ASME B18.2.3.1m Metric Hex Cap Screws

ASME B18.2.3.1M Standard covers the complete general and dimensional data for metric series hex cap screws recognized as American National Standard. The Tables measurements are also converted into millimeters to make the information clearer and easier to understand.

ASME B18.2.3.1m Metric Hex Cap Screws Dimensions

Nominal Dia.,D,and Thread Pitch	Body Dia., D s		Width Across Flats, S		Width Across Corners, E		Head Height, K		Wrenching Height, K1 1	Washer Face Thick., C		Washer Face Dia., DW
	Max	Min.	Max	Min.	Max	Min.	Max	Min.	Min.	Max	Min.	Min.
ANSI B18.2.3.1M - M5	5	4.82	8	7.78	9.24	8.79	3.65	3.35	2.4	0.5	0.2	7
ANSI B18.2.3.1M - M6	6	5.82	10	9.78	11.55	11.05	4.15	3.85	2.8	0.5	0.2	8.9
ANSI B18.2.3.1M - M8	8	7.78	13	12.73	15.01	14.38	5.5	5.1	3.7	0.6	0.3	11.6
ANSI B18.2.3.1M - aM10	10	9.78	15	14.73	17.32	16.64	6.63	6.17	4.5	0.6	0.3	13.6
ANSI B18.2.3.1M - M10	10	9.78	16	15.73	18.48	17.77	6.63	6.17	4.5	0.6	0.3	14.6
ANSI B18.2.3.1M - M12	12	11.73	18	17.73	20.78	20.03	7.76	7.24	5.2	0.6	0.3	16.6
ANSI B18.2.3.1M - M14	14	13.73	21	20.67	24.25	23.35	9.09	8.51	6.2	0.6	0.3	19.6
ANSI B18.2.3.1M - M16	16	15.73	24	23.67	27.71	26.75	10.32	9.68	7	0.8	0.4	22.5
ANSI B18.2.3.1M - M20	20	19.67	30	29.16	34.64	32.95	12.88	12.12	8.8	0.8	0.4	27.7
ANSI B18.2.3.1M - M24	24	23.67	36	35	41.57	39.55	15.44	14.56	10.5	0.8	0.4	33.2
ANSI B18.2.3.1M - M30	30	29.67	46	45	53.12	50.85	19.48	17.92	13.1	0.8	0.4	42.7
ANSI B18.2.3.1M - M36	36	35.61	55	53.8	63.51	60.79	23.38	21.62	15.8	0.8	0.4	51.1
ANSI B18.2.3.1M - M42	42	41.38	65	62.9	75.06	71.71	26.97	25.03	18.2	1	0.5	59.8
ANSI B18.2.3.1M - M48	48	47.38	75	72.6	86.6	82.76	31.07	28.93	21	1	0.5	69
ANSI B18.2.3.1M - M56	56	55.26	85	82.2	98.15	93.71	36.2	33.8	24.5	1	0.5	78.1
ANSI B18.2.3.1M - M64	64	63.26	95	91.8	109.7	104.65	41.32	38.68	28	1	0.5	87.2
ANSI B18.2.3.1M - M72	72	71.26	105	101.4	121.24	115.6	46.45	43.55	31.5	1.2	0.6	96.3
ANSI B18.2.3.1M - M80	80	79.26	115	111	132.72	126.54	51.58	48.42	35	1.2	0.6	105.4
ANSI B18.2.3.1M - M90	90	89.13	130	125.5	150.11	143.07	57.74	54.26	39.2	1.2	0.6	119.2
ANSI B18.2.3.1M - M100	100	99.13	145	140	167.43	159.6	63.9	60.1	43.4	1.2	0.6	133
(a) This size with width across flats of 15 mm is not standard. Unless specifically ordered, M10 hex cap screws with 16 mm width across flats will be furnished. All dimensions are in millimeters. Basic thread lengths, B, are the same as given in . Transition thread length, X, includes the length of incomplete threads and tolerances on grip gaging length and body length. It is intended for calculation purposes. For additional manufacturing and acceptance specifications, reference should be made to the ASME B18.2.3.1M-1979 (R1995).

