Building a Butt-Welder for Band Saw Blades

Building a Butt-Welder
for Band Saw Blades
By HAROLD P. STRAND
Fig. 1. Welding a band saw blade is easy with this handy unit. The white spot
between the electrodes is the white hot steel at the moment of the weld.
O
WNERS of band saws can use a butt-welder to weld easily and quickly the ends of
blades varying in width from .125 to ½ in.
A welder will allow the saw to do internal
cutting, when it is necessary to cut the blade so
it can be passed through a center hole in the
work. Blade stock can be bought in continuous
coiled lengths and cut off to the right measure,
and welded. Broken blades can often be salvaged
by cutting off new ends and welding, or damaged
sections 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 to
about .188, in. in diameter. This feature is useful
in model work for butt-welding small parts of
similar type.
Operation of the welder is simple. Cut off
square the ends of the blade to be welded, grind
if necessary so they will meet perfectly. Then
place them with the joint in the center of the gap
of the main clamps and tighten the screws. Line
up the ends, tapping them so they butt in good
alignment. For blades of narrow width, such as
.125 in., the #1 position of the selector switch will
probably be best. For those up to about .438 in.
use the #2 position, with #3 taking the oth-
Fig. 1A. Testing the welded blade in the gage after
grinding. The blade, less the teeth, must be able to
pass through the .027 gap of the gage, so it will not
catch in the saw guides. Also note the guard for the
wheel and the extra toggle switch for the light below,
added later.
HOME-BUILT POWER TOOLS
97
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 (transformer core). Angle
iron as req. for side brackets
1 Struthers-Dunn or similar single pole relay, 115 volt
A.C. coil
1 small receptacle and attachment plug (grinder motor
supply)
1 single pole cartridge type fuse block and 10 ampere
fuse
7 ft. #16 two-wire rubber cord
1 attachment cap
3½ lbs. (approx.) #18 Formex magnet wire, cut and
placed on two separate spools, half on each (transformer 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 knob
2 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 and
small compression spring to fit over rod
1 indicating radio knob to fit shaft
1 small flange type push button, commercial type, (annealing 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 to
head, (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 arm
1 3/8" steel collar to be welded to arm
1 10-32 and
1 8-32 Allen set screws
4 ¼" #20 flathead brass screws, 1¾" long (electrode
clamping screws)
7 ¼" #20 brass hex nuts for same
2 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 electrode)
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 switch
1 pc. ½" plywood 6" x 5½" (motor base)
Perforated sheet steel as required to box in unit
Misc. bolts, screws, washers, etc.
If it is too soon, the power will be cut off before
proper temperature has been reached. Make
adjustments on the knob, clockwise to shorten
the timing and counter clockwise to increase it,
moving it but the slightest amount, since the
Micro Switch, which it operates, moves but a
few thousandths from its on to its off position.
After satisfactory adjustment has been made,
Fig. 2. Annealing is done in the lower clamps, with
the selector switch on #1 position. The joint is allowed to reach a bright cherry red.
ers. However, an initial adjustment will have to
be made on the small knob at the right side of
the unit, which governs the timing of the automatic cut-off switch. Short pieces of blade can
be used for a test, until the cut-off switch opens
the circuit at the precise moment when the sliding electrode moves to make the weld. If this
timing is too late, the blade will be burned off.
98
Fig. 3. The grinder provides a chance to grind off
the rough edges of the weld at both sides of the blade.
SECONDARY
LEADS
E TYPE LAMINATIONS REQUIRED
STACKING
PRIMARY
LEADS
TAPED COIL
SAME TURNS
AS OWEN
FIBER
INSULATION
MAXIMUM .
COIL HEIGHT:
AFTER
TAPING
AFTER TAPING
NEXT LAYER
STRIP
MIN
CORE BUILT UP
FROM SILICON
STEEL STRIPS
ALTERNATE POSITIONS
OF EACH LAYER SO
JOINTS ARE COVERED
MAX.WIDTH OF COIL
SIDE DETAILS
TRANSFORMER
CLEARANCE
DIA.
10A FUSE
STACK
TO
ANGLE
IRON CUT
AND WELDED
CUT LENGTH OF PIECES TO FIT COIL AS SHOWN
WILL REQUIRE LARGER BASEBOARD ON UNIT
FOR GREATER SPACE
GRINDER
OUTLET
OR LONGER
IF NECESSARY
this will usually stay for some time.
