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Repairing a Bandsaw Blade

I wiped the teeth off of the plane carbon steel bandsaw blade that came with my 7x12 the other day. Had to use the little bandsaw (glad I kept it as a spare) for the last week. I ordered in a nice Lennox M42 bi-metal blade to try on the 7x12 and ... I managed to order the wrong size. Of course I didn't realize it until to late. It took a week to get here and the saw won't adjust out enough to fit it up. I've got a couple more blades coming that are the right size, but I really need my saw going.

I decided to cut an inch out of the blade, but haven't done it yet. I got the geometry for cutting and silver soldering figured out I think. However I am confused about cooling the blade afterwards. Some guys use a wet rag and fast cool it. Others seem to indicate that you should slow cool it and anneal it. To the point that they play a flame over the area around the repair to slow the cooling.

What have you done? How did it work out?

No, I don't have a blade welder. LOL.

I did stop by my local Praxair shop and pickup some Silvalloy 45%. Youch! That stuff costs almost as much as the blade. $22 for 30 grams. On the other hand it won't take much of it. Should last me the rest of my life.

Reply to
Bob La Londe
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You probably don't need to worry about annealing if you silver solder the blade. If you weld the blade, it gets a LOT hotter, and then annealing is very important or it will crack. I made a homemade electric blade welder, and then got a real one on eBay. it has an anneal function that slowly heats the blade to dull red. I hold it just below dull red for 30 seconds or so by blipping the anneal button.

I bought some 100' reels of blade from Enco years ago, they are most likely horrible stuff, but work OK on my 4 x 6" saw. They were really cheap, less than one premade blade. I hate to think what they will cost when I use those up.

Jon

Reply to
Jon Elson

I have made up bandsaw blades both with a bandsaw welder and by silver sol dering.

For silver solderirg you need to make a simple jig to hold the pieces in al ignment and with the area being soldered out in the open so the heat is not sucked away by the jig.

Next you need to scarf the blade so you have a fairly large area being sold ered. I just flip one end around and clamp it to the other piece so both ends can be scarfed at the same time using a bench grinder. After that you clamp t he blade in the fixture , apply flux and silver solder it. A good propane torch will work. I let it cool a bit before putting a wet rag on it to coo l it so I do not burn my hand.

Dan

Reply to
dcaster

YOu might practice on the old blade without teeth.

Dan

Reply to
dcaster

I finally got around to cutting an inch out of that blade and silver brazing it today. Just a few minutes ago. Of course the correct length new blades I ordered arrived yesterday. I'll probably take the brazed blade off and just keep it as a spare, but I had to put it on and slice a piece of steel with it to see if it would hold. The metal in this video is 1" (25.4mm) thick by about 3" (76.2mm) wide 4140HT. At the start of the video clip I had not yet opened up the air cylinder control valve to allow full speed. In fact I didn't realize it was open at all, and was surprised when I looked down and saw it was cutting. Never heard it start the cut.

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Improvised Brazing Jig

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Lined Up

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Before Grinding

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Reply to
Bob La Londe

Seems the first link didn't work. Try this one.

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Reply to
Bob La Londe

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