Dimensions of Flat Countersunk Nib Bolts

Nominal size and thread diameter d	Pitch of thread p	Thread Length b			Diameter of Countersunk head dk		Diameter of unthreaded shank ds'		Width of nib g		i	Depth of head k	a
	Coarse pitch	Bolt ≤ 125	Bolt 125 - 200	Bolt ≥ 200	max	min	max	min	max	min	max	max	min	max
M 6	1.0	18	24	-	12.55	11.45	6	5.52	2.5	2.10	2.5	4.0	90°	95°
M 8	1.25	22	28	41	16.55	15.45	8	7.42	3.0	2.60	3.5	5.0	90°	95°
M 10	1.5	26	32	45	19.65	18.35	10	9.42	3.2	2.72	4.2	5.5	90°	95°
M 12	1.75	30	36	49	24.65	23.35	12	11.30	3.6	3.12	5.7	7.0	90°	95°
M 16	2.0	38	44	57	32.80	31.20	16	15.30	4.2	3.72	7.5	9.0	90°	95°
M 20	2.5	46	52	65	32.80	31.20	20	19.16	5.4	4.92	5.7	11.5	60°	65°
M 24	3.0	54	60	73	38.80	37.20	24	23.16	6.6	6.02	6.7	13.0	60°	65°

d			M 6		M 8		M 10		M 12		M 16		M 20		M 24
Nominal Size	l min	l 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
20	18.95	21.05	-	9	-	11.5	-	13	-	-	-	-	-	-	-	-
25	23.95	26.05	-	9	-	11.5	-	13	-	16	-	-	-	-	-	-
30	28.95	31.05	-	9	-	11.5	-	13	-	16	-	19	-	-	-	-
35	33.75	36.25	12	17	-	11.5	-	13	-	16	-	19	-	-	-	-
40	38.75	41.25	17	22	11.75	18	-	13	-	16	-	19	-	-	-	-
45	43.75	46.25	22	27	16.75	23	11.5	19	-	16	-	19	-	-	-	-
50	48.75	51.25	27	32	21.75	28	16.5	24	11.25	20	-	19	-	24	-	-
55	53.50	56.50	32	37	26.75	33	21.5	29	16.25	25	-	19	-	24	-	-
60	58.5	61.5	37	42	31.75	38	26.5	34	21.25	30	-	19	-	24	-	28
65	63.5	66.5	42	47	36.75	43	31.5	39	26.25	35	17	27	-	24	-	28
70	68.5	71.5	47	52	41.75	48	36.5	44	31.25	40	22	32	-	24	-	28
80	78.5	81.5	57	62	51.75	58	46.5	54	41.25	50	32	42	21.5	34	-	28
90	88.25	91.75	67	72	61.75	68	56.5	64	51.25	60	42	52	31.5	44	21	36
100	98.25	101.75	77	82	71.75	78	66.5	74	61.25	70	52	62	41.5	54	31	46
110	108.25	111.75			81.75	88	76.5	84	71.25	80	62	72	51.5	64	41	56
120	118.25	121.75			91.75	98	86.5	94	81.25	90	72	82	61.5	74	51	66
130	128.00	132.00			95.75	102	90.5	98	85.25	94	76	86	65.5	78	55	70
140	138.00	142.00			105.75	112	100.5	108	95.25	104	86	96	75.5	88	65	80
150	148.00	152.00			115.75	122	110.5	118	105.25	114	96	106	85.5	98	75	90
160	156.00	164.00					120.5	128	115.25	124	106	116	95.5	108	85	100

Note :
Length exceeding 50mm must be graded by steps of 10mm. Intermediate lengths should be avoided wherever possible.
For manufacturing reasons the + IT 15 tolerance is permissible for a length of 2d below head. The shark diameter may also be ≈ pitch diameter at manufacturer discretion.