NAS1291 at a glance

Specification

Item	Value
Type	Self-locking nut
Material	Steel or A286 corrosion-resistant steel (C)
Status	Check the current issue of the standard before design use.

Dimension, in	.1380-32	.1640-32	.1900-32	.2500-28	.3125-24	.3750-24	.4375-20	.5000-20	.5625-18	.6250-18
A hi — A, upper of the two stacked values	.141	.188	.188	.219	.266	.282	.328	.410	.480	.550
A lo — A, lower of the two stacked values	.115	.125	.154	.204	.251	.267	.313	.350	.420	.490
B hi — B, upper of the two stacked values	.190	.221	.252	.316	.378	.440	.504	.566	.692	.755
B lo — B, lower of the two stacked values	.181	.213	.243	.304	.367	.430	.494	.556	.680	.743
H — Height	.055	.060	.065	.090	.120	.125	.160	.225	.320	.365
W — Across flats	.244	.290	.330	.420	.520	.620	.708	.814	.912	1.014

Dimensions in inches, as tabulated for the part. Blank cells (—): not stated in the documents we hold; take them from the standard.

Part numbers as listed for the part; the standard governs and may list others.

Part	Meaning
Example	NAS1291C4M — A286 CRES, 1/4-28, dry-film lubricant, 450 °F

M indicates dry-film lubricant; C indicates corrosion-resistant steel.
A and B are listed as two stacked values per size (larger above smaller); the listing does not label them max and min.
Steel versions are listed for 7/16-20 to 5/8-18 only; 800 °F A286 versions for 7/16-20 to 5/8-18 only; 450 °F dry-film A286 versions for every size.
Part number format as commonly written; check the standard for the exact format.
Approved data governs. Use the nut the SRM, drawing or IPC calls for.

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NAS1291 — Nut, Self-Locking, Low Height, Lightweight, Flanged, Steel and A286 CRES — nominal sizes and part numbers.