Tube Markup and Phasing

What’s your workflow? What do you view as a must do, nice to do, and don’t really need to do?


  • Marking butts, centerlines, compass points, cut references…
  • How many tube blocks on TT, DT, ST? Do you move them around during a build?

I mark butts on my main tubes by looking inside them with a ceiling light shining through and using a piece of brazing rod as a depth gauge. Then mark on the tube. It’s really easy to see the butt ramps. You don’t need mm precision here.

The main tubes get a Paragon tube block positioned to hopefully avoid any future bottle bosses. I measure the gaps in the tube block and adjust until they’re equal.

I hand tighten the bolts on the Cobra Miter Daddy and use a large machinist’s square on the mill table and set it against the tube block to phase it. Then snug the bolts down. Repeat for the second cut.

For measuring cut lengths, I use a 40" vernier caliper, some layout dye, and a scribe.


How tight do you go on the Miter Daddy? /do you clamp down with one or both of the tube holders? I just got it and have been a little afraid of dimpling the tubes, but have also had a scoche of slippage.


I mark butts via the shining light method and also roll the tube on the surface plate and mark the center line in line with the bow in the tube. I also check the run out if there is an excessive light gap. I use mitre templates a lot so tube blocks aren’t fixed. I also do all of my tube additions ie. bottle bosses, cable stops, internal lines, front hanger etc. before joining any tubes together.


I use both holders whenever possible. It’s hard to say how tight, maybe between 2-4Nm. Less than a stem bolt but more than a water bottle bolt maybe.


Awesome thank you so much! Great reference points.

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Here is how @Neuhaus_Metalworks indexes a bent downtube:

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Thanks everyone. @manzanitacycles @DEVLINCC I took a peek through my tubes, it seems pretty clear this is the ramp, right?


That’s probably it. The ramp is usually more polished than the rest of the tube.

I’ve always just marked the butts based on the manufacturer’s tube specs. Is there reason to doubt those specs?

Also, it sounds like I should buy a set of individual tube blocks from Paragon so that I can leave them on the main tubes for the duration of the mitering operations. I have been using the nifty “three-fer” blocks I bought from UBI when I took their framebuilding course. They’re great, but not meant to leave in place on the tubes.

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It’s very common for butts to be out of spec.