass stock. 3 3/8" x ½" x ½", bent and cut to

fit, (lower switch operating arm)1 pc. brass stock, ½" x ½" x ½" (block fitted to lower

end of arm)1 pc. 3/16" steel rod, threaded on end, 10-32, ¼" long,

(lower switch adjusting screw). Also 10-32 nut andsmall compression spring to fit over rod

1 indicating radio knob to fit shaft1 small flange type push button, commercial type, (an-

nealing push button)1 pc. mild steel, 4¼" x ¾" x ¼". (cut and shaped for

inside vertical arm)

1 ¾" x 24 cap screw, threads not to run quite up tohead, (operating arm shaft)

2 3/8" x 24 hex nuts (for shaft)1 pc. ¾" angle iron, 3 3/8" long, cut and shaped to form

operating arm1 3/8" steel collar to be welded to arm1 10-32 and1 8-32 Allen set screws4 ¼" #20 flathead brass screws, 1¾" long (electrode

clamping screws)7 ¼" #20 brass hex nuts for same2 steel spacer sleeves 9/16" O.D. ¼" I.D. ½" long-

(sliding electrode)1 expansion spring 5/16" O.D. 1 1/8" long, about .043

wire (sliding electrode)1 extension spring 5/16" O.D. 2" long, about .038 wire

(vertical arm return spring)1 compression spring 13/32" O.D. ½" long, 5 turns .054

wire (attaches to vertical arm)4 pcs. ¾ x 3/16" angle iron, 2 ¾" long (electrodes)2 pcs. brass stock, 1" x ½" x 3/8" (electrode clamps)2 brass thumb screws, 5/16" x 18, 1" long (electrode

clamping screws)2 pcs. mild steel, 1 ½" x ½" x 3/8 (annealing clamps)2 10-32 thumb screws ½" long (annealing clamping

screws)1 pc. steel plate, 3" x 1 ½" x 1/8" (plate welded to back

of sliding electrode)1 pc. steel stock 1 ½" x 3/8" x 1/8" (electrode stop)2 pcs. Bakelite 3" x l ½" x 1/8" (insulation of fixed elec-

trode)2 Bakelite sleeves 3/8" O.D. ½" I.D. 3/8" long (insulation

of fixed electrode)1 steel spacer sleeve 3/8" O.D. ¼" I.D. .002 longer than

thickness of panel, (sliding electrode)1 capacitor motor, 1/30 H.P., 1725 speed with 3" fine

grit wheel, fitted with switch1 pc. ½" plywood 6" x 5½" (motor base)Perforated sheet steel as required to box in unitMisc. bolts, screws, washers, etc.

If it is too soon, the power will be cut off beforeproper temperature has been reached. Makeadjustments on the knob, clockwise to shortenthe timing and counter clockwise to increase it,moving it but the slightest amount, since theMicro Switch, which it operates, moves but afew thousandths from its on to its off position.After satisfactory adjustment has been made,

Fig. 2. Annealing is done in the lower clamps, withthe selector switch on #1 position. The joint is al-

lowed to reach a bright cherry red.

ers. However, an initial adjustment will have tobe made on the small knob at the right side ofthe unit, which governs the timing of the auto-matic cut-off switch. Short pieces of blade canbe used for a test, until the cut-off switch opensthe circuit at the precise moment when the slid-ing electrode moves to make the weld. If thistiming is too late, the blade will be burned off.

Fig. 3. The grinder provides a chance to grind offthe rough edges of the weld at both sides of the blade.

98

this will usually stay for some time.With the blade in the clamps (Fig.

1), press down in a positive and rea-sonably quick manner on the oper-ating lever. There will be a quick showof white heat, and the sliding elec-trode will move slightly as springtension presses the joint together.Then the power will automaticallybe cut off. Hold the lever down afew seconds until the joint is some-what cooled. Remove blade fromclamps and place in lower annealingclamps (Fig. 2). However, the jointwill be very hard and brittle fromwelding, so handle it carefully toavoid breaking. With the selectorswitch on #1 position, press the an-nealing button. Allow blade to be-come a bright cherry red, then re-lease the button. Remove roughedges of weld from both sides ofblade on the grinder (Fig. 3). In agood weld, a raised ridge of uniformappearance will be found on bothsides of the blade and the ends willbutt in good alignment (Fig. 4), fol-lowing the first operation. If one endhas climbed over the other, the endsdid not butt properly when placedin the clamps.

