Sounds like a candidate for a HSM project. I wonder how much current
blade welders deliver. Don't know if a 105-amp MIG would be enough
but a re-wound microwave oven transformer surely would be.


On Wed, 14 Sep 2016 12:15:17 -0400, "Jim Wilkins"
wrote:


"Tom Gardner" wrote in message
...
On 9/13/2016 5:45 PM, Ignoramus16559 wrote:
We just bought a spool of band saw blade stock and we want to cut
it
in sections and weld blades. How do we weld them so that they hold
up?


Spring for the blade welder, you won't regret it.

I've seen several at machine shop auctions but they always went for
more than I could justify..
--jsw


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Don Foreman wrote:


Sounds like a candidate for a HSM project. I wonder how much current
blade welders deliver. Don't know if a 105-amp MIG would be enough
but a re-wound microwave oven transformer surely would be.
Before I snagged a German blade welder on eBay, I had built a very bad
homebrew one. I found a transformer that had a lot of available "window"
still open, and wound a couple turns of battery cable through that, and made
up a clamp for the blade. It worked remarkably well for a total jury-rig
setup. I know if I had kept on working on it, it could have made decent
blade welds. The transformer in a Do-All welder is remarkably small, but
obviously purpose-built for the job.

Jon

On Thu, 15 Sep 2016 16:08:30 -0500, Jon Elson
wrote:

Don Foreman wrote:


Sounds like a candidate for a HSM project. I wonder how much current
blade welders deliver. Don't know if a 105-amp MIG would be enough
but a re-wound microwave oven transformer surely would be.
Before I snagged a German blade welder on eBay, I had built a very bad
homebrew one. I found a transformer that had a lot of available "window"
still open, and wound a couple turns of battery cable through that, and made
up a clamp for the blade. It worked remarkably well for a total jury-rig
setup. I know if I had kept on working on it, it could have made decent
blade welds. The transformer in a Do-All welder is remarkably small, but
obviously purpose-built for the job.

Jon

Any chance you could slip a clamp-on ammeter on that puppy while
welding, and also voltage?

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Nevermind!
Looks like 1 to 3 volts at 100 to 200 amps. Looks like a primary of
354 turns of #15 or two paralleled #18 wires, tapped at 150 and 200
turns. Laminated core center post area of 3.65 in^2. Secondary
winding of four rectangular formex wires each .105 x .165, 4 turns.


On Thu, 15 Sep 2016 17:36:34 -0500, Don Foreman
wrote:


Any chance you could slip a clamp-on ammeter on that puppy while
welding, and also voltage?



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On 2016-09-15, Don Foreman wrote:
On Thu, 15 Sep 2016 16:08:30 -0500, Jon Elson
wrote:

Don Foreman wrote:


Sounds like a candidate for a HSM project. I wonder how much current
blade welders deliver. Don't know if a 105-amp MIG would be enough
but a re-wound microwave oven transformer surely would be.
Before I snagged a German blade welder on eBay, I had built a very bad
homebrew one. I found a transformer that had a lot of available "window"
still open, and wound a couple turns of battery cable through that, and made
up a clamp for the blade. It worked remarkably well for a total jury-rig
setup. I know if I had kept on working on it, it could have made decent
blade welds. The transformer in a Do-All welder is remarkably small, but
obviously purpose-built for the job.

Jon

Any chance you could slip a clamp-on ammeter on that puppy while
welding, and also voltage?

Which one -- the home-brew or the Do-All?

From personal experience with an import version of the welder
(came from eBay a few years ago), the weld pulse is too quick to get a
reasonable reading with a clamp-on ammeter. Add an electronic meter
which can measure the peak current very quickly and you will do better,
but that is typically lab bench equipment, not hand-held. Maybe a
storage oscilloscope, or a digital one and you could look at the
waveform out of the clamp-on probe.

Now -- if you operate it from perhaps as low as 6V or so, you
can measure the input and output voltages and calculate the turns ratio.
Then, from that, you can look at the fuse rating in series with the
primary to calculate the maximum current out of the secondary. Assume a
very low resistance load. Remember, the blade forms a complete loop as
it is being welded, so the resistance between the clamps and the ends
has to be a lot lower than the resistance though the blade the long way.

Good Luck,
DoN.

