How do you weld bandsaw blades

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?

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Ignoramus16559 wrote:

There are 2 ways . You can cut a bevel arross the thickness and silversolder them or you can build or buy a resistance welder (similar to a spot welder) that fuses the ends together under compression . And here's a link to one made by Ernie Liemkuhler that uses a TIG welder to fuse the ends.
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http://www.doallsaws.com/240weld-blade-welder
Hold the two ends together, one atop the other, with the teeth facing in opposite directions, and grind the ends straight and even. Freehand is fine, the angle across doesn't have to be 90 degrees because if the blade edges are held parallel when ground their 'supplementary' angles will add to 180 degrees.
Clamp the ends in the welder and set the energy level for the blade width. Weld, then anneal the joint.
Grind down the welding flash on either side only enough that it doesn't foul the guides. Run the grind scratches lengthwise so they don't concentrate tension stress.
The grinding wheel should be dressed straight. I prefer a pedestal grinder to do the ends, though the little one on some blade welders is more convenient to remove the flash.
Folding them into three smaller loops:
https://www.youtube.com/watch?v=f-7x8X6I3RA
I couldn't preview it with my XP, IE8 and dialup.
The 1-1/4" x 16' blades for my sawmill are a real challenge to fold. I unfold them by throwing them onto the lawn.
--jsw
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Ignoramus16559 wrote:

I used to silver solder them, with mixed results. Some held for the life of the blades, some let go in minutes.
I have welded blades on the Do-All saw at work, and it is AMAZING. No training, just clamped a blade in there, set the dial and pop, beautiful weld. If you can get one of these, do it.
I have an antique German blade welder that apparently has home-made blade clamps. They are pretty good, but not quite right, and sometimes one blade end climbs up on the other one. I keep fiddling with it, and it gets a bit better. But, I can usually get a weld that will work for a couple months, but they often fail before the blade is completely worn out. I make my blades extra long so I can re-weld them a couple times before they get too short.
Jon
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There are a ton of posts in the archives (Google groups) on welding band saw blades. There are 2 ways: welding with a dedicated machine and silver brazing. For occasional use, the machine is too expensive and brazing is just as good, but slower. For details, search the archives.
Bob
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On 9/13/2016 5:45 PM, Ignoramus16559 wrote:

Spring for the blade welder, you won't regret it.
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I've seen several at machine shop auctions but they always went for more than I could justify.. --jsw
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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"

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Don Foreman wrote:

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
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wrote:

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

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    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 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:

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    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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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
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On 9/14/2016 12:15 PM, Jim Wilkins wrote:

Ig can justify it.
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I am eyeing one right now
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Be aware that blade welders are rated for the maximum blade width they are capable of welding. It would be wise to purchase a welder with extra capacity. Avoid the china blade welders.
Best Regards. Tom.
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    Is your spool bi-metal or single material? If a single material, there are lots of welders which clamp the two blade ends to large electrodes, and when you hit the button, the ends are slammed together while a lot of current is pulsed through them to melt them into one piece. There is typically a grinder mounted in the same thing to remove welding flash so it will pass through the guides properly. You also have an "anneal" button, which puts a lower current through the joined ends (it gets at least to red, and you give in successively shorter pulses so it cools slowly.)
    However -- many of these don't put enough current to handle the bi-metal blades (an edge of HSS welded onto the main backing and that takes more current to weld the HSS part. Usually it will work as long as your blade is a width or two below the maximum for the welder.
    Another approach is to take the two ends, grind a shallow angle onto each so they partially overlap, and then use a torch to join them with silver solder. I've read (here) from people who made their own jigs to both hold the blades to grind the same angle on both, and to hold them together for the Silver Soldering.
    If you have a big vertical bandsaw (and *you* likely do), those often have a blade welder mounted in the left column, so you may already have that -- it is just a matter of learning to use it. One reason for that is so you can cut a (good) blade, thread it through a hole drilled in a workpiece, weld it back together, thread it back into the bandsaw, and use it to cut out a hole which does not reach the outer edge of the workpiece.
    Enjoy,         DoN.
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