AN310 at a glance

AN310, nut, plain, castellated, airframe — AN310

AN310 engineering drawing with dimensions — AN310

Current standard: NASM310. AN310 is now controlled by NASM310 (AN310 Rev. 10 Notice 2). The part numbers do not change: AN310-3 is still the number on drawings, IPCs and bags, and it is the same part. Order it by that number; the current document is NASM310.

Specification

Item	Value
Current standard	NASM310 (part numbers unchanged)
Type	Castellated nut
Material	Steel, aluminum alloy and 300 series corrosion-resistant steel (see procurement specification; 400 series CRES inactive for design after 1 Jan 1992)
Strength	Minimum ultimate tensile strength per table (steel and aluminum alloy columns)

Item	Value
Locking	Castellated; slots for a cotter pin (no self-locking feature)
Finish	Steel: cadmium plate per QQ-P-416, Type II, Class 2 (Class 3 plating may be furnished from supplier's stock until 1 Jan 1975). Aluminum alloy: anodize per MIL-A-8625, Type II. CRES: passivate per QQ-P-35
Procurement	FF-N-836
Status	Inactive for new design since 4 Apr 1998 (Notice 1; no longer used except for replacement purposes). Cancelled and superseded by NASM310 (Notice 2, 22 Jun 1999); part numbers unchanged. Supersedes AN355.

Dimensions by size

Dimension, in	No. 10-32 UNF-3B	1/4-28 UNF-3B	5/16-24 UNF-3B	3/8-24 UNF-3B	7/16-20 UNF-3B	1/2-20 UNF-3B	9/16-18 UNF-3B	5/8-18 UNF-3B	3/4-16 UNF-3B	7/8-14 UNF-3B	1-12 UNF-3B	1-14 NF-3	1-1/8-12 UNF-3B	1-1/4-12 UNF-3B
A — Width across flats	.375	.438	.500	.563	.625	.750	.875	1.000	1.125	1.313	1.500	1.500	1.688	1.875
A_tol — Tolerance on A	+.002 / -.010	+.002 / -.010	+.002 / -.010	+.002 / -.010	+.002 / -.011	+.002 / -.012	+.002 / -.012	+.002 / -.014	+.002 / -.016	+.002 / -.017	—	+.002 / -.019	+.002 / -.021	+.002 / -.023
B — Width across corners (approx.)	7/16	1/2	37/64	21/32	23/32	7/8	1-1/64	1-5/32	1-19/64	1-33/64	1-47/64	1-47/64	1-61/64	2-11/64
E — E (see drawing)	7/64	1/8	11/64	7/32	17/64	23/64	25/64	15/32	9/16	21/32	3/4	3/4	13/16	7/8
H — Overall height	1/4	9/32	21/64	13/32	29/64	9/16	39/64	23/32	13/16	29/32	1	1	1-5/32	1-1/4
J — Slot width (+1/32 -0)	5/64	5/64	5/64	1/8	1/8	1/8	5/32	5/32	5/32	5/32	5/32	5/32	5/32	5/32
M — M (see drawing)	.110	.125	.172	.218	.265	.359	.390	.468	.562	.656	.750	.750	.844	.938
R — Radius R	3/32	3/32	3/32	3/32	3/32	1/8	5/32	5/32	3/16	3/16	3/16	3/16	1/4	1/4

Maximum – minimum as tabulated in AN310 Rev. 10; letters as on the standard's drawing.

Part numbers

Part no.	Size	Steel min. tensile, lb	Al alloy min. tensile, lb
AN310-3	No. 10-32 UNF-3B	2,210	1,100
AN310-4	1/4-28 UNF-3B	4,080	2,030
AN310-5	5/16-24 UNF-3B	6,500	3,220
AN310-6	3/8-24 UNF-3B	10,100	5,020
AN310-7	7/16-20 UNF-3B	13,600	6,750
AN310-8	1/2-20 UNF-3B	18,500	9,180
AN310-9	9/16-18 UNF-3B	23,600	11,700
AN310-10	5/8-18 UNF-3B	30,100	14,900
AN310-12	3/4-16 UNF-3B	44,000	21,800
AN310-14	7/8-14 UNF-3B	60,000	29,800
AN310-15	1-12 UNF-3B	80,700	40,000
AN310-16	1-14 NF-3	80,700	40,000
AN310-18	1-1/8-12 UNF-3B	101,800	50,500
AN310-20	1-1/4-12 UNF-3B	130,200	64,400

Every part number of AN310 Rev. 10, each with its own link. Codes (material, finish) build the full number in the box below.

Part number

What each code means

Part	Meaning
Format	AN310{material}<dash>
-	Material: Steel, cadmium plated (standard; hyphen kept before the dash number)
D	Material: Aluminum alloy, anodized (D replaces the hyphen)
C	Material: Corrosion-resistant steel, passivated (C replaces the hyphen)
Example	AN310-5 — Steel castellated nut, 5/16-24 UNF-3B (AN310D5 = aluminum alloy; AN310C5 = corrosion-resistant steel)

Notes from the standard

Thread T per MIL-S-7742, countersunk 110 degrees to the O.D. of the threads.
Round or square bottom castellation optional.
Chamfer on bottom face 15 degrees to dimension A is optional.
(a) For aluminum alloy nuts larger than -5 size, tolerances on dimension A may conform to the applicable material specifications for bar and rod.
(b) The 1-14 NF thread size (-16) is inactive for design after 27 Mar 1967.
Unless otherwise specified, tolerances: fractions +/-1/64, decimals +/-.010, angles +/-1 degree. Remove all burrs.
Add D before the dash number for aluminum alloy nuts; add C before the dash number for corrosion-resistant steel nuts.
Strengths are minimum ultimate tensile loads in pounds.

Sources

AN310 Rev. 10, 17 May 1991 — Nut, Plain, Castellated, Airframe — dimensions, part numbers and notes. Public domain, distribution unlimited. Notices: Notice 1 (4 Apr 1998): AN310 inactive for new design and no longer used, except for replacement purposes.; Notice 2 (22 Jun 1999): AN310 Rev. 10 cancelled and superseded by NASM310; the part identification numbers of AN310 and the part numbers of NASM310 are identical (example AN310-3).

Educational reference only. not approved data. Always consult the applicable SRM, AMM, or AC 43.13-1B and your certifying authority.