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US round and octagon ceiling boxes (3-1/2, 4 in): size, cubic inches, fixture screw spacing

Name: US round and octagon ceiling boxes (3-1/2, 4 in): size, cubic inches, fixture screw spacing dimension sheet
Creator: Xem Studio
License: https://creativecommons.org/licenses/by/4.0/

What is the fixture screw spacing of a 4 in octagon or 3-1/2 in round ceiling box? · Standard part · basis: Hubbell RACO, Southwire, Allied Moulded and ABB Steel City sheets; only printed numbers

Also called: ceiling box screw spacing, octagon box dimensions, 4 inch octagon box dimensions, round ceiling box dimensions, fixture box screw spacing, 3 1/2 round box, ceiling fan box dimensions, light fixture mounting screw spacing, octagon box cubic inches, canopy adapter plate

Exact dimensions. True size, with no printing tolerance added.

length: 101.6 mm
width: 101.6 mm
height: 2.0 mm

Notes

US round and octagon ceiling / fixture boxes, 3-1/2 and 4 in: the sizes and cubic inches the makers print, and the two screw spacings that are printed in words: 3-1/2 in between fixture ears on the Southwire 4 in octagon box and 2-3/4 in between the screws of the RACO 3-1/2 in round cover and Steel City 4 in cover.
A fixture strap's own slot length and the ears of a 3-1/2 in box are not printed as numbers on the sheets found, so only the spacings above are given. Some Hubbell sheets print depth and width values that disagree with the title (the 4 in octagon RACO 175 shows 2.633 in for a 2-1/8 in box): those are left out.
The octagon file is 4 in across flats (the sheet prints width 4 in and height 4 in) with both hole pairs; the round cover file is the printed 3.500 in diameter and 0.119 in thickness. The #8-32 hole size is the thread major diameter, 0.164 in: the Hubbell sheet prints no thread, the Steel City ring pages print 8-32.
Both files are templates for designing a fixture adapter or canopy: no knockouts, ears, bosses or radii (not printed).

US round and octagon ceiling boxes (3-1/2, 4 in): size, cubic… size chart

parameter	value
4 in octagon, drawn, 1-1/2 in deep (RACO 125)	15.5 cu in; 4 x 4 in; actual depth 1.563 in
4 in octagon, 2-1/8 in deep, fixture ears (Southwire 54171-DEOW)	20.0 cu in; fixture ears 3-1/2 in o.c.
3-1/2 in octagon, drawn, 1-1/2 in deep (RACO 112)	11.8 cu in; 3.500 x 3.500 in; depth 1.563 in
3-1/2 in round old work ceiling box, 2 in deep (Allied 9338-EK)	14.0 cu in; 3-1/2 in diameter; tapped device holes
3-1/2 in round cover (RACO 703)	3.500 in diameter, 0.119 in thick; screw centres 2-3/4 in
4 in octagon/round cover, 5/8 in raised (Steel City 54C3)	tapped ears on 2-3/4 in centres
4 in octagon ring, 1/4 in raised (Steel City 501-CS)	ears 8-32 on 2-23/32 in centres
fixture screws, 3-1/2 and 4 in round and octagon	3-1/2 in o.c. (box ears) and 2-3/4 in (cover ears)
ear positions on 3-1/2 in boxes, wall thickness, radii	not printed: not modelled

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Hubbell RACO	125 4 in octagon box, drawn, 1-1/2 in deep (spec sheet)	web	Publisher's page; dimensions are facts
Hubbell RACO	112 3-1/2 in octagon box, drawn, 1-1/2 in deep (spec sheet)	web	Publisher's page; dimensions are facts
Hubbell RACO	703 3-1/2 in round cover, screw centres 2-3/4 in (spec sheet)	web	Publisher's page; dimensions are facts
Southwire	54171-DEOW 4 in octagon box, 2-1/8 in deep, fixture ears 3-1/2 in o.c.	web	Publisher's page; dimensions are facts
Platt Electric (Allied Moulded data)	9338-EK 3-1/2 in round old work ceiling box (14 cu in, 2 in deep)	web	Publisher's page; dimensions are facts
ABB (Steel City)	54C3 4 in octagon/round cover, 5/8 in raised, tapped ears on 2-3/4 in centres	web	Publisher's page; dimensions are facts
ABB (Steel City)	501-CS 4 in octagon ring, ears 8-32 on 2-23/32 in	web	Publisher's page; dimensions are facts

Free files

★ Free files 2 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

octagon-4-in-fixture-plate	4 in octagon template plate (4 in across flats), 2 mm thick: two #8-32 holes 3-1/2 in apart (fixture ears) and two 2-3/4 in apart turned 90 degrees (cover ears)	STEP · STL
round-cover-3-1-2-in-raco-703	3-1/2 in round cover, 0.119 in thick (RACO 703): two #8-32 holes 2-3/4 in apart; centre knockout not modelled	STEP · STL

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Plain text: sheet.txt · JSON: /api/geometry?object=ceiling-boxes-us