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Silver solder for band saw blade repair

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  • Silver solder for band saw blade repair

    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.

    [email protected]

    ------------------
    John M. Elko
    [email protected]
    Phone 530-527-7892
    John M. Elko
    [email protected]
    Phone 530-527-7892

  • #2
    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).]

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    • #3
      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.
      ----------
      Try to make a living, not a killing. -- Utah Phillips
      Don't believe everything you know. -- Bumper sticker
      Everybody is ignorant, only on different subjects. -- Will Rogers
      There are lots of people who mistake their imagination for their memory. - Josh Billings
      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
      Don't own anything you have to feed or paint. - Hood River Blackie

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      • #4
        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)

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        • #5
          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

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          • #6
            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.

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            • #7
              A propane torch will work -- not a problem with that small amount of mass to heat up.
              ----------
              Try to make a living, not a killing. -- Utah Phillips
              Don't believe everything you know. -- Bumper sticker
              Everybody is ignorant, only on different subjects. -- Will Rogers
              There are lots of people who mistake their imagination for their memory. - Josh Billings
              Law of Logical Argument - Anything is possible if you don't know what you are talking about.
              Don't own anything you have to feed or paint. - Hood River Blackie

              Comment


              • #8
                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

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                • #9
                  John:

                  http://beaumontmetalworks.com/shoptips.html

                  Pics and info on silver-brazing bandsaw blades.

                  Regards,

                  Neil

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                  • #10
                    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...

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                    • #11
                      The 450* stuff is for jewellers. Buy high strength silver solder at a welding or industrial supplier for the proper stuff - use a lap joint - butt joint is for fusion or spot welding (more like displacement or upset weld than a spot weld).

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                      • #12
                        Metal Working, Bk 2 has plans for an excellent little jig for soldering (brazing)bandsaw blades, and another jig for grinding the bevels.

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                        • #13
                          Thanks for all your replies. Usin the 58%, .029" dia., melt at 1200 degree Alpha silver solder, I finally have learned to make repairs that hang together cutting through a 4" HD channel(my blade test).

                          Using High Strength brazing rod did not work well, must be too brittle. I marked the base plate of my 1" belt sander about 1 1/2 inches from belt center on each side. I aligned one blade edge with teeth to the right, and touched the belt about 4" up the belt at its center. This would produce both a wide bevel and an angel of near 30 degrees. By placing the other blade end at the opposite index mark, with teath still toward the right, I could get a matching angle and bevel. (Check to see the blade is straight and not twisted in the last 6 inches.)

                          I polished up the joint area to bright metal to get rid of any contamination,and clamped it into my jig. After applying the Alpha flux, a 9/16" length of solder was laid along the joint.

                          I heated the joint with a Victor Nr 0 (small) welding tip, turned way down low. I found the best repair was when the metel did not turn red, the wire just disapeared as it was fully wicked into the joint, resulting in a small ridge of solder exposed along the full length of the joint on the underside. This usually was not thick enough to require grinding off.

                          Thanks again for your responses.

                          Keep on Machining!

                          John M. Elko
                          [email protected]
                          John M. Elko
                          [email protected]
                          Phone 530-527-7892

                          Comment


                          • #14
                            The fixtures that are mentioned are the way to fly. Having a surface grinder, I machined a grinding fixture for the blades. That way I get a perfect scarf joint everytime. There is a "silver solder" that the plumbers use for copper pipe/tube and there are several "silver brazing " alloys available at your welding supply. I use the smallest diameter wire and and the white flux. Until recently I have used the stuff with the cadmium, now I use the stuff without---results about the same.

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                            • #15
                              After machining my blade brazing jig, I find that Harbor Frieght Tools, 1-800-423-2567 now offers a Silver Brazing Kit, Item 40311-2CKA for $9.99. Has a jig, flux, .040 dia solder, and instructions. (Page 76, catalog 459) Keep watch, it will be discounted later.

                              JME
                              John M. Elko
                              [email protected]
                              Phone 530-527-7892

                              Comment

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