Nominal Screw Diameter and Thread Pitch	Fillet Transition Diameter, Da		Fillet Length, Lf		Fillet Radius for Short and Long Screws, R, Min.	Body Diameter for Short Screws, Dsi, Min.
	For Short Screws, Min.	For Short and Long Screws, Max.	For Long Screws, Max.	For Short Screws, Max.
M5	5.1	5.7	1.2	0.7	0.2	4.36
M6	6.2	6.8	1.4	0.9	0.25	5.21
M8	8.3	9.2	2.0	1.1	0.4	7.04
M10	10.2	11.2	2.0	1.2	0.4	8.86
M12	12.2	13.7	3.0	1.3	0.6	10.68
M14	14.1	15.7	3.0	1.4	0.6	12.50
M16	16.5	17.7	3.0	1.6	0.6	14.50
M20	20.7	22.4	4.0	2.1	0.8	18.16
M24	24.5	26.4	4.0	2.3	0.8	21.80
M30	30.8	33.4	6.0	3.0	1.0	27.46
M36	36.6	39.4	6.0	3.1	1.0	33.12
M42	. . .	45.6	8.0	3.4	1.2	38.78
M48	. . .	52.6	10.0	4.0	1.6	44.43
M56	. . .	63.0	12.0	4.8	2.0	52.09
M64	. . .	71.0	13.0	5.0	2.0	59.74
M72	. . .	79.0	13.0	5.0	2.0	67.74
M80	. . .	87.0	13.0	5.0	2.0	75.74
M90	. . .	97.0	13.0	5.0	2.5	85.74
M100	. . .	107.0	13.0	5.5	2.5	95.72

ASME B18.2.3.1m Metric Hex Cap Screws Thread Length

Nominal Screw Diameter and Thread Pitch	Thread Length, B, Ref			Transition Thread Length, X, Ref	Screws Threaded Full Length
	Screw Lengths, L ≤ 125	Screw Lengths, L > 125 & ≤ 200	Screw Lengths, L > 200		Screw Lengths, L, Under	Unthreaded Length Under Head, A, Max. [Note (1)]	Screw Lengths, L		Unthreaded Length Under Head, A, Max.
							At Least	Under
M5	16	22	35	4.0	10	1.2	10	25	2.4
M6	18	24	37	5.0	12	1.5	12	30	3.0
M8	22	28	41	6.25	16	1.9	16	40	4.0
M10	26	32	45	7.5	20	2.2	20	45	4.5
M12	30	36	49	8.75	24	2.6	24	50	5.3
M14	34	40	53	10.0	28	3.0	28	60	6.0
M16	38	44	57	10.0	32	3.0	32	65	6.0
M20	46	52	65	12.5	40	3.8	40	80	7.5
M24	54	60	73	15.0	...	...	...	90	9.0
M30	66	72	85	17.5	...	...	...	110	10.5
M36	...	84	97	20.0	...	...	...	140	12.0
M42	...	96	109	22.5	...	...	...	160	13.5
M48	...	108	121	25.0	...	...	...	180	15.0
M56	...	...	137	27.5	...	...	...	220	16.5
M64	...	...	153	30.0	...	...	...	260	18.0
M72	...	...	169	30.0	...	...	...	280	18.0
M80	...	...	185	30.0	...	...	...	300	18.0
M90	...	...	205	30.0	...	...	...	340	18.0
M100	...	...	225	30.0	...	...	...	360	18.0

