GOST 1759.4-87 (ISO 898-1-78) Bolts, Screws and Studs

GOST 1759.4-87 (ISO 898-1-78) establishes requirements for the mechanical properties of bolts, screws and studs by property class, their designation system, materials, and inspection and test methods.

1. DESIGNATION SYSTEM

The designation system for property classes of bolts, screws and studs is given in Table 1. The abscissa axis shows the nominal tensile strength ?v in N/mm2; the ordinate axis shows the elongation ?5 in %. The property class designation consists of two digits: the first corresponds to 1/100 of the nominal tensile strength in N/mm2; the second corresponds to 1/10 of the ratio of the nominal yield strength to the tensile strength, expressed as a percentage. The product of these two digits corresponds to 1/10 of the nominal yield strength in N/mm2. The minimum (or proof) yield strength and the minimum tensile strength are equal to or greater than their nominal values.

Table 1

Minimum or tensile strength in N/mm²
		300		400		500		600		700		800		900			1000			1200			1400
Minimum elongation₃ in %	7
	8
	9								6.8												12.9
	10																	10.9
							5.8								9.8
	12
													8.8
	14
					4.8
	16
	18								6.6
	20
	22						5.6
	25				4.6
	30		3.6
Ratio of yield strength to tensile strength
Nominal yield strength t											100, %					60			80			90
Nominal tensile strength v
Second digit of the symbol																.6			.8			.9

Applies only to products with thread diameter d≤16 mm. Not all property classes given in Table 1 can be used for all fasteners. Guidance on the application of specific property classes for standardized products is given in the relevant standards for those products. For non-standardized products, selection by analogy is recommended.

2. MATERIAL

Table 2 specifies the steels used to manufacture bolts, screws and studs of various property classes and their heat treatment. The chemical composition of the steel is mandatory only for fasteners that cannot be tested in tension. The minimum tempering temperature given in Table 2 is mandatory for property classes 8.8 to 12.9.

Table 2

Property class	Material and treatment	Chemical composition (check analysis), %						Tempering temperature, C, min
		carbon		phosphorus		sulfur
		Min.	Max.		Max.		Max.
3.6*	Carbon steel	-	0.20		0.05		0.06	-
4.6* 4.8*		-	0.55		0.05		0.06
5.6		0.15	0.55		0.05		0.06
5.8* 6.6 6.8 “		-	0.55		0.05		0.06
8.8**	Carbon steel with additives (boron, manganese or chromium), quenched and tempered	0.15***	0.40		0.035		0.035	425
8.8**	Carbon steel without additives, quenched and tempered	0.25	0.55		0.035		0.035
9.8	Carbon steel with additives (boron, manganese or chromium), quenched and tempered	0.15***	0.35		0.035		0.035
	Carbon steel without additives, quenched and tempered	0.25	0.55		0.035		0.033
10.9*⁴	Carbon steel with additives (boron, manganese or chromium), quenched and tempered	0.15***	0.35		0.035		0.033	340
10.9*⁵	Carbon steel without additives, quenched and tempered	0.25	0.55		0.035		0.035	425
10.9*⁵	Carbon steel with additives (boron, manganese or chromium), quenched and tempered	0.20***	0.55		0.035		0.035	425
	Alloy steel, quenched and tempered*⁷	0.20	0.55		0.035		0.035
12.9⁵⁶	Alloy steel, quenched and tempered*⁷	0.20	0.50		0.035		0.035	380

For these property classes, free-cutting steels with sulfur, phosphorus and lead content not exceeding 0.34; 0.11; 0.35% respectively are permitted. For sizes above M20, to achieve the necessary hardenability, steels recommended for property class 10.9 products may be used. In the case of ordinary carbon steel with boron additives, with a carbon content below 0.25% (ladle sample analysis), the minimum manganese content must be 0.06% for property class 8.8 and 0.7% for property classes 9.8 and 10.9. Such products must be additionally marked by underlining the property class symbol (see GOST 1759.0-87). Materials intended for these property classes must have sufficient hardenability to produce a structure containing approximately 90% martensite in the core of the threaded section of the fastener in the as-quenched condition prior to tempering. Fasteners of property class 12.9 subjected to tensile stress must not exhibit a white phosphide layer as determined by metallographic examination. Alloy steel must contain one or more alloying elements: chromium, nickel, molybdenum or vanadium. Other materials and heat treatments may be used by agreement between the manufacturer and the customer, provided the manufacturer guarantees that all mechanical properties specified in this standard are met.

3. MECHANICAL PROPERTIES

When tested by the methods described in Section 6, bolts, screws and studs must have the mechanical properties specified in Table 3 at room temperature (at elevated temperatures — in accordance with Appendix 2). Recommended manufacturing processes for bolts, screws and studs are given in Appendix 1.

Table 3

Clause number	Mechanical properties			Property class
				3.6	4.6	4.8		5.6	5.8		6.6	6.8				8.8				9.8			10.9		12.9
																d****16 mm	d****16 mm
3.1	Tensile strength v**,*** N/mm²		Nom.	300	400			500			600					800	800			900			1000		1200
3.2			Min.	330	400	420		500	520		600					800	830			900			1040		1020
3.3	Vickers hardness, HV		Min.	95	120	130		155	160		190					250	255			290			320		385
			Max.	250												320	335			360			380		435
3.4	Brinell hardness, HB		Min.	90	114	124		147	152		181					238	242			276			304		366
			Max.	238												304	318			342			361		414
3.5	Rockwell hardness, HR	min.	HRB	52	67	71		79	82		89					-	-			-			-		-
			HRCe	-	-	-		-	-		-					22	23			28			32		30
		max.	HRB	99.5												-	-			-			-		-
			HRCe	-												32	34			37			39		44
3.6	Surface hardness HV 0.3 max			-												*⁴
3.7	Yield strength t*⁵, N/mm²	Nom.		180	240	320		300	400		360	480
		Min.		100	240	340		300	420		360	480				-	-			-			-		-
3.8	Proof yield strength 0.2, N/mm²	Nom.		-												640	640			720			900		1080
		Min.		-												640	660			720			940		1100
3.9	Stress from proof load p	n/t or 0.2		0.94	0.94	0.91	0.93			0.90	0.92					0.91	0.91			0.90			0.88		0.88
		N/mm²		180	225	310	280			380	440					580	600			650			830		970
3.10	Elongation after fracture ₅, %	Min.		25	22	14	20			10	16		8			12	12			10			9		8
3.11	Wedge tensile strength***			The wedge tensile strength of whole bolts and screws (except studs) must be not less than the minimum tensile strength value specified in clause 3.2.
3.12	Impact energy, J (Impact toughness, J/cm²)	Min.		-			25 (50)			-	20 (40)			-		30 (60)		30 (60)	25 (50)			20 (40)				15 (30)
3.13	Head-to-shank joint strength			Absence of cracks under the head
3.14	Minimum height of non-decarburized zone E			-											1/2 H₁						2/3 H₁			3/4 H₁
	Maximum depth of complete decarburization G, mm			-											0.015

Only for nominal thread diameters d≤16 mm. Minimum tensile values apply to products with a nominal length l=2.5 d. Minimum hardness applies to products with length l<2.5d and other products that cannot be tensile tested (for example, due to head configuration). For testing of whole bolts, screws and studs, the loads specified in Tables 6-9 must be used. Surface hardness must not exceed the measured core hardness of the product by more than 30 Vickers units when measured at HV0.3. For property class 10.9, any increase in surface hardness exceeding 390 HB is not permitted. In cases where the yield strength cannot be determined, measurement of the proof yield strength is permitted.

4. INSPECTION OF MECHANICAL PROPERTIES

Table 5 gives two test programmes, A and B, for inspecting the mechanical properties of bolts, screws and studs using the test methods given in Section 6. Programme B is preferred for all products and mandatory for products with a breaking load of less than 500 kN. Programme A is used for testing machined specimens and products whose shank cross-sectional area is smaller than the nominal cross-sectional area of the threaded section. Table 4 gives the key to the test programmes (see Table 5).

Table 4

Dimensions	Bolts, screws and studs with thread diameter d4 mm or length l**<2.5** d	Bolts, screws and studs with thread diameter d**>4 mm and length** l****2.5d
Acceptance-determining test	○	●

If the wedge tensile test gives satisfactory results, the tensile test is not performed. Minimum hardness applies only to products with a nominal length l<2.5d and other products that cannot be tensile tested (for example, due to head configuration). Hardness may be measured using the Vickers, Brinell or Rockwell method. In case of dispute, Vickers hardness measurement is decisive for acceptance. Bolts and screws with a special head design that is weaker than the threaded section are not subjected to the wedge tensile test. The test is performed only for bolts, screws and studs with thread diameter d≤16mm and only at the customer’s request; separate requirements apply only to property class 5.6, and also to products with thread diameter d≤16mm at lengths too short for the wedge tensile test.