The main component is a heavy-duty transformer (Fig. 5), built inthe shop. It is designed for 115 volt,60 cycle primary, with three second-ary voltages, 1 volt, 2 volts and 3volts, through the selector switch onthe panel. This type of welding re-quires anywhere from 100 to 200amps., according to the size of thestock to be heated, and very heavysecondary wire must be used. Sincethe highest current will be requiredwhen welding wide blades and steel rods, the#3 position of the switch should be used. Thewider the blade, the greater the care must betaken to have the ends of the blade square andmeeting their full width.

The core for the transformer was taken from an

old one formerly used in a motor control unitand the necessary dimensions of the E lamina-tions are given in Fig. 6. The window area givenis the minimum size that will accommodate thecoil when wound. If you can't locate simi-lar laminations, use strips of silicon transformer

Fig. 9. To stack the core around the coil, alternate the positions of

the E and straight pieces so as to cover the butt joints of each layer

with the succeeding one.

HOME-BUILT POWER TOOLS 99

E TYPE LAMINATIONS REQUIREDSTACKING

TAPED COILSAME TURNSAS OWEN

LEADSSECONDARY

PRIMARYLEADS

NEXT LAYERSTRIP

MINCLEARANCE

FIBERINSULATION

CORE BUILT UPFROM SILICONSTEEL STRIPS

TRANSFORMER

SIDE DETAILS

MAXIMUM .COIL HEIGHT:

AFTERTAPING

MAX.WIDTH OF COIL

AFTER TAPING

ALTERNATE POSITIONSOF EACH LAYER SOJOINTS ARE COVERED

CUT LENGTH OF PIECES TO FIT COIL AS SHOWNWILL REQUIRE LARGER BASEBOARD ON UNIT

FOR GREATER SPACE

STACKTO

ANGLEIRON CUT

AND WELDED

DIA.

OR LONGERIF NECESSARY

10A FUSEGRINDEROUTLET

Fig. 4. Work done with the welder in which a blade and a 3/16 in.steel rod hare been butt-welded is shown above.

Fig. 8. The coil is shown complete, ready for taping. Four stripsof rectangular Formex wire are use for the secondary winding.

steel, 26 gage, to build up a core (Fig. 7).Winding the Coil

Be careful to make the center block of the coilform slightly larger than width and stacking ofcore, so coil will fit over this leg properly. Blockshould be about .125 in. shorter than depth ofwindow space so coil will fit down in positionjust below the ends of the E.

The primary consists of a total of 354 turns oftwo #18 Formex wires wound on together inparallel, or one #15 can be substituted. Loopsare brought out at the 150th and 200th turns, astaps about 8 in. long. Both the taps and the startand finish ends should be equipped with cottonsleeving of different color for identification andadded insulation. With a turn of .015 Duro orsimilar insulating paper over the form block be-fore winding, place another layer over the fin-ished primary, and secure with Scotch tape. Allleads must be brought out at one of the narrowsides of the form, or it will not be possible to in-stall the coil on the core later. Then tie up thecoil, through the slots provided in the form andremove the sides. Tap out the center block care-fully and place four added tie strings around thecoil at the four corners, then replace the blockfor support while the secondary is wound on.

The secondary wire used by the author con-sisted of four rectangular Formex wires, .105 x.165, laid together, taped lightly at intervals, andwound on as one heavy conductor. Four turnsare required and as this wire is quite stiff, it canbest be put on by hand. If laminations with agreater window area are on hand, use wire ofgreater size if possible, but in the case illustratedthe finished coil would not have fitted in thecore. Start by bending one end of the four strips,which should be cut about 6 ft. long, to 90°, aboutan inch from the end. This is then tightly tiedaround and over the insulated primary coil. Windon the four turns carefully, shaping the wire asyou go. The end is also bent and tied to thestart with a strong string. This finish end shouldbe cut off with a hacksaw to about an 8 in. lengthfor the present. Later it is cut again to fit cor-rectly up to one of the electrode terminal bolts.Then tightly wind the coil with white cotton coil

tape and dip in insulating baking varnish. Afterdraining, bake it in an oven for 3 to 4 hours at200-275° F. Lacking oven facilities, dip the coilin air drying insulating varnish and hang up ina warm place for a day or two. Fig. 8 shows thecoil after winding, just prior to taping. Stringsplaced around coil keep secondary in shape; allleads come out at narrow side of coil.

