Marking tube centrelines

[Ben Hudson]

Currently I clamp tubes in v-blocks, lay them on the table and run the edge of another block down each side in turn to scratch two centrelines exactly 180 degrees apart, but recently I’ve gotten annoyed by how the hardened-but-not-very-sharp edge of the block doesn’t leave the fine sharp line I’d really like. Consequently a couple of bottle bosses have gone a bit awol and required time-wasting rectification.

Having used one with success in the past I think what I really need is a block with sharp ground corners, but I thought I’d first ask whether anyone else has any good alternative techniques.

Cheers
Ben

[e-RICHIE]

I take a flat file, smooth cut, any length, and drag it along using my eye as a guide.

[Amaro Bikes]

Never underestimate the eye accuracy

[jon_norstog]

I use small aluminum angle extrusion and a sharp scriber or a black marker. As long as the tube is straight, this will give you a straight line on the tube. Works well for lining up bottle bosses, cable stops, etc. I also use them to position decals properly on the finished frame.

jn