[Beowulf] case (de)construction question

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Fri Feb 19 16:37:43 PST 2010

> -----Original Message-----
> From: beowulf-bounces at beowulf.org [mailto:beowulf-bounces at beowulf.org] On Behalf Of David Mathog
> Sent: Friday, February 19, 2010 3:44 PM
> To: beowulf at beowulf.org
> Subject: [Beowulf] case (de)construction question
> Many rack cases have threaded standoff's directly attached to the case
> metal.  On the outside of the case one sees a hexagonal nut, and on the
> inside the cylindrical standoff - with no sign of the hexagonal nut.  We
> even have one type of case with a removable motherboard tray, which is
> quite thin, and even here this type of standoff is employed.
> The question is, how are these things put together,

Those are "self clinching fasteners" of one sort or another. PEMs from Penn Engineering (http://www.pemnet.com/) are the ones I've used

" PEM(r) self-clinching concealed-head studs and standoffs install permanently in steel or aluminum sheets as thin as .062" / 1.6mm to provide strong and reusable threads for mating hardware in a wide range of thin-metal assembly applications.  Their concealed-head feature contributes particular design benefits by allowing the side of the sheet opposite installation to remain smooth and untouched."

http://www.pemnet.com/fastening_products/pdf/chdata.pdf reveals all.

Those ones actually install in a blind hole, but there are other ones that insert in a through hole.

 and more
> specifically, how are they to be taken apart? 
They aren't designed to be dismantled.  You can sometimes use a suitable press with appropriate dies to press the nut out, but the whole pressing the stud in process deforms the metal.

 Some of the standoffs are
> in the way of a larger power supply that needs to go into one of these
> cases. Is there a more elegant way of removing these than by grinding
> them off or drilling them out?  

Saw and grind. Dremel tools are your friend.

I have already tried unscrewing one, on
> the theory the standoff might be threaded into the hex nut, but it
> wouldn't budge.

No, it's actually one continuous piece of metal.  The hexagonal form factor is to allow the part to be clamped in the pressing process without spinning.

> Thanks,
> David Mathog
> mathog at caltech.edu
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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