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Cutting Threads in a Unthreaded Frame?(8 posts)

Cutting Threads in a Unthreaded Frame?beck
Aug 15, 2001 10:51 AM
Does anyone know if it possible to install threads in BB shell that was left unthreaded from the factory.It is a Easton aluminum frame that has never been threaded and there is plenty of unmachined metal in the BB shell.I dont know how why it was made this way but I am stuck with the frame.Has anyone dealt with this problem using a machine shop or otherwise?Thanks to any replies!
Most likely, yes.alex the engineer
Aug 15, 2001 11:00 AM
All BB's are initially unthreaded. This frame was probably ordered this way, so that the customer could decide which type of threading to use. A machinist can cut threads in just about anything. It all depends what type of BB threading you want (italian, swiss, or french). It only requires some money.
machine shops probably won't have those thread sizes....C-40
Aug 15, 2001 2:19 PM
I doubt that the bottom bracket threading was omitted intentionally.

As a fellow engineer, and former machinist, it's important to note that the inside diameter of the BB shell must first be verified to be correct. If it's not, boring it out at most machine shops would be costly.

The tap size for bicycle bottom brackets would be very unusual for a machine shop to have. Right-hand and left-hand taps are required, except for Italian threading, which uses right hand threads on both sides. These are oddballs common to bikes. A good bike shop or frame builder would be able to thread the BB.
No Thread BBwes
Aug 15, 2001 7:00 PM
I have an old Mavic BB that requires no threading in the BB. I think it was from '92. The thing is as heavy as a rock, but spins like nothing I've ever seen. (ok, ok, maybe Campy is a little better).

The thing just slides right in and has lockrings on both sides. Depending on the diameter of the BB shell as it currently is, and if you don't mind the extra 3 ounces, you might want to search one of these puppies out.

I have it because it will last forever and spins nice. It is heavy and will be very hard to find. If you need more info, I can take it out and figure out the model# or whatever.

BTW - It goes in my Ritchey Road Classic which is almost definitely English threaded (for BB shell size - I don't know if they are different)

No Thread BBMark Andersen
Aug 16, 2001 12:00 PM
The model is Mavic 610. They came in 114 and 118 MM widths. It requires a special "chamfering" tool that a good pro shop that has been around awhile should have.

As stated above, they are HEAVY, but will probably outlive you. Something to leave to your grandchildren. If you do manage to runout the bearings, they are easily changed.

They usually go for ~50-100 on ebay.

No Thread BBdvan
Aug 21, 2001 5:09 PM
I have a New Old Stock 114mm Mavic bottom bracket. Contact me at if you want it.
how could I forget?alex the engineer
Aug 16, 2001 3:43 AM
I's probably for one of those old press-in BB's of 10-15 years ago. The diameter might not be right for common BB's.
BTW, an engine lathe can cut any threads you want, but set-up could be costly.
re: Cutting Threads in a Unthreaded Frame?Crankist
Aug 16, 2001 7:23 AM
Hi. Make some calls to local machine shops and determine which has thread milling capabilities. Bring the frame for an estimate - this should be no chg. When you select a shop, bring the BB for fit and emphasize that your tendencies run homocidal when you see scratched bike paint. Expect to drop about $50 - $125.00.
Have Fun, Mike