#1
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Secrets to no undercutting?
I'm working on an old grille to send for chrome plating and I'm filling the little dings etc silicon bronze but I'm getting this undercut at the edge of the weld, how do I avoid it?
I'm Tig'g. Thanks, Oj
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oj higgins |
#2
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Hi,
It is a little hard to explain. Run the current level high enough for your first pass to get enough penatration/adhesion. Make a second pass at a much lower current setting to make a cold weld to fill in the under cut. I define a cold weld as a bloppy, tall bead. The current level is just high enough to melt the welding rod. Hope it helps. Bill
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Bill Tromblay "A sign of a good machinist, is one who can fix his F$@& Ups" My mentor and friend, Gil Zietz Micro Metric Machine. |
#3
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Sounds like a little too much heat. Or, the metal is some sort of cast or leaded steel.
You'll aslo want to keep your arc length very short.
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Andrew Slater HANGAR 18 FABRICATION |
#4
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I manuevered and manipulated enough to get it finished, I'm thinking the undercutting might have been into the original brass under the chrome! Isn't that what the chrome shop does as part of the plating, a layer of brass or copper?
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oj higgins |
#5
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OJ, Are you tigging SiBr onto a brass grille? HAs the chrome been stripped off already? You might be digging a hole when you could be sanding your fill smooth ....?
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. |
#6
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Good chrome over base metal is usually copper nickle, chrome
polished after each layer. I usually have the chrome people strip to base metal since they will be doing anyway. Then I make the repairs ( no soft solder as the buffer can pull that out and you'll have dips) If the chrome shop has good buffers the copper can be moved around a bit and level slight divets. For cheapie replating brass If I recall the chrome layer is right over the polished brass. Ron
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Ron |
#7
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That is/was likely your problem. Low melting alloying elements will do things like that. If you encounter a chunk of "steel" doing the same thing, it is usually a free machining leaded steel like 12L14.
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Andrew Slater HANGAR 18 FABRICATION |
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