Welding tungsten to stainless

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 .
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Perhaps you could explain to her the advantages of a press fit in a bored hole.
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On 6/20/2018 10:25 AM, Jim Wilkins wrote:

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The simplest collet I know how to make is a male pipe thread on the end of the hollow shaft, slit lengthwise after threading. The collet closer nut is a drilled pipe cap.
Making a holder for an existing collet involves boring an internal taper accurately or machining and hardening a tapered D drill or reamer.
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wrote:


Even better!
- When you radically activate on the side of the Left, you call forth compensatory forces. And they're not under your control. --Jordan B Peterson Go Trump! MAGA
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wrote:

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
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On Wednesday, June 20, 2018 at 7:36:16 AM UTC-4, Terry Coombs wrote:

I think Eric has the solution.
One more suggestion depends on the diameters of the tungsten and the stainless. If there is enough meat , you could use a set screw to hold the tungsten in the stainless.
You can get stainless set screws on AliExpess at a low price, but they will be metric.
Dan
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On 20/06/18 12:36, Terry Coombs wrote:

How about the mandrel pin vice listed here https://www.arrowsprings.com/html/holding_tools.html about 2/3 the way down the page.
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"Terry Coombs" wrote in message
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 .
I am sure you already considered silvalloy silver brazing, but silvalloy (expensive) is stronger than your regular plumbing solder and has a higher melting point. (around 1600 F I think) Having said that I kind of liked the idea of a press fit, and maybe even a mandrel fit in case differential heat expansion doesn't allow for a press fit to workwell enough. Drill, thread, and taper the end of a rod to hold the insert. Slide a threaded closer up over the other end to clamp down on the insert. If they drop it and break the insert it may be replaceable if heat cycling hasn't frozen the threads.
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