ISO 888: Thread lengths for ISO metric fasteners (bolts)
Calculation of thread lengths
Typical, unless specified in a product standard, dimensions for thread lengths (b) is calculated as follow:
- for l <= 125 mm: b = 2d + 6mm
- for 125 mm < l <= 200 mm: b = 2d + 12mm
- for l > 200mm: b = 2d + 25mm
Where l is length of the bolt and b is the threaded part of the bolt.
For bolt, where lengths l <= 0.5d the bolt should be fully threaded.
Typical thread lengths (b) for popular sizes of fasteners
|l <= 125||30||38||46||50||54||60||66||72||78|
|125 < l|
l <= 200
|l > 200||–||57||65||69||73||79||85||91||97|