# 19-inch rack rail holes (EIA-310: 15.875 / 15.875 / 12.7 mm pitch, 465.1 mm spacing, 9.5 mm square) and M5 / M6 / 10-32 / 12-24 cage nuts + 2U square-hole rail gauge

> What size is the square hole in a server rack rail, and what size are M5, M6, 10-32 and 12-24 cage nuts?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: EIA-310 hole pattern as printed by Digital Loggers, Schneider Electric and Rack Solutions; cage nut sizes from RS PRO, Essentra, StarTech, Rapid Electronics (R-TECH), Hammond, HDBOLT and nVent Hoffman; one 2U rail gauge file
- Page: https://xemstudio.com/objects/rack-cage-nuts-and-rail-holes/ · JSON: https://xemstudio.com/api/geometry?object=rack-cage-nuts-and-rail-holes · Plain text: https://xemstudio.com/objects/rack-cage-nuts-and-rail-holes/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 88.9 | 25.0 | 2.0 |

**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## Notes

- Rail data: the vertical hole pitch repeats 5/8, 5/8, 1/2 in (15.875, 15.875, 12.7 mm) with a U of 44.45 mm starting in the middle of the 1/2 in gap; the hole columns of the two rails are 465.1 mm apart (18 5/16 in); equipment clears 450 mm between rails. These are the figures three makers print as EIA-310 (Schneider cites EIA/ECA-310-E). None of the three pages gives the hole sizes, the rail flange width or the thickness, and the standard itself was not read, so the 9.5 mm square hole comes from the cage nut sheets.
- Square hole: 9.5 mm (RS PRO's description, HDBOLT 'most common'), 9.53 mm (RS PRO's attribute table) and 0.375 in = 9.54 mm (Hammond). Those are the same 3/8 in rounded; the file uses 9.525 mm. Round-hole and tapped-hole rails (for 10-32, 12-24 and M6 screws) also exist; no source read gives their hole sizes, so they are not on this page.
- Cage nut body sizes are what each seller prints and they are not a standard: Essentra M5 12.5 × 9.0 mm and M6 12.5 × 9.3 mm (overall length × height), M8 16.3 × 11.6 mm; StarTech M5 about 13 × 13 × 9 mm; RS PRO M6 15 mm overall width; RS PRO prints panel thickness 0.8 – 6 mm, Rapid's R-TECH parts print panel ranges 0.7 – 1.6 and 1.7 – 2.5 mm. Rapid's sheet lists eight dimension values (A to H) without a mapping and they are shown as printed. The cage nuts snap into the square hole from the rail face. Hammond's datasheet calls out 10-32, 12-24 and M6 cage nuts for 0.375 in (9.54 mm) holes and gives torque figures that conflict between versions, so none is shown.
- File: a 2U strip of rail face, 25 mm wide, 2 mm thick, with six 9.525 mm square holes on the 15.875 / 15.875 / 12.7 mm pitch, U boundaries in the middle of the 12.7 mm gaps. Width and thickness are Xem's choices. It is a hole gauge for a cage nut or square-hole cutout, not a model of a rail. Rack ears and unit heights: rack-19in-ears. Cage nuts have a clip and a captive threaded plate; no model is drawn because the clip geometry is not published as numbers.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| square hole | 9.525 mm (3/8 in) square; pitch 15.875, 15.875, 12.7 mm per 44.45 mm U | cage nut cutout 9.53 mm (RS PRO) for panels 0.8 to 6 mm; the nut clips in | clamp | rack-rail-square-hole-gauge* |