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I kludged together a jig to hold blades for silver soldering. It has
been improved over the years.
Two pieces of a hardwood slat. two bolts and two wing nuts make a jig
to grind an equal shallow angle on the ends.
Two pieces of scrap shallow Al chanel were fixed together, flat side to
flat side and offset. and a square hole milled in the middle and the
fence formed by the side of the upper channel, four hold down bolts
were afixed to hold the blade. If you don't use two on each side the
natural bow of the blade will give a bad weld. Two pieces of thin
approx 1/4 wide metal are used to hold the blade up so that the set of
the blade does not tilt it [the metal strips from a Peneflex hanging
file folder are fine]. This is mounted on a piece of channel. This last
is what I think makes it succesful. A 1/2 inch ferrul type Cu fitting
is fixed below the weld point. The ferrul is split to take 1/2 in
carbon rod. The end is flatened and raised level with the lower flat.

Grind you blades, place them in the jig. Carefully align on top of the
carbon rod, do not leave any gap.
Gently raise up one side and flux [I am using 50 year old]. Cut a thin
[probably 5 mil] piece of silver solder the shap of the ground surface
and place it between the ground surfaces. Take your propane torch heat
the weld until you see the solder melt, remove the flame as you press
down on the weld with another piece of carbon. This presses out any
excess solder.

The next is what I saw at a saw shop many years ago when they made
bades for me. I was a half round maybe 10/12" in dia. with two toggle
clamps. they put the welded blad over the half round and clampd it
down one side at a time and cleaned up the weld. Mine is just a piece
of plywood half rounded on one end with two toggles and held in a vise.

I don't do a lot with bandsaws, but what I do is some times pretty
rough. Mine seem to last.

CP

I did that to a spot welder I had in the lab Used my 1000 amp HP clamp
on into a HP meter.

The current was just shy of 1000 amps and the voltage was 1.5 open
circuit.

That was a 1/4" spot weld into a sheet of Al.

I think in the way back mode of this group, a home brew was made and
worked. Maybe Don made it or second sourced the design... :-)

Martin


On 9/15/2016 8:43 PM, DoN. Nichols wrote:
On 2016-09-15, Don Foreman wrote:
On Thu, 15 Sep 2016 16:08:30 -0500, Jon Elson
wrote:

Don Foreman wrote:


Sounds like a candidate for a HSM project. I wonder how much current
blade welders deliver. Don't know if a 105-amp MIG would be enough
but a re-wound microwave oven transformer surely would be.
Before I snagged a German blade welder on eBay, I had built a very bad
homebrew one. I found a transformer that had a lot of available "window"
still open, and wound a couple turns of battery cable through that, and made
up a clamp for the blade. It worked remarkably well for a total jury-rig
setup. I know if I had kept on working on it, it could have made decent
blade welds. The transformer in a Do-All welder is remarkably small, but
obviously purpose-built for the job.

Jon

Any chance you could slip a clamp-on ammeter on that puppy while
welding, and also voltage?

Which one -- the home-brew or the Do-All?

From personal experience with an import version of the welder
(came from eBay a few years ago), the weld pulse is too quick to get a
reasonable reading with a clamp-on ammeter. Add an electronic meter
which can measure the peak current very quickly and you will do better,
but that is typically lab bench equipment, not hand-held. Maybe a
storage oscilloscope, or a digital one and you could look at the
waveform out of the clamp-on probe.

Now -- if you operate it from perhaps as low as 6V or so, you
can measure the input and output voltages and calculate the turns ratio.
Then, from that, you can look at the fuse rating in series with the
primary to calculate the maximum current out of the secondary. Assume a
very low resistance load. Remember, the blade forms a complete loop as
it is being welded, so the resistance between the clamps and the ends
has to be a lot lower than the resistance though the blade the long way.

Good Luck,
DoN.

On 2016-09-19, Martin Eastburn wrote:
I did that to a spot welder I had in the lab Used my 1000 amp HP clamp
on into a HP meter.

The current was just shy of 1000 amps and the voltage was 1.5 open
circuit.

That was a 1/4" spot weld into a sheet of Al.

I think in the way back mode of this group, a home brew was made and
worked. Maybe Don made it or second sourced the design... :-)

I believe so -- but it was not I. IIRC, it was a young fellow
who was at first making the mistake of drawing arcs off carbon rods
without eye protection. Not sure what happened to him, but he was
fairly active here for a while.

Enjoy,
DoN.

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