TIG welding bandsaw blades

the last (nearly new) band for my horizontal , figured I have nothing to lose but a little time , a bit of shield gas and some 'lectrons - oh ,
and I'll need to make a clamp block to keep the blade aligned as I weld on it . Got a new blade on the way , but just got a bug to try this . I know low amps DCEN , what filler ? Got ER70S2 ,ER70S6 (MIG wire) , ER 308/309/312 and some Invar 42 nickel/iron . The blade is an Irwin (IIRC) bimetal 10/14 pitch . Am I going to need to anneal the weld ? O/A torch OK for the task if it's needed ? I know I want to minimize the HAZ .
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wrote:


For whatever it is worth, I seem to remember a band saw with an attached blade welder that clamped the blade in a holder with two sections, a fixed clamp and a movable clamp. When you hit the switch the current was applied and the spring loaded clamp moved that end of the blade toward the fixed end of the blade, sort of like a spot welder. There was no filler material. When the weld was finished there was some "bead" on both sides of the blade and the welder had a small grinding wheel attachment so that the weld "beads" could be ground smooth. No annealing or filler metal
Earlier on we used to grind each end of the blade to a knife edge, and then overlap the ends and silver solder them together.
Given that most band saws have large enough wheels that the blade is not bent sharply I suspect that the joining is not a really critical thing.
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http://www.neme-s.org/Shaper%20Books/Doall/DOALL%20Butt%20Welder.pdf
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On 3/4/2019 4:14 AM, John B. Slocomb wrote:


BUT the one that I used did have an anneal function , and it did help extend blade life . I suppose I could rig up something to do that butt weld using my TIG welder as a power source ... it has a spot weld function .
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On Monday, March 4, 2019 at 7:40:11 AM UTC-5, Terry Coombs wrote:

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I would suggest ordering some silver solder and flux. Band saw blades ca n be tig welded, but it is easy to screw it up. Silver solder is easier. Mean while make a jig to hold the blade and try tigging. You can anneal u sing a hand held propane torch.
Long term make a band saw blade welder. A microwave oven transformer can b e rewound to have a low voltage winding.
Dan
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On Mon, 4 Mar 2019 08:31:54 -0800 (PST), " snipped-for-privacy@krl.org"



If you want to ake a big project of it, that would be one way to go. But, as Gunner said, it's hard to beat scarfing the break and silver-brazing it with O/A. That, too, requires a jig to hold it, but it's a simple one. It's not used in industry as often as it once was, because it's not as fast as just placing the ends in a jig and pushing a button.
It's not widely recognized that a properly-gapped and -heated silver braze joint can achieve over 100,000 pounds per square inch of shear strength. You won't quite achieve that with a simple jig (the gap is catch-as-catch-can; ideally, it's around 0.001 - 0.002 inches), but it still is stronger than the parent metal, because the scarf multiplies the joint area by a factor of three or so. Just the bulk strength of the silver braze metal is on the order of 1/3 the strength of the blade. And the embrittlement problem that comes from heating and self-quenching with electric welding methods more or less solves itself.
I used to do it, but I haven't broken a blade in a long while.
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Ed Huntress

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On 3/4/2019 10:56 AM, Ed Huntress wrote:



bandsaw blades ... got flux and know where it is , but the SS has eluded me for now . I'll find it a couple of days after I order more .
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wrote:




I have numerous collections of things like that. It becomes worse as I grow older and buy bulk quantities of things from Costco.
I'll never have to buy a pack of contractor's plastic bags for the rest of my life. d8-)
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On Mon, 4 Mar 2019 11:40:19 -0600
<snip>

It was the handy little roll of bailing wire you used a while back :)
Seriously, sometimes I luck out by thinking I have some in my hand and where would I go stash it right now...
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Leon Fisk
Grand Rapids MI
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On 3/4/2019 1:42 PM, Leon Fisk wrote:

computer desk ... and I just looked again to make sure ! I'm pretty sure it made it out to the shop , but exactly where in the shop is a true puzzler . It should be in the plastic tub that all the welding/brazing supplies are in . It ain't .
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On Mon, 4 Mar 2019 14:43:58 -0600