Stacking the CoreWhen stacking the core (Fig. 9), place the E

pieces in alternate position, so that the butt jointsof the preceding layer will be covered by thenext. A wooden V block under the coil greatlyfacilitates this work. Stack the core, in the caseof the laminations detailed, to 2.625 in., which, witha center leg of 1.625 in., gives an approximately4 sq. in. cross-sectional area to the core. Shouldthe width vary somewhat from 1.625 in., the heightcan be adjusted to give around the same area.Strips cut 1¾ in. wide and stacked to about 2¼in. will also give an area close enough to 4 in., ifa core of this type is selected. If it is found thatthe finished coil is too large to fit in between theoutside legs of the E laminations, place it in avise with two blocks of wood and compress itcarefully. Usually it is possible to do quite a bitof compressing before the I.D. of the coil is re-duced so it will not fit over the center leg, sincecoil may spring out after removal from form.

Fig. 10 shows the completed transformer withits side brackets of angle iron. Wooden wedgeshave been driven between the ends of the coiland the core center leg, to tighten the lamina-tions at that point. At the sides of the coil, whereit made close contact with the core, thin fiber wasused when stacking to avoid having a groundedcoil. Solder the heavy copper lugs to the endsof the secondary (Fig. 11) using a six-volt solder-ing iron transformer. Do this after the panel hasbeen finished, so the exact length of the long leadcan be determined by fitting. Solder one lug tothe bent end of start of winding, as close aspossible to coil, taking care to clean off insulationwell. To this lug, bolt one end of the lug-equippedheavy jumper of #1 flexible cable. Place a shortpiece of large sleeving over the long lead beforeattaching the lug.

100

Fig. 10. Completed transformerwith side supports of angle iron.

Fig. 11. Use your 6-volt soldering iron transformer to solder the heavycopper lugs to the secondary.

The panel (Fig. 13) ismade of a piece of .125 in.steel plate, attached in aver t ica l position withtwo side brackets toa ¾ in. plywood base.Two clamp-type elec-trodes are used on thepanel (Fig. 14). The righthand one is insulatedand is fixed (Fig. 15),while the other is not in-sulated and is made toslide about .063 in., byslightly slotting the boltholes (Fig. 16). The boltsof the sliding member areequipped with short steelsleeves, which are cutabout .002 longer thanthe thickness of the pan-el. The slotted holes aremade a close but freefit for these sleeves. Inthis way, it is possible to tighten the nuts at theback of the panel and yet allow the piece to slidefreely. A coiled spring is fitted to keep this partback against the stop on the front of the panel(Fig. 16), which is placed in position so as tolimit the sliding motion to about .063 in.

The main operating lever (Fig. 18A) is at-

Fiq. 12. A right side view shows the adjustingknob, which regulates the timing of the weld.

¼" HOLE DRILLED IN ANGLE IRON FOR EXTENSION AND

18 THUMB SCREW STEELPANEL

ANGLEIRON

DETAIL OF FIXEDELECTRODE

SAW CUT TO FIT-STANDARD

BLADES

tached to a .375 in. x 24cap screw (Fig. 18B)which is used as a shaftthrough the panel. Onthe back side a verticallever (Fig. 18C) is se-cured to the shaft so itwill be moved by thefirst one. A short butquite heavy compressionspring is secured to thelever with a single screwin the center whichbears against a steelspacer sleeve on one ofthe bolts (Fig. 14). Thisspring causes the com-pression of the ends ofthe blade after heat hasmelted the steel. An-other coiled spring (Fig.14) is used at the top ofthe lever to return itto its original position.

A Micro Switch has been placed so thatmovement of the inside lever will compress itsplunger. These switches have three terminalswith one common so that they may be connectedeither as normally open or normally closedswitches. This one should be a normally openswitch Another switch is placed in a lower

BACK VIEWposition with an arm attached to the copper busbar and an adjusting screw bearing against itsplunger. This one is a normally closed switch.The switches are connected in series and con-nect the line to the coil of the relay (Fig. 19).In operation, pressing down on the lever causesthe top switch to close and, since the lower oneis already closed, a current flows through therelay coil. The relay contacts close and senda heavy current of low voltage to the welderelectrode clamps. With the ends of the bladepreventing the sliding electrode from moving,current flows until the steel has become plastic,then, with the sliding of the movable electrode,the lower switch contacts are opened, which re-

HOME-BUILT POWER TOOLS 101

8-32 PANEL SCREWS10"

