Nonconductive tailstock/tooling material

Date 01-04-2006 16:00

Hello: We have to replace our tailstock fixtures frequently due to arc wander and flash. We GTAW 1/4" diameter rods in automatic lathes. The weld pool is about 1/4" from the tailstock. Is there a material that is non-cunductive and relatively tough that we can machine? The tailstock is pneumatically driven so it can not be brittle. It could be a coating or plating. I thought about ceramics but I do not know enough about them. Any ideas?? We're using about 40 amps, DCEN. Fixture temperature would not exceed 300° F
Bob V had suggested isolating the tailstock base. Good suggestion but the current path through the part is still active.

By RonG

Date 01-04-2006 17:24

Not sure I under stood "the current path through the part is still active". If the Tail stock is insolated there is no current flow in it.

Where are you placing the ground?

You might consider Micarta. It is very good in such applications.

Have you tried a ground strap ( Flat woven Copper) that rides on the work?

By captaintom62 (*)

Date 01-04-2006 17:43

The weld puddle is very close to the tailstock. The end of the part has no center so we use a female concaved cone to center the part. So the tailstock fixture is larger in diameter than the part. Shorter distance = better arc path = problem.

The "Ground" is connected through the Head stock. Occasionally the arc will wander through the tailstock then through the piece and then home to the headstock completing the circuit. Micarta might work. I will look into it. Thanks, tom

By Bill M

Date 01-04-2006 18:13

As Ron asked, where exactly is the ground? Is your current path on a rotating ground on the far end of the headstock shaft...or are you clamping the ground on the frame of the lathe and welding through the headstock bearings?

By captaintom62 (*)

Date 01-05-2006 16:44

You are correct in that the ground is connected through the head stock on a rotating DC brush system.

By RonG

Date 01-05-2006 17:27

If possible you should look into the flat woven Copper ground strap and hang it down both sides of the work (add some weights to each end).

We sometimes use this on technique on million $ + tubine rotors with no problem.

By Bill M

Date 01-05-2006 18:01

If the current is intermittently travelling through the tailstock end, there must be a better path of least resistance there. Has this always happened, or is this a recent occurance?

Are you welding with high frequency on continuously or just at the start?

As Ron suggested to totally isolate the tailstock: take off the tailstock, mill the bottom the Micarta thickness, glue the Micarta, scrape it flat, re-align the tailstock.