Do I have an aneurysm or do the "10 inch standard" dimensions from Wikipedia not add up?

[benmillerat]

I'm currently in the process of 3d modelling some "standardised" templates for panels and mounts and so forth and when trying to get the cutouts for the screw holes right I encountered numbers on the Wikipedia diagram that don't seem to add up. Have I forgotten how to calculate, or is this graph incorrect? https://github.com/geerlingguy/mini-rack?tab=readme-ov-file#the-10-mini-rack-standard

If the inner distance is 222.25 mm and the distance between the centers of the rack rail holes is 236.525 mm, then the distance between the inner distance (usable space) and the centers of the rack rail holes is not 7.9375 mm, but 7.1375 mm.

• 254,00 mm (total width) - 222,25 mm (usable space) = 31,75 mm (combined width left and right for the rack rails)
• 31,75 mm / 2 = 15,875 mm (width of a rack rail, as it shows on the graphic. BUT this means that the distance between the centers of the screw holes on both rack rails can't be 236,525 mm, but is 238,125 mm.)
• Inner distance (222,25 mm) + distance to the centers of each rack rail screw hole (7,9375 mm x 2 = 15,875 mm) = 238,125 mm.

What do I get wrong here? As Jeff mentioned, there is no real standard but even the dimensions in the Wikipedia diagram are contradictory, aren't they?

How much usable space between rack rails is or should be there actually? And where should I position the screw holes in my panels?

[geerlingguy]

The best option is to give some wiggle room for the screw hole positions :)

Most rack gear has an oval opening for the rack screws since even the 19" standard is more of a standard-ish standard.

And again, for the gap between the rails, I like to play it safe and keep things under like 200mm if at all possible.

[benmillerat]

Hi Jeff, thank you very much for the feedback! It's much appreciated. Well, that tingles my brain a bit, at the least the German half of my brain that needs DIN standards to survive, while the Austrian half observes with amusement.

Would you mind verifying the clearance width measurements for a DeskPi Rackmate T2 (or other popular 10-inch racks you have come across)? I don't want a 10 inch rack to be the trigger for the start of my midlife crisis, I'm too young for that and don't have enough money for a Porsche. 😩

I tried verifying with DeskPI but even they seem to be confused what the dimensions of their own products are.

• Here DeskPI states the clearance width of the Rackmate with 212mm
• Here DeskPi states the inner width of their "DeskPi RackMate Accessories Rack Shelf 10 inch 1U Rack for T0/T1 Server Cabinet" with 215mm (which obviously wouldn't fit within 212mm)
• Here DeskPI states a completely different total width of the rack itself.
• In their Wiki, DeskPi states the width of the Rackmate with exactly "width of 10 inches" in the first sentence, but following up with "11 inches" in the second sentence, showing "11,02 inches" in the diagram right below that sentence and "11.06 inches" on another product page of theirs.

With many mini/tiny PCs measuring 180–200 mm in width and mini racks becoming increasingly popular, every millimetre counts. As you said here and on the main project page, the usable horizontal space within the rails of a 10-inch rack is stated by various parties as anything between 200 mm and 222.25 mm (Wikipedia), or 228.6 mm according to DIN 41494 Part 7. Even a difference of ±5 mm can be decisive in determining whether a module will fit – and especially with 3D printed parts where you have to consider their strength.