Obviously I'm doing something wrong here as my joints are brittle and don't hold worth squat. I ground the ends of the blade to about
45 degrees and cleaned the ends with sandpaper. I put on plenty of flux and wedged a small piece of silver solder in the scarf joint. Both ends are held in a jig so nothing moves during the soldering. The saw blade is 3/16 wide and .025 thick. I'm using oatey 53013 silver solder. I'm using a propane torch w/ pencil tip burner. I've tried heating just till the solder melts & flows, and hotter, up to the blade turning a cherry red. Nothing worked. So what am I doing wrong? technique? Wrong solder? Art
I've only welded blades, not brazed them, but I'm going to guess the blade is cooling fast enough to quench it, making it brittle. After you've made the joint remove it from your jig, shine it up with sandpaper, then heat it gently by waving your torch flame around 'til the steel turns blue. You've tempered the steel enough that it should no longer be brittle.
Winston fired this volley in news: snipped-for-privacy@news2.newsguy.com:
Winston! Winston... Winston...
50313 is a lead-free plumbing solder. It's NOT "silver solder" in the sense of brazing alloys, even if it might contain some silver (which Oatey does not state in the specs)
First of all, get some 'real' silver solder -- the stuff you buy in the Forney section of an ACE hardware, or at a welding shop. Second, be prepared to see the metal red before the solder will flow. The Oatey
53013 will flow at about 700F, which will barely make the blade smoke, much less glow dull cherry red.
IIRC We always welded them and then did some annealing process to soften the weld so it wasn't brittle by giving shots or current after the weld and grind. Been a long time since then...LOL
"Ned Simmons" wrote in message news: snipped-for-privacy@4ax.com... I've only welded blades, not brazed them, but I'm going to guess the blade is cooling fast enough to quench it, making it brittle. After you've made the joint remove it from your jig, shine it up with sandpaper, then heat it gently by waving your torch flame around 'til the steel turns blue. You've tempered the steel enough that it should no longer be brittle.
Aha! Thanks Winston, that's a nice site. He's using 1/2" on a .035 blade so 3/8" on my .025 ought to be in the ballpark. Now to figure out how to do it - the Dremels out for sure. I've give it a shot on the grinder or beltsander. Art
It is soldering and not brazing that I'm trying to do so I don't *think* I need the 'real' stuff. I'm attempting to do what these guys are doing without buying their package.
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they use a butane torch I doubt they really are brazing. Art
Lloyd is right. You're using a soft solder and it=92ll never hold for this job. The real silver solder that you need is a hard solder and melts at a brazing temperature. Usually you use oxy-acetylene for silver soldering. You just have the wrong tools to do this job properly. See:
As they use a butane torch I doubt they really are brazing.
You can count on it. True silver solder is not gonna melt with that joke kit. At the very least you will probably need propylene fuel, if not oxy/acetylene. Quit clowning around and invest in a welder.
You CAN silver solder band saw blades, very well, with a propane torch and hard silver solder. Been there, done that with never a break. You don't have to weld them.
This is the best flux for silver solder. You need the Stay-Silv white. Note the temps. A propane torch should get you there. Still better off with the welder. Good luck.
Nearly all solder is silver, although some looks grey, and some old stuff may have rust stains on it if it's been on a rusty steel spool.
If you can wind the solder around a finger for several turns without serious discomfort, it's soft solder. Soft solders that contain silver are more clearly referred to as silver-bearing solder.
Hard silver solders are hard wire, stiffer than copper wire, more like brazing rods in stiffness. Even mild steel wire isn't as stiff as hard solders.
Brazing is the process for joining parts with hard silver solders. Brazing steel is identically the same operation, and if you've brazed steel, you're familiar with red-hot temperatures, flux flowing, etc. Oxy-acetylene or MAPP gas (used with a MAPP torch) are both capable of brazing bandsaw blades. Some say that MAPP won't work, but I've brazed and silver soldered steel parts with much more mass than the lap joint of a bandsaw blade, so I know MAPP brazes. Maybe some folks don't get the right results because of the torch that the MAPP is used with.
Silver soldering bandsaw blades can also be performed with electrical brazing fixtures. I found an old machine specifically designed to braze bandsaw blades with hard silver solder. The machine doesn't force the ends of the blade stock to fuse together the way a blade resistance welder does.. it just uses electrical current to generate heat in the blade stock joint so the flux and hard solder make a secure scarfed joint.
Electric bandsaw blade welding is generally accomplished with squared ends being butt welded together by resistance welding.
Electric bandsaw blade brazing is approached in the same way as (gas) brazing of the scarfed joint.
Yep, wrong stuff, as the other posters have said. If you google up "bandsaw blade brazing jig", you'll get a ton of hits, including how- to videos. Won't go into the usual rant about calling silver brazing silver soldering, you've found out the difference. If you want the right stuff at the welding supply, you ask for "silver brazing filler", or you'll end up with mostly tin soft solder. The next question will be what alloy and there you'll have to see what they have, literally hundreds of alloys and trade names out there, what I've got available here isn't going to be what anyone else will have around. You'll need the line sheet for what they carry and decide what you need from the properties listed.
Used to be HF had a cheap kit including a jig, apparently no longer. A jig can be made out of a length of aluminum angle and a couple of bulldog clips. Whack a gap in the center of the piece on one side for joint clearance, put the untouched side in the vise and use the bulldog clips to hold the blade ends in position in the gap. You can scarf the ends by flipping one, placing them on top of each other even- up and grinding both at the same time. Angles match that way and any fore-and-aft angular mis-match is compensated for if you grind things straight. You've got to have things spotless, including the silver braze itself, degrease with acetone, MEK or the brake cleaner of choice. For this sort of work, you need almost foil thickness for the filler, hammer what you get down really thin, sandwich a sliver between the ends. It was supplied that way in the kits. Flux has to match, too. The blades are pretty thin, so unless you use some really high-temp braze, a turbo torch should work. See what the line sheet says for the alloy, it'll have melting points on it, and choose one that's lower temp. Air-acetylene or oxy-acetylene will be faster, probably won't do the job any better and definitely will cost more. If you really want to go fancy, you could use some stop-off or anti- flux to keep your after-action filing and cleanup down to a reasonable amount. I've used it on gun work to keep the filler from wicking all over a part, won't do a job without it now.
Have read of hammering out a silver dime, using solid borax for a flux and a kerosene blowtorch for doing the job in a really old book, so they've been brazing ends together a looong time. A lot longer than there have been dedicated pushbutton electric welding machines to do the job.
Just thought I'd throw this in: I wouldn't even attempt to weld/solder a NEW blade, much less a broken one.. WHY did it break? Old? Bound up? Bad weld? If any of the above, I wouldn't reuse the blade anyway.. I buy good blades for less than $15 each (105") and if it's dull, bent or whatever, it gets recycled.. Not worth the few bucks I might save to take a chance on a bad joint popping loose and ruining the work or a body part, IMHO..
Winston fired this volley in news: snipped-for-privacy@news3.newsguy.com:
Plumbing solder is a "soft solder". It's designed to melt at low temperatures, is brittle when frozen, and is NOT designed to be structural in any sense -- it's job is to seal a joint well against leakage when sweated properly.
Your knife repair would have been better served by making the repair with a good hard solder, then re-hardening and re-tempering the blade.
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