With the blade in the clamps (Fig.
1), press down in a positive and reasonably quick manner on the operating lever. There will be a quick show
of white heat, and the sliding electrode will move slightly as spring
tension presses the joint together.
Then the power will automatically
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.
be cut off. Hold the lever down a
few seconds until the joint is somewhat cooled. Remove blade from
clamps and place in lower annealing
clamps (Fig. 2). However, the joint
will be very hard and brittle from
welding, so handle it carefully to
avoid breaking. With the selector
switch on #1 position, press the annealing button. Allow blade to become a bright cherry red, then release the button.
Remove rough
edges of weld from both sides of
blade on the grinder (Fig. 3). In a
good weld, a raised ridge of uniform
Fig. 8. The coil is shown complete, ready for taping. Four strips
of rectangular Formex wire are use for the secondary winding.
appearance will be found on both
sides of the blade and the ends will
butt in good alignment (Fig. 4), following the first operation. If one end
has climbed over the other, the ends
did not butt properly when placed
in the clamps.
The main component is a heavyduty transformer (Fig. 5), built in
the shop. It is designed for 115 volt,
60 cycle primary, with three secondary voltages, 1 volt, 2 volts and 3
volts, through the selector switch on
the panel. This type of welding requires anywhere from 100 to 200
amps., according to the size of the
stock to be heated, and very heavy
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
secondary wire must be used. Since
with the succeeding one.
the highest current will be required
old
one
formerly used in a motor control unit
when welding wide blades and steel rods, the
and the necessary dimensions of the E lamina#3 position of the switch should be used. The
tions are given in Fig. 6. The window area given
wider the blade, the greater the care must be
is the minimum size that will accommodate the
taken to have the ends of the blade square and
coil when wound. If you can't locate simimeeting their full width.
lar laminations, use strips of silicon transformer
The core for the transformer was taken from an
HOME-BUILT POWER TOOLS
99
Fig. 10. Completed transformer
with side supports of angle iron.
Fig. 11. Use your 6-volt soldering iron transformer to solder the heavy
copper lugs to the secondary.
steel, 26 gage, to build up a core (Fig. 7).
Winding the Coil
Be careful to make the center block of the coil
form slightly larger than width and stacking of
core, so coil will fit over this leg properly. Block
should be about .125 in. shorter than depth of
window space so coil will fit down in position
just below the ends of the E.
The primary consists of a total of 354 turns of
two #18 Formex wires wound on together in
parallel, or one #15 can be substituted. Loops
are brought out at the 150th and 200th turns, as
taps about 8 in. long. Both the taps and the start
and finish ends should be equipped with cotton
sleeving of different color for identification and
added insulation. With a turn of .015 Duro or
similar insulating paper over the form block before winding, place another layer over the finished primary, and secure with Scotch tape. All
leads must be brought out at one of the narrow
sides of the form, or it will not be possible to install the coil on the core later. Then tie up the
coil, through the slots provided in the form and
remove the sides. Tap out the center block carefully and place four added tie strings around the
coil at the four corners, then replace the block
for support while the secondary is wound on.
The secondary wire used by the author consisted of four rectangular Formex wires, .105 x
.165, laid together, taped lightly at intervals, and
wound on as one heavy conductor. Four turns
are required and as this wire is quite stiff, it can
best be put on by hand. If laminations with a
greater window area are on hand, use wire of
greater size if possible, but in the case illustrated
the finished coil would not have fitted in the
core. Start by bending one end of the four strips,
which should be cut about 6 ft. long, to 90°, about
an inch from the end. This is then tightly tied
around and over the insulated primary coil. Wind
on the four turns carefully, shaping the wire as
you go. The end is also bent and tied to the
start with a strong string. This finish end should
be cut off with a hacksaw to about an 8 in. length
for the present. Later it is cut again to fit correctly up to one of the electrode terminal bolts.
Then tightly wind the coil with white cotton coil
100
tape and dip in insulating baking varnish. After
draining, bake it in an oven for 3 to 4 hours at
200-275° F. Lacking oven facilities, dip the coil
in air drying insulating varnish and hang up in
a warm place for a day or two. Fig. 8 shows the
coil after winding, just prior to taping. Strings
placed around coil keep secondary in shape; all
leads come out at narrow side of coil.
