Frank Turley Posted June 27, 2012 Share Posted June 27, 2012 We talked briefly about band saw brazing with spelter on another thread: "Hammers; Overkill". It is done by straight/bevel scarfing the ends to be joined and clamping them in the center of the jig. The brazing tongs sometimes have 1" square jaws. The tongs are heated to an incandescence and squeezed onto the joint which has been sprinkled with spelter (brass filings and borax mixture). The conducted heat melts the brass, and the braze takes place. Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted June 27, 2012 Share Posted June 27, 2012 i havetried silver soldering in the past with little success,,,Thanks so much Frank a genuuine pear of wisdom! Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 27, 2012 Share Posted June 27, 2012 I have a set of brazing tongs, they are the heaviest tongs on my rack and I use them to demonstrate that the size of stock a set of tongs holds is only loosely correlated to the size of the tongs. Quote Link to comment Share on other sites More sharing options...
Frank Turley Posted June 27, 2012 Author Share Posted June 27, 2012 Rich, This is something I haven't tried. The clamp came into my hands years ago, and I'm certain it was manufactured for that purpose. Whether such a braze would work on recent alloy and bi-metal blades, I cannot say. I think the clamp is shown in Schwarzkopf, "Plain and Ornamental Forging." Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 27, 2012 Share Posted June 27, 2012 Frank; do you have a set of the brazing tongs? Quote Link to comment Share on other sites More sharing options...
Frank Turley Posted June 27, 2012 Author Share Posted June 27, 2012 No I don't. I have seen a pair, though, in the olden days. I looked in my 1894 catalog, and they offered a more elaborate clamp and even furnished silver solder with the sale. Quote Link to comment Share on other sites More sharing options...
doc Posted June 27, 2012 Share Posted June 27, 2012 Years ago we used to "solder/braze" our blades this way, The only problem seemed to be that the heat took the temper out of the teeth and caused them to dull almost immediately.Thus causing all the rest of the teeth to wear and chip sooner than if welded in the modern convectional way. Quote Link to comment Share on other sites More sharing options...
MOblacksmith0530 Posted June 27, 2012 Share Posted June 27, 2012 There is a book on google books that is free called The Blacksmiths' guide by James Francis Sallows that has a chapter near the end about this. He is a bit full of himself but has some real interesting info on the methods of around 100 years ago for all kinds of stuff. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 27, 2012 Share Posted June 27, 2012 Frank do you want a set? You would probably get more mileage out of them that I will. Quote Link to comment Share on other sites More sharing options...
Frank Turley Posted June 27, 2012 Author Share Posted June 27, 2012 No thanks Thomas, At my age, I'm in the getting rid of phase. Quote Link to comment Share on other sites More sharing options...
knots Posted June 28, 2012 Share Posted June 28, 2012 My home built version. I used to silver braze all of my blades. The silver braze analysis is important. In the past I have had silver wire that I simply could not make flow. I now use 56% silver, flux coated brazing rod . After cleaning/preparing the blade with the V ground ends place the blade in the blade jig with a few thousandths " between the blade ends . Just enough to compensate for heat expansion so that, when heated, the blade ends just touch or close. Otherwise the blades can bulge or over lap if the ends press together. Flux, heat, and apply silver. Not at all hard to do, and very strong. I don't recall ever having a silver brazed joint breaking. Quote Link to comment Share on other sites More sharing options...
knots Posted June 28, 2012 Share Posted June 28, 2012 Here is the Blade jig. Quote Link to comment Share on other sites More sharing options...
