T47 BB Facing on a Bridgeport?

I’m finishing up my first TIG build with a T47 on it. For my previous builds I ended up making all my own BB chasing and facing tools and taps (for English BBs).

I got the taps made for T47 but I’m not happy with how my facing tooling ended up.

Anyway, I’m wondering if anyone has ever just dialed in the BB internal threads really well on a Bridgeport, face one side, then flip and face the other?

It sort of feels like the “line boring” style facer is used most of the time because bike shops don’t have rigid machine tools at their disposal. I feel like I could get a good result just dialing everything in carefully.

1 Like

I haven’t done this, but it should work well. If you have a tool like a long T-slot cutter, Woodruff cutter, or small milling cutter on an arbor, you may be able to reach through the BB shell and face the opposite side. Do it all in one setup to save time and get both faces parallel.

As in this photo, but long enough to get through:


Thanks for the advice @mark_pmw.

I ended up getting it done on the bridgeport. Went through the tool drawers and couldn’t find anything that quite worked. I ended up making up a single flute boring tool with a flat face and parallel cutting edges top and bottom.

Facing the top side was easy but the bottom side squealed and chattered a bit but cleaned up fine with a flat stone. Took some setup and made me wish I had a horizontal mill but I got my dimensions within .001"


Nice work! .001" is probably better than you could do with a hand facer.


I know this was from a while ago but it’s peaked my interest. How are you reference the horizontalness (is that word?) of the frame on the table? Are you referencing off the top face of a tap in the BB or is that a tool you’ve made to go inside the BB?

That piece you see inside the BB is my shop made T47 tap. The faces are ground so I dialed off of that and then also swept vertically on the outside of the BB shell to double check my initial sweep. I think I got it all really parallel.

This whole setup was massively time consuming but the money that I would have to spend on the whole BB facing and chasing setup is a lot.