On Wed, 14 Jul 2004 03:37:17 GMT, Rich Grise wrote:

on Tuesday 13 July 2004 06:02 pm, Eric R Snow wrote:

Greetings to all the microwave oven scroungers,
I have a job coming up that requires soldering the corners of brass
frames. These frames are made of 1 1/2 x 1 1/2 x 1/4 brass angle. In
the past I've used a torch to heat the brass. This leads to a little
distortion. This can be troublesome because the brass expands so much
that it moves the joint even though everything is clamped. The parts
must then be straightened when cool. Because of the application and
fit the frames must be straight within .010" in 36".

All you need is to work on your torch technique. Try preheating.
There's a NG - news:sci.engr.joining.welding where they discuss this
sort of thing. And don't use OA - use propane/air. (i.e. Bernz-O-
Matic o.e.)

I've seen spot welders (well, web pages with them) that used a
microwave transformer, and they replaced the secondary with
enough turns of wire to get 4V. That sounds like a good starting
ballpark. Use #2 or #4 weld cable, and big copper electrodes.

A simple timed on-off switch should work, like a 555 one-shot,
tranny, and relay (or SSR). You control the heat by on-time.
You might even be able to use the SSR out of the microwave
itself. :-)
My technique is not the problem. Even preheating the whole frame does
not solve the problem. I'm good at this. Had lots of practice. It's
because of the really close straightness tolerance.
ERS