[time-nuts] Machining some aluminum help!

Chris Albertson albertson.chris at gmail.com
Fri May 19 15:33:16 EDT 2017

To tell the truth I had not worked this out.    But I wonder of the screws
fail first on
they are in aluminum holes with only 1/4 of thread.

Which fails depends on the material and the number of engaged threads,

But if what you say is right for this case.  It strengthens my case for
using self threading screws.  I try and use these when I can.

What you do is center punch the screw location around the end plate.  Then
glue the end plat in place using blue lock tight. (or even two tiny daps of
"Super Glue")  then go to the drip pressed drill through the endplate into
the edge of the wall and insert one screw.  The right size the type screw
will cut its own thread as you screw it in.  Then drill neither hole and
put in another screw.   It is imported to place the screw as you drill to
keep alignment, even when using the glue.   Later take out the screw and
break the glue, reassemble.

On Thu, May 18, 2017 at 5:13 PM, jimlux <jimlux at earthlink.net> wrote:

> 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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Chris Albertson
Redondo Beach, California

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