need help; bandsaw blade welder

[SteveD]

I just purchased a used MSC blade welder BM-16. It has been since '98 since I used one of these, no instructions with it. I am having a hard time getting welds to hold. Any insight would be helpful.

Thanks,

[ESjaavik]

What do you mean by hold?
Do they break, does it not weld, does the weld burn off, or....

[HuFlungDung]

Steve,

These things can be a little finicky to run, and I don't know exactly what your machine looks like but it likely has similar functions to machines made by other companies.

Make sure the clamp jaws are clean for good contact.

First off, are you getting a nice sound weld zone, with a little bit of flash on both sides?

If you are, then the trick might be in the tempering of the completed weld. You don't want to overdo it or underdo it. The machine I use has kind of a "jog" button to provide the current to do the tempering. How long you hold it on, is as long as the heat builds up. There is a Hi/Lo toggle switch to provide two different heat ranges for blades under/over the 1/2inch width range.

Anyways, I always have tempered the blade immediately after the weld has cooled. This would only be maybe 10 seconds wait. Then, I start jabbing the tempering button, and because I work in a darkened corner, I can plainly see when I am getting up to a very dull red heat. You do not want to go much brighter, because this overdraws the weld and will make it too weak. Once I have reached this color for the draw, I then back off on jabbing the temper button, but still give it an occasional jab, so that a little more heat is applied to prevent too rapid of a cooldown. Each jab gets progressively timed further and further apart.

Then, I take the blade out and grind the welds off and brighten up the weld zone. Then, I take it back and temper it one last time, but this time, I only watch for the blue, dark blue, violet colors to appear in the weld zone. This is like 600 degree heat. This temp needs to be approached slowly, so that the coloration is maybe 1/2" wide or more. I call this second tempering "insurance" against breakage, in case the first tempering was a little too fast. I've had really good success with this technique.