How important is bolt preload? 4

[TJK1]

For a grade 8 hex head bolt I believe the recommended preload is .90 x proof strength x bolt tensile area. If I torque it as to develop less than the recommended preload, will that have any effect on the overall external load carrying capacity of the bolt?

 

[desertfox]

Hi TJK1

Pre-load for a bolted joint should be based on the external forces the bolt as tow ithstand during service have a look at this web site it should explain everything.

http://www.boltscience.com/pages/info.htm

Best regards

Desertfox

 

[diamondjim]

Most torque recommendations is 75
to 80 percent of the proof load
depending on how the bolt is tightened
and of what magnitude the dynamic
loads impose on the bolts. If you
have only static loads and use a
very sophisticated bolt tensioning
device, you might consider using 90
percent of the proof load.

 

[R1100S]

Preload is very important to load carrying.

http://www.boltscience.com

has a good writeup, or try the machinery's handbook