5. MINIMUM BREAKING LOADS AND PROOF LOADS

Tables 6 and 7 give the minimum breaking loads and proof loads for bolts, screws and studs with coarse thread. Tables 8 and 9 give these for bolts, screws and studs with fine thread.

Table 6

Minimum breaking loads for bolts, screws and studs with coarse thread

Test group	Properties		Test programme A			Test programme B
			Test method	Property class		Test method	Property class
				3.6 4.6 5.6 6.6	8.8 9.8 10.9 12.9		3.6 4.6 4.8 5.6 5.8 6.6 6.8	8.8 9.8 10.9 12.9
I	3.1 and 3.2	Minimum tensile strength v	6.1. Tensile test	●	●	6.2. Tensile test	●	●
	3.3	Minimum hardness**	6.3. Hardness measurement	○	○	6.3. Hardness measurement***	○	○
	3.4 and 3.5	Maximum hardness		● ○	● ○		● ○	● ○
	3.6	Maximum surface hardness			● ○			● ○
	3.7	Minimum yield strength, t	6.1. Tensile test	●
	3.8	Proof stress Rp0.2	6.1. Tensile test.		●
II	3.9	Stress under proof load (t)				6.4. Proof load test	●	●
	3.10	Minimum elongation ₅	6.1. Tensile test	●	●
III	3.11	Wedge tensile strength*⁴				6.5. Wedge tensile test	●	●
IV	3.12	Minimum impact toughness	6.6. Impact toughness test*⁵	*⁶ ●	●
	3.13	Head-to-shank joint strength*⁷				6.7. Head-to-shank joint strength test	○	○
V	3.14	Maximum decarburization zone	6.8. Decarburization test		● ○	6.8. Decarburization test		● ○
	3.15	Minimum tempering temperature	6.8a. Re-tempering test		● ○	6.8a. Re-tempering test		● ○
	3.16	Presence of surface defects	6.9. Surface quality inspection	● ○	● ○	6.9. Surface quality inspection	● ○	● ○

Table 7

Proof loads for bolts, screws and studs with coarse thread

Nominal thread diameter d**, mm**	Thread pitch P, mm	Nominal stress area As, mm²	Minimum proof load, N, for property class
			3.6	4.6	4.8	5.6	5.8	6.6; 6.8	8.8	9.8	10.9	12.9
3	0.5	5.03	1660	2010	2110	2510	2620	3020	4020	4530	5230	6140
3.5	0.6	6.78	2240	2710	2850	3390	3530	4070	5420	6100	7050	8270
4	0.7	8.78	2900	3510	3690	4390	4570	5270	7020	7900	9130	10700
5	0.8	14.2	4690	5680	5960	7100	7380	8520	11350	12800	14800	17300
6	1	20.1	6630	8040	8440	10000	10400	12100	16100	18100	20900	24500
7	1	28.9	9540	11600	12100	14400	15000	17300	23100	26000	30100	35300
8	1.5	36.6	12100	14600	15400	18300	19000	22000	29200	32900	38100	44600
10	1.5	58.0	19100	23200	24400	29000	30200	34800	46400	52200	60300	70800
12	1.75	84.3	27800	33700	35400	42200	43800	50600	67400	75900	87700	103000
14	2	115	38000	46000	48300	57500	59800	69000	92000	104000	120000	140000
16	2	157	51800	02800	05900	78500	81600	94000	125000	141000	163000	192000
18	2.5	192	63400	76800	80600	96000	99800	115000	159000	-	200000	234000
20	2.5	245	80800	98000	103000	122000	127000	147000	203000	-	255000	299000
22	2.5	303	100000	121000	127000	152000	158000	182000	252000	-	315000	370000
24	3	353	116000	141000	148000	176000	184000	212000	293000	-	367000	431000
27	3	459	152000	184000	193000	230000	239000	275000	381000	-	477000	560000
30	3.5	561	185000	224000	236000	280000	292000	337000	466000	-	583000	684000
33	3.5	694	229000	278000	292000	347000	361000	416000	576000	-	722000	847000
36	4	817	270000	327000	343000	408000	425000	490000	678000	-	850000	997000
39	4	976	322000	390000	410000	488000	508000	586000	810000	-	1020000	1200000
42	4.5	1120	370000	448000	470000	560000	582000	672000	930000	-	1165000	136600
45	4.5	1306	431000	542000	550000	653000	679000	784000	108400	-	1360000	1590000
48	5.0	1472	486000	586000	618000	736000	765000	883000	122200	-	1531000	1700000

Table 8

Minimum breaking loads for bolts, screws and studs with fine thread

Nominal thread diameter d**, mm**	Thread pitch P, mm	Nominal stress area As, mm²	Proof load, N, for property class
			3.6	4.6	4.8	5.6	5.8	6.6; 6.8	8.8	9.8	10.9	12.9
3	0.5	5.03	910	1130	1560	1410	1910	2210	2920	3270	4180	4880
3.5	0.6	6.78	1220	1530	2100	1900	2580	2980	3940	4410	5630	6580
4	0.7	8.78	1580	1980	2720	2460	3340	3860	5100	5710	7290	8520
5	0.8	14.2	2560	3200	4400	3980	54100	6250	8230	9230	11800	13800
6	1	20.1	3620	4520	6230	5630	7640	8840	11600	13100	16700	19500
7	1	28.9	5200	6500	8960	8090	11000	12700	16800	18800	24000	28000
8	1.5	36.6	6590	8240	11400	10200	13900	16100	21200	23800	30400	35500
10	1.5	58.0	10400	13000	18000	16200	22000	25500	33700	37700	48100	56300
12	1.75	84.3	15200	19000	26100	23600	32000	37100	48900	54800	70000	81800
14	2	115	20700	25900	35600	32200	43700	50600	66700	74800	95500	112000
16	2	157	28300	35300	48700	44000	59700	69100	91000	102000	130000	152000
18	2.5	192	34600	43200	59500	53800	73000	84500	115000	-	159000	186000
20	2.5	245	44100	55100	76000	68600	93100	108000	147000	-	203000	238000
22	2.5	303	54500	68200	93900	84800	115000	133000	182000	-	252000	294000
24	3	353	63500	79400	109000	98800	134000	155000	212000	-	293000	342000
27	3	459	82600	103000	142000	128000	174000	202000	275000	-	381000	44500
30	3.5	561	101000	126000	174000	157000	213000	247000	337000	-	466000	544000
33	3.5	694	125000	156000	215000	194000	264000	305000	416000	-	570000	673000
36	4	817	147000	184000	253000	229000	310000	359000	490000	-	678000	792000
39	4	976	176000	220000	303000	273000	371000	429000	586000	-	810000	947000
42	4.5	1120	202000	252000	347000	314000	426000	493000	672000	-	930000	1086000
45	4.5	1306	235000	294000	405000	366000	496300	574500	784000	-	1084000	1267000
48	5.0	1472	265000	33100	456000	412000	559000	648000	783000	-	122200	1428000

Table 9

Proof loads for bolts, screws and studs with fine thread

Nominal thread diameter d**, mm**	Thread pitch P, mm	Nominal stress area As, mm²	Minimum proof load, N, for property class
			3.6	4.6	4.8	5.6	5.8	6.6; 6.8	8.8	9.8	10.9	12.9
8	1	39.2	12900	15700	16500	19600	20400	23500	31360	35300	40800	47800
10	1.25	61.2	20200	24500	25700	30600	31800	36700	49000	55100	63600	74700
12	1.25	92.1	30400	36800	38700	46000	47900	55300	73700	82900	95800	112000
14	1.5	125	41200	50000	52500	62500	65000	75000	100000	112000	130000	152000
16	1.5	167	55100	66800	70100	83500	86800	100000	134000	150000	174000	204000
18	1.5	216	71300	86400	90700	108000	112000	130000	179000	-	225000	264000
20	1.5	272	89800	109000	114000	130000	141000	163000	226000	-	283000	332000
22	1.5	333	110000	133000	140000	166000	173000	200000	276000	-	346000	406000
24	2	384	127000	154000	161000	192000	200000	230000	319000	-	399000	469000
27	2	496	164000	194000	208000	248000	258000	298000	412000		516000	605000
30	2	621	205000	248000	261000	310000	323000	373000	515000	-	646000	758000
33	2	761	251000	304000	320000	380000	396000	457000	632000	-	791000	928000
36	3	865	285000	346000	363000	432000	450000	519000	718000	-	900000	1050000
39	3	1030	340000	112000	433000	515000	536000	618000	855000	-	1070000	1260000
42	3	1205	398000	482000	506000	603500	627000	723000	1000000		1253000	1470000
45	3	1400	162000	560000	588000	700000	728000	840000	1120000	-	1456000	1708000
48	3	1603	529000	641000	673000	802000	834000	962000	1330000	-	1667000	195600

6. TEST METHODS

6.1. Tensile test of specimens machined from fasteners. The test procedure is in accordance with GOST 1497-84. When tensile testing machined specimens, the following mechanical properties are determined:

a) tensile strength ?v;

b) yield strength ?t or proof yield strength ?0.2;

c) elongation.

