Rack rails - standards?

[Mr Ian Primus]

> The standard defines the spacing between left and
> right front rails 
> (17.75"), between the hole centres on the left and
> right rails (18.25"), 
> and vertically between the holes (see below).  The
> 19" designation you 
> often see is the width of the front panel that bolts
> onto the rails. 

The width of the devices and the mounting holes in the
racks themselves are all the same - I knew there was a
standard for that much. Sorry if I didn't explain
myself very well. That wasn't what I was referring to.
The problem I am having is finding rails that will
bolt to the sides of the devices themselves. The holes
on the sides of various devices (Fujitsu Eagle, Cipher
F880, Sun server, etc) don't seem to match up with
each other or any of the other rails.

> The distance from front rail to back rail isn't
> standardised and in 
> practice that does vary widely between racks, in
> fact some racks only 
> have rails at the front.  

I was wondering about that too - the Sun rack I have
is deeper than some of the other racks, this no-name
rack I have has the rear post abou an inch closer to
the front than the Dec rack, etc.

> American racks often have round holes (I've seen
> Sun, DEC and SGI racks 
> like this) and use Tinnerman nuts, usually 10-32 UNF
> thread,

I'd noticed that there were a couple styles, the Sun
rack and the no-name rack I have use tapped, threaded
holes that take the 10-32's and the Dec rack and the
Prime racks have unthreaded round holes and use
tinnermans.

 European racks
> tend to have square 
> holes to put cage nuts into;

Ah - that explains the weird square tabs and latches
on these Dell rails - must be meant for one of those
racks. I have never seen one like that.

Things are making more sense - thanks for your
informative post. I knew about the hole spacing in the
uprights, but didn't know that square holes were a
standard - I figured it was something Dell did to get
you to buy one of their racks :). Now, about the hole
spacing on the sides of the devices... Is there a
standard for that?

Thanks!

-Ian