MS51967 Hex Nut Decoder: Dash Numbers & Sizes

What Size Is MS51967-8?

MS51967-8 is a 3/8-16 UNC-2B hex nut, carbon steel grade B, cadmium plated. MS51967 numbers carry no code: the dash number is a lookup into the standard's Table I. Type a part number and the decoder gives the thread, grade, width across flats, thickness and tolerances in inches and millimetres.

Going the other way? Type a thread size, such as 1/2-13 or 5/16, to get the grade B and grade C part numbers. Old MS35690 numbers work too. MS51967 is inactive for new design (2022): use it for replacement parts only.

MS51967 DECODER

hex nuts · carbon steel · cad plated · UNC-2B MS51967 Rev D, Mar 1970

Part number or thread size

Examples:

Part number	Thread	F in	H in	Grade	Status

How an MS51967 Part Number Works

MS51967 the standard 8 dash number from Table I: sets thread size and grade

Each size has three dash numbers in a row: grade A (cancelled), grade B, grade C. So the grade B number is always 2 more than a multiple of 3 (2, 5, 8 … 59) and grade C is a multiple of 3 (3, 6, 9 … 60). The sheet's own example is MS51967-2.

Dash Numbers by Thread Size (Table I)

Size, in	Thread	Grade B	Grade C	Grade A (cancelled) → use
1/4	1/4-20 UNC-2B	MS51967-2	MS51967-3	1 → 2
5/16	5/16-18 UNC-2B	MS51967-5	MS51967-6	4 → 5
3/8	3/8-16 UNC-2B	MS51967-8	MS51967-9	7 → 8
7/16	7/16-14 UNC-2B	MS51967-11	MS51967-12	10 → 11
1/2	1/2-13 UNC-2B	MS51967-14	MS51967-15	13 → 14
9/16	9/16-12 UNC-2B	MS51967-17	MS51967-18	16 → 17
5/8	5/8-11 UNC-2B	MS51967-20	MS51967-21	19 → 20
3/4	3/4-10 UNC-2B	MS51967-23	MS51967-24	22 → 23
7/8	7/8-9 UNC-2B	MS51967-26	MS51967-27	25 → 26
1	1-8 UNC-2B	MS51967-29	MS51967-30	28 → 29
1-1/8	1-1/8-7 UNC-2B	MS51967-32	MS51967-33	31 → 32
1-1/4	1-1/4-7 UNC-2B	MS51967-35	MS51967-36	34 → 35
1-3/8	1-3/8-6 UNC-2B	MS51967-38	MS51967-39	37 → 38
1-1/2	1-1/2-6 UNC-2B	MS51967-41	MS51967-42	40 → 41
1-3/4	1-3/4-5 UNC-2B	MS51967-44	MS51967-45	43 → 44
2	2-4 1/2 UNC-2B	MS51967-47	MS51967-48	46 → 47
2-1/4	2-1/4-4 1/2 UNC-2B	MS51967-50	MS51967-51	49 → 50
2-1/2	2-1/2-4 UNC-2B	MS51967-53	MS51967-54	52 → 53
2-3/4	2-3/4-4 UNC-2B	MS51967-56	MS51967-57	55 → 56
3	3-4 UNC-2B	MS51967-59	MS51967-60	58 → 59

All nuts are carbon steel, cadmium plated. Grade A was cancelled after 8 September 1966 (Table II).

Dimensions in Inches (Table I)

Size, in	Threads per inch	Across flats F, nom	F min–max	Across corners G, min–max	Thickness H, nom	H min–max
1/4	20	7/16	.428–.4375	.488–.505	7/32	.212–.226
5/16	18	1/2	.489–.5000	.557–.577	17/64	.258–.273
3/8	16	9/16	.551–.5625	.628–.650	21/64	.320–.337
7/16	14	11/16	.675–.6875	.768–.794	3/8	.365–.385
1/2	13	3/4	.736–.7500	.840–.866	7/16	.427–.448
9/16	12	7/8	.861–.8750	.982–1.010	31/64	.473–.496
5/8	11	15/16	.922–.9375	1.051–1.083	35/64	.535–.559
3/4	10	1-1/8	1.088–1.1250	1.240–1.299	41/64	.617–.665
7/8	9	1-5/16	1.269–1.3125	1.447–1.516	3/4	.724–.776
1	8	1-1/2	1.450–1.5000	1.653–1.732	55/64	.831–.887
1-1/8	7	1-11/16	1.631–1.6875	1.859–1.949	31/32	.939–.999
1-1/4	7	1-7/8	1.812–1.8750	2.066–2.165	1-1/16	1.030–1.094
1-3/8	6	2-1/16	1.994–2.0625	2.273–2.382	1-11/64	1.138–1.206
1-1/2	6	2-1/4	2.175–2.2500	2.480–2.598	1-9/32	1.245–1.317
1-3/4	5	2-5/8	2.538–2.6250	2.893–3.031	1-1/2	1.460–1.540
2	4-1/2	3	2.900–3.0000	3.306–3.464	1-23/32	1.675–1.763
2-1/4	4-1/2	3-3/8	3.262–3.3750	3.719–3.897	1-59/64	1.874–1.970
2-1/2	4	3-3/4	3.625–3.7500	4.133–4.330	2-9/64	2.089–2.193
2-3/4	4	4-1/8	3.988–4.1250	4.546–4.763	2-23/64	2.303–2.415
3	4	4-1/2	4.350–4.5000	4.959–5.196	2-37/64	2.518–2.638

