US screw sizes

Drills for screw holes

Screw size75% thread50% threadForming tapClearance
#0-803/64”55(54)52–50
#2-565049(5/64”)43–41
#4-4043413932–30
#6-3236321/8”27–25
#8-3229272518–16
#10-242520(11/64”)9–7
#10-322118(16)9–7
#12-241612(9–8)2–1
1/4”-2077/32”(1)17/64”–9/32”

Use 75% thread for aluminum, 50% for steel. Forming taps are spec’d for 65% thread. Numbers in parentheses indicate that I do not have a forming tap for that screw size.

Dimensions of socket cap screws

Screw sizeMinor diam.Major diam.Head diam.
#0-800.045”0.060”0.096”
#2-560.070”0.086”0.140”
#4-400.089”0.112”0.183”
#6-320.100”0.138”0.226”
#8-320.126”0.164”0.270”
#10-240.139”0.190”0.312”
#10-320.152”0.190”0.312”
#12-240.165”0.216”0.324”
1/4”-200.189”0.250”0.375”

Note: Head height is the same as major diameter for all sizes.

Head diameters of flathead screws

Screw sizeHead diam.
#00.112”
#20.162”
#40.212”
#60.262”
#80.312”
#100.362”
#120.412”
1/4”0.477”

Note: Head angle is 82°.

Sources