Quote:
Originally Posted by crystallographic
Pinpoint shrinks are done with a sharp, hot (oxidizing) flame.
Point the torch flame straight down (90deg to panel) and with the inner cone a nickel's thickness away. Count one-two, and pull flame off and hit the metal with the flat-faced hammer. (Hold the hammer and torch with the same hand - the torch won't mind the bouncy ride, if the pressure is right.)
Back your work with a 2" thick block of wood, about a 4" X 4" face. This avoids stretching, and adds a romantic aroma to the shop.
Remember that the metal keeps shrinking until it is ALL the same ambient temp. I have measured for this, many times.
Hammer until the metal is only warm to the touch - then wipe with a wet rag - no hissing allowed, just steam.
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Thank you, I have a great excuse now to get some oxy/acetylene tanks and pull my torches out of storage. So much you can do with them compared to MIG.