MS51960 Flat Countersunk Machine Screw Part Number Decoder: Thread, Length, Head Dimensions, Black Oxide and Self-Locking Codes

What Size Is MS51960-65?

MS51960-65 is a #10-32 UNF screw, 1/2 in long. MS51960 covers 82° flat countersunk, cross-recessed machine screws in 300-series stainless steel with UNF-2A threads. The dash number (1–174) is a lookup in Table I: it sets the thread and the length. A trailing B adds black oxide. A trailing L adds a self-locking element.

Type a part number to get the head size, tolerances, tensile load and material. Or type a size, such as 10-32 x 1/2, to get the part number. Old AN510, MS35201 and MS35250 numbers are translated too.

MS51960 DECODER
82° flat head · CRES · UNF-2A MS51960 Rev D, Apr 2011
Examples:
Part numberThreadLengthL inHead Ø inDriverTensile lb
How an MS51960 Part Number Works
MS51960 basic number 65 dash number, Table I (.190-32 × .50) B black oxide coating (optional) L self-locking element (optional)

The sheet's own example is MS51960-65BL. When both letters are used, B comes first. With no letters, the screw is plain passivated stainless steel.

Dash Numbers by Thread Size and Length (Table I)
Length L, inTol, in#0-80#2-64#4-48#6-40#8-36#10-321/4-285/16-243/8-247/16-201/2-209/16-185/8-183/4-16
.12 (1/8)+.00 / −0.0316152641
.19 (3/16)+.00 / −0.032716274260
.25 (1/4)+.00 / −0.03381728436178
.31 (5/16)+.00 / −0.03491829446279
.38 (3/8)+.00 / −0.03510193045638095
.44 (7/16)+.00 / −0.0311203146648196
.50 (1/2)+.00 / −0.0312213247658297110
.62 (5/8)+.00 / −0.0313223348668398111123*
.75 (3/4)+.00 / −0.0314233449678499112124*135*
.88 (7/8)+.00 / −0.032435506885100113125*136*146*156*
1.00 (1)+.00 / −0.032536516986101114126*137*147*157*166*
1.25 (1-1/4)+.00 / −0.0637527087102115127*138*148*158*167*
1.50 (1-1/2)+.00 / −0.0638537188103116128*139*149*159*168*
1.75 (1-3/4)+.00 / −0.0639547289104117129*140*150*160*169*
2.00 (2)+.00 / −0.0640557390105118130*141*151*161*170*
2.25 (2-1/4)+.00 / −0.0956*7491106119131*142*152*162*171*
2.50 (2-1/2)+.00 / −0.0957*7592107120132*143*153*163*172*
2.75 (2-3/4)+.00 / −0.0958*76*93*108*121133*144*154*164*173*
3.00 (3)+.00 / −0.0959*77*94*109*122134*145*155*165*174*

L is the overall length, top of head to point. * Inactive for new design after 20 August 1974. Italic numbers have an undercut head (Note 2: the cells above the dotted line on the sheet). Every number from 1 to 174 is used; there are no gaps.