Been there, done that :) Try not to move stuff around much anymore because I always go to where it used to be, not where I moved it too...
Mine is suppose to be in the little box/tray on the front of the Oxy/Acy cart. Bought it years ago for just in case and have never needed it so far. Knock on wood...
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Leon Fisk
Grand Rapids MI
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On Mon, 04 Mar 2019 11:56:46 -0500, Ed Huntress



El-cheapo propane torch works fine for me! My jig is a piece of channel with angle attached and clamp screws to hold the blade between the flange of the channel and the inside of the leg of the angle and a gap cut in the flange of the channel to let the flame come up under the joint. To scarf the joint, I just clamp two ends together and touch them on the grinder. After brazing, I do touch up with the Dremel.
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wrote:



was bandsawing metal -- right down to the Dremel.
Now I bandsaw wood and composites. No breaks for years.
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On Mon, 04 Mar 2019 17:14:52 +0700, John B. Slocomb wrote:

Yes, DoAll saws have a built-in shear/welder/grinder. Very simple, does an AMAZING job. I got an ancient German blade welder on eBay, it works but not as well as the DoAll. No filler needed, it is resistive welding, and the jaws move together under light pressure to "upset" the weld area a little. Then, you grind down the flash at the weld and anneal.
Jon
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    These are made both to build into the bandsaw, and for benchtop use. They also include a lever-operated shear to cut the blade cleanly.
    One reason for them being mounted on the bandsaw is so you can drill a hole in the workpiece, thread the cut blade through the hole, weld the blade, and then cut along a line which never intersects the outside edge of the workpiece, to cut out an inner piece.
    An example of the benchtop version (similar to what I have) is this one on eBay:
    Auction # 273699228238
Note the semi-repaired "Anneal" switch. After the welding, you are supposed to loosen the clamps, slide them back, center the welded spot between the clamps, and then start out with long pulses of the anneal switch, moveing slowly to very short ones to let it cool slowly. After this, you grind off the flash.
    The rotary switch sets the current for the width of the blade. And you need more current for a bi-metal blade than for a carbon-steel one.     

    You do want to anneal it properly -- especially if you have something like my 4x6 Horizontal/Vertical bandsaw.
    Enjoy,         DoN.
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wrote:


I use bi-metal blades. They are hard to weld properly with the resistance weld method. TIG welding with SS works very well though. Just for kicks I decided, years ago, to see how well TIG welding would work. See this link: https://groups.google.com/forum /#!topic/sci.engr.joining.welding/uPXdZXEsyGc Ernie Leimkuhler explains how he does it. I didn't have any of the filler he was using so I tried ER309 filler. I was sawing 5" diameter 6061 bar. Very aggressively with a coarse variable pitch blade. The blade was old and broke. I ended up welding the blade in 3 places. None of my welds failed. After the blade broke in yet another place I switched blades. Eric
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On 3/4/2019 11:55 AM, snipped-for-privacy@whidbey.com wrote:


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wrote:


You're welcome. Ernie's very good at welding and welding advice. Somewhere he also explains how to make a fixture to hold the blades but I couldn't find the link. Doesn't matter though, you'll figure it out easily enough. When I made my blade welding guide I milled a little pocket under the weld zone so that the argon would also flow under the weld and prevent sugaring. Eric
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On 4/03/2019 2:16 pm, Terry Coombs wrote:

I had a Roll-In saw that seemed to be hard on blades, breaking well before they dulled. Machined up a fixture to hold the blade in alignment, and tig welded with 308SS rod, no anneal. Never had a blade break at the weld. Had one blade with 5 or 6 welds before it dulled enough to discard. Gave the fixture to my friend whose welder I'd been using. Took a picture last time I was visiting, if I can dig it up, will email.
Jon
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