What are cage nuts and how do you use them?
There are three different kinds of hole types across server racks, rails and shelves: threaded, square and unthreaded. Cage nuts allow users to mount any type of rail or shelf into square hole racks.
Being able to have a standardized square hole for server racks improves compatibility and makes things easier to repair. Before square holes existed, a threaded hole being damaged might have meant that you needed a new server. Now, all you have to do is replace a cage nut.
Different types of rack holes
Originally, threaded holes were the standard for server racks. A hole being threaded means that it supports traditional screws without any adaptation necessary.
Unthreaded holes were the next popular hole type. They are simply round holes that require a clip nut adapter for any shelves and rails that require threaded screws. These didn’t last long after the adoption of square holes.
Square holes sparked innovation in tool-less kits. The shape of these holes made it easy to develop rapidly deploy-able rails because of their ability to latch. Because of the new shape, cage nuts were created to allow support for threaded bolts.
Currently, most OEMs and independent server rack manufacturers are developing square hole racks.
How cage nuts work
There are three different types of cage nuts: 10-32, 12-24 and M6. Each of these work with accordingly sized screws.
Cage nuts are built to latch into the square holes of a server, creating the ability for threaded screws to be inserted. They can be installed and removed by hand, but doing so can damage your hand. There are tools to make the process much easier.
RackSolutions has been producing a highly rated cage nut tool for years. It is basically a necessity for installing data centers as there will be thousands of cage nuts used. They work great, but improvements might be coming in the near future to make the job even easier.
Another benefit to using cage nuts is that they can be replaced if the threaded hole is stripped. If a hole in a threaded rack becomes stripped, the process of fixing, ignoring or exchanging the rack was very inconvenient. Keeping all physical parts of the rack itself in a like-new state increases the resale value as well.
Cage nuts are a necessity for square hole racks unless you are using tool-less rails and shelves.
How to install and remove cage nuts
Use case 1: Cage nuts that are used for installing rails and shelves are installed from the back of the square hole, with the spring clips facing towards you. The cage nut might have a bit of slack but that will go away once an appliance is screwed in.
Use case 2: A cage nut that is used for attaching a thumb screw gets inserted from the front, with spring clips facing away from you. Thumb screws are used to secure servers onto a rack.
If you decide to use a cage nut tool, installation is only a tiny bit different.
First, you will insert one edge of the clip into the square hole and then you will need to latch onto the other end with your tool.
Second, simply push the cage nut into the hole using the tool.
To remove the cage nut, place the tool between the rail and the spring clip then push in and forward. When one side is removed, you the cage nut is loose enough to come out.