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Threaded fastener security

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Mar 31, 2010 4:57 am Post subject: Threaded fastener security

 	  Quote: 	
		  At 07:22 AM 3/31/2010, you wrote:


B: The laws of physics including a study of basic machines, 

coefficients of friction and sliding forces tending to move down an 

inclined plane will show that no threaded fastener torqued to design 

values will rotate on its mate unless for some reason tension on the 

bolt is relaxed or strong but transient forces vibrations) tend to 

overcome the breaking coefficient of friction in the threads is overcome.



J: I agree.  The only advantage of using a jam nut that I see is 

that if the load on the bolt is relaxed, the two nuts will still be 

tight against each other.


	


    Right. As Paul mentioned yesterday:



P: You are correct. The application of a jam nut for locking is only 

applicable when one cannot wrench on the other end of the bolt. And 

never in a critical application. An example that comes to mind is a 

big relay where the bolt is molded into the plastic.



    The jam nut makes sense when installed tension on the bolt

    is intended by design to be much less than the strength of

    the bolt. In this case the role of the threaded fastener

   is more like that of a rivet. Very good in sheer, and moderately

    useful in tension.  The two nuts become something of a

    "second head" of the same bolt.



    Bob . . .

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raymondj(at)frontiernet.n
Guest

Posted: Wed Mar 31, 2010 1:30 pm Post subject: Threaded fastener security

FWIW, one application where the recommended locking mechanism is a 

locknut is on the rocker arm studs on WW conversion Corvair motors. I am 

not aware of any failures in this application.



Just another data point for consideration.



Raymond Julian

Kettle River, MN



Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>

 

 

> At 07:22 AM 3/31/2010, you wrote:

> 

> <fran4sew(at)banyanol.com>

> B: The laws of physics including a study of basic machines, 

> coefficients of friction and sliding forces tending to move down an 

> inclined plane will show that no threaded fastener torqued to design 

> values will rotate on its mate unless for some reason tension on the 

> bolt is relaxed or strong but transient forces vibrations) tend to 

> overcome the breaking coefficient of friction in the threads is overcome.

>

> J: I agree.  The only advantage of using a jam nut that I see is that 

> if the load on the bolt is relaxed, the two nuts will still be tight 

> against each other.

 

    Right. As Paul mentioned yesterday:

 

 P: You are correct. The application of a jam nut for locking is only 

 applicable when one cannot wrench on the other end of the bolt. And 

 never in a critical application. An example that comes to mind is a big 

 relay where the bolt is molded into the plastic.

 

    The jam nut makes sense when installed tension on the bolt

    is intended by design to be much less than the strength of

    the bolt. In this case the role of the threaded fastener

   is more like that of a rivet. Very good in sheer, and moderately

    useful in tension.  The two nuts become something of a

    "second head" of the same bolt.

 

    Bob . . .

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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