Test specimen

The tensile test uses the specimen shown in Fig. 1.

d — nominal thread diameter;

d0 — diameter of the test specimen (d0 less than the minor diameter of the thread);

b — thread length (b≥d);

L0= 5d0;

Lc — length of the cylindrical part of the specimen (L0+d0);

Lt — total length of the specimen (Lc+2R+b);

Lu — length after fracture;

S0 — cross-sectional area;

R — fillet radius (R≥4mm).

When machining a specimen from a heat-treated bolt or screw with thread diameter greater than 16 mm, the shank diameter may be reduced by no more than 25% of the original diameter (about 44% of the cross-sectional area).

6.2. Tensile test of full-size bolts, screws and studs. The tensile test of full-size bolts, screws and studs is performed in the same way as the tensile test of machined specimens (see 6.1). This test is performed to determine the tensile strength. The tensile strength is calculated from the cross-sectional area, where d2 is the pitch diameter of the thread and d3 is the minor diameter of the thread.

During the test, the length of the loaded threaded section must equal one thread diameter. The product is considered to have passed the test if failure occurs in the shank or thread, but not at the head-to-shank joint. The nut used in the test must have a height of not less than 0.8 of the thread diameter. The loading rate, as determined by the freely moving crosshead, must not exceed 25 mm/min. The grips of the tensile testing machine must be self-centring to avoid side-loading the specimen.

6.3. Hardness measurement. In routine checks, the hardness of bolts, screws and studs may be determined on the head, end face or shank after removing the coating and preparing the specimen accordingly. For property classes 4.8, 5.8 and 6.8, hardness must be determined only on the end face of the bolt, screw or stud. If the hardness exceeds the maximum permissible value, a secondary measurement must be made on a cross-section at a distance of one diameter from the end of the shank, at a point located half a radius from the surface. At this point, the maximum permissible hardness must not exceed the specified limit. In doubtful cases, the Vickers hardness test is decisive for acceptance. Surface hardness is measured on the end faces or flats of the hexagon, which must be lightly ground or polished to ensure the necessary accuracy of the measurement results. The decisive test for checking surface hardness is a Vickers measurement with a 300 g load. Surface hardness values at HV0.3 must be compared with the core hardness values of the material at HV0.3 to assess a relative excess of up to 30 Vickers units. An excess of more than 30 Vickers units indicates carburization. For property classes 8.8-12.9, the difference between core hardness and surface hardness is decisive for assessing the condition of carburization in the surface layer of the bolt, screw or stud. There may be no direct relationship between hardness and the theoretical tensile strength. Maximum hardness values are selected based on other considerations unrelated to the theoretical maximum stresses (for example, to avoid brittleness).

Note. A clear distinction must be made between an increase in hardness caused by carburization and an increase in hardness resulting from heat treatment or cold working of the surface.

6.3.1. Vickers hardness measurement — in accordance with GOST 2999-75.

6.3.2. Brinell hardness measurement — in accordance with GOST 9012-59.

6.3.3. Rockwell hardness measurement — in accordance with GOST 9013-59.

6.4. Proof load test. The proof load test consists of the following basic operations:

a) application of the specified proof load (Fig. 2);

b) measurement of the permanent elongation (if any) resulting from the proof load.

dh — hole diameter per the second series of GOST 11284-75; A — the required type of contact between the spherical surface of the measuring pin and the conical surface of the hole in the end of the bolt. The proof load must be applied along the axis of the bolt (screw, stud) using a standard tensile testing machine. The full proof load must be held for 15 s. The length of the free threaded part under load must equal 6 thread pitches (6P). For bolts and screws with thread running up to the head, the length of the free threaded part under load must be as close as possible to 6 thread pitches. To measure the permanent elongation, 60° countersunk centre holes are drilled in the ends of the bolt (screw, stud). Before and after load application, the product is placed on the prism of the measuring instrument between two measuring pins with spherical ends. Gloves or tongs should be used during measurement to minimize measurement error. Under the conditions of the proof load test, the length of the bolt, screw or stud after loading must be the same as before loading, within a tolerance of ±12.5 µm for measurement error. The loading rate, as determined by the freely moving crosshead, must not exceed 3 mm/min. The machine grips must be self-centring to prevent side-loading of the specimen. Due to the influence of certain variables, such as deviations from coaxiality and straightness (plus measurement error), the elongation under the initial proof load application may exceed the permissible value. In such cases, the products may be retested with a load exceeding the original by 3%. The test result may be considered satisfactory if, after the repeat loading, the length of the product is the same as after the first loading (with a measurement error tolerance of 12.5 µm).