Pat Roy Posted June 28, 2012 Share Posted June 28, 2012 Just wondering if this operation is more successful with a ten dollar bill in the picture. Quote Link to comment Share on other sites More sharing options...
chichi Posted June 28, 2012 Share Posted June 28, 2012 Knox, Where do you get your silver brazing rod. Can a regular brazing rod be used to join a saw blade ? I assume brazing requires too much heat? Quote Link to comment Share on other sites More sharing options...
knots Posted June 28, 2012 Share Posted June 28, 2012 Knox, Where do you get your silver brazing rod. Can a regular brazing rod be used to join a saw blade ? I assume brazing requires too much heat? I got mine at Air Gas. My store does not normally stock the flux coated silver brazing rod but they were able to order it . The problem is that since it was a special order I had to take the whole packet. As I remember ther were three rods about a 16" long. The cost per rod was about 10-12 bucks a rod. But I keep some in my supply at all times for blades anf repairs where welding is not practical and strength is needed . A little goes a long way. The last packet that I bought was maybe 20 years ago . Look for a place that will sell one stick or buy a pack. Yes braze at red heat. Dock is right about the band annealing in the area joined however With a clamp like mine that captures the blade between steel angle and bar, the clamp acts as a heat sink and reduces that problem. I have only noticed dulling over a short run of blade and have not really been bothered by it. I have never used bronze rod or spelter for brazing band saw blades so can't really comment. However the silver that I use has a tensil strength of 60,000 psi, and does not seem to mind being flexed. I have had blades break but not at the silver joint . Just found it: Mine is a Radnor/Harris product Safety-Silv 56, flux coated silver brazing alloy. Fluidity rating = 8 . The use of old technology like brazing tongs, presumeably preheated to a red heat and used in lieu of a torch to make the braze is very interesting . Think I will make up a tong and give it a try. It should give a very controlled heat. Thank you Frank. Quote Link to comment Share on other sites More sharing options...
Jacques Posted June 28, 2012 Share Posted June 28, 2012 We braze and occasionally silver solder our woodworking band saw blades, since the closest place that do it is far away. The longest I've had a blade last was for 7 full days of working, and then the job was finished. That was exceptional. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 28, 2012 Share Posted June 28, 2012 You can always ask a refrigeration repair place about scrap pieces of silver brazing rods as they use them as of the last time I consulted one. I have this heavy set of brazing tongs but will probably never use them. Frank; getting rid of stuff??? Just remember that I am *down hill* of you!!!!!! Quote Link to comment Share on other sites More sharing options...
chichi Posted June 29, 2012 Share Posted June 29, 2012 When a band saw blade is say brazed, I assume both ends are ground on the flat and then overlapped a little? Or, are they just butted edge to edge? Quote Link to comment Share on other sites More sharing options...
mtforge Posted June 29, 2012 Share Posted June 29, 2012 We used to do this in my shop. Instead of rod I used very thin silver alloy. Cut it to size with scissors, flux it, clamp it down with a little pressure holding the silver in the joint and use a small propane torch for heat. Get the silver to run and then let it cool. You can get the whole kit or just the silver on ebay. We went to bi-metal blades from Mcmaster.com and have gotten a lot more life from them. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted June 29, 2012 Share Posted June 29, 2012 They are just butted Quote Link to comment Share on other sites More sharing options...
mtforge Posted July 2, 2012 Share Posted July 2, 2012 Mine were slightly beveled. The silver solder chip was held in the bevel. Quote Link to comment Share on other sites More sharing options...
knots Posted July 2, 2012 Share Posted July 2, 2012 We used to do this in my shop. Instead of rod I used very thin silver alloy. Cut it to size with scissors, flux it, clamp it down with a little pressure holding the silver in the joint and use a small propane torch for heat. Get the silver to run and then let it cool. You can get the whole kit or just the silver on ebay. We went to bi-metal blades from Mcmaster.com and have gotten a lot more life from them. I always cut a chip off of my brazing rod for the braze and use V joints . It is also important to use the correct alloy. Not all silver braze alloys are equal. Jacues said that the joint life for his applications is max 7 days. What is the life expectancy of yours ? Quote Link to comment Share on other sites More sharing options...
mtforge Posted July 6, 2012 Share Posted July 6, 2012 When I was using it it lasted the life of the teeth. Quote Link to comment Share on other sites More sharing options...
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