## Sizes

| part | item | thread | dimension / value | source / note |
|---|---|---|---|---|
| rail | rack unit (U) height | — | 44.45 mm (1.75 in) | Schneider; Rack Solutions; Digital Loggers (1.75 in) |
| rail | vertical hole pitch within a U | — | 5/8, 5/8, 1/2 in = 15.875, 15.875, 12.7 mm (Schneider prints 15.9, 15.9, 12.7) | Digital Loggers prints 1/2, 5/8, 5/8 in repeating; Schneider 5/8, 5/8, 1/2 |
| rail | where a U starts | — | at the middle of the 1/2 in (12.7 mm) gap between holes; a 1U device covers three holes with the notched hole in the middle | Rack Solutions; Schneider |
| rail | horizontal hole spacing (between the two rails' hole columns) | — | 18 5/16 in = 465.1 mm (18.312 in); Schneider ±1.6 mm | Digital Loggers; Rack Solutions; Schneider |
| rail | clearance between rails (minimum) / outside edges of rails (minimum) | — | 450 mm (17.72 in) / 483.4 mm | Digital Loggers; Schneider |
| rail | equipment front panel width | — | 19 in (482.6 mm) | Digital Loggers; Rack Solutions (19 in) |
| rail | square hole size | — | 9.5 mm (RS description, HDBOLT) / 9.53 mm (RS attribute) / 0.375 in = 9.54 mm (Hammond) | all three are 3/8 in rounded three ways; 9.525 mm is used for the file |
| rail | round hole, tapped hole, rail flange width and thickness | — | no published value found in the pages read | — |
| cage nut | M6, RS PRO | M6 | overall width 15 mm; cutout 9.53 × 9.53 mm; for panel 0.8 – 6 mm | RS PRO |
| cage nut | M5 and M6 steel, Essentra | M5 / M6 | overall length 12.5 mm; height 9.0 mm (M5) and 9.3 mm (M6) | Essentra (item codes 34002400 and 34002401) |
| cage nut | M8 steel, Essentra | M8 | overall length 16.3 mm; height 11.6 mm | Essentra (item 34002402) |
| cage nut | M5, StarTech CABCAGENUTS | M5 | length 0.5 in, width 0.5 in, height 0.4 in (1.3 × 1.3 × 0.9 cm) | StarTech (product dimensions, rounded) |
| cage nut | M5 and M6, R-TECH 33-7135 to 33-7138 | M5 / M6 | eight values as printed, letters A to H not mapped on the sheet read: 13.72, 14.22, 6.1, 9.53, 9.53, 0.8°, and panel 0.7 – 1.6 or 1.7 – 2.5 mm | Rapid Electronics (the 33-7137 panel range prints '0.7.16', read as 0.7 – 1.6) |
| cage nut | 10-32, 12-24, M6 (CAGNUT series) | 10-32 / 12-24 / M6 | for 0.375 in (9.54 mm) square holes; M6 sold rear-loading (CAGNUTM6) and front-loading (1421CNBF); no body dimensions on the datasheet | Hammond |
| cage nut | M5, PM5CN | M5 | snaps into square-hole rack angles; no dimensions on the page | nVent Hoffman |
| cage nut | common thread sizes | M5, M6, 10-32, 12-24 | 10-32 UNF and 12-24 UNC are the inch pair; M5 and M6 are metric | HDBOLT; Hammond |

