ASTM F568M Externally Threaded Carbon and Alloy Steel Metric Fasteners

ASTM F568M Specification for Carbon and Alloy Steel Externally Threaded Metric Fasteners

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Mechanical Requirements for Bolts, Screws, and Studs

Property Class	Nominal Diameter of Product	Full Size Bolts, Screws, and Studs			Machined Test Specimens of Bolts, Screws, and Studs				Surface Hardness	Product Hardness
		Proof Load		Tensile Strength, MPa	Yield Strength, MPa^B	Tensile Strength, Mpa	Elongation, %	Reduction of Area, %	Rockwell 30N	Rockwell		Vickers
		Length Measurement Method, Mpa	Yield Strength Method, Mpa	Min	Min	Min	Min	Min	Max	Min	Max	Min	Max
4.6	M5–M100	225	240	400	240 C	400	22	35	. . .	B67	B95	120	220
4.8	M1.6–M16	310	340	420	340	420	14	35	. . .	B71	B95	130	220
5.8	M5–M24^D	380	420	520	420	520	10	35	. . .	B82	B95	160	220
8.8	M20–M80	600	660	830	660	830	12	35	53	C23	C34	255	336
8.8.3	M20–M36	600	660	830	660	830	12	35	53	C23	C34	255	336
9.8	M1.6–M16	650	720	900	720	900	10	35	56	C27	C36	280	360
10.9	M5–M100	830	940	1040	940	1040	9	35	59	C33	C39	327	382
10.9.3	M16–M36	830	940	1040	940	1040	9	35	59	C33	C39	327	382
12.9 ^E	M1.6–M100	970	1100	1220	1100	1220	8	35	63	C38	C44	372	434
^B Yield strength is stress at which a permanent set of 0.2 % of gage length occurs. ^C Yield point shall apply instead of yield strength at 0.2 % offset for Class 4.6 products. ^D Class 5.8 applies only to bolts and screws with lengths 150 mm and shorter and to studs of all lengths. ^E Caution is advised when considering the use of Class 12.9 bolts, screws, and studs. Capability of the bolt manufacturer, as well as the anticipated in-use environment, should be considered. High-strength products of Class 12.9 require rigid control of heat-treating operations and careful monitoring of as-quenched hardness, surface discontinuities, depth of partial decarburization, and freedom from carburization. Some environments may cause stress corrosion cracking of nonplated as well as electroplated products.

Property Class Identification Symbols

Property Class	Identification Symbol
	Specification A 325M Bolts	Specification A 490M Bolts	Other Bolts and Screws	Studs
	Specification A 325M Bolts	Specification A 490M Bolts	Other Bolts and Screws	M4 and Smaller	M5 to M10 incl.	M12 and Larger
4.6	^A	^A	4.6	^A	^A	4.6
4.8	^A	^A	4.8	^A	^A	4.8
5.8	^A	^A	5.8	^A	^A	5.8

8.8 ^B	8S	^A	8.8	^A	^A	8.8
8.8.3	8S3	^A	8.8.3	^A	^A	8.8.3
9.8 ^B	^A	^A	9.8	^A	+	9.8

10.9 ^B	^A	10S	10.9	^A	□	10.9
10.9.3	^A	10S3	10.9.3	^A	^A	10.9.3
12.9	^A	^A	12.9	^A	▲	12.9
^A Not applicable. ^B Products made of low-carbon martensite steel shall be additionally marked by underlining the property class symbol.

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