| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|
| Grade | Properties of finished bolts | ||||||
| Minimum tensile strength (see NOTE 1) |
Stress for proof load (see Table 5) |
Minimum elongation on a gauge length 4√area (see NOTE 2) |
Minimum Izod impact value | Brinell hardness numbers [see Clause 4 d)] |
|||
| Diameter or width across flats | |||||||
| Up to 3/4 in | Over 3/4 in up to and including 1 1/8 in | Over 1 1/8 in | |||||
| tonf/in² | tonf/in² | per cent | ft lbf | ft lbf | ft lbf | HB10/3 000 | |
| A | 28 | — | 10/14 (see NOTE 3) |
— | — | — | — |
| B | 28 | — | 17 | — | — | — | — |
| P | 35 | 20 | 15 | 20 | 15 | 10 | 152/240 |
| S | 50 | 38 | 18 | 35 | 30 | 20 | 223/310 |
| T | 55 | 41 | 16 | 35 | 30 | 20 | 248/335 |
| V | 65 | 49.5 | 14 | 35 | 30 | 20 | 293/370 |
| X | 75 | 60 | 12 | 15 | 15 | 10 | 341/410 |
NOTE 1: The cross sectional area of the thread used in calculation is obtained by the following formula. Area = π ((Basic effective diametera + basic minor diametera) / 4)2 NOTE 2: BS 18 now specifies a gauge length of 5.65√Area, but elongation values appropriate to this length are not yet available for the higher grades of steel. The values in Column 4 have therefore been retained pending further information on this subject. NOTE 3: For Grade A bolts or screws the minimum elongation shall be 10 per cent for 1/4 in and 5/16 in in nominal sizes and 14 per cent for all other sizes up to and including 2 in. a As specified for the thread in question in BS 1580 “Unified screw threads.” |