Inch series1 standard1 specification page

1/4 Fasteners

Every 1/4 washer in the database. 1/4 is a washer designation rather than a thread: the washer is bored to clear a 1/4 in bolt, across 1 standard. Rivets are not on this page: they carry no thread, so they are indexed by shank diameter rather than by size designation.

Inside Ø0.281 in

Outside Ø0.625 in

Thickness0.065 in

Fits1/4-20

1/4 washer dimensions

Full specification

Inside diameter d1: 0.281 in
Outside diameter d2: 0.625 in
Thickness h: 0.065 in
Nominal bolt Ø: 0.25 in — 1/4-20 UNC
Diametral clearance: 0.031 in (0.79 mm)
Standard: ASME B18.22.1

The inside diameter is the hole the bolt passes through, so it is always larger than the bolt it is sized for — here by 0.031 in across the diameter. The outside diameter sets the bearing area under the head or nut.

ASME B18.22.1 flat washer series

6 sizes

For bolt	Inside Ø (in)	Outside Ø (in)	Thickness (in)
1/4	0.281	0.625	0.065
5/16	0.344	0.688	0.065
3/8	0.406	0.812	0.065
1/2	0.531	1.062	0.095
5/8	0.656	1.312	0.095
3/4	0.812	1.469	0.134

1/4 Washers

1 pages

ASME B18.22.1Plain Washer — Inch Series

1/4

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M2 M2.5 M3 M3.5 M4 M5 M6 M8 M10 M12 M14 M16 M18 M20 M22 M24 4-40 6-32 8-32 10-24 1/4 1/4-20 5/16 5/16-18 3/8 3/8-16 1/2 1/2-13 5/8 5/8-11 3/4 3/4-10 7/8-9 1-8