Head Dimensions, Driver and Tensile Load (Table I)
ThreadBody Ø D, inHead Ø A (sharp), inHead height H (full), ref, inHead height H1 (undercut), inR max, inR1 max, inDriver sizeTensile load, lb min
#0-80 (.060)0.0496–0.06000.105–0.119 (abs min 0.099)0.0350.018–0.0250.0240.0090140
#2-64 (.086)0.0733–0.08600.156–0.172 (abs min 0.147)0.0510.028–0.0360.0340.0131310
#4-48 (.112)0.0954–0.11200.207–0.225 (abs min 0.195)0.0670.038–0.0470.0450.0171530
#6-40 (.138)0.1184–0.13800.257–0.279 (abs min 0.244)0.0830.048–0.0590.0550.0212810
#8-36 (.164)0.1424–0.16400.308–0.332 (abs min 0.292)0.1000.058–0.0700.0660.02521,180
#10-32 (.190)0.1658–0.19000.359–0.385 (abs min 0.340)0.1160.068–0.0810.0760.02821,600
1/4-28 (.250)0.2225–0.25000.477–0.507 (abs min 0.452)0.1530.092–0.1070.1000.03832,910
5/16-24 (.3125)0.2806–0.31250.600–0.635 (abs min 0.568)0.1910.116–0.1340.1250.04744,640
3/8-24 (.375)0.3430–0.37500.722–0.762 (abs min 0.685)0.2300.140–0.1610.1500.05647,020
7/16-20 (.4375)0.3995–0.43750.767–0.812 (abs min 0.723)0.2230.133–0.1560.1750.06649,500
1/2-20 (.500)0.4619–0.50000.831–0.875 (abs min 0.775)0.2230.130–0.1560.2000.075412,800
9/16-18 (.5625)0.5205–0.56250.950–1.000 (abs min 0.889)0.2600.153–0.1820.2250.084416,200
5/8-18 (.625)0.5828–0.62501.069–1.125 (abs min 1.002)0.2980.176–0.2080.2500.094520,500
3/4-16 (.750)0.7029–0.75001.306–1.375 (abs min 1.230)0.3720.223–0.2600.3000.112529,800

All values in inches, as printed on the sheet. Multiply by 25.4 for mm. Tensile loads are based on 80,000 psi (552 MPa) minimum on the thread stress area per FED-STD-H28/2. As printed, 7/16 and 1/2 in share a head height (.223 in) that is lower than 3/8 in.

AN510 Numbers Replaced by MS51960 (Table II)
Canceled AN510AN510 dash → new MS51960 dash
AN510C0 (#0-80)-2 → 1, -3 → 2, -4 → 3, -5 → 4, -6 → 5. No replacement: -7, -8.
AN510C1-2 to -8: no replacement
AN510C2 (#2-64)-3 → 7, -4 → 8, -5 → 9, -6 → 10, -7 → 11, -8 → 12, -10 → 13, -12 → 14. No replacement: -9, -11.
AN510C3-3 to -12: no replacement
AN510C4 (#4-48)-3 → 16, -4 → 17, -5 → 18, -6 → 19, -7 → 20, -8 → 21, -10 → 22, -12 → 23, -14 → 24, -16 → 25. No replacement: -9, -11, -13, -15, -18, -19, -20, -21, -22, -23, -24, -25, -26, -27, -28.
AN510C5-4 to -28: no replacement
AN510C6 (#6-40)-4 → 28, -5 → 29, -6 → 30, -7 → 31, -8 → 32, -10 → 33, -12 → 34, -14 → 35, -16 → 36, -20 → 37, -24 → 38, -28 → 39, -32 → 40. No replacement: -9, -11, -13, -15, -18, -22, -26, -30, -34, -36, -38, -40.
AN510C8 (#8-36)-4 → 43, -5 → 44, -6 → 45, -7 → 46, -8 → 47, -10 → 48, -12 → 49, -14 → 50, -16 → 51, -20 → 52, -24 → 53, -28 → 54, -32 → 55, -36 → 56, -40 → 57, -44 → 58, -48 → 59. No replacement: -9, -11, -13, -15, -18, -22, -26, -30, -34, -38, -42, -46.
AN510C10 (#10-32)-4 → 61, -5 → 62, -6 → 63, -7 → 64, -8 → 65, -10 → 66, -12 → 67, -14 → 68, -16 → 69, -20 → 70, -24 → 71, -28 → 72, -32 → 73, -36 → 74, -40 → 75, -44 → 76, -48 → 77. No replacement: -9, -11, -13, -15, -18, -22, -26, -30, -34, -38, -42, -46.
AN510C416 (1/4-28)-6 → 80, -7 → 81, -8 → 82, -10 → 83, -12 → 84, -14 → 85, -16 → 86, -20 → 87, -24 → 88, -28 → 89, -32 → 90, -36 → 91, -40 → 92, -44 → 93, -48 → 94. No replacement: -9, -11, -13, -15, -18, -22, -26, -30, -34, -38, -42, -46.

