TIG Welding Bandsaw Blades

[jakeru]

Hey guys -

I picked up a new toy this week (vintage craftsman metal cutting bandsaw) but I needed a blade to try it out. Naturally, I wanted to try welding my own. I picked up 5 feet of the bandsaw material from the local sharpening shop for about $6.
Attachment 1847

I wanted bimetal, but they didn't have it in the thickness I needed, so I went with what they had. (It is a carbon steel, with hardened teeth, and annealed main body.) .025" thick. You can see how I set it up to try and keep it straight during tack welding.
Attachment 1848

Anyhow I first tried TIG welding it using a sequence of small tack welds, keeping heat input low. I even had it on a chiller block. I used little short arc bursts to weld like a laser with about 50 amps or so (torch on/off switch.) I used a .040" tungsten. I was able to add a smaller filler rod one droplet at a time, using E70S6 wire I cut off from a MIG spool. Here is what it looked like after welding before further work to grind it down and straighten it:
Attachment 1849

This method actually did not work very well for this kind of steel. The fast cooling weld beads hardened the metal like you wouldn't believe. It would not bend readily to straighten it perfectly, because it was so hard. And when I tried hammering it with a punch to get one side to expand (to straighten the bandsaw blade), all it did was just just dented the punch and my vice I had it resting on, because the welded metal was so hard. The fast cooling weld beads were just too hard and brittle. After being over-worked, it finally fractured when I was installing it. I did sand it down flush too by the way.

So on to attempt number two, this time trying a different technique. This time I elevated the saw (no chiller block, it was suspended in the air, after getting the first tack weld on it at least) and used a lower current setting of about 25 amps, for longer time period to let the heat soak into the metal. I got it glowing red hot, taking seconds to cool back down to non-glowing. That worked great. It left the blade quite ductile, able to bend it without huge effort and without any cracks forming. I ground it down and bent it afterwards so it is within about .0015 of the original thickness, and also pretty flat.
Attachment 1850
Attachment 1851

One tip if the saw needs to be straightned, just add some weld material onto the end that needed to be shrunk. The hot, thick metal will easily pull the rest of the blade tight. Then you can sand it off and have a straight blade.

Here is the saw it will be going in: (My new little toy, a vintage craftsman metal cutting bandsaw)
Attachment 1852

I already tried it out on its first cut, and that saw was making nice smooth shavings!

[dirtyfarmer]

If you have ever used a built-in blade welder on a large industrial bandsaw, they have an "aneal" process that allows you to heat your just welded blade to almost red hot and slowly back down the heat to draw the hardness out of the metal. Works sometimes.