AN320 at a glance

AN320, nut, plain, castellated, shear — AN320

AN320 engineering drawing with dimensions — AN320

Current standard: NASM320. AN320 is now controlled by NASM320 (AN320 Rev. 14 Notice 1). The part numbers do not change: AN320-1 is still the number on drawings, IPCs and bags, and it is the same part. Order it by that number; the current document is NASM320.

Specification

Item	Value
Current standard	NASM320 (part numbers unchanged)
Type	Castellated shear nut
Material	Steel, Grade C, for nominal size .4375 and larger, heat treated to Rockwell C 24-32; aluminum alloy; or 300 series corrosion-resistant steel (see procurement specification)
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 in accordance with QQ-P-416, Type II, Class 2. Aluminum alloy: anodize in accordance with MIL-A-8625, Type II. Corrosion-resistant steel: passivate in accordance with QQ-P-35
Procurement	FF-N-836
Status	Cancelled and superseded by NASM320 (Notice 1, 22 Jun 1999); part numbers unchanged.

Dimensions by size

Dimension, in	.1380-40 UNF-3B	.1640-36 UNF-3B	.1900-32 UNF-3B	.2500-28 UNF-3B	.3125-24 UNF-3B	.3750-24 UNF-3B	.4375-20 UNF-3B	.5000-20 UNF-3B	.5625-18 UNF-3B	.6250-18 UNF-3B	.7500-16 UNF-3B	.8750-14 UNF-3B	1.0000-12 UNF-3B	1.0000-14 NF-3B	1.1250-12 UNF-3B	1.2500-12 UNF-3B
A — Width across flats	.313	.344	.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 / -.010	+.002 / -.010	+.002 / -.011	+.002 / -.012	+.002 / -.012	+.002 / -.014	+.002 / -.016	+.002 / -.017	+.002 / -.019	+.002 / -.019	+.002 / -.021	+.002 / -.023
B — Width across corners (reference)	.359	.391	.438	.500	.578	.656	.719	.875	1.016	1.156	1.297	1.516	1.734	1.734	1.953	2.172
E — E (+/-.015)	.078	.078	.094	.094	.094	.109	.109	.141	.188	.188	.250	.313	.375	.375	.406	.469
H — Overall height	.156	.156	.188	—	.188	.219	.219	.250	.313	.313	.375	.438	.500	.500	.563	.625
J — Slot width (+.031 -.000)	.078	.078	.078	.078	.078	.078	.125	.125	.156	.156	.156	.156	.156	.156	.156	.156

Maximum – minimum as tabulated in AN320 Rev. 14; letters as on the standard's drawing.

Part numbers

Part no.	Size	Steel min. tensile, lb	Al alloy min. tensile, lb
AN320-1	.1380-40 UNF-3B	-	-
AN320-2	.1640-36 UNF-3B	-	-
AN320-3	.1900-32 UNF-3B	1,105	550
AN320-4	.2500-28 UNF-3B	2,040	1,015
AN320-5	.3125-24 UNF-3B	3,250	1,810
AN320-6	.3750-24 UNF-3B	5,050	2,510
AN320-7	.4375-20 UNF-3B	6,800	3,375
AN320-8	.5000-20 UNF-3B	9,250	4,590
AN320-9	.5625-18 UNF-3B	11,800	5,850
AN320-10	.6250-18 UNF-3B	15,050	7,450
AN320-12	.7500-16 UNF-3B	22,000	10,900
AN320-14	.8750-14 UNF-3B	30,000	14,900
AN320-15	1.0000-12 UNF-3B	40,350	20,000
AN320-16	1.0000-14 NF-3B	40,350	20,000
AN320-18	1.1250-12 UNF-3B	50,900	25,250
AN320-20	1.2500-12 UNF-3B	65,100	32,700

Every part number of AN320 Rev. 14, 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	AN320{material}<dash>
-	Material: Steel, cadmium plated (standard; hyphen kept before the dash number)
D	Material: Aluminum alloy, anodized (D in place of the hyphen)
C	Material: Corrosion-resistant steel, passivated (C in place of the hyphen)
Example	AN320-7 — Steel shear castellated nut, .4375-20 UNF-3B (AN320D7 = aluminum alloy; AN320C7 = corrosion-resistant steel)

Notes from the standard

Thread T per MIL-S-7742, countersunk 110 degrees (ref) to the O.D. of the threads; .016 (ref) chamfer step as drawn.
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 nominal thread size (-16) was inactivated for new design after 27 Mar 1967 but is still procurable.
Marking in accordance with SAE AS478.
Unless otherwise specified, tolerances: decimals +/-.010, angles +/-1 degree. Remove all burrs.
Nuts manufactured to previous revisions 11, 12 and 13 may be furnished from supplier's stock until 20 Aug 1998.
Dash -1 and -2 have no tensile strength values printed. Dash -15 and -16 differ only in thread pitch (12 UNF and 14 NF).

Sources

AN320 Rev. 14, 20 Aug 1996 — Nut, Plain, Castellated, Shear — dimensions, part numbers and notes. Public domain, distribution unlimited. Notices: Notice 1 (22 Jun 1999): AN320 Rev. 14 cancelled and superseded by NASM320; the part identification numbers of AN320 and the part numbers of NASM320 are identical (example AN320-1).

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