Frame building basics #1 - common threads found on bicycles

 - Introduction

Bicycles that were built in the last 20-30 years have a set of common threads that are used for parts and accessories. While many manufacturers use common bottom bracket threads, children's bicycles and BMX bicycles have a different bottom bracket size and thread.

 - Bottom bracket (Please note that these threads are cut to 55 degrees (included angle)):

Imperial – 1-3/8-24 TPI . Meaning that the diameter of the thread is 1 inch and 3/8ths with a thread pitch of 24.

Metric – 34.80x1.05mm. Rarely used in metric standard, since all taps and dies are according to Imperial standard.

Please note I am not including French, Italian bottom bracket sizes as they are less common these days.

 - Accessory lugs (bottle cages etc):

 

Imperial – 3/16-24 TPI. Thread is 3/16ths in diameter with a thread pitch of 24.

Metric – M5x0.8. Thread is 5mm in diameter with a pitch of 0.8mm.

 - Rear derailleur hanger(that connects the derailleur to the hanger):

Imperial – none as far as I know(please email me if you have this info)

Metric – M10x1.0. Thread diameter is 10mm with a pitch of 1mm.

 - Rear hub axle threads (for cone nuts and locking nuts. While the sizes are similar, they are not interchangeable):

 

Imperial – 3/8-24 TPI.

Metric – M10x1.0.

 - Quick release sqewers:

 

Imperial – 3/16-24 TPI. Thread is 3/16ths in diameter with a thread pitch of 24.

Metric – M5x0.8. Thread is 5mm in diameter with a pitch of 0.8mm.

 - Thru-axle sizes (double check before buying replacements):

Metric: M12x1, M12x1.25 and M12x1.75mm. While the diameter is the same, the thread pitch is completely different (1mm is fine thread, 1.75mm is coarse thread and are NOT combatible).

 

Please note - all articles will be updated every few weeks with new and available information.