[time-nuts] Machining some aluminum help!

jimlux jimlux at earthlink.net
Thu May 18 20:13:14 EDT 2017

On 5/18/17 2:36 PM, Chris Albertson wrote:
> It would be easy to re-design the job for cheaper machining..  Do you
> really need to tap the holes?  You might use self taping screws.  Id the
> would work then you can do the work yourself with just a hand drill.
> OK it you must use machine threads and they must be #4 size try "rivets"
> these work like pop rivets but leave a hollow thread insert in the hole
> that will take screws.  Takes all of 5 seconds to install a thread hole.
> Think again about threading aluminum.  It is not very strong, it would be
> easy for an end user to strip the #4 threads.  Better to use the rivet or
> other steel thread insert.    Even native nuts  installed with flush rivets
> is better

Interestingly enough, for 4-40 hardware, the screws fail before the 
aluminum does.  The area of the thread engagement is quite a bit larger 
than the cross section of the fastener that is not thread.

For large fasteners, where the thread depth is a smaller fraction of the 
fastener diameter, this may not be the case (as anyone who has stripped 
the threads on an aluminum cylinder head with a steel sparkplug will 
know, in a deep and visceral way).

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