The difficulty with using an electric impact tool for that is that most all of them I've seen have a very short stroke. Actually, most of them use a rotary motion on a plate to set up the impact, so the "stroke" is only a few hundredths of an inch. Not sure how well that would work for planishing.

Air tools, on the other hand, usually have a pretty decent stroke, and I often use a muffler gun to planish sheets of metal. They sell planishing bits to fit standard .401" air chisels and I have a couple of them. They also work just dandy for upsetting the ends of bars, etc. For the noise, I just wear ear plugs and muffs over them - stops both the percussive and bone conduction noises.

Rich

Try a pnuematic air hammer like this one:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47868

You can take the chisels and cut off the ends (which are punches and cutters) and grind down to form slightly radius'd shapes or weld on a larger piece of steel for planishing or forming. Works great and cheap if you already have a compressor. Give it a try.

I have to agree with Rich here......the electric alternatives don't seem to move enough material. I too have used the hand held air hammer to texture sheets of copper. Makes quick work of a 4'x8' sheet. Also done some large scaled repousse with the same approach.
Bill

Hi all: well,everybody is pointing at air hammers.That is exactly what I needed,a relyable source of information from people who`s had experience with them, or simply know better. So only rest to thank Richard, Bill, Will, and the visitor too. Great! Nelson.