"Trumble" wrote in message
...
I've never TIG welded - only amateur MIG & stick welding......


As part of an assembly process would the following be possible:


I've got a 304 stainless steel tube with some electronics embedded
in polyurethane inside it.

I want to put a 304 stainless cap on the end of the tube capable of
handling say 20 kg pulling force.

When fitted to the end of the tube the gap from the cap to the
polyurethane potting material will be 1/32"



How much heat would spot TIG'ing the cap onto the tube introduce to
the assembly?

Cool it with a damp cloth immediately after welding?



SPOT TIG HERE
|
\/
======================================|====\
| |==== \
| | |
POLYURETHANE POTTING | | O |
COMPOUND | | |
| |==== /
======================================|====/
^
|
SPOT TIG HERE

|---Tube 1/2" OD x 1/16 wall----------|-cap-|




Should I be looking at threading the cap into the end of the tube?

1/2-20 is a readily available size for taps and dies. Here are the
other standard choices:
http://www.efunda.com/designstandard...=64&finish=147
1/2-32 leaves ~3/4 of your wall thickness intact.

I've been collecting 32 pitch taps and dies to cut and repair
electrical instrument threads. The F connector for video cables is
3/8-32, toggle switches are 15/32-32.

Not all lathes can cut 27 TPI but the others are easy. I cut threads
in thin-walled tubing part way on the lathe and finish with a die,
which starts straight and doesn't deform the work if it removes only a
little metal to reach final size.

-jsw