Stacking the Core
When stacking the core (Fig. 9), place the E
pieces in alternate position, so that the butt joints
of the preceding layer will be covered by the
next. A wooden V block under the coil greatly
facilitates this work. Stack the core, in the case
of the laminations detailed, to 2.625 in., which, with
a center leg of 1.625 in., gives an approximately
4 sq. in. cross-sectional area to the core. Should
the width vary somewhat from 1.625 in., the height
can be adjusted to give around the same area.
Strips cut 1¾ in. wide and stacked to about 2¼
in. will also give an area close enough to 4 in., if
a core of this type is selected. If it is found that
the finished coil is too large to fit in between the
outside legs of the E laminations, place it in a
vise with two blocks of wood and compress it
carefully. Usually it is possible to do quite a bit
of compressing before the I.D. of the coil is reduced so it will not fit over the center leg, since
coil may spring out after removal from form.
Fig. 10 shows the completed transformer with
its side brackets of angle iron. Wooden wedges
have been driven between the ends of the coil
and the core center leg, to tighten the laminations at that point. At the sides of the coil, where
it made close contact with the core, thin fiber was
used when stacking to avoid having a grounded
coil. Solder the heavy copper lugs to the ends
of the secondary (Fig. 11) using a six-volt soldering iron transformer. Do this after the panel has
been finished, so the exact length of the long lead
can be determined by fitting. Solder one lug to
the bent end of start of winding, as close as
possible to coil, taking care to clean off insulation
well. To this lug, bolt one end of the lug-equipped
heavy jumper of #1 flexible cable. Place a short
piece of large sleeving over the long lead before
attaching the lug.
tached to a .375 in. x 24
The panel (Fig. 13) is
cap screw (Fig. 18B)
made of a piece of .125 in.
which is used as a shaft
steel plate, attached in a
through the panel. On
v e r t i c a l position with
the back side a vertical
two side b r a c k e t s to
lever (Fig. 18C) is sea ¾ in. plywood base.
cured to the shaft so it
Two clamp-type elecwill be moved by the
trodes are used on the
first one. A short but
panel (Fig. 14). The right
quite heavy compression
hand one is insulated
spring is secured to the
and is fixed (Fig. 15),
lever with a single screw
while the other is not inin the center which
sulated and is made to
bears a g a i n s t a steel
slide about .063 in., by
spacer sleeve on one of
slightly slotting the bolt
the bolts (Fig. 14). This
holes (Fig. 16). The bolts
spring causes the comof the sliding member are
pression of the ends of
equipped with short steel
the blade after heat has
sleeves, which are cut
melted the steel. Anabout .002 longer than
other coiled spring (Fig.
the thickness of the panFiq. 12. A right side view shows the adjusting
14) is used at the top of
el. The slotted holes are
knob, which regulates the timing of the weld.
the lever to return it
made a close but free
to its original position.
fit for these sleeves. In
A Micro Switch has been placed so that
this way, it is possible to tighten the nuts at the
back of the panel and yet allow the piece to slide movement of the inside lever will compress its
freely. A coiled spring is fitted to keep this part plunger. These switches have three terminals
back against the stop on the front of the panel with one common so that they may be connected
(Fig. 16), which is placed in position so as to either as normally open or normally closed
switches. This one should be a normally open
limit the sliding motion to about .063 in.
The main operating lever (Fig. 18A) is at- switch Another switch is placed in a lower
10"
8-32 PANEL SCREWS
START
DRILL HOLES
AS REQ. TO FIT
SET SCREW
6-32 SCREWS
FOR MICRO
SWITCH
STEEL PLATE
STOP
PLATE
HOLE
2"
HOLES CAN BE
LOCATED ON
PANEL FROM
THOSE ON
ELECTRODES
BETWEEN ENDS
OF ANGLE IRON
NUT
BETWEEN
SPRING
PLATES
SCREW STOP
SPRING BEARS
AGAINST SPACER
SLEEVE
ATTACH FLEXIBLE JUMPER
SECONDARY LEAD HERE (START)
CUT OFF
SWITCH
ARM ASSEMBLY SLIDES
WITH ELECTRODE
ANGLE
IRON
BAKELITE
COPPER
BUS
20
BRASS
CLAMP
BRASS
SCREW
BRASS
HEX NUTS
HOME-BUILT POWER TOOLS
SURFACE
MILLED FLAT
SAW CUT TO FITSTANDARD
BLADES
FIXED
ELECTRODE
ATTACH
FINISH END OF
SECONDARY
HERE
BRASS ARM
SOLDERED TO BLOCK
TAP 10-32
CUT OFF SWITCH ARM BLOCK
STEEL
PANEL
SECONDARY
LEAD
BAKELITE
STEEL
PANEL
BAKELITE
SLEEVE
DETAIL OF FIXED
ELECTRODE
4 POINT OHMITE
TAP SWITCH
COPPER
BUS
6-32 SCREWS
FOR
MICRO SWITCH
18 THUMB SCREW
BRASS
SPACER SLEEVE
RETURN
SPRING
SCREW
10-32
FRONT VIEW
10-32
THUMB
SCREW
ARM
PUSH BUTTON
SLIDING ELECTRODE
SPRING
RETURNS
ELECTRODE
¼" HOLE DRILLED IN ANGLE IRON FOR EXTENSION AND
ADJUSTING SCREW
SCREW
TURNED FOR
SHOULDER
WIRE
3
BAKELITE PLATE
8"
I OFF-NO
2
SWITCH
8- 32 SPRING
SCREW
BACK VIEW
position with an arm attached to the copper bus
bar and an adjusting screw bearing against its
plunger. This one is a normally closed switch.
