re: loads on keenserts follow-up

[glulambeam]

thread404-275179

referring to this earlier thread:

http://www.eng-tips.com/viewthread.cfm?qid=275179

Don't the threads on the insert take any amount of the external load?

I've been usually adding the preload + the full amount of external load to check and see if the parent material the insert is installed into, doesn't shear out, but this conservative approach naturally doesn't work if the external load is large. Is it just the case that the insert sees whatever load that the bolt sees? The bolt is typically calculated as carrying the preload plus some percentage of the external load (I usually just top it off at 33%, though I've heard that the theoretical limit is 25%).

 

[drawoh]

glulambeam,

The insert sees whatever force it is the bolt exerts. If the external force on your plate is less than the pre-load, the screw and insert should be seeing approximately the pre-load. If your external load is in excess of the pre-load, then the bolt sees the external force, only.

You do not specify an insert like this unless you are serious about the strength of your fastener. If the manufacture of the insert does not provide pull-out forces, don't buy the insert. This would be good information to include in the MIL specification.

--
JHG

 

[glulambeam]

Hey Draw...thanks. When re-reading Shigley, the same though occurred to me. It's no different than when checking a nut (some people have gotten crazy enough to go that far around my office).

 

[tbuelna]

If you take a look at this sales drawing for commercial Keenserts, you will see a minimum shear engagement area provided for the external thread based on their recommended installation procedure. This should allow you to calculate the insert axial load capability for whatever base material it is installed into.