Are fine threads preferred when vibrations are present 1

[alan54]

In application where an agitator is secured with bolts in tapped hole, should fine threads be used (rather than coarse threads)? i.e., aren't they less likely to loosen due to smaller incline angle?

 

[jek147]

I commonly use exciters with fixtures which use threaded fasteners. I generally use pitches in the range of 40 to 60 and have not had any problems. However, I usually do not exceed 10kHz.

 

[ChasBean1]

Less likely to loosen and I agree w/your logic, but more likely to strip & fail. If that's a concern, double-nut it...

 

[ChasBean1]

woops - just read again & realize you have no nuts! (nothing personal) - then it looks like a tradeoff between what thread strength you need versus ability to keep tight. Should be a happiest medium somewhere between the two...

 

Fine pitches improve our assembly to withstand vibration but it also depend of mode (linear or rolling x,y,z). In case of tapped hole the "helicoil" system (a kind of spring that you insert between screw and tapped hole) work very well in aerospace products. We recomand to remove the insert and reinstall a new one after the third maintenance operation.