Dimensions in Millimetres (Table III)

Size, in (mm)	Across flats F, min–max	Across corners G, min–max	Thickness H, nom	H min–max
1/4 (6.350)	10.871–11.112	12.395–12.827	5.556	5.385–5.740
5/16 (7.938)	12.421–12.700	14.148–14.656	6.747	6.553–6.934
3/8 (9.525)	13.995–14.288	15.951–16.510	8.334	8.128–8.560
7/16 (11.112)	17.145–17.462	19.507–20.168	9.525	9.271–9.779
1/2 (12.700)	18.694–19.050	21.336–21.996	11.112	10.846–11.379
9/16 (14.288)	21.869–22.225	24.943–25.654	12.303	12.014–12.598
5/8 (15.875)	23.419–23.812	26.695–27.508	13.891	13.589–14.199
3/4 (19.050)	27.635–28.575	31.496–32.995	16.272	15.672–16.891
7/8 (22.225)	32.233–33.338	36.754–38.506	19.050	18.390–19.710
1 (25.400)	36.830–38.100	41.986–43.993	21.828	21.107–22.530
1-1/8 (28.575)	41.427–42.862	47.219–49.505	24.606	23.851–25.375
1-1/4 (31.750)	46.025–47.625	52.476–54.991	26.988	26.162–27.788
1-3/8 (34.925)	50.648–52.388	57.734–60.503	29.767	28.905–30.632
1-1/2 (38.100)	55.245–57.150	62.992–65.989	32.538	31.623–33.452
1-3/4 (44.450)	64.465–66.675	73.482–76.987	38.100	37.084–39.116
2 (50.800)	73.660–76.200	83.972–87.986	43.662	42.545–44.780
2-1/4 (57.150)	82.855–85.725	94.463–98.984	48.819	47.600–50.038
2-1/2 (63.500)	92.075–95.250	104.978–109.982	54.370	53.061–55.702
2-3/4 (69.850)	101.295–104.775	115.468–120.980	59.919	58.496–61.341
3 (76.200)	110.490–114.300	125.959–131.978	65.482	63.957–67.005

Millimetre values are copied from the sheet's Table III, not recomputed. The thread pitch is the same in mm (for example 20 threads per 25.4 mm). For nominal thickness above 1-3/8 in the sheet converted the fraction rounded to three decimals, so these differ from an exact conversion by up to 0.009 mm. Nominal values are for reference; the limits govern.

Cancelled Numbers and Their Replacements (Table II)

Size, in	MS35690 dash	MS51967 grade A	→ Grade B	MS35690 dash	→ Grade C
1/4	402, 403, 405, 406	1	MS51967-2	408, 409	MS51967-3
5/16	502, 503, 505, 506	4	MS51967-5	508, 509	MS51967-6
3/8	602, 603, 605, 606	7	MS51967-8	608, 609	MS51967-9
7/16	702, 703, 705, 706	10	MS51967-11	708, 709	MS51967-12
1/2	802, 803, 805, 806	13	MS51967-14	808, 809	MS51967-15
9/16	902, 903, 905, 906	16	MS51967-17	908, 909	MS51967-18
5/8	1002, 1003, 1005, 1006	19	MS51967-20	1008, 1009	MS51967-21
3/4	1202, 1203, 1205, 1206	22	MS51967-23	1208, 1209	MS51967-24
7/8	1402, 1403, 1405, 1406	25	MS51967-26	1408, 1409	MS51967-27
1	1602, 1603, 1605, 1606	28	MS51967-29	1608, 1609	MS51967-30
1-1/8	1802, 1803, 1805, 1806	31	MS51967-32	1808, 1809	MS51967-33
1-1/4	2002, 2003, 2005, 2006	34	MS51967-35	2008, 2009	MS51967-36
1-3/8	2202, 2203, 2205, 2206	37	MS51967-38	2208, 2209	MS51967-39
1-1/2	2402, 2403, 2405, 2406	40	MS51967-41	2408, 2409	MS51967-42
1-3/4	2802, 2803, 2805, 2806	43	MS51967-44	2808, 2809	MS51967-45
2	3202, 3203, 3205, 3206	46	MS51967-47	3208, 3209	MS51967-48
2-1/4	3602, 3603, 3605, 3606	49	MS51967-50	3608, 3609	MS51967-51
2-1/2	4002, 4003, 4005, 4006	52	MS51967-53	4008, 4009	MS51967-54
2-3/4	4402, 4403, 4405, 4406	55	MS51967-56	4408, 4409	MS51967-57
3	4802, 4803, 4805, 4806	58	MS51967-59	4808, 4809	MS51967-60

