Nut, Self-Locking, 800 °F, Reduced Hexagon, Reduced Height, Ring Base, Corrosion Resistant Steel, from MS21043 Rev. E. Every row below is transcribed from the standard and has its own link.
MS21043 at a glance
MS21043Engineering drawing · dimensions in inches
Current standard: NASM21043. MS21043 is now controlled by NASM21043 (MS21043E Notice 1). The part numbers do not change: MS21043-04 is still the number on drawings, IPCs and bags, and it is the same part. Order it by that number; the current document is NASM21043.
Specification
Item
Value
Current standard
NASM21043 (part numbers unchanged)
Type
Self-locking nut
Material
Corrosion and heat resistant steel per AMS 5525 (A286), AMS 5731 (A286) or AMS 5732. Magnetic permeability less than 2.0 (air = 1.0) at 200 oersteds, tested with an indicator per MIL-I-17214.
Strength
Axial strength and wrenching torque per table (test bolts 180,000 psi min)
Locking
All-metal self-locking element (tool mark or distortion permitted in the locking area)
Item
Value
Max. temperature
800 °F
Finish
Silver plate on all threaded surfaces per AMS 2410 (threads shall show complete coverage); silver plating on other surfaces optional. Tarnishing or discoloration of the silver is not cause for rejection. Lubricant must be soluble in the cleaner specified in MIL-N-25027.
Procurement
MIL-N-25027 (now NASM25027)
Status
Cancelled by Notice 1 (29 Feb 2000) and superseded by NASM21043; part numbers unchanged. Rev. E (30 Jun 1994) supersedes MS21043D (27 Sep 1985).
Dimensions by size
Dimension, in
4-40 UNJC-3B
6-32 UNJC-3B
8-32 UNJC-3B
10-32 UNJF-3B
1/4-28 UNJF-3B
5/16-24 UNJF-3B
3/8-24 UNJF-3B
A — Ring base diameter, max (ØA)
.206
.244
.290
.330
.420
.520
.620
B — Ring base diameter, min (ØB)
.176
.214
.260
.290
.386
.482
.575
C — Width across wrenching corners, min
.171
.207
.244
.277
.347
.419
.491
D — Countersink / counterbore diameter (ØD)
.142 – .112
.168 – .138
.194 – .164
.220 – .190
.280 – .250
.342 – .312
.405 – .375
E — Minimum length of each wrenching corner
.050
.055
.060
.065
.090
.120
.125
F — Minimum distance from washer face to start of E
.028
.039
.041
.043
.057
.077
.089
G — Ring base dimension G (see drawing)
.027 – .005
.031 – .006
.031 – .006
.031 – .006
.036 – .007
.042 – .008
.042 – .008
H — Overall height
.125 – .103
.141 – .115
.188 – .125
.188 – .154
.219 – .204
.266 – .251
.282 – .267
J — Dimension J, min (see drawing)
.010
.010
.015
.015
.019
.023
.030
W — Width across flats (includes deformation of the locking element)
.158 – .150
.190 – .181
.221 – .213
.252 – .243
.316 – .304
.378 – .367
.440 – .430
X — Squareness of bearing surface (pitch diameter within X)
.003
.003
.003
.003
.003
.004
.004
Maximum – minimum as tabulated in MS21043 Rev. E; letters as on the standard's drawing.
Every part number of MS21043 Rev. E, 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
MS21043-<dash>
Example
MS21043-4 — 1/4-28 nut, silver plated (no code after the dash number denotes silver plate).
Notes from the standard
Threads per MIL-S-8879 (UNJC for dash 04 to 08, UNJF for 3 to 6).
MS21043 nuts can universally replace NAS679, NAS1021, NAS1022 and NAS1291 nuts with similar dimensions, material and finish, but the NAS part numbers cannot replace the MS21043 part numbers (see Table II of the standard).
Design and usage limitations per MS33588.
Surface roughness not greater than 125 microinches per ANSI/ASME B46.1.
Dash number 5, dimension J: the Rev. E table prints .230; Amendment 1 corrects it to .023, which is the value used here.
