Tight welding in a keyway slot...

[Crack of Dawn]

I'm welding a worn corner on a 3/8" keyway slot using TIG and I do not want my arc to drift . In fact, I would like to cut a small brass bar and lay in in the slot to dam the molden metal so only the bad side will get any deposit. Any suggestions for insulating in the vicinity of the arc with something that will take the heat? TIA

[Franz]

Use a carbon block instead of brass. Break the carbon out after the weld cools.

[Guest]

I agree with Franz...the carbon block is the way to go.

[Crack of Dawn]

Tuesday's Weld

Great, carbon it is.

I'm going to show my age and ask an old welding joke from the sixties. If you're under 45, this might not make any sense.

'If Tuesday had a tourch, could she Weld?"

[Crack of Dawn]

Additional information requested:

"Carbon block" please define. Is this something like a square carbon brush (removed from an electric motor) used to block the weld?

I've been searching MSC for a source and was thinking along the line of a square carbon rod that could be cut, much like a brass bar. Graphite rolls run above 50 bucks, so I don't think you mean that.

Please recommend common source for carbon blocks.

Sincere regards,

Crack of Dawn

[Guest]

The carbon block we have is a solid blocks of various thicknesses. I think the last one I saw was 1" x 4" x 12" solid carbon that you can grind or machine to the right size. Don't know where it came from.

Oh, yeah, I forgot we used carbon air arc gouging rods, too. They come in fairly large sizes. I forgot just how big, though. Be sure and remove the copper coating.

Hope this helps.

[Franz]

I get mine from my welding supplier. Just machine the carbon to the shape of the key, and weld up to the carbon.
The unique property of carbon is that it shrinks when heated, rather than expand, so you can fill in next to a carbon block, and only have minimal machining to do post welding.
Carbon can also be found from motor brush manufacturer/suppliers.
One thing I caution against, do NOT use the carbon rod from an old battery, don't ask.