Pedal Threading

Very useful if you have an old bicycles from france and you want to change the pedals...  

Standard-3-piece cranks             
9/16" (0.56") x 20 tpi    14.28 x 1.27 mm  
One-piece (American) Cranks   
1/2" (0.50") x 20 tpi       12.7 x 1.27 mm  
Old French                                    
0.55" 20.32 tpi             14 mm x 1.25 mm 

More information at sheldonbrown