Jon Elson wrote:

This sounds quite promising. You need the right amount of upset (maybe
1/8" or so), the right pressure, VERY accurate movement to keep the
blade ends parallel, and the weld current needs to turn off as soon as
the upset completes.
I think you need to be able to turn down the current quite a bit, maybe
to 1000 - 1500 A or it will just blow the joint to bits.
The blade holders on mine were shop-made, I'm guessing in a
previous-previous life the welder was adapted for something else, and
they are not quite perfect, but workable.

Well, maybe I will experiment with this then. I have linear
slide assembly that's too rough to do much else with, but
still as or more precise as anything I could make up. Just
need to make SURE one side is insulated from the rest!

There's no way to vary current, except perhaps to use a
couple extra feet of welding cable. Ratings drop
significantly from 6" tongs out to 18" tongs, resistance
losses in the copper tongs I'm guessing?

Timing, I'd just have to wing it I think. I've got good
reflexes still, I think I could do it. And, it would be easy
to anneal, just as with a purpose made welder, bump the weld
button until the blade is the right color.

I think I'll try the silver solder first as it's the
easiest, but for sure I'll try using the spot welder too. If
that works out, I'll do up plans/notes/photos for the drop box.

Jon