Standard for Nut

Grade

Hardness

Dimensional style of nut

Nominal nut size

Proof Load Stress                                                    ksi

Head Marking

in.

Non-Zinc coated Nuts

Zinc coated Nuts

A194

2

HRB159-352

hex

1/4 to 1-1/2

135

135

heavy hex

1/4 to 4

150

150

2H

≦1-1/2: 248-352，                ﹥1-1/2 : 212-352

hex

1/4 to 1-1/2

150

150

heavy hex

1/4 to 4

175

175

2HM

HRB159-235

hex

1/4 to 1-1/2

135

135

heavy hex

1/4 to 4

150

150

4

248-327

hex

1/4 to 1-1/2

150

150

heavy hex

1/4 to 4

175

175

7

248-327

hex

1/4 to 1-1/2

150

150

heavy hex

1/4 to 4

175

175

7M

HRB159-235

hex

1/4 to 1-1/2

135

135

heavy hex

1/4 to 4

150

150

8

126-300

hex

1/4 to 1-1/2

75

75

heavy hex

1/4 to 4

80

80

8M

126-300

hex

1/4 to 1-1/2

75

75

heavy hex

1/4 to 4

80

80