Shapes and Dimensions of Hexagon Bolts (Part Grade A) (Excerpt from JIS B 1180-1985)

2026/06/15

[Scope of Application]

This standard specifies the properties of hexagonal bolts made of steel, stainless steel, and non-ferrous metals.

*This page provides an overview of hex bolts with the following specifications: "Name: Nominal diameter hex bolt," "Thread pitch: Standard pitch," and "Material grade: A."

Unit [mm]

Nominal diameter (d)		M3	M4	M5	M6	M8	M10	M12	M16	M20	M24
Thread pitch (P)		0.5	0.7	0.8	1	1.25	1.5	1.75	2	2.5	3
b (for reference)	ℓ ≤ 125	12	14	16	18	22	26	30	38	46	54
b (for reference)	125 < l ≤ 150	18	20	22	24	28	32	36	44	52	60
c	Minimum	0.15	0.15	0.15	0.15	0.15	0.15	0.15	0.2	0.2	0.2
c	Max	0.40	0.40	0.50	0.50	0.60	0.60	0.60	0.8	0.8	0.8
da	Max	3.6	4.7	5.7	6.8	9.2	11.2	13.7	17.7	22.4	26.4
ds	Maximum (Standard Dimensions)	3.00	4.00	5.00	6.00	8.00	10.00	12.00	16.00	8:00 PM	12:00 AM
ds	Minimum	2.86	3.82	4.82	5.82	7.78	9.78	11.73	15.73	19.67	23.67
dw	Minimum	4.57	5.88	6.88	8.88	11.63	14.63	16.63	22.49	28.19	33.61
e	Minimum	6.01	7.66	8.79	11.05	14.38	17.77	20.03	26.75	33.53	39.98
f	Max	1	1.2	1.2	1.4	2	2	3	3	4	4
k	Nominal (Standard Dimension)	2	2.8	3.5	4	5.3	6.4	7.5	10	12.5	15
	Minimum	1.875	2.675	3.35	3.85	5.15	6.22	7.32	9.82	12.285	14.785
	Max	2.125	2.925	3.65	4.15	5.45	6.58	7.68	10.18	12.715	15.215
k'	Minimum	1.31	1.87	2.35	2.70	3.61	4.35	5.12	6.87	8.6	10.35
r	Minimum	0.1	0.2	0.2	0.25	0.4	0.4	0.6	0.6	0.8	0.8
s	Maximum (Standard Dimensions)	5.50	7.00	8.00	10.00	13.00	4:00 PM	6:00 PM	12:00 AM	11:00 PM	36.00
s	Minimum	5.32	6.78	7.78	9.78	12.73	15.73	17.73	23.67	29.67	35.38

*Avoid using screws with nominal diameters in parentheses whenever possible.

Unit [mm]

Thread size			M3	M4	M5	M6	M8	M10	M12	M16	M20	M24
ℓ			ℓ s and ℓ g		ℓ s and ℓ g		ℓ s and ℓ g		ℓ s and ℓ g		ℓ_s and ℓ_g		ℓ s and ℓ g		ℓ s and ℓ g		ℓ s and ℓ g		ℓ s and ℓ g		ℓ s and ℓ g
Nominal length (standard dimension)	Minimum	Maximum	ℓ s Minimum	ℓ g Max	ℓ s min	ℓ g max	ℓ s min	ℓ g max	ℓ s min	ℓ g max	ℓ s min	ℓ g max	ℓ s min	ℓ g max	ℓ s min	ℓ g max	ℓ s min	ℓ g max	ℓ s min	ℓ g max	ℓ s min	ℓ g max
20	19.58	20.42	5.5	8
25	24.58	25.42	10.5	13	7.5	11	5	9
30	29.58	30.42	15.5	18	12.5	16	10	14	7	12
35	34.5	35.5			17.5	21	15	19	12	17
40	39.5	40.5			22.5	26	20	24	17	22	11.75	18
45	44.5	45.5					25	29	22	27	16.75	23	11.5	19
50	49.5	50.5					30	34	27	32	21.75	28	16.5	24	11.25	20
55	54.4	55.6							32	37	26.75	33	21.5	29	16.25	25
60	59.4	60.6							37	42	31.75	38	26.5	34	21.25	30
65	64.4	65.6									36.75	43	31.5	39	26.25	35	17	27
70	69.4	70.6									41.75	48	36.5	44	31.25	40	22	32
80	79.4	80.6									51.75	58	46.5	54	41.25	50	32	42	21.5	34
90	89.3	90.7										56.5	51.25	60	42	52	31.5	44	21	36
100	99.3	100.7										66.5	61.25	70	52	62	41.5	54	31	46
110	109.3	110.7											71.25	80	62	72	51.5	64	41	56
120	119.3	120.7											81.25	90	72	82	61.5	74	51	66
130	129.2	130.8													76	86	65.5	78	55	70
140	139.2	140.8													86	96	75.5	88	65	80
150	149.2	150.8													96	106	85.5	98	75	90

*The recommended nominal length (ℓ) for each screw size is indicated within the ■ box.

Shapes and Dimensions of Hexagon Bolts (Part Grade A) (Excerpt from JIS B 1180-1985)

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