Common thread and fastener sizes found on Classic motorcycles.

American AF /SAE UNF UNC
spanner jaw (in) bolt diam (in) threads per inch bolt diam (mm)
    SAE Regular SAE Fine UNF UNC  
  1/8     48 40 3.17
             
7/16 1/4 36 28 28 20 6.35
1/2 5/16 32 24 24 18 7.93
9/16 3/8 32 24 24 16 9.53
5/8    
11/16 7/16 28 20 20 14 11.11
3/4 1/2 28 20 20 13 12.70
7/8 9/16 24 18 18 12 14.28
15/16 5/8 24 18 18 11 11.00
1 1/8 3/4 20 16 16 10 19.05
             
             
Metric ISO
spanner jaw (mm) bolt diam (mm)

pitch (mm)

tpi
    Fine Coarse F C
10 6 0.75 1.00 33.86 25.4
11 7 --- 1.00 --- 25.4
           
13 8 1.00 1.25 25.4 20.32
           
           
17 10 1.00*
1.25
1.50 25.4
20.32
16.93
19 12 1.25* 1.75 20.32 14.51
22 14 1.50
1.25*
2.00 16.93 12.70
24   16 --- 2.00 ---- 12.70
27 18 *1.50 2.50 16.93 10.16
* spark plug threads

 

Cycle
bolt diam (in) tpi
1/8 40
1/4 26
5/16 26
3/8 26
7/16 26 or 20
1/2 26 or 20
9/16 26 or 20
5/8 26 or 20
11/16 26 or 20
3/4 26 or 20
7/8 24 or 20
1 24
BSF
bolt diam (in) tpi
   
1/4 26
5/16 22
3/8 20
7/16 18
1/2 16
9/16  16
5/8 24
11/16 14
3/4 12
7/8 11
1 10
BSW
bolt diam (in) tpi
1/8 40
1/4 20
5/16 18
3/8 16
7/16 14
1/2 12
9/16  12
5/8 11
11/16 11
3/4 10
   
   
BSP
tube bore (in) tpi
1/8 28
1/4 19
   
3/8 19
   
1/2 14
   
   
   
   
   
   
BA
size no. pitch (mm)
0 1.00
1 0.90
2 0.81
3 0.73
4 0.66