"Jimmie D" wrote in message
...

"JB MacDonald" wrote in message
. ..
I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for example
a 20 foot pipe , or tubing . If we had a 20 foot layout table fine , clamp
pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Use a Loooong v block, a piece of angle or channel iron/aluminum.

OR use a couple of short one with a drill press. The last time I did this I
used a v bolck to dril a hole through the end of the boom the placed a 3 ft
piece of all thread through the boom and hung a 20lb weight on the other
end of the all thread. Gravity will now keep things in a straight line.