Vertical hole spacing is defined as a repeating pattern of holes within one rack unit (RU or U) of 1.75″. The hole spacing alternates at 1/2″ – 5/8″ – 5/8 and repeats. The start and stop of the RU is in the middle of the 1/2″ spaced holes.
The horizontal spacing of the vertical rows of holes is specified by EIA-310 at 18 5/16″ (18.312″ or 465.1 mm). However, many manufacturers use equipment mounting slots instead of holes to allow for variations in this dimension.
The rack opening is specified as a minimum of 17.72″ (450 mm). Square hole racks tend to be very close to the minimum opening.
A fixed rail is a long L-shaped bracket that supports the edge of the equipment. Fixed rails serve as an alternative to sliding or telescoping rails, which are sometimes too large to fit within a rack. They may include a cabling crossbar in the rear to dress out any cables present. It’s important to note […]
Button or keyhole mounting is a toolless feature designed to speed up the installation process of vertically mounting power distribution units (PDU) and cable management ducts in a rack. The button mounts are installed on the back of equipment prior to installation, while the keyhole mounting points can be found alongside the rack.
A filler or blanking panel is a flat piece of metal or plastic that matches the height of one or more rack units (1U is equivalent to 1.75″). Typical sizes range from 1-8 rack units. Filler or blanking panels are used to close openings that are not being used in a rack enclosure. This helps […]
A rack unit, U or RU is a unit of measurement that describes the height of equipment designed to mount in a 19″ rack. Racks offer room for equipment that is 19″ wide, and have variable heights, which are expressed in rack units. One rack unit (1U) is 1.75″ (44.45 mm) of vertical space, or […]
A 19″ rack is the standard EIA-310 server rack. The term comes from the width of the equipment in the rack. The only dimension on a 19″ rack that actually measures 19″ is the width of the front panel of the rack mount equipment. This means the distance between the mounting flanges of a rack […]
Cage nuts are used almost exclusively in rack angles with square mounting holes. They consist of a square nut wrapped in a spring metal cage that is slightly larger than the nut. This spring steel has two flanges that when pinched together allow the component to fit into the square hole on 19″ racks. The […]
Rack screws are used to attach equipment to the rack angles of a 19″ rack. There are several sizes available, but 10-32, 12-24 and M6 are the most common. Exact threads can vary by manufacturer. 10-32 ThreadsThe number “10” is a size designator with no numerical meaning. The number “32” refers to 32 threads per […]
Rack mount depth is commonly confused with the overall rack depth including the door. Mounting depth is defined as the dimension from the front of the front rack angle to the back of the back rack angle. Many racks have adjustable mounting depth so it’s best practice to ensure that the rails being used for […]
EIA stands for the Electronic Industries Association. EIA-310 is a specification for the “standard rack”. This specification standardizes several important features of 19″ racks, such as the Rack Unit (RU or U), vertical hole spacing, horizontal hole spacing, rack opening and front panel width. The specification also sets tolerances on each of these dimensions. The […]