MS35690 numbers were cancelled after 30 September 1965 and MS51967 grade A numbers after 8 September 1966. Cancelled nuts may be used until stocks run out, but cannot always replace the new nuts. Use the new numbers for design and replacement.

Reference Guide: MS51967 Hex Nuts

Reading the Number

The sheet says the part number is the MS number plus the dash number. Its example is MS51967-2. Nothing is coded in the dash number. You look it up in Table I to get the size and grade. There is no letter for the finish: every MS51967 nut is cadmium plated.

MS51967-2: 1/4-20 UNC-2B, grade B (the sheet's example).
MS51967-8: 3/8-16 UNC-2B, grade B.
MS51967-15: 1/2-13 UNC-2B, grade C.

Cancelled numbers

Dash numbers 1, 4, 7 … 58 were grade A nuts. They were cancelled after 8 September 1966 and replaced by the grade B number one higher. The older MS35690 standard was cancelled after 30 September 1965. Table II maps each MS35690 number to MS51967: the leading digits are the size in sixteenths of an inch (6 = 3/8 in), and the last two digits pick grade B (02, 03, 05, 06) or grade C (08, 09). The decoder accepts both kinds of old number.

Grade, Finish, Thread and Shape

Material: carbon steel, grade B or C, per the procurement specification FF-N-836. Finished nuts must meet the proof loads in FF-N-836. The MS sheet itself gives no proof load or hardness values.
Finish: cadmium plate per FF-N-836.
Thread: UNC, class 2B, per Handbook H28 (Screw-Thread Standards for Federal Services).

Notice 6 maps the grades to ASTM A563 Grade B and Grade C. Proof loads are in FF-N-836 and ASTM A563.

Shape

Two designs are acceptable. One has a 30° chamfer on top and a washer face about 1/64 in (0.40 mm) high on the bearing side. The other has a 30° chamfer on both faces. F is the width across flats, G across corners, H the thickness. Sizes run from 1/4 to 3 in.

Status and the Replacement for New Design

MS51967 Revision D is dated 30 March 1970. It was first approved 20 January 1964 and revised in 1964 (A), 1966 (B and C) and 1970 (D, which added the metric sheet). It superseded MS35690 in part and BUNX1 in part.

Notice 3 (10 Sep 2003): reactivated for new or existing design.
Notice 6 (15 Apr 2022): inactive for new design. Use only for replacement.

Notices 1 and 2 (validation 1988, inactivation 2000) and 4 and 5 (validations, Notice 5 dated 12 Feb 2019) are listed in the ASSIST history.

New design: ASME B18.24

Notice 6 says to use nuts per ASME B18.24, and gives the parts of the ASME part identification number (PIN):

AEN04	ASME B18.2.2 hex nut
C	UNC-2 thread
size code	B18.24 Tables 3-1 and 4-1
AZ5 / AZ9	ASTM A563 Grade B / Grade C
QX	zinc-nickel, MIL-PRF-32647 Type K16, preferred to replace cadmium

The notice's example: AEN04C250000AZ5QX1 is a 1/4 in UNC hex nut, A563 grade B, zinc-nickel, no extra features. Size codes for other sizes are in ASME B18.24; this page does not list them.

Source and Checks

Source: MS51967 Revision D, sheets 1 to 3, and Notices 3 and 6 (DLA ASSIST, Distribution A). The inch values agree with the sheet's metric Table III.

MS51967 Hex Nut Part Number Decoder: UNC-2B Thread, Grade B or C, Width Across Flats, Thickness and Tolerances

Reading the Number

Grade, Finish, Thread and Shape

Status and the Replacement for New Design

Source and Checks

Cite This Work