GOST 1759.5-87 Nuts. Mechanical Properties and Test Methods

GOST 1759.5-87

NUTS Mechanical properties and test methods Nuts. Mechanical properties and test methods	GOST 1759.5-87 ST SEV 5958-87

Validity period from 01.01.89 to 01.01.94.

This standard applies to nuts made of carbon unalloyed and alloyed steels with metric thread to GOST 24705-81, diameter from 1 to 48 mm, thread tolerance class 6H, width across flats to GOST 24671-84, and nominal height greater than or equal to 0.5d.

This standard does not apply to self-locking nuts, or to nuts with special properties: weldability, increased corrosion resistance, operability at temperatures above plus 300 °C (plus 250 °C for free-cutting steel) and below minus 50 °C.

1. Designation system

1.1. Nuts with nominal height equal to or greater than 0.8d

Property classes of nuts with nominal height equal to or greater than 0.8d (effective thread engagement length equal to or greater than 0.6d) are designated by a digit indicating the highest property class of bolts with which they can be mated in a joint (Table 1). Failure of a threaded joint under overtightening may occur either due to fracture of the bolt shank or due to stripping of the nut and/or bolt thread. Bolt shank fracture occurs suddenly and is easily detected. Thread stripping in the nut occurs gradually and is more difficult to detect, so there remains a risk of partially failed fasteners being present in joints.

It is advisable to design threaded joints so that any possible failure always occurs through the bolt shank. However, guaranteeing this type of failure in all cases would require an excessively large nut height, due to the many variable factors affecting thread resistance to stripping.

A bolt or screw assembled with a nut of the corresponding property class according to Table 1 shall provide a joint that can be tightened up to the bolt’s proof load value without thread stripping.

Table 1

Nut property class	mating bolts
	Property class	Thread diameter
4	3.6; 4.6; 4.8	> M16
5	3.6; 4.6; 4.8	<M 16
	5.6; 5.8	<M48
6	6.8	<M48
8	8.8	<M48
9	8.8	> M16<M48
	9.8	<M 16
10	10.9	<M48
12	12.9	<M48

Note. As a rule, nuts of higher property classes may replace nuts of lower property classes. Such replacement is recommended for bolt-nut joints in which the stress will exceed the yield strength or the proof load stress of the bolt.

If the joint will be tightened beyond the bolt’s proof load, the nut design shall ensure that at least 10% of failures (resulting from overtightening) occur through the bolt shank — to warn the user of incorrect assembly of the fastener joint.

1.2. Nuts with nominal height equal to or greater than 0.5d and less than 0.8d

Property classes of such nuts (effective thread engagement length equal to or greater than 0.4d and less than 0.6d) are designated by a combination of two digits: the second digit corresponds to 1/100 of the nominal proof load stress in a hardened test mandrel, and the first digit indicates that the load-bearing capacity of the joint between this nut and a bolt is lower than with a hardened mandrel, and also lower than that of the bolt-nut joint described in 1.1. The actual load-bearing capacity of the nut is determined not only by the hardness of the nut material and the effective thread engagement length, but also by the tensile strength of the bolt with which the nut is mated.

Table 2 shows the designation system for property classes of low nuts and the proof load stress.

(Revised edition, Amendment No. 2).

Table 2

Nut property class	Proof load stress, N/mm²
	nominal	minimum
04	400	380
05	500	500

2. Material

2.1. Nuts shall be made of steels whose chemical composition conforms to that specified in Table 3.

Table 3

Nut property class	Limit values of element content (check analysis), %
	C, max	Mn, min	P, max	S, max
4 * ; 5 * ; 6 *	0.50	-	0.110	0.150
8; 9; 04 *	0.58	0.25	0.06	0.150
10 ** ; 05 **	0.58	0.30	0.048	0.058
12 **	0.58	0.45	0.048	0.058

2.2. Nuts of property classes 05; 8 (d > M16); 10 and 12 shall be subjected to quenching and tempering.

Note. Nuts of property classes 8 and 10 with a height of not less than 0.9d are permitted not to undergo heat treatment.

(Revised edition, Amendment No. 2).

2.3. Recommended steel grades and manufacturing processes for nuts are given in the appendix.

3. Mechanical properties

3.1. The mechanical properties of nuts, when tested by the methods of Section 4 at room temperature, shall conform to those specified in Table 4.

(Amended edition, Amendment No. 1).

3.2. Proof load values

Nut proof loads are determined by multiplying the proof load stress σf by the nominal cross-sectional area As of the hardened mandrel:

Pf = σf · As.

The stress area is determined by the formula, where d₂, d₃ and H are per GOST 24705-81, and σf is the proof load stress according to Table 4.

Proof load values for nuts with thread tolerance class 6H are given in Tables 5 and 6.