6.5. Wedge tensile test. The wedge tensile test of bolts and screws must be carried out in accordance with Fig. 3.

A 45° chamfer is permitted. The hardness of the wedge washer shall be not less than 45 HRCe. Dimensions of the wedge washer are given in Tables 9a, 10.

Table 9a

Nominal thread diameter d**, mm**	Thread pitch P, mm	Nominal stress area As, mm²	Proof load, N, for property class
			3.6	4.6	4.8	5.0	5.8	0.6; 0.8	8.8	9.8	10.9	12.9
8	1	39.2	7060	8820	12200	11000	14900	17200	22700	25500	32500	38000
10	1.25	61.2	11000	13800	19000	17100	23300	26900	35500	39800	50800	59400
12	1.25	92.1	16600	20700	28600	25800	35000	40500	53400	59900	76400	89300
14	1.5	125	22500	28100	38800	35000	47500	55000	72500	81200	104000	121000
16	1.5	167	30100	37600	51800	46800	63500	73500	96900	109000	139000	162000
18	1.5	216	38900	48600	67000	60500	82100	95000	130000	-	179000	210000
20	1.5	272	49000	61200	84300	76200	103000	120000	163000	-	226000	264000
22	1.5	333	59900	74900	103000	93200	126000	146000	200000	-	276000	323000
24	2	384	69100	86400	119000	108000	146000	169000	230000	-	319000	372000
27	2	496	89300	112000	154000	139000	188000	218000	298000	-	412000	481000
30	2	621	112000	140000	192000	174000	236000	273000	373000	-	515000	602000
33	2	761	137000	171000	236000	213000	289000	335000	457000	-	632000	738000
36	3	865	156000	195000	268000	242000	329000	381000	519000	-	718000	838000
39	3	1030	185000	232000	319000	288000	391000	453000	618000	-	855000	999000
42	3	1205	217000	271000	374000	337000	458000	530000	723000	-	1000000	1170000
45	3	1400	252000	315000	434000	392000	532000	616000	840000	-	1160000	1360000
48	3	1603	289000	361000	497000	449000	609000	705000	962000	-	1330000	1550000

Continuation of Table 9a

Nominal thread diameter d	3	3.5	4	5	6	7	8	10	12	14	16	18
dh	3.4	3.9	4.5	5.5	6.6	7.6	9.0	11.0	13.5	15.5	17.5	20.0
R	0.7	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.8	1.3	1.3	1.3

Nominal thread diameter d	20	22	24	27	30	33	36	39	42	45	48
dh	22.0	24.0	26.0	30.0	33.0	36.0	39.0	42.0	45.0	48.0	52.0
R	1.3	1.6	1.6	1.6	1.6	1.6	1.6	1.6	1.6	1.6	1.6

Table 10

Nominal thread diameter d**, mm**	Property class for
	bolts and screws with a plain shank length of 2d		bolts and screws with thread up to the head or with a plain shank length <2d
	3.6, 4.6, 4.8, 5.6. 5.8, 8.8, 6.6, 9.8, 10.9	6.6, 12.9	3.6, 4.6, 4.8, 5.6, 5.8, 8.8, 6.6, 9.8, 10.9	6.8, 12.9
	Wedge angle ±30
df20	10°	6°	6°	4
20<d48	6°	4	4	4

The distance from the thread runout of the bolt to the contact surface of the test nut of the clamping device shall be equal to the thread diameter d. The wedge washer is installed under the bolt head. The tensile test is carried out until fracture of the bolt occurs. The test results are considered satisfactory if the bolt fractures in the shank or thread, but not at the transition from the head to the shank. In this case the requirement for the minimum tensile strength (either in the wedge washer test or in an additional tensile test without the wedge washer) must be met in accordance with the values specified for the corresponding property classes. Screws with thread up to the head are considered to have passed the test if the crack causing failure starts on the free thread section (even if it spreads at the moment of fracture to the fillet under the head or to the head). For products of product grade C, the radius R for the washer is calculated using a formula, where da max is the largest diameter of the circle of intersection of the bearing surface under the head with the bearing plane; ds min is the smallest diameter of the bolt shank. For products with a head bearing surface diameter greater than 1.7d that have failed the test, the head may be machined down to 1.7d, and the test repeated using the wedge angle in accordance with Table 10. For products with a head bearing surface diameter greater than 1.9d, the 10° wedge angle may be reduced to 6°.

