I don t know why the article says the next innovation in rack design has been the square hole rack.
19 inch rack hole spacing.
Eia 310 also sets the specifications for the hole spacing both vertically and horizontally of rack units within racks and cabinets.
The term 19 inch comes from the width of the front panel of the boxes that are installed in the rack see the image below.
The size denotes the width of the faceplate for the installed equipment.
To determine if your rack is a 19 rack measure the hole to hole spacing.
Horizontal spacing of vertical rows is specified by eia 310 at 18 5 16 18.
The specification also sets tolerances on each of these dimensions.
The rack or cabinet must meet the eia standard eia 310 d for 19 inch racks.
Preceding unsigned comment added by 194 237 142 21 14 36 20 september 2010 utc.
Both the ibm 7014 model t00 and model t42 and the ibm 2101 model n00 racks conform but some other racks including a few from ibm do not.
The u space starts and stops in the middle of the 1 2 holes.
Racks are divided into regions 1 75 inches in height within which there are three complete hole pairs in a vertically symmetric pattern the holes being centred 0 25 inch 6 4 mm 0 875 inch 22 2 mm and 1 5 inch 38 1 mm from the top or bottom of the region.
Rack hole spacing for rack unit mounts.
Hole spacing is either on 1 inch 25 mm centers western electric standard or the same as for 19 inch 482 6 mm racks 0 625 in or 15 9 mm spacing.
1u occupies 1 75 inches 44 45 mm of vertical space.
All racks used for n series storage system installation must conform to the specifications in this section.
The hole spacing for standard 19 inch racks on the mounting flange is spaced in groups of three holes.
Do not mix etsi 500 mm wide rack 515 mm between mounting holes with 23 inch rack.
Rack nuts are not standard.
19 rack 18 5 16 18 312 465 1 mm.
The whole spacing alternates at 1 2 5 8 5 8 and then repeats.
This three hole group is defined as a rack unit ru or sometimes just call a u.
The rack unit is a measure of vertical spacing and is common to both the 19 and 23 inch racks.
Vertical hole spacing is defined as a repeating pattern of holes within one rack unit of 1 75.
Horizontal spacing of rack units depend on whether or not the holes are drilled and tapped in the rack versus the use of cage nuts.
The funny thing is.
Such a region is commonly known as an ru or u for rack unit or unit.