GOST 7785-81 Countersunk Nibbed Head Bolts, Product Grade C. Construction and Dimensions

GOST 7785-81 applies to countersunk nibbed head bolts, product grade C, with nominal thread diameter from 5 to 24 mm. The standard fully complies with ST SEV 217-86.

The construction and dimensions of the bolts shall conform to those shown in the drawing and in Tables 1 and 2. d₂ is approximately equal to the pitch diameter of the thread. The taper of the nib’s side faces shall not exceed 5°.

COUNTERSUNK NIBBED HEAD BOLTS, PRODUCT GRADE C Construction and Dimensions Countersunk nibbed head bolts, product grade C. Construction and dimensions.	GOST 7785-81* (ST SEV 217-86) Supersedes GOST 7785-72

Example of designation for a bolt with thread diameter d = 12 mm, coarse thread pitch with tolerance class 8g, length l = 60 mm, property class 4.6, with zinc coating 6 µm thick, applied by cathodic reduction, chromated:

Bolt M12×60.46.016 GOST 7785-81

Nominal thread diameter d		5	6	8	10	12	16	20	24
Head diameter D		10	12	16	20	24	32	32	38
Head height k, max		3.0	4.0	5.0	5.5	7.0	9.0	11.5	13.0
Nib width V		2.0	2.5	3.0	3.2	3.6	4.2	5.4	6.6
Angle a		90°						60 °
Nib height W, not less than		2.3	2.8	3.5	4.2	5.7	7.5	5.5	6.7
Thread length b	For l ≤ 120	16	18	22	26	30	38	46	54
	For l > 120	-	-	-	32	36	44	52	60

Thread — per GOST 24705-81, thread pitch — coarse. Thread runout and incomplete thread — per GOST 27148-86. Bolt ends — per GOST 12414-66.

Tolerances and methods for checking dimensions and deviations of form and location of surfaces — per GOST 1759.1-82. By agreement between the manufacturer and the customer, bolts may be made with thread tolerance class 6e.

Surface defects and inspection methods — per GOST 1759.2-82.

The diameter of the plain part of the shank d₁ is approximately equal to the pitch diameter of the thread or equal to the nominal thread diameter.

Technical requirements — per GOST 1759.0-87. The mechanical properties of the bolts shall conform to property classes 3.6, 4.6, 4.8, 5.6 and 5.8.

Bolt length l	Nominal thread diameter d
	5	6	8	10	12	16	20	24
16			-	-	-	-	-	-
20					-	-	-	-
25						-	-	-
30							-	-
35							-	-
40								-
45								-
50								-
55								-
60
65
70
75
80
90	-
100	-
110	-	-
120	-	-
130	-	-
140	-	-
150	-	-
160	-	-	-
170	-	-	-	-	-
180	-	-	-	-	-
190	-	-	-	-	-
200	-	-	-	-	-
Notes. 1. Bolts are manufactured with lengths between the bold lines. 2. Bolts in the range from the upper bold line to the dashed line are manufactured with thread up to the nib.

Rounding of the nib tip is permitted, as well as manufacturing M20 bolts with an angle α = 90° and diameter D = 36 mm.

The theoretical mass of bolts is given in the reference appendix.

Bolt length, l, mm	Theoretical mass of bolts, kg, at nominal thread diameter d, mm
	5	6	8	10	12	16	20	24
16	2.588	4.057	-	-	-	-	-	-
20	3.061	4.734	9.12	15.26	-	-	-	-
25	3.651	5.579	10.66	17.71	26.90	-	-	-
30	4.241	6.424	12.20	20.15	30.44	59.95	-	-
35	4.949	7.269	13.74	22.59	33.98	66.48	-	-
40	5.421	8.114	15.28	25.03	37.52	73.00	105.5	-
45	6.011	8.960	16.82	27.47	41.06	79.53	115.7	-
50	6.601	9.804	18.36	29.92	44.60	86.06	125.9	-
55	7.191	10.649	19.90	32.36	48.14	92.58	136.2	-
60	7.781	11.494	21.43	34.80	51.68	99.11	146.4	214.1
65	8.371	12.340	22.97	37.24	55.23	105.64	156.6	228.8
70	8.961	13.184	24.51	39.69	58.77	112.16	166.9	243.6
75	9.551	14.029	26.05	42.13	62.31	118.69	177.1	258.3
80	10.142	14.874	27.59	44.57	65.85	125.22	187.3	273.1
90	-	16.564	30.67	49.45	72.93	138.27	207.8	302.5
100	-	18.255	33.75	54.34	80.01	151.33	228.3	332.0
110	-	-	36.83	59.22	87.10	164.38	248.7	361.5
120	-	-	39.91	64.11	94.17	177.43	269.2	390.9
130	-	-	42.99	68.99	101.25	190.49	289.7	420.4
140	-	-	46.07	73.88	108.33	203.54	310.2	449.8
150	-	-	49.15	78.76	115.41	216.60	330.6	479.3
160	-	-	-	83.64	122.49	229.65	351.1	508.8
170	-	-	-	-	-	242.70	371.6	538.3
180	-	-	-	-	-	255.76	392.0	567.7
190	-	-	-	-	-	268.79	412.5	597.2
200	-	-	-	-	-	281.87	432.9	626.7

Complies with DIN 604.