On Sun, 21 Sep 2008 09:08:12 -0700 (PDT),
wrote:

On Sep 21, 12:05 am, Jon Anderson wrote:
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



I built a band saw blade welder in the early '90's... It was briefly
described in HSM and Projects in Metal #7 IIRC.

The most important parameters are stick-out of the blade ends from the
clamps, upsetting force, shut-off of welding current at the end of the
upset stroke, and post-weld annealing.

The actual welding current is not THAT critical it the current is shut
off automatically at the end of the welding stroke. If the current is
way too high the band saw blade ends will disappear in a shower of
sparks; too little current and the weld is incomplete. Between these
two limits there is considerable latitude.

There are some very good power control circuits published on the 'net
using 40 amp triacs. At 220 VAC that ought to be enough for any band
saw.

After successful welding the annealing process makes or breaks the
joint. Follow the directions on the blade container TO THE LETTER. I
learned this the hard way. For example on my DART blades box it
says: "Anneal in subdued light to faint red." Following this rule I
found every weld a winner.

Wolfgang


Ive got 3 commercial blade welders, and damned if I can get any of
them to work properly.

Id be tickled to have someone snag all 3, fix em up and give me back
one that works properly and they could keep the rest.

Gunner

"Obama, raises taxes and kills babies. Sarah Palin - raises babies
and kills taxes." Pyotr Flipivich