On Mon, 18 Feb 2008 18:45:29 GMT, Grant Erwin
wrote:

I have a 4" tube which I want to scribe lines on. The two lines will be
parallel to the tube axis and should be exactly 180 degrees apart, i.e.
on the opposite sides of the tube.

I know how to draw one line down a tube, but I am looking for a good trick
to locate the other line.

Ideas?

Grant

Clamp tube to bench. Set height gage for 1/2 tube dia. Scribe both
sides of tube.