Threads with a fine pitch have more threads per unit length than a standard metric coarse pitch bolt or screw. For example, an M10 coarse pitch has threads 1.5mm apart,
whilst an M10 fine pitch has this figure at 1.25mm.
These different thread pitches would be written as:
- M10 - standard metric coarse pitch (1.5mm)
- M10 x 1.25 - metric fine pitch
- M10 x 1 - metric extra fine pitch
Matching these thread pitches and diameters between nut and bolt will ensure that the two parts are compatible.
The advantages of fine pitch threads are:
- increased tensile and shear strength due to the size and depth of the fine thread, which is more apparent as the bolt/screw diameter gets smaller.
- requires less torque in assembly to achieve the same pre-load.
- allows for greater adjustment accuracy, and the thread finishes closer to the head.
- less likely to loosen with vibration.
- better for tapping into thin walled components as it needs a shorter engagement length.
The disadvantages of fine pitch threads are:
