When you select Calculated tensile stress area (Connector-Bolt PropertyManager), the program calculates the tensile stress area (At), which is the mimimum area of the threaded section of the bolt, according to the formula: At = [(d3 + d2) / 2)]2 * π /4
- P = pitch, axial distance between two adjacent threads
- n = 1 / P, number of bolt threads per inch (ANSI) or millimeter (ISO)
- d = nominal bolt shank diameter
ISO Bolt threads
- d3 = d - 1.2268 * P
- d2 = d - 0.6495 * P
The formula for the tensile stress area becomes: A
t = 0.7854 * [d - (0.9382 * P)]
2
Substituting P = 1 / n results to At = 0.7854 * [d - (0.9382 / n)]2, where d is given in mm, and n is given in threads/mm.
ANSI threads
A similar approach is followed for the calculation of the tensile stress area:
At = 0.7854 * [d - (0.9743 / n)]2, where d is given in inches, and n is given in threads/inch.
Reference: Machinery's Handbook published by Industrial Press.
The table below provides the nominal bolt diameter and pitch values for the main ISO M large thread bolts.
Table 1. ISO M Metric Bolt Threads, ISO 724 (DIN 13 T1)| Nominal Diameter d (mm) |
Pitch P (mm) |
|---|
| M 1.60 |
0.35 |
| M 2.00 |
0.40 |
| M 2.20 |
0.45 |
| M 3.00 |
0.50 |
| M 4.00 |
0.70 |
| M 4.50 |
0.75 |
| M 5.00 |
0.80 |
| M 6.00 |
1.00 |
| M 8.00 |
1.25 |
| M 10.00 |
1.50 |
| M 12.00 |
1.75 |
| M 16.00 |
2.00 |
| M 20.00 |
2.50 |
| M 24.00 |
3.00 |
| M 30.00 |
3.50 |
| M 36.00 |
4.00 |
| M 42.00 |
4.50 |
| M 48.00 |
5.00 |
| M 56.00 |
5.50 |
| M 64.00 |
6.00 |