Which surface do you measure from when beveling pipe?

Answer 1

Get a piece of filler wire and put half it's length inside the top of the pipe, call it the x-axis. Bend the outer half of the wire straight up to a 90 deg. angle, call it the y-axis. The angle measured from this y-axis to the face of the bevel is the bevel angle. Put another way, measure from the perpendicular line relative to the length of pipe, to the bevel. Industry standard is a 37.5 deg bevel. Now keep your bent filler wire handy and use as a gauge to check bevel angle. The angle of the wire is 90 deg minus the 37.5 deg = 52.5 deg.