UNC Thread, Tapping Drills

The UNC thread has a 60° angle and has a flat at the tip and root of the thread, it is the same as the American standard coarse thread.

The flat is defined as ⅛ the size the pitch or Flat= pitch / 8

The thread depth is defined as 0.64951 of the pitch or Depth= pitch x 0.64951

Ø = diameter
" = inch
TPI = threads per inch

Nominal
Ø "		 TPI Pitch " Tapping drill
Ø mm
No. 1 64 0.0156 1.55
No. 2 56 0.0179 1.85
No. 3 48 0.0208 2.10
No. 4 40 0.025 2.35
No. 5 40 0.025 2.65
No. 6 32 0.0313 2.85
No. 8 32 0.0313 3.50
No. 10 24 0.0417 3.90
No. 12 24 0.0417 4.50
1/4" 20 0.05 5.10
5/16" 18 0.0556 6.60
3/8" 16 0.0625 8.00
7/16" 14 0.0714 9.40
1/2" 13 0.0769 10.80
9/16" 12 0.0833 12.20
5/8" 11 0.0909 13.50
3/4" 10 0.1 16.50
7/8" 9 0.1111 19.50
1" 8 0.125 22.25
1 1/8" 7 25.00
1 1/4" 7 28.00
1 3/8" 6 30.75
1 1/2" 6 34.00
1 3/4" 5 39.50
2" 4.5 45.00