6.6. Determination of impact toughness. Determination of impact toughness shall be carried out in accordance with GOST 9454-78 on type 8 specimens with a U-shaped notch. The test specimen is cut from bolts, screws and studs in the longitudinal direction, as close to the surface as possible. The unnotched side of the specimen shall be located as close as possible to the surface of the bolt. Products with thread diameter d≥M16 are subject to this test.

6.7. Head-to-shank joint strength test. The head-to-shank joint strength test shall be carried out in accordance with Fig. 4. Values of dh and R are given in Table 9a. Die thickness — more than 2d. Values of angle ? are given in Table 11. After several hammer blows, the head shall bend through an angle of 90°-? with no signs of cracking in the fillet under the head, when inspected at a magnification of not less than 8? and not more than 10?. Screws with thread up to the head are considered to have passed the test even if cracks appear in the first thread turn, provided the head does not break off.

Table 11

Property class	3.6; 4.6; 5.6	4.8; 5.8; 6.6; 6.8; 8.8; 9.8; 10.9; 12.9
Angle	60°	80°

Bolts and screws with thread diameter d≤M16 that do not have sufficient length to carry out the wedge washer tensile test are subject to this test. This test may also be carried out for longer bolts and screws, however the wedge washer test is decisive for them.

6.8. Decarburization check. Using a suitable measurement method (items 6.8.2.1 and 6.8.2.2) on a longitudinal section of the threaded portion, the height of the base metal zone (E) and the depth of the fully decarburized zone (G) are checked for compliance with the established standards (Fig. 5). The minimum value of E and the maximum value of G are given in Table 3.

1 — partial decarburization; 2 — full decarburization; 3 — base metal; H1 — external thread profile height. Values of H1 are given in Table 12.

Table 12

Thread pitch, P, mm*		0.5	0.6	0.7	0.8	1	1.25	1.5	1.75	2	2.5	3	3.5	4
H₁, mm		0.307	0.368	0.429	0.491	0.613	0.767	0.920	1.074	1.227	1.534	1.840	2.147	2.454
E, mm, not less than, for property classes	8.8 9.8	0.154	0.184	0.215	0.245	0.307	0.384	0.460	0.537	0.614	0.767	0.920	1.074	1.227
	10.9	0.205	0.245	0.286	0.327	0.409	0.511	0.013	0.710	0.818	1.023	1.227	1.431	1.636
	12.9	0.230	0.276	0.322	0.308	0.400	0.575	0.090	0.806	0.920	1.151	1.380	1.610	1.811

6.8.1. Definitions

6.8.1.1. Base metal hardness — the hardness at a point located as close as possible to the surface (from the axis toward the outer diameter), immediately before the zone where hardness increases or decreases due to carburization or decarburization.

6.8.1.2. Decarburization — a reduction in carbon content on the surface of steel products.

6.8.1.3. Partial decarburization — decarburization causing a slight difference in the structure of tempered martensite and a significant reduction in hardness compared to the hardness of the adjacent base metal zone.

6.8.1.4. Full decarburization — decarburization with loss of carbon to such an extent that metallographic analysis shows clearly defined ferrite grains.

6.8.1.5. Carbon restoration — the process of restoring carbon lost during heat treatment in the surface layer by holding in a furnace with a controlled potential.

6.8.1.6. Carburization — the process of saturating the surface with carbon in an amount exceeding its content in the base metal.

6.8.2. Measurement methods

6.8.2.1. Microscopic method. This method allows determination of the parameters E and G. The specimen intended for examination is cut along the axis of the thread at a distance of one diameter from the end of the bolt, screw or stud, after all heat treatment operations to which the product is to be subjected. For grinding and polishing, the specimen is placed in clamps or embedded in plastic (the latter is preferred). After embedding, the specimen is ground and polished in accordance with the requirements of metallographic analysis. To reveal changes in the microstructure caused by decarburization, the specimen is etched in a 3% solution of nitric acid in ethyl alcohol. Microscopic examination is carried out at a magnification of 100?, unless otherwise agreed. If a microscope with a ground-glass screen is used for the examination, the decarburization value is measured directly on the scale. If an eyepiece is used for measurement, it shall have a grid or scale.

