Photos of main tube mitering fixtures for bridgeport

[ftwelder]

I have the same type of stuff you guys have but have always wanted to explore making the tube holding blocks that move with the tube rather than staying in the machine to help keep weird tubes in phase.

[back40]

Hi -- Nice work! I'm a fan of abrasive mitering as well. Mind if I ask a few questions?
Do you hog out material manually (shears/nibbler/bandsaw) prior, or do you do the entire miter w/ the abrasive?
What do you like for grit/abrasive?
Do you use dif grit/abrasive for carbon than for steel?
Any heating issues w/ resin in the carbon?
THx, JF

-For steel I cut the tubes off at the miter angle leaving a 1/16" extra material. For the carbon tubes I don't bother, just cut to length.
-I've tried a variety of belts and found that course 50-80G seems to work well with steel. I'm still experimenting with the carbon but 80G works well so far.
-Cutting the steel can get a little hot near the thin tips. Carbon gets warm but I tend to cut it with a slower feed rate to avoid heating it too much.

[back40]

I have the same type of stuff you guys have but have always wanted to explore making the tube holding blocks that move with the tube rather than staying in the machine to help keep weird tubes in phase.

The thin V blocks on my fixture come off the rail easily and stay clamped on the tubes. I tend to leave them on the tubes until I've fit them in the jig. That way I can put the tubes back on the mill and cut another .01" off if I want and not worry about position, angle or orientation. The clamp closest to the cut is located in a slot for accurate placement back on the rail.
back40 bicycleworks: Tube Cutting and JIG Fitting

You can see the thin V blocks on the down tube in the jig here.
back40 bicycleworks: Test Frame

[afwalker]

Did you make the abrasive mitering tool yourself?
It's looks very well done, I wonder if you have some plans for it or the name of who did build it for you?
I'd like to try to make one.
cheers
andy walker

[back40]

I made the tool myself. No plans available and I would make a few changes if I built another. It needs more adjustment range for a wider range of mandrel sizes. The crowned roller on the spring loaded end tracks Ok but could be better. The belt wanders as it heats up depending on where the cut is taking place. An attachment to collect dust and grit would be handy as well. I may rebuild it for my small horizontal mill as a dedicated tube mitering setup.

Glen J
back40 bicycleworks