The switches are connected in series and connect the line to the coil of the relay (Fig. 19).
In operation, pressing down on the lever causes
the top switch to close and, since the lower one
is already closed, a current flows through the
relay coil. The relay contacts close and send
a heavy current of low voltage to the welder
electrode clamps. With the ends of the blade
preventing 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 re101
PANEL
SECONDARY
LEAD
STEEL PLATE WELDED ON
STEEL PLATE
WASHER
WELDED
.002
CLEARANCE
STEEL SLEEVE
.002 LONGER
THAN PANEL
THICKNESS
I D.
HOLES IN PANEL
SLOTTED ABOUT
TO PROVIDE
SLIDING MOTION
SET SCREW
SPACER
SLEEVE
O.D.
O.D.
SET SCREW
SLIDING
ELECTRODE
20 BRASS
F.H. SCREW
FIXED ELECTRODE
LOCK WASHER
TOP VIEW OF ELECTRODES
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 leads
are attached to the selector switch. The heavy
jumper, which should be extra flexible cable of
at least #1 gage insulated copper stranded wire,
connects from the start of the secondary to the
movable electrode. The finish end of the secondary can just be seen at the right, with its lug
attached to the insulated electrode. The relay
can be any type of single pole variety, with
reasonably heavy contacts and a 115 volt 60
cycle coil. It is placed at the right of the transformer, with a fuse block located at the left.
Another rear view, showing the protecting cage
and grinder is given in Fig. 21. Note the small
plug-in receptacle that has been mounted to the
base at the left for connection of the grinder
motor. The latter is a 1/30 hp capacitor type
fitted with a 3 in. wheel and running at 1725
rpm, and is ample for the light grinding of blades.
The wiring diagram (Fig. 19) gives all of the
connections.
Fig. 22 is a front view to illustrate panel details. The annealing push button is a small but
heavy duty commercial type, flange mounted, and
DIA.
24 THREAD
DIA.
SMOOTH
SHANK
B
TAP 10-32
SCREW
FOR SET
CAP SCREW
SHAFT
ANGLE IRON
COLLAR WELDED ON
A
C
OPERATING LEVER
DETAIL OF VERTICAL ARM
MATERIAL-MILD STEEL
Fig. 20. View of back of panel shows operating parts. The heavy flexible jumper,
bolted to the secondary, is visible. The
other secondary lead is attached to the
insulated electrode at the right.
102
Fig. 28. The lamp is shown in its socket, but the
light shield has been removed in above photo.
serves to close the relay for annealing. With the
selector switch on #1, approximately 1 volt will
flow through the blade, which heats the portion
between the annealing clamps quite slowly, especially on the wider blades. These clamps are
merely pieces of ½ x 3/8 in. mild steel stock, saw
cut to a depth of ½ in. and fitted with 10-32
thumb screws. They are welded or screwed to the
underside of the main clamps ½ in. apart.
SLIDING
GROUNDED
CLAMP
NORMALLY
OPEN S.W.
FIXED
INSULATED
CLAMP
ANNEALING
PUSH
BUTTON
4-POINT
S.W.
OFF
#1
FLEXIBLE CABLE
NORMALLY
CLOSED S.W.
354T
200T
150T
2 LUGS
BOLTED
4-TURN
SEC.