Table 4

Nominal thread diameter d, mm		Property class
		04					05					4
		Proof load stress σF, N/mm²	Vickers hardness HV		Rockwell hardness HRC		Proof load stress σF, N/mm²	Vickers hardness HV		Rockwell hardness HRC		Proof load stress σF, N/mm²	Vickers hardness HV		Rockwell hardness HRC
from	to		min	max	min	max		min	max	min	max		min	max	min	max
-	4	380	188	302	-	30	500	272	353	27.8	36	-	-	-	-	-
4	7
7	10
10	16
16	48											510	117	302	-	30
-	4	520	130	302	-	30	600	150	302	-	30	800	170	302	-	30
4	7	580					670					810	188		-
7	10	590					680					830
10	16	610					700					840
16	48	630	146		-		720	170		-		920	233	353	-	38
-	4	900	170	302	-	30	1040	272	353	28	38	1150	295	353	31	38
4	7	915	188		-		1040					1150
7	10	940					1040					1160
10	16	950					1050					1190
16	48	920					1060					1200	-		-

Notes:

1. Hardness values are given only for nuts with coarse thread pitch.
2. Minimum hardness values are mandatory only for heat-treated nuts and nuts that cannot be tested with a proof load. For all other nuts, the minimum hardness value is given for reference only.
3. In addition to determining hardness by the Vickers (HV) or Rockwell (HRC) method, determination of hardness by the Brinell method (HB) is permitted. Permissible Brinell hardness values shall correspond to the Vickers hardness values specified in the table.

Table 5. Proof loads for nuts with coarse thread pitch

Nominal thread diameter d, mm	Thread pitch P, mm	Mandrel cross-sectional area A, mm²	Proof load, N, for property classes
			04	05	4	5	6	8	9	10	12
1.6	0.35	1.27	480	640	-	660	760	1020	1140	1320	1460
2	0.40	2.07	790	1040	-	1080	1240	1660	1860	2150	2380
2.5	0.45	3.39	1290	1700	-	1760	2030	2710	3050	3530	3900
3	0.5	5.03	1910	2500	-	2600	3000	4000	4500	5200	5800
3.5	0.6	6.78	2580	3400	-	3550	4050	5400	6100	7050	7800
4	0.7	8.78	3340	4400	-	4550	5250	7000	7900	9150	10100
5	0.8	14.2	5400	7100	-	8250	9500	11500	13000	14800	16300
6	1	20.1	7640	10000	-	11700	13500	16300	18400	20900	23100
7	1	28.9	11000	14500	-	16800	19400	23400	26400	30100	33200
8	1.25	36.6	13900	18300	-	21600	24900	30400	34400	38100	42500
10	1.5	58.0	22000	29000	-	34200	39400	48100	54500	60300	67300
12	1.75	84.3	32000	42200	-	51400	59000	70800	80100	88500	100300
14	2	115	43700	57500	-	70200	80500	96000	109300	120800	136900
16	2	157	59700	78500	-	95800	109900	131900	149200	164900	186800
18	2.5	192	73000	96000	97900	121000	138200	176600	176600	203500	230400
20	2.5	245	93100	122500	125000	154400	176400	225400	225400	259700	294000
22	2.5	303	115100	152000	154500	190900	218200	278800	278800	321200	363000
24	3	353	134100	176500	180000	222400	254200	324800	324800	374200	423600
27	3	459	174400	229500	234100	289200	330500	422300	422300	486500	550800
30	3.5	561	213200	280500	286100	353400	403900	516100	516100	594700	673200
33	3.5	694	263700	347000	353900	437200	499700	638500	638500	735600	832800
36	4	817	310500	408500	416700	514700	588200	751600	751600	866000	980400
39	4	976	370900	488000	497800	614900	702700	897900	897900	1035000	1171000
42	4.5	1120	426000	560000	570000	706000	803000	1030000	1030000	1190000	1340000
45	4.5	1305	496000	653000	670000	830000	940000	1200000	1380000	1380000	1570000
48	5	1472	560000	736000	750000	930000	1060000	1350000	1350000	1560000	1800000

Table 6. Proof loads for nuts with fine thread pitch

Nominal thread diameter d, mm	Thread pitch P, mm	Mandrel cross-sectional area A, mm²	Proof load, N, for property classes
			04	05	4	5	6	8	9	10	12
8	1	39.2	14900	19600	-	23100	26700	32500	36800	40800	45500
10	1.25	61.2	23300	30600	-	36100	41600	50800	57500	63600	71000
12	1.25	92.1	35000	46000	-	56200	64500	77400	87500	96700	109600
14	1.5	125	47500	62500	-	76300	87500	105000	118800	131000	149000
16	1.5	167	63500	83500	-	102000	117000	140000	158700	175000	199000
18	1.5	216	82100	108000	110000	136000	156000	199000	199000	229000	259000
20	1.5	272	103000	136000	138000	171000	196000	250000	250000	288000	326000
22	1.5	333	127000	167000	170000	210000	240000	306000	306000	353000	400000
24	2	384	146000	192000	196000	242000	276000	353000	353000	407000	461000
27	2	496	188000	248000	253000	312000	357000	456000	456000	526000	595000
30	2	621	236000	311000	317000	391000	447000	571000	571000	658000	745000
33	2	761	289000	381000	388000	479000	548000	700000	700000	807000	913000
36	3	865	329000	433000	441000	545000	623000	796000	796000	917000	1038000
39	3	1030	391000	515000	525000	649000	740000	948000	948000	1090000	1236000
42	3	1205	458000	603000	615000	759000	868000	1109000	1109000	1277000	1446000
45	3	1400	532000	700000	714000	882000	1008000	1290000	1290000	1484000	1680000
48	3	1603	609000	802000	818000	1010000	1154000	1475000	1475000	1699000	1924000

When using other thread tolerance classes for nuts, the possible reduction in thread strength shall be taken into account in accordance with Table 7.

