Comments on: Define: EIA-310

By: Sintesis Modular (Parte 1) | Racó tècnic

Sintesis Modular (Parte 1) | Racó tècnic — Thu, 19 Nov 2009 12:28:49 +0000

[…] servidores. Las medidas del formato se basan basada en las espeficaciones definadas en la EIA-310 . El ancho esta normalizado, siempre es de 19″, recordemos que 1″(pulgada) = 2,54cm […]

By: A W Covert

A W Covert — Tue, 28 Apr 2009 15:15:15 +0000

RE: Front panel width definition above:

A SMART equipment manufacturer will make his faceplate slightly smaller than 19″ - such as 18-31/32″ to avoid any problems with rubbing in tight racks.

I once had an AP Audio patch bay that actually measured 19-1/32″ and would not go into my all-steel welded rack (Premier or Bud). I e-mailed the mfg. and they said they saw no problem with it becuase no one else had complained before! Well, not everyone has cheap plywood racks with enough ‘give’ in the sides.

By the same token, I suppose a smart rack manufacturer would error a little on the wide side when spacing his (recessed) rails.

This kind of goes along with Jakob’s statement above where he notes “What is truly missing from this article are actual tolerance ranges for each number”. Amen!

By: Jakob Bohm

Jakob Bohm — Sun, 29 Mar 2009 17:06:06 +0000

Mr. Castelino is wrong here, Mr. Edelson is right. The change from 1/0.03997 to 25.4 by US congress was BECAUSE of mfg facilities around the world becoming a reality. The other countries still using inches at the time almost simultaneously passed similar laws or regulations adjusting their (slightly different!) conversion ratios to 25.4 too. The only people still using the 0.03997″ ratio are a few ultra-conservative industries (such as US surveyors) and people who were taught the wrong ratio from outdated schoolbooks.

That said, this article commits the deadly sin of randomly rounding specifications differently and inconsistently. If you want to be inexact, do it consistently. 18.312″ (465.14mm) OR 18.31″ (465.1mm) OR 18.3″ (ca. 465mm) OR 18 5/16″ (ca. 46 1/2 cm). The ca. (circa) in front of 465 mm is needed because 465 looks like a human-chosen exact specification, even though it is not.

What is truly missing from this article are actual tolerance ranges for each number (e.g. the center distance of holes should be at least 18.???” (46?.? mm) and at most 18.???” (46?.? mm) but in reality varies between 18.?” (46? mm) and 18.?” (46? mm).

By: Carlos

Carlos — Thu, 05 Feb 2009 20:12:21 +0000

Y cual es el estandar del calibre de los parales para los Rack´s ????????

By: Ken Morenz

Ken Morenz — Tue, 27 Jan 2009 22:54:16 +0000

OMG this is funny. There’s a debate over a 0.0002% error in the definition of a millimeter / inch conversion about something that probably varies 1% or more.

By: Alwyn Castelino

Alwyn Castelino — Tue, 15 Jul 2008 14:04:19 +0000

when US congress adapted they didnt clealy seen mfg facility available around the globe! so nobody belives in US standards as practice for more sophiticated work we can adapt 25.400050800101600203200406400813mm=1″
but as we go do the enclosure or any panel work there its difficult to maintain the acuracy

cheeerz

By: J Edelson

J Edelson — Fri, 23 May 2008 18:58:48 +0000

Not quite:

As _currently_ defined, the inch is 2.54 cm _exactly_.

When the US congress adopted the meter as the standard of measure (in the mid 1800’s), it also adopted the standard that a yard was exactly 3600/3937 of a meter, which made the meter 39.37″ and the mm 0.03937″ as Joseph states.

However in the mid 1900’s the inch was _redefined_ to be 2.54 cm.

This leads to there being two different definitions of the foot in common use. The ’survey foot’ uses the old definition.

By: Joseph B. Mattheeussen

Joseph B. Mattheeussen — Tue, 08 Apr 2008 22:57:12 +0000

Actually, the ‘correct’ mm to inch Conversion Standard is the inverse of .03937″ (=’s 1mm)… Therefore the EXACT inverse is actually: 25.400050800101600203200406400813, or 25.40005 for short!!! Multiply any ‘inch’ number by the Conversion factor of 25.40005 and you get the mm equivalent, and the opposite goes by dividing the ‘X’mm number by the Conversion factor to get the actual inch equivalent… -Can you tell I’m a Design Eng’r?!

By: Craig McCluskey

Craig McCluskey — Fri, 09 Nov 2007 16:41:34 +0000

http://electronics.ihs.com/collections/abstracts/eia-310.htm says,

Section 1
Description: This section is the soft metric conversion of the superseded EIA-310-C to
conform with U.S. Public Law 100-418.

I’m sure this means rounding off.

It also says,

Section 2
Description: This section is an adaptation of IEC 917 recommendations for Cabinets,
Racks and Panels. It is compatible with the IEC 25 millimeter practices….

Whatever 25 millimeter practices are. Is that different than 25.4 mm = 1 inch?

Craig

By: Bob Mimlitch

Bob Mimlitch — Sat, 27 Oct 2007 04:43:05 +0000

Yep. 18.312″ (18 5/16″) = 165,10448mm. I’m sure they rounded it off. However, the EIA-301 RevD states 465mm. The older EIA-301 RevC uses 18 5/16″ (18.312″), so you’re both right.