PRI.
TRANSFORMER
10 AMP
FUSE
115 V. COIL
REC.
OUTLET
FOB
GRINDER
RELAY
NORMALLY
OPEN
CONTACTS
115V. 60~
the shield have been soldered 6-32
nuts so the screws holding the wheel
guard in place can pass through and
engage these nuts.
The blade gage (Fig. 29) consists
of a piece of 1/8 in. steel stock, cut
out to shape and bent up so it will fit
on the front end of the motor and be
secured with the motor tie bolts. This
provides a flat surface about 1 x ¾ in.
To this surface is secured, with 6-32
screws, a piece of the same steel with
Fig. 21. A view of the completed job,
with the protecting cage removed. The
small receptacle at the lower left supplies the grinder motor.
The welder can be dressed up
further and at the same time made
more convenient to use by enclosing
the grinding wheel for better safety
and adding a light over the electrodes, so better vision is assured for
placing the ends of blades (Fig. 23).
A third addition is a gage placed on
the front end of the motor, to test the
Fig. 22. This front view shows the panel details.
welded joint for thickness after
grinding.
The wheel guard (Fig. 24) is
HP 1725 RPM. MOTOR
made from heavy galvanized sheet
SUPPORTING FIXTURE FOR
ARBOR MADE TO FIT
2 TOGGLE SWITCHES
steel, bent up as shown and attached
SHAFT AND WHEEL
MAT'L.- 24 GA. GAL. SHEET STEEL
6-32 SCREWS HOLD ASSEMBLY
to the tray under the wheel with two
TO ORIGINAL WHEEL TRAY
6-32 screws. To the underside of the
TRAY
tray is attached a candelabra base
DIA. HOLES FOR TOGGLE
SWITCH
socket to take a 15 watt 115 volt
PLYWOOD
TO 115 V.
15W. TUBULAR CANDELABRA BASE LAMP
tubular lamp (Fig. 25). The socket
RECEPTACLE
was taken from a panel type pilot
CAP.
MOUNTED
ON
LAMP
GENERAL DETAILS OF MOTOR WITH
UNDERSIDE OF
SHIELD
WHEEL GUARD AND LAMP
TOP 5CPEEN
lamp fixture and consists of a screw
shell attached to a metal strap, bent
DIMENSIONS
BASED ON
to fit as shown. Two small screws
MOTOR
HEIGHT
WHEEL
and nuts hold the socket to the tray,
S.P. TOGGLE
through drilled holes in the strip and
MOTOR
RAISED
SWITCHES
TO CLEAR
the tray.
Wires soldered to the
WHEEL NUT
IF REQUIRED
terminals of the socket are carried to
PLYWOOD
BASE
the wiring at the side of the motor
LAMP
where the single toggle switch is reWIRING DIAGRAM
placed with two switches on a new
DIA. TO CLEAR
6-32 SCREW
wider support (Fig. 26). Thus a switch
1"
is provided for the motor and anDETAILS
OF
WHEEL
GUARD
MATERIAL24
GA.
GAL.
.027 GAP FOR
other for the lamp. The lamp wires
SHEET STEEL
.025 SAY
BLADES
TO FIT
are spliced to one side of the 115 volt
MOTOR
TO 110 VOLTS
BOLTS
line and one terminal of the new
TO FIT MOTOR
BEND STRAP 90º
6-32 SCREWS
BLADE
switch.
A short jumper connects
SHIELD
DETAILS OF
115-V. 15W.
COVERS
RUBBER
BLADE GAGE
the other side of the switch to the
TUBULAR LAMP
FRONT
GROMMET
OF LAMP
TO BE MOUNTED
BLADE SHOULD SLIDE THROUGH
other side of the line. The wiring
ON MOTOR
GAGE NOT INCLUDING TEETH
MAT'L.COLD
CANDELABRA SOCKET AND STRAP FROM A
diagram shows these connections in
PANEL TYPE PILOT LAMP FIXTURE
ROLLED STEEL
detail (Fig. 27).
a spacer of .027 between. Since standard blades
The next step is to make a front shield for the
are .025 in thickness, this allows .002 clearance.
lamp, and some of the same galvanized steel is
All blades after grinding should be able to pass
used. In Fig. 28 this shield is shown removed to
through this gage (Fig. 1A.).
get a view of the lamp assembly. To the tabs on
CAD
HOME-BUILT POWER TOOLS
103