What happens when bolt threads in member joint?

[franc11]

Hi,

I have this little question. Does it make any difference on the bolt prelaod or clamping force wheter the bolt thread in the second member or it is clamp with a nut outside de member?

Thanks!

 

[CoryPad]

It can make a few differences. First of all, it can change the grip length, which changes elastic deflections during tightening, which can change preload. Secondly, it can change thread friction coefficient (and hence, preload) since tapped holes routinely have cut threads with higher friction than formed threads in nuts (especially if the nut is coated with a low friction coating). There are others...

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Screwman]

The biggest difference is going to be the reduction in effective fastener length when using the tapped plate. This is going to reduce your available elastic length and make it harder to retain stretch in the bolt and preload.
That being said, using a seperate nut is adding an additional component to the assembly and also requiring more clearance on the backside of the joint.

As with most things in fastening, you end up have to make compromises to assemble your product.