6.8.2.2. Hardness measurement method. The decisive method for partial decarburization. This method is applied to threads with a pitch of 1.25 mm and greater. Hardness is measured at three points in accordance with Fig. 6. Values of parameter E are given in Table 3. The load during hardness measurement shall be 300 g.

Hardness determination at point 3 shall be carried out on the pitch diameter line of the thread, on the turn adjacent to the turn on which the measurements at points 1 and 2 are made. The Vickers hardness value at point 2 shall be equal to or greater than the value at point 1 minus 30 Vickers units. In this case, the height of the non-decarburized zone E shall be at least equal to the value specified in Table 12. The Vickers hardness value at point 3 shall be equal to or less than the value at point 1 plus 30 Vickers units. An increase in hardness of more than 30 Vickers units indicates that carburization has occurred. Full decarburization up to the maximum value specified in Table 3 cannot be determined by hardness measurement.

6.8a. Re-tempering test. Re-tempering is carried out at a temperature 10°C lower than the minimum tempering temperature established for the given product, for 30 minutes. The arithmetic mean of three hardness values of the bolt, screw or stud, measured before and after re-tempering, shall not differ by more than 20 Vickers units.

6.9. Surface quality control. Surface quality control of bolts, screws and studs is carried out in accordance with GOST 1759.2-82. In program A tests, bolts, screws and studs are inspected before machining.

APPENDIX 1

Recommended

Recommended manufacturing processes for bolts, screws and studs made of non-alloy and alloy steels, and steel grades

APPENDIX 2

For reference

Properties of fasteners at elevated temperatures

Property class	Manufacturing processes	Steel grade	Standard designations
3.6	Hot forming. Cold forming followed by softening heat treatment	10, 10 kp	GOST 10702-78
4.6	Hot forming. Cold forming followed by softening heat treatment	20	GOST 1050-38
4.8	Cold forming	10, 10 kp	GOST 10702-78
5.6	Hot forming. Cold forming followed by softening heat treatment	30, 35	GOST 1050-83, GOST 4543-71, GOST 10702-78
5.8	Cold forming	10, 10 kp, 20, 20 kp
6.6	Hot forming followed by quenching and tempering. Cold forming followed by quenching and tempering	35	GOST 1050-88, GOST 4543-71, GOST 5663-79, GOST 10702-78
	Hot forming	45, 40G
6.8	Cold forming	20, 20 kp	GOST 1050-88, GOST 5603-79, GOST 10702-78
8.8-12.9	Hot forging followed by quenching and tempering. Cold forming followed by quenching and tempering. Machining followed by quenching and tempering. Cold forming from heat-strengthened metal	35, 35Kh, 38KhA, 45G 40G2, 40Kh, 30KhGSA, 35KhGSA 16KhSN 20G2R*	GOST 45.13-71, GOST 10702-78

The reference data given in the table indicate the approximate reduction in the tensile mechanical properties of fasteners under conditions of elevated temperatures. This data shall not be used as requirements for bolts, screws and studs during testing.

INFORMATIONAL DATA

1. DEVELOPED AND SUBMITTED BY the Ministry of Ferrous Metallurgy of the USSR

DEVELOPERS

B. M. Rigmant, N. G. Andreeva, T. E. Yurchenko

2. APPROVED AND INTRODUCED by Resolution of the USSR State Committee for Standards dated 30.12.87 No. 5112

3. Review date — 1993

4. The standard fully complies with the international standard ISO 898/1-78

5. Supersedes GOST 1759-70 (with respect to mechanical properties and test methods for bolts, screws and studs)

6. REFERENCED REGULATORY AND TECHNICAL DOCUMENTS

Designation of the referenced regulatory document	Item, sub-item number of the appendix
GOST 1050	Appendix 1
GOST 1497	6.1
GOST 1759.0	2
GOST 1759.2	6.9
GOST 2999	6.3.1
GOST 4543	Appendix 1
GOST 5663	Appendix 1
GOST 9012	6.3.2
GOST 9013	6.3.3
GOST 9454	6.6
GOST 10702	Appendix 1
GOST 11284	6.4
GOST 24705	Introductory part

7. REISSUE (October 1990) with Amendment No. 1, approved in November 1989 (IUS 2-90)