Example: AN510C10-8 is replaced by MS51960-65. AN510 numbers with an R in place of the dash (AN510C10R8) take the same replacement. The AN510 dash number is the length in 16ths of an inch.

Reference Guide: MS51960 Machine Screws
01

Reading the Number

Requirement 9: the part number is the basic MS number, a dash number from Table I, then the code letters if needed. B (black oxide) comes before L (self-locking). With L only, the L follows the dash number directly.

  • MS51960-65: .190-32 UNF-2A × .50 in, passivated CRES.
  • MS51960-65B: the same screw, black oxide coated.
  • MS51960-65L: the same screw with a self-locking element.
  • MS51960-65BL: both (the sheet's example).
What the number does not say

There is no letter for recess type, material grade or passivation. The recess is a cross recess per NASM9006 in the driver size shown in Table I. The sheet does not name a recess type in the part number.

Dash numbers run 1–174 with no gaps. Each thread size takes a block of numbers, shortest length first.
02

Material, Finish and Threads

  • Material (Req. 1): 300-series corrosion resistant steel per SAE AMS-QQ-S-763: type 304 or 316, or interchangeable 16:18 or 18:8 chromium-nickel steel.
  • Surface (Req. 2): passivated per the procurement specification.
  • Coating (Req. 3): black oxide per the procurement specification, only when the part number ends in B.
  • Magnetic permeability (Req. 4): per the procurement specification.
  • Self-locking (Req. 8): element per MIL-DTL-18240 when the part number ends in L.
  • Threads (Req. 5): UNF-2A per FED-STD-H28/2, gaged per FED-STD-H28/20, System 21.
  • Thread length (Req. 6): lengths up to 2.00 in are threaded to within 2 threads of the head bearing surface. Longer screws have at least 1.50 in (38.1 mm) of full thread.
  • Head: 80°–82° included angle (Figure 1). The top edge may be flat or rounded.
  • Length tolerance: +.00 / −.03 in to 1 in, −.06 in for 1-1/4 to 2 in, −.09 in for 2-1/4 to 3 in.
The acquisition requirements are this sheet plus FF-S-92 (Federal screw specification).
03

Old Numbers: AN510, MS35201, MS35250

MS51960 supersedes MS35201 and MS35250, and in part MS35358, MS35363 and AN510 (Note 3). The sheet gives replacement tables for AN510, MS35201 and MS35250 only. The canceled screws cannot always replace the new ones: use them only until stocks run out.

Table III rules
  • MS35250-1 to -5: MS51960 with the same number.
  • MS35250-6 to -12: no replacement.
  • MS35250-13 to -181: subtract 7 (MS35250-72 → MS51960-65).
  • MS35201-1 to -50: MS51960-6 to -55.
  • MS35201-51 to -65: MS51960-61 to -75.
  • MS35201-66 to -79: MS51960-79 to -92.
  • MS35201-80 to -92: MS51960-95 to -107.
  • MS35201-93 to -105: MS51960-110 to -122.
MS35201 and MS35250 numbers were canceled after 19 December 1963. Type one in the decoder to get its MS51960 number.
04

Status and Source

MS51960 is active. Revision D (20 April 2011) superseded Revision C (29 March 1991). Notice 3 (21 April 2026) found it valid for use in acquisition. Revision D changed the format and updated the cited documents (QQ-S-763 to SAE AMS-QQ-S-763, MS9006 to NASM9006, MIL-F-18240 to MIL-DTL-18240). Table I, the B and L codes and the example are the same in both revisions.

Source: MS51960 Revision D, pages 1 to 6, and Notice 3 (DLA ASSIST, Distribution A).

Related: MS16555 dowel pin decoder, NAS1149 washer decoder, AN960 washer decoder.

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