Andrew R Stewart 

After you miter a bunch of tubes for a bunch of frames and you go through the various attempts to quicken up the process you learn which method works well for your skills, tooling and needs. No other way to say it. Practice and experimention go a long ways to teaching how to do a miter well and quickly.

I started with tube blocks, a vice and file then comparing to a drafting for angle check. Then I bought a notcher and found that the angle does drift from the set one, the centering isn't spot on and I would finish off the miter with tube blocks and file any way. Then I had access to a mill with a very solid tube fixture. Much better initial cut with very little filing after. But that's a lot of tooling and $. Now I rough cut with a hacksaw, bench grinder to a close fit and file to finish. Takes about 15 minutes each if I'm drinking a beer, maybe twice that for the second miter on the top tube.

I bought a used belt sander miter device last year but haven't yet set it up and checked it out. I plan to still rough grind the miter first to lessen the time and wear to the belts. It will be next winter before my new house's shop is done and I also have the time to build frames again. Andy.

duanedr 

I file all of my miters - it seems like chucking up a tool and aligning everything would take just as much time. For the chainstays, it's fiddly business but has worked well on both of my 2 frames to date. I've been too cheap to purchase anything to do it by machine. I file each stay as perpendicular to the ovalization as I can and at an angle so when lined up to the BB, it angles out to provide the right dropout spacing. From there, I just fiddle with it to get it just right. I made a little dummy axle/holder fixture to hold the chainstays at the right point to provide BB drop/spacing and then tack them to the BB. I find that a large (10 or 12in) half round file has the right contour to match the BB shell so that makes that part pretty easy.


I was at a local builder's shop and they had a custom made belt sander set above a rotary table that had tubing clamps and a spot for the chainstay jig and they could just rotate the table, and push the tube against the belt to grind the miter. That seemed like a fast/accurate/reliable/repeatable way to do this. They had many machines all set up for one step in the process.

Scooper

This month's EAA Sport Aviation has an interesting tip in the "Hints for Homebuilders" section on shaping chromoly tubes. I'm going to try this using tubemiter templates on my next project.

fietsbob

spent a couple days Mid Bike tour with a Nottingham frame builder to the Pros, including Raleigh team riders , there was a rack of half round files
in the basement of the 500 year old house he used for his shop.