On Wed, 20 Jun 2018 06:36:20 -0500, Terry Coombs
wrote:

Had another chat with the glass bead maker that wants me to fabricate
some tooling . She needs some mandrels made that are a piece of tungsten
rod welded/brazed to a stainless steel handle . The join is not subject
to the full heat of molten glass . Am I right in assuming that a TIG
torch set on DCEN will melt and fuse these two metals without filler ?
What filler is recommended ? I have on hand 308 309/309l , and some 312
in various sizes . I also have some ER70S2 on hand and some Invar42
nickel/iron filler . She indicates that these must be pretty straight ,
no wobbles when they are spun or rolled across a flat surface . I'm
thinking a long vee block with a cutout in the middle , maybe a spring
on one end to keep things pushed together . We're getting into uncharted
territory here for me , I'm open to suggestions - that pertain to the
task at hand , please .
You will not be able to TIG weld the tungsten to the stainless with
any reasonable success. But you can silver braze to tungsten easily.
And with silver brazing, AKA silver soldering, you can get the two
pieces quite coaxial. Drill a hole that is about .500" deep and a
light press fit for the tungsten into the stainless. Then open up the
hole about .004" over the diameter of the tungsten but only about
..190" deep. Grind or file a small flat on the tungsten that is about
..550" long. The flat acts as a vent to allow any air trapped in the
hole to escape. So it doesn't need to be very big.Then press the
tungsten into the SS and silver solder it in. Of course make sure
everything is clean.
Eric