Prop nut

[Graham_Wright]

M30 X 3.5
M30 X 2.0
M30 X 1.5

These are all standard threads. What are the arguments for and against the various pitch options.

(We've already addressed material choice and that could have a bearing also.)

 

[rogerthebodger]

Generally the softer the material the larger the pitch i.e. use a course pitch in you aluminium mast.

The smaller the pitch the greater the self locking effect and the greater the tension of the shaft/[prop can be tightened for given tightening force.

I have use the smallest pitch on my stainless shaft and nut but if you are using bronze maybe the middle one would be the best compromise.