After building a few frames I felt the need to build myself a tube butt gauge. When building a frame the tubes have a “short butt” and a “long butt” (pause for jokes…… 🙂 ). A butt is when the tubes are thicker at the ends (near the joints) for strength. The manufacturer of the tube often paints one end to identify the short or long side. Columbus , for example paints the short butt.
Why? The short butt is the starting point. Make your first miter there then, when you trim the tube to length the long butt will leave you enough thicker wall to braze (or weld) on.
Just to make sure I have my butts in order I figured I’d make this simple gauge.
The idea is to have two posts run parallel and about an inch apart, with a dial indicator perpendicular to measure the difference.
This will be the base that holds the two posts apart and parallel.
While I braze bike frames I can still tig weld…. sorta. Ha!
The top hole holds the dial indicator and the bottom hole is tapped for a 10-32 screw. The screw supports the ID of the tube.
The final product.
You might not be able to read what’s written on the tubes so I’ll type it out. Where the indicator is in the above pic the tube is .038″ thick. Then the wall thickness tapers to .024″ thick.
Henry James / True Temper shows this very well. The butt on the left is the short butt.
Thanks for checking this out. Leave a comment if you like it. 🙂