Imperial Brass Standoff Dimensions

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Imperial brass standoff dimensions — thread ↔ hex pairings

There is no ASME dimensional standard for hex standoffs — imperial standoff dimensions follow a de-facto US catalog convention shared across the major manufacturers: thread size sets the standard hex across-flats, and body lengths are stocked from 1/8 to 2 in. in 1/16 in. steps. The chart below gives the verified catalog-standard pairings, 2-56 to 1/4-20.

Imperial UNC brass hex standoff dimensions — across flats A/F, body length L and thread depth

Female-female hex standoff — across flats (A/F), length (L) and tap depth (t) conventions charted below.

Thread	Standard hex A/F	Also offered
2-56	3/16 in.	1/8 in. (some catalog lines)
4-40	3/16 in. and 1/4 in.	—
6-32	1/4 in. (most common)	5/16 in. · 3/8 in.
8-32	1/4 in. and 5/16 in.	3/8 in. · 1/2 in.
10-32	5/16 in. and 3/8 in.	1/4 in. (thin-wall) · 1/2 in.
1/4-20	1/2 in.	5/8 in. (some catalog lines)

Pairings follow the de-facto catalog convention shared across major US standoff manufacturers (verified against multiple published catalogs, July 2026) — not an ASME table. Any thread–hex combination can be machined to drawing, including 1/4-20 on 3/8 in. hex. Threads per ASME B1.1, class 2A/2B.

Lengths & tolerances (catalog conventions)

Feature	Catalog convention
Stocked body lengths	1/8 in. through 2 in. in 1/16 in. steps; specific lines extend to 10 in. for larger hex bodies
Custom length increments	Commonly 1/32 in.
Typical length tolerance	±.005 in. up to 4 in. · ±.008 in. from 4–6 in. · ±.010 in. over 6 in.
Female-female thread depth	Tapped through on short bodies; long bodies tapped from both ends, depth adjusted where the body will not permit full depth — manufacturer-specific, call it out on the drawing
Male-female stud length	Per the individual catalog drawing

Because no governing standard exists, the controlling document for any order is the drawing — these conventions are the starting point, not a specification.

Hex/thread pairings, length ranges and thread-depth conventions verified across multiple published US standoff manufacturer catalogs and cross-reference tables (July 2026). Threads per ASME B1.1.

Why there is no “ASME standoff standard”

Unlike hex nuts (ASME B18.2.2) or socket set screws (ASME B18.3), electronic hex standoffs were standardized by the market, not by a committee: the big US catalog houses converged on shared thread↔hex pairings and length series, and everyone else followed. The pairings above are that convention. When a drawing and a catalog disagree, the drawing wins — which is also why made-to-drawing manufacturing covers every combination the catalogs do not stock.

Need these standoffs in brass?

Product

Imperial Brass Hex Standoffs

M-F, F-F and M-M standoffs, 2-56 to 1/4-20, machined in C36000 to convention or drawing.

View → Hub

Imperial & ANSI Brass Parts

The full UNC/UNF/NPT range — nuts, set screws, standoffs, inserts and flare nuts.

View → Metric equivalent

Brass Hex Standoffs (Metric)

The metric M2.5–M8 standoff range.

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More reference charts & tools

Chart

ASME B18.6.3 Machine Screw Nuts

#0–3/8 nut dimensions — the nuts that pair with these standoffs.

View → Tool

Thread Size Chart

UNC/UNF, metric, BSP and NPT thread dimensions side by side.

View → Tool

Tap Drill Chart

Tap-drill sizes for metric, UNC, BSP (G) and NPT threads.

View →

Frequently asked questions

Is there an ASME standard for hex standoff dimensions?

No. Electronic hex standoffs have no ASME dimensional standard — hex across-flats, lengths and thread depths are industry catalog conventions that the major US manufacturers share. That is why this page charts catalog pairings and why the controlling document for an order is always the drawing.

What hex size is standard for a 4-40 standoff?

3/16 in. or 1/4 in. across flats — both are stocked as standard across US catalogs. 6-32 most commonly runs on 1/4 in. hex, 8-32 on 1/4 or 5/16 in., and 10-32 on 5/16 or 3/8 in.

What hex size takes a 1/4-20 standoff?

1/2 in. across flats is the common catalog size, with 5/8 in. offered in some lines. Other thread–hex combinations, such as 1/4-20 on 3/8 in. hex, are machined to order.

What lengths are standard for imperial standoffs?

Standard stocked body lengths across US catalogs run 1/8 in. through 2 in. in 1/16 in. steps; specific catalog lines extend to 10 in. for the larger hex bodies, and custom lengths are commonly offered in 1/32 in. increments. A typical published catalog length tolerance is ±.005 in. up to 4 in., ±.008 in. from 4–6 in. and ±.010 in. over 6 in.

How deep are the threads in a female-female standoff?

Short bodies are tapped through. On long bodies the threads are tapped from both ends, and internal thread depth is adjusted where the body cannot take full depth — the exact minimum tap depth is manufacturer-specific, so specify it on the drawing.

Last reviewed: July 2026. This chart records catalog conventions, not a governing standard — the controlling document for any order is your drawing.