Effects of reduced major diameter of a bolt on the nut? 1

[TylerClimber]

A supplier conducted a proof load test on a nut, using a test bolt whose major diameter is .004 inches smaller than the original requirement. Does having a smaller major diameter (while keeping everything else the same) reduce the stress on the bolt and increase the stress on the nut? This means that with a smaller major diameter on the bolt, a lower tensile load can be applied in the test without causing the nut to fail, correct?

Edit: my initial wording was off, I meant that with a smaller major diameter on the bolt, the forced that's required to fail the nut's thread is now decreased.

 

[SnTMan]

"0.004 inches" on a #8-32 or on a 1"-8?

Do you think the difference matters?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[SWComposites]

the proof load test is a tension test?
what failed first, the bolt or the nut?
are you referring to the major diameter of the bolt thread area? or shank area?
with a smaller major thread diameter on the bolt, and a failure in the nut, then the test is likely conservative. if it failed in the bolt, then the test may be unconservative for the nut.

 

[TylerClimber]

SnTMan,
On a M6-1.0, I think its pretty significant for fasteners this size?

 

[TylerClimber]

SWComposites,
Yes, tensile load. No failure yet, but the goal is to fail the nut, the bolt has a higher UTS.
Major diameter of the bolt threaded area. So I guess I was correct earlier?

 

[SWComposites]

If its just a proof test to a defined load, and they achieved that load, then there should be no problem. If anything its a conservative test of the nut.

 

[Tmoose]

The "major diameter is .004 inches smaller than the original requirement. "

Was that "requirement" based on a standard like ISO 965 (?) etc?

Is the pitch diameter within ISO tolerances?

 

[desertfox]

Hi Tylerclimber

0.004” down on the major diameter of M6 external thread is still within the normal tolerance range for a thread standard see this link :-

https://international.optimas.com/technical-resources/iso-metric-screw-thread-tolerances/

so I doubt there will be a significant effect on the bolt strength. Why do you want the nut to fail first?



“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein