Racks Screws
Attaching equipment to an equipment rack requires rack screws. There are three different thread types for rack screws: 10-32, 12-24, and M6. Now, with the introduction of the square hole rack and the use of cage nuts, different thread and screw sizes can be used for a given rack.
10-32 Threads
10-32 rack screws are the original and most common. The standards for 10-32 screw was published by ANSI B1.1-1974 from Unified and American Screw Threads for Bolts, Nuts, and Machine Screws. The “10″ is only a size designator without any meaning. “32″ refers to 32 threads per inch.
12-24 Threads
12-24 screws are now more common. They are slightly larger and have coarser threads. The term 12-24 comes from Unified and American Screw Threads for Bolts, Nuts, and Machine Screws standards published by ANSI B1.1-1974. “12″ is only a size designator without any meaning. The number “24″ refers to 24 threads per inch.
M6 Threads
M6 refers to a metric 6mm screw. The outside diameter of the threads is 6mm. The standard metric rack screw is M6 x 0.1mm. The number “0.1mm” refers to 0.1 threads per millimeter. These are commonly used by HP.