8- 32 SPRINGSCREW

DRILL HOLESAS REQ. TO FIT HOLE 6-32 SCREWS

FOR MICROSWITCH

STEEL PLATEBAKELITE PLATE8"

2"

HOLES CAN BELOCATED ONPANEL FROMTHOSE ONELECTRODES

BETWEENPLATES

BETWEEN ENDSOF ANGLE IRON

STOPPLATE

RETURNSPRINGSCREW10-32

STEELPANEL

NUTSPRING

6-32 SCREWSFOR

MICRO SWITCH

ADJUSTING SCREW

FRONT VIEW

BRASSBAKELITE

SLEEVE

COPPERBUS

BAKELITE

SCREWTURNED FOR

SHOULDER

20

BRASSSCREW

BRASS

HEX NUTS10-32THUMBSCREW

SECONDARYLEAD

SURFACEMILLED FLAT

BRASSC L A M P

START

SWITCH

SET SCREW

SCREW STOP

SPRINGRETURNSELECTRODE

PUSH BUTTON

SLIDING ELECTRODE

SPACER SLEEVE4 POINT OHMITETAP SWITCH

BAKELITE

FIXEDELECTRODE

COPPERBUS

ATTACHFINISH END OF

SECONDARY

HERE

SPRING BEARSAGAINST SPACER

SLEEVE

ATTACH FLEXIBLE JUMPERSECONDARY LEAD HERE (START)

BRASS ARM

SOLDERED TO BLOCKTAP 10-32

CUT OFFSWITCH

ARM ASSEMBLY SLIDESWITH ELECTRODE

CUT OFF SWITCH ARM BLOCK

OFF-NOWIRE

ARM3

2I

suits in a shutting off of the power.A view of the back of the panel, with all parts

in place, is given in Fig. 20. The primary leadsare attached to the selector switch. The heavyjumper, which should be extra flexible cable ofat least #1 gage insulated copper stranded wire,connects from the start of the secondary to themovable electrode. The finish end of the second-ary can just be seen at the right, with its lugattached to the insulated electrode. The relaycan be any type of single pole variety, withreasonably heavy contacts and a 115 volt 60cycle coil. It is placed at the right of the trans-former, with a fuse block located at the left.

Another rear view, showing the protecting cageand grinder is given in Fig. 21. Note the smallplug-in receptacle that has been mounted to thebase at the left for connection of the grindermotor. The latter is a 1/30 hp capacitor typefitted with a 3 in. wheel and running at 1725rpm, and is ample for the light grinding of blades.The wiring diagram (Fig. 19) gives all of theconnections.

Fig. 22 is a front view to illustrate panel de-tails. The annealing push button is a small butheavy duty commercial type, flange mounted, and

serves to close the relay for annealing. With theselector switch on #1, approximately 1 volt willflow through the blade, which heats the portionbetween the annealing clamps quite slowly, espe-cially on the wider blades. These clamps aremerely pieces of ½ x 3/8 in. mild steel stock, sawcut to a depth of ½ in. and fitted with 10-32thumb screws. They are welded or screwed to theunderside of the main clamps ½ in. apart.

Fig. 20. View of back of panel shows op-erating parts. The heavy flexible jumper,bolted to the secondary, is visible. Theother secondary lead is attached to the

insulated electrode at the right.

102

Fig. 28. The lamp is shown in its socket, but thelight shield has been removed in above photo.

STEEL PLATE WELDED ON

SECONDARYLEAD

PANELSTEEL PLATEWASHERWELDED.002

CLEAR-ANCE 20 BRASS

F.H. SCREW

SPACERSLEEVE

O.D.HOLES IN PANELSLOTTED ABOUTTO PROVIDE

SLIDING MOTION

STEEL SLEEVE.002 LONGERTHAN PANELTHICKNESS

I D.O.D.

SET SCREW FIXED ELECTRODE

SLIDINGELECTRODE SET SCREW

LOCK WASHER

TOP VIEW OF ELECTRODES

DIA.

24 THREADDIA.SMOOTHSHANK

BCAP SCREW

SHAFTTAP 10-32SCREW

FOR SET

ANGLE IRON

COLLAR WELDED ON

OPERATING LEVERA

CDETAIL OF VERTICAL ARMMATERIAL-MILD STEEL

NORMALLYOPEN S.W.

SLIDINGGROUNDEDCLAMP

FIXEDINSULATEDCLAMP

ANNEALINGPUSH

BUTTON

4-POINTS.W.

