Fabrication

Tapping and Clearance Drills for Number Machine Screws

Screw Size Tapping Drills Clearance Drills
NumberThreads
/Inch
SeriesNom. Dia. (in) Drill Size
(65-75% thread)
Equivalents Close FitFree Fit
(decimal)(mm) Drill SizeDec. Equiv.Drill SizeDec. Equiv.
000120 0.0340 710.02600.6604 650.0350620.0380
0090 0.0470 650.03500.8890 3/64"0.0469550.0520
080NF0.0600 3/64"0.04691.1913 520.0635500.0700
156NS0.0730 540.05501.3970 480.0760460.0810
64NC 530.05951.5113
72NF 530.05951.5113
256NC0.0860 500.07001.7780 430.0890410.0960
64NF 500.07001.7780
348NC0.0990 470.07851.9939 370.1040350.1100
56NF 450.08202.0828
436NS0.1120 440.08602.1844 320.1160300.1285
40NC 430.08902.2606
48NF 420.09352.3749
540NC 0.1250 380.10152.5781 300.1285290.1360
44NF 370.10402.6416
632NC0.1380 360.10652.7051 270.1440250.1495
36NS 340.11102.8194
40NF 330.11302.8702
832NC0.1640 290.13603.4544 180.1695160.1770
36NF 290.13603.4544
40NS 280.14053.5687
1024NC0.1900 250.14953.7973 90.196070.2010
30NS 220.15703.9878
32NF 210.15904.0386
1224NC0.2160 160.17704.4958 20.221010.2280
28NF 140.18204.6228
32NEF 130.18504.6990
1420NS0.2420 100.19354.9149 D0.2460F0.2570
24NS 70.20105.1054
NumberThreads
/Inch
SeriesNom. Dia. (in) Drill Size
(65-75% thread)
(decimal)(mm) Drill SizeDec. Equiv.Drill SizeDec. Equiv.
Equivalents Close FitFree Fit
Screw Size Tapping Drills Clearance Drills


Notes

Thread Series
National Coarse (NC)
National Fine (NF)
National Extra Fine (NEF)
National Special (NS)

1 inch = 25.4 millimeters

Tap Drill Size (65-75% thread) = Nominal Diameter - One Pitch Length
example:  Tap Drill for #6-32 NC screw is #36, closest drill to 0.1067 inches (0.1067 = 0.1380 - 0.0313)
Nominal Diameter of Number Screw (in.) = (Screw Number x 0.0130) + 0.0600
example:  Nominal Diameter of #6 screw is 0.1380 inches [0.1380 = (6 x 0.0130) + 0.0600]
Pitch (in.) = 1 / (Threads per Inch)
example:  Pitch of 32 threads per inch is 0.0313 inches (0.0313 = 1/32)

Other Resources


[  Index  |  Technical Notes  ]

DISCLAIMER

Page author: Dawn Rorvik (rorvikd@evergreen.edu)
Last modified: 05/20/2003