Table 7

Nominal thread diameter		proof load for threads with tolerance class, %
from	to	6 H	7 H	6 G
-	2.5	100	-	95.5
2.5	7	100	95.5	97.0
7	16	100	96.0	97.5
16	48	100	98.0	98.5

3.3. Breaking loads for nuts with nominal height of 0.5d

Table 8 gives, for reference, breaking loads for nuts with bolts of various property classes. For bolts of low property classes, the anticipated failure will be bolt thread stripping; for bolts of high property classes, it will be nut thread stripping.

Table 8

Nut property class	Nut proof load stress, N/mm²	Minimum stresses in the bolt shank at thread stripping, N/mm², for bolts of property class
		6.8	8.8	10.9	12.9
04	380	260	300	330	350
05	500	290	370	410	480

When using bolted joints with fine thread pitch, it is recommended to use for the nuts the next higher property class compared to the property class of bolts with coarse thread pitch.

Example: nuts of property class 10 — bolts of property class 8.8.

4. Test methods

4.1. Proof load test

The proof load test is performed whenever the test equipment permits, and is decisive for nuts with a diameter > M5.

Nut 1 is screwed onto hardened mandrel 2 as shown in the drawing. The decisive test is an axial tension test (Drawing A): 1 — nut; 2 — test mandrel; 3 — hardened plate; dh — according to the first series of GOST 11284-75.

The proof load is applied to the nut in the axial direction and held for 15 s. The nut shall withstand the load without failure or thread stripping and shall be unscrewed by hand. If the mandrel thread is damaged during the test, the test is considered invalid. When unscrewing, a wrench may be used for no more than 1/2 turn, after which the nut shall be unscrewed by hand.

The hardness of the test mandrel shall be not less than 45 HRC.

The thread tolerance class of the mandrel is 5h6g, except for the major diameter tolerance, which shall be 1/4 of the 6g tolerance at its lower limit.

(Revised edition, Amendment No. 2).

4.2. Hardness test

The hardness test is performed on one of the bearing surfaces of the nut at three points offset from each other by 120°; the hardness value is determined as the arithmetic mean of the three measurements.

In disputed cases, hardness is checked on a longitudinal section passing through the axis of the nut, at points located as close as possible to the nominal major diameter of the nut thread.

The Vickers hardness test is decisive; wherever possible, the HV30 load shall be applied.

Vickers hardness testing is performed according to GOST 2999-75, Brinell according to GOST 9012-59, and Rockwell according to GOST 9013-59.

(Revised edition, Amendment No. 2).

4.3. Surface quality control

Surface quality control of nuts is performed according to GOST 1759.3-83.

(Added, Amendment No. 2).

Appendix (recommended)

Recommended manufacturing processes for nuts made of unalloyed and alloyed steels, and steel grades

Property class	Manufacturing processes	Steel grade	Standard designation
4	Hot forming	20 St3kp3 St3sp3	GOST 1050-88
5	Cold forming	10, 10kp	GOST 10702-78
	Hot forming	20	GOST 1050-88
6; 04	Cold forming	10, 10kp 15, 15kp	GOST 10702-78
8; 9	Hot forming	35	GOST 1050-88, GOST 4543-71, GOST 10702-78
	Cold forming	20, 20kp
10: 12; 05	Hot forming	35×38KhA	GOST 4543-71, GOST 10702-78
	Cold forming	20G2R*
	Machining followed by quenching and tempering	16KhSN

• Nuts of the specified property classes may be made from free-cutting steel by agreement between the manufacturer and the customer. In this case, the sulfur, phosphorus and lead content shall not exceed: S — 0.34%; P — 0.12%; Pb — 0.35%.

** When it is necessary to improve the mechanical properties of nuts of the specified property classes, steels with alloying element additions may be used for their production.

Informational data

Designation of the referenced regulatory document	Item, sub-item, appendix number
GOST 1050-88	Appendix
GOST 2999-75	4.2
GOST 4543-71	Appendix
GOST 9012-59	4.2
GOST 9013-59	4.2
GOST 10702-78	Appendix
GOST 24705-81	Introductory part

Review date — 1993. The standard fully complies with ST SEV 5958-87 and international standard ISO 898/2-80. Supersedes GOST 1759-70 (with respect to mechanical properties and test methods for nuts).

(Amended edition, Amendment No. 1).