PVD Tube Butt Gauge
From Pvdwiki
Every framebuilder needs a way of measuring where the butts and tapers within a tube begin and end. I finally got around to making a simple tool to do this after seeing a similar one built by Shand Cycles.
I made my tool quite a bit more ridgid than theirs. I used solid bar welded to 1/2" plate and a precision clamp over a 440C ball bearing. The tool is still quite flexible, so I suggest going nuts on ridgidity when making one of these tools.
This gauge will measure butts up to 300mm.