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Old 11-29-2018, 12:20 PM
crystallographic crystallographic is offline
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Join Date: Dec 2010
Location: Western Sierra Nevadas, Badger Hill, CA
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Default TIG tacks - why? for gas welding?

Quote:
Originally Posted by Stretch View Post
Hi Kent. Why would they tack with Tig prior to gas welding? Surely that's counter productive in terms of time taken etc? I'm curious as to what would the benefit be?
Thanks, Matt

Radius joints are notorious for holding/clamping/restraining while tacking. Rolled strips of scrap can help but then there is the clamping .... and the weight of the clamps, the bulk, and three hands to do it ... non-starter for tanks, fenders, dash installs, etc etc.
Since the TIG cup can press down for the tacking moment, it is also self aligning on the radius joints.
Tacking by fusion is brief and only needs to hold for subsequent gas welding.
Otherwise, it can be a tough process as both aluminum edges expand in 4 directions when the heat is thrown in .... both edges going up or down independently and mostly never going together.
RSK dash 01322_n_17akygewna1211.jpg
I really had to fight to get this RSK dash tacked in. On the next car it was a snap with the TIG-tack method, learned from my new helper guy - who had built for Prudhomme and had also worked with both Jim Hume and Nye Frank ...


BTW - all the drag and salt tanks are gas welded. And many other race aluminum tanks - with the builders traditionally never leak-testing.
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"All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919.
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