There's an article in the current issue of "Machinist's Workshop" which is a
review of the HF spot welder. They found the same issue with the tips you did.
They made up some out of bronze, said they worked fine. I like the idea of
drilling out for Miller tips, though. I wouldn't think you'd need any kind of
heatsink grease on a large-area copper-to-copper contact, but I still think
that's what that white stuff was. Might try a dab on an ordinary nut/bolt and
see if it binds up, then I'm wrong. Copper is notorious for sticking when
machined, maybe the tap tore something which bound up. I might try a steel
3/8-24 SHCS and run it into the newly-threaded hole in the tong and make sure it
bottoms out cleanly before you try the Miller tip again.

I had a Miller MSW-41 on the pedestal awhile ago, real nice machine, took up too
much space though, so I sold it. I've been monkeying some with sheet metal
lately and have wondered about the little HF unit. Timely writeup, thanks.

GWE

JR North wrote:

Anyway, this welder has never been particularly powerful. It will spot
weld up to about 18GA; any thicker, and you should pack food and water
for the wait...WTF, it's HF after all. Right? Wrong.
It started loosing serious amps, and sparked/smoked from under the
lever. The switch stuck on also. I disassembled it enough to remove the
switch. No big deal. The switch is repairable. Fixed, I thought. Well,
the switch was. Still low current and sparking under the handle.
Round 2.
Found very high resistance in the braided strap connections supplying
current to the moveable jaw. Cleaned both sides of the connection, wire
wheeled the tong ends and brushed the sockets they mount in.
Now it rocks! Welds in 18GA take less than half the time they did when
it was new. Hit the switch, and it's right there.
I drilled out the tongs and tapped 3/8-24 for Miller tips. The OE tips
suck. The Miller package contained a squeeze tube of some white goo. Oh,
something to improve the power flow through the threads, I thought.
Wrong.
It's some sort of anaerobic thread locker. Assholes!
The new Miller tip screwed in 3/4 way and stopped. Dead. It would not
unscrew. I even heated the tong red hot; just snapped the tip off the
threaded end. I drilled it out to a thin threaded barrel and collapsed
it with a small punch. Didn't touch the threads. Damn I'm good
This is a good little spot welder for light stuff if you clean up the
current path and throw some good tips on. Just watch the duty cycle.
JR
Dweller in the cellar