Bandsaw blade welding

[Vinny]

I've got a bandsaw blade welder and have made several blades. Sometimes, however, they break while grinding them smooth. Most of the instructions I've seen say to grind it before annealing it. But I've seen a few that say to grind it after. Which is correct? I've been doing it before and just a few minutes ago I broke it while grinding and I wasn't really flexing it that much. At least no more than usual and probably much less.

[TomG]

• Weld it
  
• Anneal it bright red (not orange)
  
• Grind it
  
• Temper it to blue
  
• If that doesn't work, build my soldering fixture and silver solder it
  

          Tom

[Vinny]

"Temper it to blue" I've never seen that stage in any of the docs. Tips on how to do it?

[dallen]

I would think that after you grind it to put it back in to the welder and heat it until the welded spot turns blue then quench it in oil probably

[TomG]

Just heat it with the welder or a torch until it turns blue and call it good.

Tom

[Vinny]

Blue is before orange, right?

[TomG]

WAY before. Blue is 575ºF, orange is 1700ºF.

The idea is to heat the weld to 1400ºF-1500ºF (bright or cherry red) to anneal it so it doesn't break while grinding. Grinding will re-harden the blade, so it needs to be tempered to 550ºF (blue) to make the welded area the same hardness as the rest of the blade. Otherwise the weld will harden even more as it flexes and ultimately break. Be careful to not go too far when tempering. It will go to straw, to brown to purple to blue, and it goes fast.

Tom

[Highpower]

Cheat sheet:

[Vinny]

Ok. Now I got it. I'll putt the saw back out later (the blade's already on it but I haven't used it yet) and hit it with a torch.

Thanks!!

[TomG]

You should be able to temper it with the welder, but a torch will work as well.

Tom