Specifications of historical Thread Standards

Used in the U.S.A. until 1909. The flank angle is 60°.

Thread SizeNominal
Diameter
mm
Tapping
Drill Size
mm
TPIPitch
mm
1/4"6.354.15201.27
5/16"7.945.50181.41
3/8"9.526.78161.59
7/16"11.117.97141.81
1/2"12.709.04122.12
9/16"14.2910.63122.12
5/8"15.8711.87112.31
11/16"17.4613.46112.31
3/4"19.0514.65102.54
13/16"20.6416.24102.54
7/8"22.2217.3492.82
15/16"23.8118.9392.82
1"25.4019.9083.17
1 1/8"28.5722.2973.63
1 1/4"31.7525.4773.63
1 3/8"34.9227.5864.23
1 1/2"38.1030.7664.23
1 5/8"41.2732.4755.08
1 3/4"44.4535.6555.08
1 7/8"47.6237.844 1/25.64
2"50.8041.024 1/25.64
2 1/8"53.9744.194 1/25.64
2 1/4"57.1547.374 1/25.64
2 3/8"60.3250.544 1/25.64
2 1/2"63.5052.5045.64
2 5/8"66.6755.6745.64
2 3/4"69.8558.8545.64
2 7/8"73.0262.0445.64
3"76.2063.643 1/27.26
3 1/8"79.3766.813 1/27.26
3 1/4"82.5569.993 1/27.26
3 3/8"85.7272.183 1/27.82
3 1/2"88.9073.363 1/27.82
3 5/8"92.0778.533 1/27.82
3 3/4"95.2580.5938.47
3 7/8"98.4283.7638.47
4"101.6086.9438.47
Sharp V Thread