American threads mainly found on HD HR Holdens

National fine ( NF or UNF ) and National Coarse ( NC or UNC ) threads were standardised in 1918 amalgamating the American Society of Mechanical engineers (ASME) and the Society of Automotive Engineers (SAE)

Both UNC and UNF have a thread angle of 60o

   UNF         UNC       UNEF    
Dia (inch) TPI Basic Dia   Dia (inch) TPI Basic Dia   Dia (inch) TPI  
No 8 36 0.164   No 8 32 0.164        
No 10 32 0.190   No 10 24 0.190        
No 12 28 0.216   No 12 24 0.216   No 12 32 0.216
1/4 28 0.25   1/4 20 0.25   1/4 32 0.25
5/16 24 0.3125   5/16 18 0.3125   5/16 32 0.3125
3/8 24 0.375   3/8 16 0.375   3/8 32 0.375
7/16 20 0.4375   7/16 14 0.4375   7/16 28 0.4375
1/2 20 0.500   1/2 13 0.5   1/2 28 0.5
9/16 18 0.5625   9/16 12 0.5625   9/16 24 0.5625
5/8 18 0.625   5/8 11 0.625   5/8 24 0.625
3/4 16 0.750   3/4 10 0.75   3/4 20 0.75
7/8 14 0.875   7/8 9 0.875   7/8 20 0.875
1 12 1.00   1 8 1.00   1 20 1.00
                     
                    e&o.e.

 

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