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My google-fu is failing me on this one.

What are the little things called that let you mount devices like switches which expect threaded round holes in a server rack with square holes?

Jeff Atwood
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Grant
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2 Answers2

29

Are you looking for cage nuts?

cage nuts

Jeff Atwood
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Oliver
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    http://static.ddmcdn.com/gif/hammer-1.jpg – Basil Jun 29 '12 at 13:48
  • As mentioned in the wikipedia article, the type A "slide-on" cage nut, or the "clip nut", is one alternative to the traditional cage nut that we have had great success with and I cant recommend enough. In my experience clip nuts are much easier to install and dont require a cage-nut puller (or a screw driver and scarred up hands) to remove from the rack. – faultyserver Jun 29 '12 at 17:35
22

Cage nuts is the proper English term.

Be warned: They come in several sizes so you need to buy bolts of the same size too !.
It's common practice to throw away the screws/bolts that come with the equipment and use your own in stead. That way you are certain you got the right bolt/nut combination.

You usually buy them in bags of 100 pieces. (Either nuts or bolts.)

There are also plastic washers available. They prevent spontaneous loosening of the bolts if the rack is subject to vibrating (which is usually the case with all those hard-drives and fan's). (Again: Make sure they are the right size for the bolts.)

The bolts are available with Philips heads or with the regular heads for flat screw-drivers. Most people prefer the Philips version as the screw-driver will not as easily slip of the head, making for easier screwing/unscrewing.

Another nice thing to have is a cage-nut puller.

cage nut puller

This is a specially formed piece of metal that you can use to insert/extract the nut from the rack without cutting you fingers to shreds. You sometimes get one for free with a bag of cage-nuts. (They are hard to come by otherwise.)

Jeff Atwood
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Tonny
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    +1 for the cage-nut puller. I've gotten some real bad cuts pulling those things in and out. – jwegner Jun 29 '12 at 16:46
  • @Jeff Atwood: Thank you for providing the picture. I was pressed for time when writing the answer and couldn't find one quickly myself. – Tonny Jun 29 '12 at 18:38
  • @jwegner :-) I had already baptized several racks with my blood before I discovered the existence of the puller. Now I always have one in the toolbox, one in the laptop bag and a spare one in the glove-box of my car. (I once lost 2 on the same day. 1 got nicked by another tech, the other I accidentally dropped through a grate in the floor. Still had 4 more racks to assemble.) – Tonny Jun 29 '12 at 18:53
  • Our cage-nut puller looks sorta like oversized nail clippers, like the bottom picture here: http://dalvenjah.foxfire.net/2010/01/the-real-cage-nut-tool/ – freiheit Jun 29 '12 at 18:56
  • The cage nut pullers I've encountered have always been made out of cheap metal and were very prone to breakage. The large flat screwdriver blade on any (Victorinox) Swiss Army Knife is a very handy tool for installing and removing cage nuts. – Andrew Beals Jun 29 '12 at 18:59
  • @freiheit Tried those, but didn't like them. To fiddly as you need to grab the nut just right. And to bulky if you need to reach around cables/equipment. – Tonny Jun 29 '12 at 22:17
  • @AndrewBeals I encountered 3 types: Aluminium, which will break or bend. Plate steel, which bends, but rarely breaks. And memory-metal (like the one in the picture). Those are the best. They bend, but snap back into shape. Never managed to break one and I have several that I have used at least once a week for over 10 years. I fall back on the flat screwdriver too if I don't have a puller handy. Some people swear by a slot-plate from a PC case, but I find those just to bendy to be useful. (Ok in a pinch for 3-4 nuts, not for an entire rack.) – Tonny Jun 29 '12 at 22:27
  • This one actually looks like one of the expansion slot covers, slightly bent. Knowing IT people, that's probably how they were invented. – Simon Richter Jun 30 '12 at 00:47
  • @SimonRichter You may be right about the origin. Sounds plausible to me :-) But the one in the picture is the real thing as far as I can tell. A slot-plate has a 90 degree bent at the top and a hole for the screw. Straightening that out would be visible I think. I do admit that the metal looks thicker than usual for a memory-metal puller. So it is most likely a plain steel version. – Tonny Jun 30 '12 at 10:01
  • @Tonny - I've had the plain steel ones break on me in fairly short order, which is what led me to using my SAK when I had to deal with square-hole racks. I don't think that I've seen either an aluminum or a memory metal one. The latter would likely work well. – Andrew Beals Jul 03 '12 at 18:34
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    @AndrewBeals The steel ones (and aluminium) usually develop metal-fatigue very quickly and then snap. The steel ones Rittal includes with a bag of cage-nuts are good though. Don't bend or break. Cisco used to throw a memory-metal one in the box with the first generation 4500 switch chassis. I got 12 of those that way. Friend of mine got some with Juniper equipment. I never found any place to buy them from. – Tonny Jul 03 '12 at 20:39