Holes are arranged in a repeating pattern of three, with centers spaced at 0.6250.625 0.6250.625 Front Panel Width: Equipment faceplates must be inches wide.
If you only need the , many open references and manufacturers (e.g., Middle Atlantic, Rittal, APC) provide summarized dimension drawings based on EIA-310-D. These are not the full standard but may suffice for mechanical design. eia310d standard pdf