ASME B18.2.3.1m Metric Hex Cap Screws Length Tolerance

Nominal Length		Nominal Screw Diameter
Over	Thru	M5	M6	M8	M10	M12	M14	M16-M24	>M24
6	10	±0.29	±0.29	±0.29	±0.29	...	...	...	...
10	18	±0.35	±0.35	±0.35	±0.35	±0.35	±0.35	±0.35	...
18	30	±0.42	±0.42	±0.42	±0.42	±0.42	±0.42	±0.42	±1.05
30	50	±0.50	±0.50	±0.50	±0.50	±0.50	±0.50	±0.50	±1.25
50	60	±1.50	±0.60	±0.60	±0.60	±0.60	±0.60	±0.60	±1.50
60	80	±1.50	±1.50	±0.60	±0.60	±0.60	±0.60	±0.60	±1.50
80	100	±1.75	±1.75	±1.75	±0.70	±0.70	±0.70	±0.70	±1.75
100	120	±1.75	±1.75	±1.75	±1.75	±0.70	±0.70	±0.70	±1.75
120	140	±2.00	±2.00	±2.00	±2.00	±2.00	±0.80	±0.80	±2.00
140	150	±2.00	±2.00	±2.00	±2.00	±2.00	±2.00	±0.80	±2.00
150	180	±2.00	±2.00	±2.00	±2.00	±2.00	±2.00	±2.00	±2.00
180	250	±2.30	±2.30	±2.30	±2.30	±2.30	±2.30	±2.30	±2.30
250	315	±2.60	±2.60	±2.60	±2.60	±2.60	±2.60	±2.60	±2.60
315	400	±2.85	±2.85	±2.85	±2.85	±2.85	±2.85	±2.85	±2.85
400	500	±3.15	±3.15	±3.15	±3.15	±3.15	±3.15	±3.15	±3.15

ASME B18.2.3.1m Metric Hex Cap Screws Body Grip Gaging Lengths

Nominal Length, L	M5		M6		M8		M10		M12		M14		M16		M20		M24		M30		M36
	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.	Lg Max.	Ls Min.
8	1.2	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...
10	2.4	...	1.5	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...
12	2.4	...	3.0	...	1.9	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...
16	2.4	...	3.0	...	4.0	...	2.2	...	2.6	...	3.0	...	...	...	...	...	...	...	...	...	...	...
20	2.4	...	3.0	...	4.0	...	4.5	...	2.6	...	3.0	...	...	...	...	...	...	...	...	...	...	...
25	9.0	5.0	3.0	...	4.0	...	4.5	...	5.3	...	3.0	...	3.0	...	...	...	...	...	...	...	...	...
30	14.0	10.0	12.0	7.0	4.0	...	4.5	...	5.3	...	6.0	...	3.0	...	3.8	...	...	...	...	...	...	...
35	19.0	15.0	17.0	12.0	4.0	...	4.5	...	5.3	...	6.0	...	6.0	...	3.8	...	9.0	...	...	...	...	...
40	24.0	20.0	22.0	17.0	18.0	11.75	4.5	...	5.3	...	6.0	...	6.0	...	7.5	...	9.0	...	10.5	...	...	...
45	29.0	25.0	27.0	22.0	23.0	16.75	19.0	11.5	5.3	...	6.0	...	6.0	...	7.5	...	9.0	...	10.5	...	...	...
50	34.0	30.0	32.0	27.0	28.0	21.75	24.0	16.5	20.0	11.25	6.0	...	6.0	...	7.5	...	9.0	...	10.5	...	12.0	...
60	...	...	42.0	37.0	38.0	31.75	34.0	26.5	30.0	21.25	26.0	16.0	6.0	...	7.5	...	9.0	...	10.5	...	12.0	...
70	...	...	...	...	48.0	41.75	44.0	36.5	40.0	31.25	36.0	26.0	32.0	22.0	7.5	...	9.0	...	10.5	...	12.0	...
80	...	...	...	...	58.0	51.75	54.0	46.5	50.0	41.25	46.0	36.0	42.0	32.0	34.0	21.5	9.0	...	10.5	...	12.0	...
100	...	...	...	...	...	...	74.0	66.5	70.0	61.25	66.0	56.0	62.0	52.0	54.0	41.5	46.0	31.0	10.5	...	12.0	...
120	...	...	...	...	...	...	...	...	90.0	81.25	86.0	76.0	82.0	72.0	74.0	61.5	66.0	51.0	54.0	36.5	12.0	...
150	...	...	...	...	...	...	...	...	...	...	...	...	106.0	96.0	98.0	85.5	90.0	75.0	78.0	60.5	66.0	46.0
200	...	...	...	...	...	...	...	...	...	...	...	...	...	...	148.0	135.5	140.0	125.0	128.0	110.5	116.0	96.0
300	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	...	215.0	197.5	203.0	183.0