Thread dimensions & tap drill sizes

Basic dimensions per ISO 68-1 / ISO 724 and ASME B1.1. Tap drill for metric threads = D − P; for unified threads ≈ 75 % thread engagement.

ISO metric coarse thread

Size	Pitch P (mm)	Pitch Ø d2 (mm)	Minor Ø d3 (bolt) (mm)	Minor Ø D1 (nut) (mm)	Tap drill (mm)
M1	0.25	0.838	0.693	0.729	Ø 0.75
M1.2	0.25	1.038	0.893	0.929	Ø 0.95
M1.4	0.3	1.205	1.032	1.075	Ø 1.1
M1.6	0.35	1.373	1.171	1.221	Ø 1.25
M2	0.4	1.74	1.509	1.567	Ø 1.6
M2.5	0.45	2.208	1.948	2.013	Ø 2.05
M3	0.5	2.675	2.387	2.459	Ø 2.5
M3.5	0.6	3.11	2.764	2.851	Ø 2.9
M4	0.7	3.545	3.141	3.242	Ø 3.3
M5	0.8	4.48	4.018	4.134	Ø 4.2
M6	1	5.351	4.773	4.918	Ø 5
M8	1.25	7.188	6.466	6.647	Ø 6.75
M10	1.5	9.026	8.16	8.376	Ø 8.5
M12	1.75	10.863	9.853	10.106	Ø 10.25
M14	2	12.701	11.546	11.835	Ø 12
M16	2	14.701	13.546	13.835	Ø 14
M18	2.5	16.376	14.933	15.294	Ø 15.5
M20	2.5	18.376	16.933	17.294	Ø 17.5
M22	2.5	20.376	18.933	19.294	Ø 19.5
M24	3	22.052	20.319	20.753	Ø 21
M27	3	25.052	23.319	23.753	Ø 24
M30	3.5	27.727	25.706	26.211	Ø 26.5
M33	3.5	30.727	28.706	29.211	Ø 29.5
M36	4	33.402	31.092	31.67	Ø 32
M39	4	36.402	34.092	34.67	Ø 35
M42	4.5	39.077	36.479	37.129	Ø 37.5
M45	4.5	42.077	39.479	40.129	Ø 40.5
M48	5	44.753	41.866	42.588	Ø 43
M52	5	48.753	45.866	46.588	Ø 47
M56	5.5	52.428	49.252	50.046	Ø 50.5
M60	5.5	56.428	53.252	54.046	Ø 54.5
M64	6	60.103	56.639	57.505	Ø 58

Size	Pitch P (mm)	Pitch Ø d2 (mm)	Minor Ø d3 (bolt) (mm)	Minor Ø D1 (nut) (mm)	Tap drill (mm)
M3×0.35	0.35	2.773	2.571	2.621	Ø 2.65
M4×0.5	0.5	3.675	3.387	3.459	Ø 3.5
M5×0.5	0.5	4.675	4.387	4.459	Ø 4.5
M6×0.75	0.75	5.513	5.08	5.188	Ø 5.25
M8×1	1	7.351	6.773	6.918	Ø 7
M10×1	1	9.351	8.773	8.918	Ø 9
M10×1.25	1.25	9.188	8.466	8.647	Ø 8.75
M12×1.25	1.25	11.188	10.466	10.647	Ø 10.75
M12×1.5	1.5	11.026	10.16	10.376	Ø 10.5
M14×1.5	1.5	13.026	12.16	12.376	Ø 12.5
M16×1.5	1.5	15.026	14.16	14.376	Ø 14.5
M18×1.5	1.5	17.026	16.16	16.376	Ø 16.5
M20×1.5	1.5	19.026	18.16	18.376	Ø 18.5
M20×2	2	18.701	17.546	17.835	Ø 18
M22×1.5	1.5	21.026	20.16	20.376	Ø 20.5
M24×1.5	1.5	23.026	22.16	22.376	Ø 22.5
M24×2	2	22.701	21.546	21.835	Ø 22
M27×2	2	25.701	24.546	24.835	Ø 25
M30×2	2	28.701	27.546	27.835	Ø 28
M33×2	2	31.701	30.546	30.835	Ø 31
M36×3	3	34.052	32.319	32.753	Ø 33
M42×3	3	40.052	38.319	38.753	Ø 39
M48×3	3	46.052	44.319	44.753	Ø 45

Size	TPI	Major Ø (in / mm)	Pitch P (mm)	Tap drill (mm)
#2-56 UNC	56	0.086″ / 2.18	0.454	Ø 1.74
#4-40 UNC	40	0.112″ / 2.84	0.635	Ø 2.23
#5-40 UNC	40	0.125″ / 3.18	0.635	Ø 2.56
#6-32 UNC	32	0.138″ / 3.51	0.794	Ø 2.73
#8-32 UNC	32	0.164″ / 4.17	0.794	Ø 3.39
#10-24 UNC	24	0.19″ / 4.83	1.058	Ø 3.79
1/4-20 UNC	20	0.25″ / 6.35	1.27	Ø 5.11
5/16-18 UNC	18	0.3125″ / 7.94	1.411	Ø 6.56
3/8-16 UNC	16	0.375″ / 9.52	1.588	Ø 7.98
7/16-14 UNC	14	0.4375″ / 11.11	1.814	Ø 9.34
1/2-13 UNC	13	0.5″ / 12.7	1.954	Ø 10.8
9/16-12 UNC	12	0.5625″ / 14.29	2.117	Ø 12.23
5/8-11 UNC	11	0.625″ / 15.88	2.309	Ø 13.63
3/4-10 UNC	10	0.75″ / 19.05	2.54	Ø 16.58
7/8-9 UNC	9	0.875″ / 22.22	2.822	Ø 19.48
1-8 UNC	8	1″ / 25.4	3.175	Ø 22.31

Size	TPI	Major Ø (in / mm)	Pitch P (mm)	Tap drill (mm)
#4-48 UNF	48	0.112″ / 2.84	0.529	Ø 2.33
#6-40 UNF	40	0.138″ / 3.51	0.635	Ø 2.89
#8-36 UNF	36	0.164″ / 4.17	0.706	Ø 3.48
#10-32 UNF	32	0.19″ / 4.83	0.794	Ø 4.05
1/4-28 UNF	28	0.25″ / 6.35	0.907	Ø 5.47
5/16-24 UNF	24	0.3125″ / 7.94	1.058	Ø 6.91
3/8-24 UNF	24	0.375″ / 9.52	1.058	Ø 8.49
7/16-20 UNF	20	0.4375″ / 11.11	1.27	Ø 9.88
1/2-20 UNF	20	0.5″ / 12.7	1.27	Ø 11.46
9/16-18 UNF	18	0.5625″ / 14.29	1.411	Ø 12.91
5/8-18 UNF	18	0.625″ / 15.88	1.411	Ø 14.5
3/4-16 UNF	16	0.75″ / 19.05	1.588	Ø 17.5
7/8-14 UNF	14	0.875″ / 22.22	1.814	Ø 20.46
1-12 UNF	12	1″ / 25.4	2.117	Ø 23.34

Values are guide values for orientation. Always check them against the machine, clamping and workpiece. No liability for results.