Grade 7M

ASTM A194 Grade 7M Specification for high tensile nuts and other internally threaded fasteners, made from heat treated chromium molybdenum alloy steel. ASTM A194 Grade 7M is a standard material specification for high tensile nuts and other internally threaded fasteners, made from chromium molybdenum alloy steel. Grade 7M nuts can be produced by means of hot forging, cold forging or machining from bar stock (Grade Type AISI 4140/4142/4145/4140H/4142H/4145H) followed by heat treatment. ASTM A194 specification covers requirements for chemical composition, heat treatment, hardness, proof load, etc., for Grade 7M nuts.

Chemical Composition

Element	Alloy Steel
	Chromium Molybdenum Steel
	CompositionA, %
Carbon	0.37 - 0.49
Manganese	0.65 - 1.10
Phosphorus	0.035 max
Sulfur	0.04 max
Silicon	0.15 - 0.35
Chromium	0.75 - 1.20
Molybdenum	0.15 - 0.25

^AThe intentional addition of Bi, Se, Te, and Pb is not permitted.

Hardness

Grade	Completed Nuts			Sample Nut After Heat Treatment
	Brinell Hardness, BHN	Rockwell Hardness		Brinell Hardness, BHN, min	Rockwell Hardness, HRB, min
		HRC	HRB
7M	159 - 235	...	84 - 99	159	84

Heat Treatment: Grade 7M shall be quenched and tempered at a temperature of at least 1150 °F [620 °C].

Proof Load

Nominal Size, Inch.	Threads Per Inch	Proof Load, lbf
		Heavy HexA	HexB
1/4	20	4 770	4 300
5/16	18	7 860	7 070
3/8	16	11 620	10 460
7/16	14	15 940	14 350
1/2	13	21 280	19 160
9/16	12	27 300	24 570
5/8	11	33 900	30 510
3/4	10	50 100	45 090
7/8	09	69 300	62 370
01	08	90 900	81 810
1-1/8	08	118 500	106 700
1-1/4	08	150 000	135 000
1-3/8	08	185 000	166 500
1-1/2	08	223 800	201 400

A: Based on proof stress of 150 000 psi.
B: Based on proof stress of 135 000 psi.

Nuts

Commonly Produced Grade 7M Nuts
Hex Nuts	Heavy Hex Nuts	Jam Nuts	Heavy Hex Jam Nuts	Castle Nuts
Coupling Nuts	Square Nuts	Thin Square Nuts	All Metal Lock Nuts	Dome Nuts