Name: AN525 screw — washer head (round)
Published: 2026-10-26
License: https://creativecommons.org/licenses/by/4.0/

AN525 at a glance

Specification

Item	Value
Head	washer head (round)
Drive	slotted or recessed
Thread series	UNC (No. 8) and UNF (No. 10, 1/4)
Material	Steel: AMS 6300 or MIL-S-6050, 125,000 psi min tensile. Aluminum alloy: QQ-A-200/5, 62,000 psi min tensile.

Item	Value
Finish	Steel: cadmium plate QQ-P-416 Type II Class 3, or zinc plate per ASTM B 633-78 Fe/Zn 13 Type II.
Procurement	MIL-S-7839
Status	Rev. 2 (29 Jan 1985). Notice 1 (21 Jun 2000): canceled and superseded by NASM525; the part numbers are identical. No. 8-36 size removed from the table.

Dimension, in	8-32 UNC-3A	10-32 UNF-3A	1/4-28 UNF-3A
B — head diameter	.312	.375	.437
J — slot width	.043	.047	.053
DIA nom tol	.164 +.000/-.002	.190 +.000/-.002	.250 +.000/-.002
DIA max	.164	.190	.250
DIA min	.162	.188	.248
A dia	.375	.437	.500
C rad	.078	.078	.097
E	.023 +.005/-.000	.025 +.005/-.000	.028 +.005/-.000
F rad	.312	.398	.474
H tol 005	.087	.094	.101
J tol	+.007/-.006	+.008/-.006	—
T tol 005	.049	.054	.058

Minimum – maximum as tabulated in AN525 Rev. 2; letters as on the standard's drawing.

Every part number of AN525 Rev. 2, by thread size, each with its own link.

8-32 UNC-3A17 part numbers · tolerance +/-1/32

10-32 UNF-3A17 part numbers · tolerance +/-1/32

1/4-28 UNF-3A17 part numbers · tolerance +/-1/32

Tolerances unless otherwise specified: fractions +/-1/64, decimals +/-.010, angles +/-.5 deg (as printed; scan partly legible).
Bearing surface of head must be free from burrs and tool marks.
Chamfer 45 deg x .03 approx; round end optional; maximum two imperfect threads. Under-head fillet radius .010 +/-.005.
Grip G as printed: 1/32 at -6, 1/16 at -7, 1/8 at -8, then length minus 13/32 from -9 up. The J tolerance of the 1/4-28 size is overstruck on the scan and not legible.
Recess shall be in accordance with the recess drawing named on the sheet (MS90xx; digits not legible on the scan).

AN525 Rev. 2, 29 Jan 1985 — Screw, Washer Head — dimensions, part numbers and notes. Public domain, distribution unlimited. Notices: 1 21 Jun 2000 Canceled and superseded by NASM525. Part Identification Number for AN525 and part number for NASM525 are identical.

Part	Meaning
Format	AN525[D]<size>[R or -]<length>
-832	Size No. 8-32 UNC
-10	Size No. 10-32 UNF
-416	Size 1/4-28 UNF
Length	Length in sixteenths of an inch (-6 = 6/16 = 3/8 in); length tolerance +/-1/32
Example	AN525-10-6 = 10-32 slotted head steel screw, 3/8 long, 1/32 grip; AN525D10-6 = aluminum; AN525-10R6 = recessed head steel
(none)	Material: steel
D	Material: aluminum alloy (size 8 available with NC thread only)
-	Drive: slotted head
R	Drive: recessed head