OFF

FLEXIBLE CABLE#1

NORMALLYCLOSED S.W.

354T200T150T

PRI.

2 LUGSBOLTED

RELAYNORMALLY

OPENCONTACTSTRANSFORMER

115 V. COIL10 AMPFUSE

REC.

OUTLETFOB

G R I N D E R 115V. 60~

4-TURNSEC.

HOME-BUILT POWER TOOLS 103

the shield have been soldered 6-32nuts so the screws holding the wheelguard in place can pass through andengage these nuts.

The blade gage (Fig. 29) consistsof a piece of 1/8 in. steel stock, cutout to shape and bent up so it will fiton the front end of the motor and besecured with the motor tie bolts. Thisprovides a flat surface about 1 x ¾ in.To this surface is secured, with 6-32screws, a piece of the same steel with

Fig. 21. A view of the completed job,with the protecting cage removed. Thesmall receptacle at the lower left sup-

plies the grinder motor.

The welder can be dressed upfurther and at the same time mademore convenient to use by enclosingthe grinding wheel for better safetyand adding a light over the elec-trodes, so better vision is assured forplacing the ends of blades (Fig. 23).A third addition is a gage placed onthe front end of the motor, to test thewelded joint for thickness aftergrinding.

The wheel guard (Fig. 24) ismade from heavy galvanized sheetsteel, bent up as shown and attachedto the tray under the wheel with two6-32 screws. To the underside of thetray is attached a candelabra basesocket to take a 15 watt 115 volttubular lamp (Fig. 25). The socketwas taken from a panel type pilotlamp fixture and consists of a screwshell attached to a metal strap, bentto fit as shown. Two small screwsand nuts hold the socket to the tray,through drilled holes in the strip andthe tray. Wires soldered to theterminals of the socket are carried tothe wiring at the side of the motorwhere the single toggle switch is re-placed with two switches on a newwider support (Fig. 26). Thus a switchis provided for the motor and an-other for the lamp. The lamp wiresare spliced to one side of the 115 voltline and one terminal of the newswitch. A short jumper connectsthe other side of the switch to theother side of the line. The wiringdiagram shows these connections indetail (Fig. 27).

The next step is to make a front shield for thelamp, and some of the same galvanized steel isused. In Fig. 28 this shield is shown removed toget a view of the lamp assembly. To the tabs on

a spacer of .027 between. Since standard bladesare .025 in thickness, this allows .002 clearance.All blades after grinding should be able to passthrough this gage (Fig. 1A.).

Fig. 22. This front view shows the panel details.

HP 1725 RPM. MOTOR

ARBOR MADE TO FITSHAFT AND WHEEL

6-32 SCREWS HOLD ASSEMBLYTO ORIGINAL WHEEL TRAY

TRAY

SUPPORTING FIXTURE FOR2 TOGGLE SWITCHES

MAT'L.- 24 GA. GAL. SHEET STEEL

DIA. HOLES FOR TOGGLESWITCH

TO 115 V.RECEPTACLE

CAP. MOUNTED ONUNDERSIDE OF

TOP 5CPEEN

MOTOR S.P. TOGGLESWITCHES

WIRING DIAGRAM

LAMP

1"

TO FITMOTORBOLTS

.027 GAP FOR

.025 SAYBLADES

TO FIT MOTOR

BLADE6-32 SCREWSDETAILS OFBLADE GAGETO BE MOUNTEDON MOTORMAT'L.COLDROLLED STEEL

BLADE SHOULD SLIDE THROUGHGAGE NOT INCLUDING TEETH

TO 110 VOLTSBEND STRAP 90º

SHIELDCOVERSFRONTOF LAMP

115-V. 15W.TUBULAR LAMP

CANDELABRA SOCKET AND STRAP FROM APANEL TYPE PILOT LAMP FIXTURE

RUBBERGROMMET

DETAILS OF WHEEL GUARD MATERIAL- 24 GA. GAL.SHEET STEEL

DIA. TO CLEAR6-32 SCREW

CAD

RAISEDTO CLEARWHEEL NUTIF REQUIRED

PLYWOODBASE

WHEEL

DIMENSIONSBASED ON

MOTORHEIGHT

GENERAL DETAILS OF MOTOR WITHWHEEL GUARD AND LAMP

LAMPSHIELD

15W. TUBULAR CANDELABRA BASE LAMP

PLYWOOD