On Sun, 06 Apr 2008 02:40:08 GMT, Dan@ (Dan ) wrote:

What is DOM?

Drawn Over Mandrel.

All pipe and steel tubing is made from strip stock that is folded
into a tube and the seam is butt welded. The mandrel drawing process
smooths out the welding seam left on the inside of the pipe for extra
strength, and makes sure there are no burrs on the inside of the
tubing.

For electrical conduit burrs on the inside are very bad, they cut
the wire insulation and cause shorts. For telescoping tubing internal
seams are bad, because they block you from sliding the next smaller
tubing inside that one.

-- Bruce --