Fastener Identification Marking for Nuts

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Grade Identification Marking	Specification	Material	Nominal Size In.	Proof Load Stress ksi	Hardness Rockwell		See Note
					Min	Max
No Mark	ASTM A563 – Grade 0	Carbon Steel	1/4 thru 1-1/2	69	B55	C32	3,4
	ASTM A563 – Grade A	Carbon Steel	1/4 thru 1-1/2	90	B68	C32	3,4
	ASTM A563 – Grade B	Carbon Steel	1/4 thru 1	120	B69	C32	3,4
			over 1 thru 1-1/2	105
	ASTM A563 – Grade C	Carbon Steel May be Quenched and Tampered	1/4 thru 4	144	B78	C38	5
	ASTM A563 – Grade C3	Atmospheric Corrosion Resistant Steel May be Quenched and Tampered	1/4 thru 4	144	B78	C38	5,9
	ASTM A563 – Grade D	Carbon Steel May be Quenched and Tampered	1/4 thru 4	150	B84	C38	6
	ASTM A563 – Grade DH	Carbon Steel Quenched and Tampered	1/4 thru 4	175	C24	C38	6
	ASTM A563 – Grade DH3	Atmospheric Corrosion Resistant Steel, Quenched and Tampered	1/4 thru 4	175	C24	C38	5,9
	ASTM A194 – Grade 1	Carbon Steel	1/4 thru 4	130	B70	—	7
	ASTM A194 – Grade 2	Medium Carbon Steel	1/4 thru 4	150	159	352	7,8
	ASTM A194 – Grade 2H	Medium Carbon Steel, Quenched and Tempered	1/4 thru 4	175	C24	C38	7
	ASTM A194 – Grade 2HM	Medium Carbon Steel, Quenched and Tempered	1/4 thru 4	150	159	237	7,8
	ASTM A194 – Grade 4	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 thru 4	175	C24	C38	7
	ASTM A194 – Grade 7	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 thru 4	175	C24	C38	7
	ASTM A194 – Grade 7M	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 thru 4	150	159	237	7
See Note 1,2	10

NOTES:

1. 1. In addition to the indicated grade marking, all grades, except A563 grades O, A and B, must be marked for manufacturer identification.
2. 2. The markings shown for all grades of A194 nuts are for cold formed and hot forged nuts. When nuts are machined from bar stock the nut must be additionally marked with the letter ‘B’.
3. 3. Nuts are not required to be marked unless specified by
   the purchaser. When marked, the identification marking shall be the grade letter O, A or B.
4. 4. Properties shown are those of nonplated or noncoated coarse thread hex nuts.
5. 5. Properties shown are those of coarse thread heavy hex nuts.
6. 6. Properties shown are those of coarse thread heavy hex nuts.
7. 7. Properties shown are those of coarse 8-pitch thread heavy hex nuts.
8. 8. Hardnesses are Brinell Hardness Numbers.
9. 9. The nut manufacturer, at his option, may add other markings to indicate the use of atmospheric corrosion resistant steel.
10. 10. Specifications ——
    ASTM A563 —— Carbon and Alloy Steel Nuts.
    ASTM A194/A194M —— Carbon and Alloy Steel Nuts for Bolts for High Pressure and High Temperature Service.

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