Fabrication Notes -- Tapping and Clearance Drills for Number Machine Screws

Fabrication

Tapping and Clearance Drills for Number Machine Screws

Screw Size					Tapping Drills				Clearance Drills
Number	Threads/Inch	Series	Nominal Diam. (in.)		Drill Size (65-75% thread)	Equivalents			Close Fit		Free Fit
Number	Threads/Inch	Series	Nominal Diam. (in.)		Drill Size (65-75% thread)	(decimal)	(mm)		Drill Size	Dec. Equiv.	Drill Size	Dec. Equiv.

000	120		0.0340		71	0.0260	0.6604		65	0.0350	62	0.0380
00	90		0.0470		65	0.0350	0.8890		3/64"	0.0469	55	0.0520
0	80	NF	0.0600		3/64"	0.0469	1.1913		52	0.0635	50	0.0700
1	56	NS	0.0730		54	0.0550	1.3970		48	0.0760	46	0.0810
	64	NC			53	0.0595	1.5113
	72	NF			53	0.0595	1.5113
2	56	NC	0.0860		50	0.0700	1.7780		43	0.0890	41	0.0960
2	64	NF	0.0860		50	0.0700	1.7780		43	0.0890	41	0.0960
3	48	NC	0.0990		47	0.0785	1.9939		37	0.1040	35	0.1100
3	56	NF	0.0990		45	0.0820	2.0828		37	0.1040	35	0.1100
4	36	NS	0.1120		44	0.0860	2.1844		32	0.1160	30	0.1285
	40	NC			43	0.0890	2.2606
	48	NF			42	0.0935	2.3749
5	40	NC	0.1250		38	0.1015	2.5781		30	0.1285	29	0.1360
5	44	NF	0.1250		37	0.1040	2.6416		30	0.1285	29	0.1360
6	32	NC	0.1380		36	0.1065	2.7051		27	0.1440	25	0.1495
	36	NS			34	0.1110	2.8194
	40	NF			33	0.1130	2.8702
8	32	NC	0.1640		29	0.1360	3.4544		18	0.1695	16	0.1770
	36	NF			29	0.1360	3.4544
	40	NS			28	0.1405	3.5687
10	24	NC	0.1900		25	0.1495	3.7973		9	0.1960	7	0.2010
	30	NS			22	0.1570	3.9878
	32	NF			21	0.1590	4.0386
12	24	NC	0.2160		16	0.1770	4.4958		2	0.2210	1	0.2280
	28	NF			14	0.1820	4.6228
	32	NEF			13	0.1850	4.6990
14	20	NS	0.2420		10	0.1935	4.9149		D	0.2460	F	0.2570
14	24	NS	0.2420		7	0.2010	5.1054		D	0.2460	F	0.2570

Number	Threads/Inch	Series	Nominal Diam. (in.)		Drill Size (65-75% thread)	(decimal)	(mm)		Drill Size	Dec. Equiv.	Drill Size	Dec. Equiv.
Number	Threads/Inch	Series	Nominal Diam. (in.)		Drill Size (65-75% thread)	Equivalents			Close Fit		Free 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: JavaScript Calculator for converting between inches and 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); JavaScript Calculator for calculating tap drill size.

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]; JavaScript Calculator for calculating diameter of number screw.

Pitch (in.) = 1 / (Threads per Inch): example: Pitch of 32 threads per inch is 0.0313 inches (0.0313 = 1/32); JavaScript Calculator for calculating pitch.

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This page is for INFORMATIONAL PURPOSES ONLY.

Page author: Dawn Rorvik (rorvikd@evergreen.edu)
Last modified: 01/28/2001