Size of timber inches using actual dimensions | 4x4 | 6x6 | 8x8 | 10x10 | 12x12 | |
Square inches in cross section | 16 | 36 | 64 | 100 | 144 | |
Minimum allowable crushing strength parallel to grain, p.s.i. | 5,000 | 5,000 | 5,000 | 5,000 | 5,000 | Note: Adapted from U.S. Department of Agriculture Technical Bulletin 479. Hardwoods recommended are those whose ultimate crushing strengths in compression parallel to grain are 5,000 p.s.i. (pounds per square inch) or greater. |
Maximum static load within short column range | 80,000 | 180,000 | 320,000 | 500,000 | 720,000 | Note: Slenderness ratio formula for short columns is L/d = 11, where L = length of timber in inches and d = least dimension in inches; this ratio should not exceed 11. |
Safety factor | 10 | 10 | 10 | 10 | 10 | |
Maximum recommended weight of forging hammer for timber used | 8,000 | 18,000 | 32,000 | 50,000 | 72,000 | |
Maximum allowable length of timber in inches | 44 | 66 | 88 | 100 | 132 |