GOST 24670-81 Bolts, Screws and Wood Screws. Under-Head Radii

GOST 24670-81 applies to bolts, screws and wood screws. The standard does not apply to screws and wood screws with countersunk and raised countersunk heads. The standard fully conforms to ST SEV 1014-78.

BOLTS, SCREWS AND WOOD SCREWS	GOST 24670-81
Radii under the head
Bolts, screws and wood screws. Radiws under the head

By Decree of the USSR State Committee for Standards No. 1704 of March 31, 1981, the effective date was set as 01.07.81.

Reprinted 2006.

The under-head radii of bolts, screws and wood screws shall conform to the dimensions shown in the drawing and in the table.

mm

Nominal thread diameter of the shank d	R, min	da, max, for product grade of the bolt, screw, wood screw
		A	B	C
1.0	0.10	1.4	-	-
1.2		1.6	-	-
1.4		1.8	-	-
1.6		2.0	-	-
2.0		2.6	-	-
2.5		3.1	3.1	-
3.0		3.6	3.6	-
3.5		4.1	4.1	-
4.0	0.20	4.7	4.7	-
5.0		5.7	5.7	6.0
6.0	0.25	6.8	6.8	7.2
7.0		7.8	7.8	8.2
8.0	0.40	9.2	9.2	10.2
10.0		11.2	11.2	12.2
12.0	0.60	14.2	14.2	15.2
14.0		16.2	16.2	17.2
16.0		18.2	18.2	19.2
18.0		20.2	20.2	21.2
20.0	0.80	22.4	22.4	24.4
22.0		24.4	24.4	26.4
24.0		26.4	26.4	28.4
27.0	1.00	30.4	30.4	32.4
30.0		33.4	33.4	35.4
33.0		36.4	36.4	38.4
36.0		39.4	39.4	42.4
39.0		42.4	42.4	45.4
42.0	1.20	45.6	45.6	48.6
45.0		48.6	48.6	52.6
48.0	1.60	52.6	52.6	56.8
52.0		56.6	56.6	62.6

Notes:

1. Dimension da is the diameter of the circle formed where the fillet of radius R meets the bearing plane of the head of the bolt, screw or wood screw.

2. For wood screws, the values of R and da are generally taken for product grade C.

3. Within the diameter da, mating of the shank to the head by arcs of several radii or other curves is permitted.