I have built the odd bike frame. Usually visit the local tip, grab a BSO and chop the BB, head tube and drop outs out to make the whole task a simple ‘weld a bunch of tubes together’ exercise.

I would like to step my game up a notch.

Can anyone help me with proper eng. drawings for ‘normal’ BB shells (to take MTB BB’s) with thread call out and head tubes with dimensioning and limits and fit tolerances so I can get my own designs made locally? So far only used 1 1/8″ as thats all what the bin man had in stock, but would like to use 1 1/2″ or 44mm to fatten up the front end.

Any help would be greatly appreciated.

Not many frame builders make their own bottom bracket shells. They are cheap to buy. I’d concentrate on making good frames.
Check out these guys:
http://www.thebicycleacademy.org/
http://www.btr-fabrications.com/

This lot do some good stuff;

http://www.paragonmachineworks.com/cgi-bin/commerce.cgi?search=action&category=0001

do dropouts, headtubes etc too.

$6ish for a steel BB shell

Thanks for links guys, some interesting drop out designs in there. But I definitely want to get my own made locally to give me some more freedom with regards to outside dimensions and shape, therefore require the specific call outs for internal sizing and threads from drawings.

this description has all the thread sizes for the BB shell on it;

This bottom bracket shell is machined from 1.5″ x .083″ wall 4130 steel tubing. The outside diameter is the the stock tube diameter. The width is 68.5 mm, supplied 0.5 mm oversize to allow clean up after welding. The threads are 1.370″-24, right and left hand; thread length is 0.50″. The left hand thread is identified by a radial groove on the face of the shell. The minor diameter of the thread is 1.330″/1.340″ and is relieved on the inside diameter to 1.385″/1.395″.

Thanks wwaswas, trying to work as well as keep one eye on here, missing crucial info as a result. I will delve deeper into the web site later tonight.

they have full drawings for a lot of the other stuff they do, too – like break mounts and dropouts.