IS 6623 Standard

IS 6623

Dimension for High Strength Structural Nuts

Sl No.	Thread Size, d		All dimensions in millimetres
Sl No.	Thread Size, d		M 12	M 16	M 20	(M 22)	M 24	(M 27)	M 30	M 36
(1)	(2)		(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
i)	p ¹⁾Pitch of thread		1.75	2	2.5	2.5	3	3	3.5	4
ii)	d_w	Max	13.0	17.3	21.6	23.8	25.9	29.2	32.4	38.9
ii)	d_w	Min	12.0	16.0	20.0	22.0	24.0	27.0	30.0	36.0
iii)	d_w	Max	²⁾	²⁾	²⁾	²⁾	²⁾	²⁾	²⁾	²⁾
iii)	d_w	Min	19.2	24.9	31.4	33.3	38.0	42.8	46.5	55.9
iv)	e	Min	22.78	29.56	37.29	39.55	45.20	50.85	55.37	66.44
v)	m	Max	12.3	17.1	20.7	23.6	24.2	27.6	30.7	36.6
v)	m	Min	11.9	16.4	19.4	22.3	22.9	26.3	29.1	35.0
vi)	m′	Min	9.5	13.1	15.5	17.8	18.3	21.0	23.3	28.0
vii)	m″	Min	8.3	11.5	13.6	15.6	16.0	18.4	20.4	24.5
viii)	c	Max	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.8
viii)	c	Min	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4
ix)	s	Max	21.00	27.00	34.0	35.0	41.0	46.0	50.0	60.0
ix)	s	Min	20.16	26.16	33.0	34.0	40.0	45.0	49.0	58.8

NOTES
1 Sizes shown in brackets are of second preference.
2 For hot-dip galvanized nuts, the above dimensions apply before galvanizing.

1) Pitch of thread.
2) d_{w Max} = s, actual.

7 GENERAL REQUIREMENTS

7.1 In regard to permissible surface discontinuities, the nuts shall conform to IS 1367 (Part 10).

7.2 In regard to the requirements not covered in this standard, the nut shall conform to the general requirements given in IS 1367 (Part 1).

7.3 The high strength structural bolts to be used with these nuts shall conform to the requirements of IS 3757.

7.4 The bolts shall have the property class and finish as given below for each type of nut as follows:

Sl No.	Property Class and Finish Nuts	Property Class and Finish Bolts
i)	8 S or 10 S, Dull black	8.8 S, Dull black
ii)	10 S, Hot-dip galvanized	8.8 S, Hot-dip galvanized
iii)	10 S, Dull black	10.9 S, Dull black

7.5 The hardened and tempered washers to be used with these nuts shall conform to the requirements of IS 6649.

Table 2 Proof Loads and Hardness Values of High Strength Structural Nuts (Clause 5.1)

Sl No.	Thread Size, d	Nominal Stress Area of Standard Test Mandrel As, mm²	Property Class 8 S			Property Class 10 S
			Finish			Finish
			Plain			Plain	Hot-Dip Galvanized	Plain and Hot-Dip Galvanized
			Proof load (N) (A_s × S_p)	Hardness		Proof load (N) (A_s × S_p)	Proof load (N) (A_s × S_p)	Hardness
			Proof load (N) (A_s × S_p)	Rockwell HR	Vickers HV	Proof load (N) (A_s × S_p)	Proof load (N) (A_s × S_p)	Rockwell HR	Vickers HV
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
i)	M 12	84.3	90 600			105 000	98 200
ii)	M 16	157	168 900			195 500	182 900
iii)	M 20	245	263 400	B 89	188	305 000	285 400	C 26	272
iv)	(M 22)	303	325 700	to		377 200	353 000	to
v)	M 24	353	379 500	C 38	372	439 500	411 200	C 38	372
vi)	(M 27)	459	493 400			571 500	534 700
vii)	M 30	561	603 100			698 400	653 600
viii)	M 36	817	878 300			1 017 200	951 800

NOTES:

1. Based on the following proof load stress (S_p):
  a) for nuts of property class 8 S, plain: 1 075 N/mm²,
  b) for nuts of property class 10 S, plain: 1 245 N/mm², and
  c) for nuts of property class 10 S, hot-dip galvanized: 1 165 N/mm².
2. Sizes shown within the brackets are non-preferred.

10 MARKING

10.1 The high strength structural nuts shall be marked with the following as shown in Fig. 2:

a) Manufacturer’s identification symbol; and
b) Property class 8 S or 10 S.

IS 6623

10.1.1 The marking shall be indented on either the top or bottom face of double-chamfered nuts and shall be either indented or embossed on non-bearing face of washer faced nuts.

10.2 BIS Certification Marking
The product may also be marked with the Standard Mark. Wherever it is not possible to put the Standard Mark on the product, it may be marked on the packaging.

10.2.1 The use of Standard Mark is governed by the provisions of the Bureau of Indian Standards Act, 1986 and the Rules and Regulations made thereunder. The details of conditions under which the licence for the use of Standard Mark may be granted to the manufacturers or producers may be obtained from the Bureau of Indian Standards.