## Where the files are

- Digital Loggers: [Rack specifications: 1.75 in U, hole spacing 1/2 - 5/8 - 5/8 in, hole columns 18 5/16 in (465.1 mm) apart, minimum opening 17.72 in (450 mm), 19 in front panel](https://digital-loggers.com/rackspecs.html) — web — Maker page; numbers only. No hole sizes
- Schneider Electric (FAQ FA158600): [EIA/ECA-310-E as summarised: U = 1.75 in / 44.45 mm; vertical hole spacing 5/8, 5/8, 1/2 in (15.9, 15.9, 12.7 mm); horizontal 18.3 in (465 mm) ±1.6 mm; clearance 450 mm; outside edges 483.4 mm; notched hole marks the U centre](https://www.se.com/ie/en/faqs/FA158600) — web — Maker FAQ; numbers only. No hole sizes
- Rack Solutions: [What is EIA-310: U 1.75 in, hole pattern 1/2, 5/8, 5/8 in repeating, the U starts and stops at the middle of the 1/2 in spacing, hole columns 18 5/16 in (465.1 mm), panel width 19 in](https://help.racksolutions.com/hc/en-us/articles/10431608060692-What-is-EIA-310) — web — Maker help page; numbers only. No hole sizes
- RS PRO (RS Components): [Cage nut M6: overall width 15 mm, cutout 9.53 × 9.53 mm (description 9.5 × 9.5 mm), panel thickness 0.8 to 6 mm](https://uk.rs-online.com/web/p/cage-nuts/2662265) — web — Distributor page; numbers only
- Essentra Components: [Cage nuts M5, M6, M8 (steel, zinc plated): overall length and height](https://www.essentracomponents.com/en-gb/p/cage-nuts) — web — Maker catalogue page; numbers only
- StarTech: [Cage nuts M5 (CABCAGENUTS): product length 0.5 in (1.3 cm), width 0.5 in (1.3 cm), height 0.4 in (0.9 cm); square cage nut design for racks with square holes](https://pdf.bomkeyelectronics.com/pdf/31/cabcagenuts_datasheet.pdf) — web — Maker datasheet; numbers only
- Rapid Electronics (R-TECH 33-7135 to 33-7138 sheet): [Panel cage nuts M5 and M6, spring steel: eight dimension values A to H per part (letters not mapped on the extracted sheet), panel ranges 0.7 to 1.6 and 1.7 to 2.5 mm](https://static.rapidonline.com/pdf/33-7136_v1.pdf) — web — Distributor sheet; numbers only
- Hammond Manufacturing (via SIC Components datasheet): [CAGNUT series: 10-32, 12-24 and M6 cage nuts for 0.375 in (9.54 mm) square-hole punched panel rails; spring steel](https://datasheet.sic-components.com/cagnut.pdf) — web — Maker datasheet; numbers only. No body dimensions
- HDBOLT: [Cage nut: thread sizes M5, M6, 10-32 UNF, 12-24 UNC; square hole 9.5 mm (3/8 in) most common](https://hdbolt-final.pages.dev/nuts/cage-nut.html) — web — Seller page; numbers only
- nVent Hoffman: [PM5CN cage nut package for square-hole rack angles, M5, mild steel, plated; snaps into the square holes (data sheet linked on the page was not read)](https://hoffman.nvent.com/en/hoffman/PM5CN) — web — Maker product page; no dimensions on the page

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/rack-cage-nuts-and-rail-holes/index.json

- rack-rail-square-hole-gauge-2u: [STEP](https://xemstudio.com/files/hardware/rack-cage-nuts-and-rail-holes/rack-rail-square-hole-gauge-2u.step) · [STL](https://xemstudio.com/files/hardware/rack-cage-nuts-and-rail-holes/rack-rail-square-hole-gauge-2u.stl) — 2U rack rail strip, 25 wide × 88.9 long (2 × 44.45) × 2 mm thick, six 9.525 mm square holes (3/8 in) at 6.35, 22.225, 38.1, 50.8, 66.675 and 82.55 mm from one end (pitch 15.875, 15.875, 12.7 mm per U, U boundaries in the middle of the 12.7 mm gaps); width and thickness are Xem's choices; one rail only, no mounting-flange return, no round or tapped hole

## Questions

**What size is the square hole on a 19-inch rack rail?**

About 9.5 mm (3/8 in): 9.5 mm, 9.53 mm and 0.375 in (9.54 mm) are printed by RS PRO, HDBOLT and Hammond. The pitch is 15.875, 15.875, 12.7 mm, 44.45 mm per U.

**What cage nut thread sizes are common for racks?**

M5, M6, 10-32 and 12-24 (HDBOLT, Hammond, Essentra, StarTech).

**How far apart are the two rails' hole columns?**

465.1 mm (18 5/16 in) centre to centre (Digital Loggers, Rack Solutions); Schneider prints 465 mm ±1.6.

## Fits with

- [19-inch rack units and mounting ears (EIA-310)](https://xemstudio.com/objects/rack-19in-ears/)
- [Slide-in T-nuts for 20, 30, 40, 45 mm and 1 in, 1.5 in T-slot extrusion](https://xemstudio.com/objects/slide-in-t-nuts/)
- [Rivet nuts (blind threaded inserts), flat head: hole size, grip range, body and flange dimensions, M3–M12 and #6-32 to 3/8-16](https://xemstudio.com/objects/rivet-nuts-flat-head/)
- [Tee nuts (T-nuts) for wood, 3 and 4 prong, 4-40 to 3/8-16: barrel, flange, prong height, drill size + hole gauge](https://xemstudio.com/objects/tee-nuts-for-wood-3-4-prong/)
- [Metric machine screws M1.6–M10: pan head ISO 7045 (cross) / ISO 1580 (slotted), cheese head ISO 1207, countersunk ISO 7046-1 — head sizes, recess sizes + models](https://xemstudio.com/objects/machine-screws-metric-pan-cheese-csk/)