Silver solder for band saw blade repair

[elkojm]

I saw articles in HSM or MW on reparing band saw cutoff saw blade. (Usually they are resistance welded, but my supplyer went out of business.) The article said in the old days, blades were always silver soldered. The article mentioned using a silver solder of about 60,000 psi tensle strength. Of course I can not find the article now. A search in the online index did not help, because I don't remember the article title.

After spending a day shopping in the nearest big town to the north, I found 30,000 psi solder (Alpha brand). This lasted about 30 seconds before breaking at the joint. Where can I get stronger silver solder? Need source and phone, the brand and product name.

Thanks if you can help.

elkojm@netscape.net

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John M. Elko
elkojm@netscape.net
Phone 530-527-7892

[Rotate]

Hi John,

Are you brazing the blade with a butt joint? I can't imagine this being strong enough. I would instead chamfer the two ends so that there's a bit of an overlap without increasing the thickness.

As for the source of silver soder, we have a supplier here in Canada that sells a kit for doing exactly this (www.busybeetools.com). Also Benzomatic (the guys who make propane torch for plumbing) sells nickel silver good for 85,000 PSI. You should be able to source them through Home Depot or other building suppliers.

Albert


[This message has been edited by Rotate (edited 03-18-2002).]

[SGW]

Yeah, if you're not doing it, you need to file/grind tapers on the ends of the blade so it overlaps a little. Silver soldering bandsaw blades works -- that's what I do.

Check Small Parts, Inc. and/or Brownell's for silver solder, although other places have it too.

[lynnl]

Any welding supply place should have it. That's where I've gotten it. ... along with the flux to match. It's pretty pricey, but my local welding supplier will cut it off and sell it by the inch. I've bought about a 3-4ft piece twice (temporarily lost my first piece for awhile)

[Rotate]

I forgot to mention. Make sure that the two ends are perfectly aligned and making good contact before brazing. They actually sell a jig which clamps the two end together, or even better make one. Good luck.

Albert

[Randy]

Albert hit the two important points, I'll just amplify a bit. 1) You need to make a scarf joint with a bevel long enough that you have a joint area something like 2mm wide. The two ends must be very well matched (square, flat, same angle). It would be helpful to make a grinding jig unless you're really good at off-hand grinding. If you're picky you'll get the teeth matched, too. 2) Albert used the correct term: braze. "Silver solder" is a term often used incorrectly in place of silver braze. I know Alpha makes actual silver solder that melts at about 450*F, is that what you have? You need silver brazing rod that melts at around 1200*F. The stuff I use is 56% silver BAg-7, which melts at 1205*F. It's the lowest melting point of non-cadmium bearing silver alloys. Of course you need the proper flux (I like the black stuff even though it's nore noxious than the white) and an oxy-fuel torch. You can get all the stuff at a welding shop. And thirdly, you should make a brazing jig. This is a simple affair, just a piece of flat steel about 6 " with a flat step milled along the edge, about as deep as your blade is thick, and a little narrower than your blade is wide (so the teeth overhang the edge) with a couple of screw clamps to hold the blade and a gap about an inch wide for torch access. Hope this helps, good luck.

[SGW]

A propane torch will work -- not a problem with that small amount of mass to heat up.

[Rotate]

Randy,

I thought silver soldering doesn't actually contain any silver. No?

What's this wonderful stuff that melts at 450*F for joining steel?

Albert

[n_derue]

John:

http://beaumontmetalworks.com/shoptips.html

Pics and info on silver-brazing bandsaw blades.

Regards,

Neil

[Gizmo]

Yeah, what they said. I make all my own blades that way, hand grinding the bevels, lining it up in a homemade jig (a piece of 2" angle iron with clamps and clearance window so heat isn't sucked away) and the propane torch. I never get them thinned out quite enough, so my joint is always a bit thick. Easily corrected at the grinder with micrometer in hand to check progress. I'll also stone the back of the joint a tad just to make sure the blade doesn't hump each time the joint passes the support guides. Rarely break one; unfortunately bought a cheap spool of blade mat'l and regret it because they get dull too fast for the effort involved...