Hardness Test:
Requirements:
All nuts shall meet the hardness requirements specified in Table 2.
Sample nuts of Grades 1, 2, 2H, 2HM, 3, 7, 7M, and
16 which have been given the treatment
described in
8.1.5 shall
meet the minimum hardness specified in Table 2.
Number of Tests— (Grades 1, 2,
2H, 3, 7, and 16 and
all types of Grade 6):
Tests on the number of sample nuts in accordance
with the following table shall be performed by the manufacturer following all production heat
treatments:
| Grade | Completed Nuts | Sample Nut After Heat Treatment | |||
|---|---|---|---|---|---|
| Brinell Hardness, BHN |
Rockwell Hardness | Brinell Hardness, BHN, min |
Rockwell Hardness, HRB, min |
||
| HRC | HRB | ||||
| 7 | 248 - 327 | 24 - 35 | ... | 201 | 94 |
Heat Treatment: Grade 7 shall be quenched and tempered at a temperature of at least 1100 °F [595 °C].
| Nominal Size, Inch. | Threads Per Inch | Proof Load, lbf | |
|---|---|---|---|
| Heavy HexA | HexB | ||
| 1/4 | 20 | 5 570 | 4 770 |
| 5/16 | 18 | 9 170 | 7 860 |
| 3/8 | 16 | 13 560 | 11 620 |
| 7/16 | 14 | 18 600 | 15 940 |
| 1/2 | 13 | 24 830 | 21 280 |
| 9/16 | 12 | 31 850 | 27 300 |
| 5/8 | 11 | 39 550 | 33 900 |
| 3/4 | 10 | 58 450 | 50 100 |
| 7/8 | 09 | 80 850 | 69 300 |
| 01 | 08 | 106 000 | 90 900 |
| 1-1/8 | 08 | 138 200 | 118 500 |
| 1-1/4 | 08 | 175 000 | 150 000 |
| 1-3/8 | 08 | 215 800 | 185 000 |
| 1-1/2 | 08 | 261 100 | 223 800 |
A: Based on proof stress of 175 000 psi.
B: Based on proof stress of 150 000 psi.