"Steve B" wrote in message
...
I have noticed there are two types of cutters for sheet metal. One a
nibbler, one a shear.

The one nibbler I see apparently cuts out small pieces, almost circles,
and imagine that would be for very fine work. The other "nibbler" has two
blades that are about 3/4" long that go up and down, pinching and shearing
the metal.
The third is a shear, much like a pair of electrified scissors.
A brief description of each and its use would be appreciated. When it
comes down to it, I will probably need all three for various stuff.

This one:
http://www.grizzly.com/products/Pneu...Nibbler/T23085
punches out crescent-moon shaped chips with devilishly sharp points. Mine's
inaccessible behind firewood now. IIRC you can't directly see the cut line
and have to offset the guide or drawn line. They cut fairly tight curves.

http://metal-engravings.com/wp-conte...al-Tools04.jpg
has two stationary blades straddling one that pivots up and down, like twin
scissors. It's the one that sometimes jams on me. They cut larger diameter
curves. If you make blind cutouts with them the corners will need cleanup.

I haven't tried other hand-held powered versions.

And lastly, I see some run on air. If one has a good compressor, is there
any important differences between the electric and air models?

Mine are all air so I don't risk sharp edges or splinters cutting into a
power cord.

This is going to run a few bucks, so wanted to ask first.
And is buying refurbished worth the savings or not? Problems later vs:
new?
Steve

No idea. Mine are cheap imports that don't get much use.

jsw