ASTM A194

A194 is a ASTM International specification for nuts

A194 covers a variety of carbon, alloy and stainless steel nuts in sizes 1/4″ through 4″, M6 through M100 nominal in metric. Nuts of this specification are intended for high-pressure or high-temperature use, or both.

ASTM A194

The ASTM A194 specification covers carbon, alloy, and stainless steel nuts intended for use in high-pressure and/or high-temperature service. Unless otherwise specified, the American National Standard Heavy Hex Series (ANSI B 18.2.2) shall be used. Nuts up to and including 1-inch nominal size shall be UNC Series Class 2B fit. Nuts over 1-inch nominal size shall be either UNC Series Class 2B fit or 8 UN Series Class 2B fit

A194 Grades

A194 Grade 2:

Carbon steel heavy hex nuts.

A194 Grade 2H:

Quenched and tempered carbon steel heavy hex nuts.

A194 Grade 7:

Quenched and tempered alloy steel heavy hex nuts.

A194 Grade 7L:

Quenched and tempered alloy steel heavy hex nuts, Charpy impact tested.

A194 Grade 8:

Stainless AISI 304 heavy hex nuts.

A194 Grade 8M:

Stainless AISI 316 heavy hex nuts.

NOTE: There are other grades of A194. Those listed here are the ones we receive the most requests for.

A194 MECHANICAL PROPERTIES


Grade
Marking
Size
Tempering Temp.

Fahrenheit
Proof Load Stress, ksi
Hardness Brinell

Min
Max

2
2
1/4″ – 4″
0
150
159
352

2H
2H
1/4″ – 1-1/2″
850
175
248
327

2H
2H
1-1/2″ – 4″
850
175
212
327

7
7
1/4″ – 4″
1100
175
248
327

8
8
1/4″ – 4″
–
80
126
300

8M
8M
1/4″ – 4″
–
80
126
300

A194 MECHANICAL PROPERTIES
Grade	Marking	Size	Tempering Temp. Fahrenheit	Proof Load Stress, ksi	Hardness Brinell
Min	Max
2	2	1/4″ – 4″	0	150	159	352
2H	2H	1/4″ – 1-1/2″	850	175	248	327
2H	2H	1-1/2″ – 4″	850	175	212	327
7	7	1/4″ – 4″	1100	175	248	327
8	8	1/4″ – 4″	–	80	126	300
8M	8M	1/4″ – 4″	–	80	126	300

Notes:

The markings shown for all grades of A194 nuts are for cold-formed and hot-forged nuts. When nuts are machined from bar stock, the nut must additionally be marked with the letter B. The letters H & M indicate heat-treated nuts.
Properties shown are those of coarse and 8-pitch thread heavy hex nuts.

A194 CHEMICAL PROPERTIES


Element
2, 2H
7
8 (AISI 304)
8M (AISI 316)

Carbon
0.4% min
0.37 – 0.49%
0.08% max
0.08% max

Manganese
1.0% max
0.65 – 1.1%
2.0% max
2.0% max

Phosphorus, max
0.04%
0.035%
0.045%
0.045%

Sulfur, max
0.05%
0.04%
0.03%
0.03%

Silicon
0.40% max
0.15 – 035%
1.0% max
1.0% max

Chromium

0.75 – 1.2%
18.0 – 20.0%
16.0 – 18.0%

Nickel


8.0 – 11.0%
10.0 – 14.0%

Molybdenum

0.15 – 0.25%

2.0 – 3.0%

A194 CHEMICAL PROPERTIES
Element	2, 2H	7	8 (AISI 304)	8M (AISI 316)
Carbon	0.4% min	0.37 – 0.49%	0.08% max	0.08% max
Manganese	1.0% max	0.65 – 1.1%	2.0% max	2.0% max
Phosphorus, max	0.04%	0.035%	0.045%	0.045%
Sulfur, max	0.05%	0.04%	0.03%	0.03%
Silicon	0.40% max	0.15 – 035%	1.0% max	1.0% max
Chromium		0.75 – 1.2%	18.0 – 20.0%	16.0 – 18.0%
Nickel			8.0 – 11.0%	10.0 – 14.0%
Molybdenum		0.15 – 0.25%		2.0 – 3.0%

HEX NUT DIMENSIONS


Nut Size
Heavy Hex Nut
Heavy Hex Jam Nut

A
B
A
C

1/4″
1/2
15/64
1/2
11/64

5/16″
9/16
19/64
9/16
13/64

3/8″
11/16
23/64
11/16
15/64

7/16″
3/4
27/64
3/4
17/64

1/2″
7/8
31/64
7/8
19/64

9/16″
15/16
35/64
15/16
21/64

5/8″
1-1/6
39/64
1-1/16
23/64

3/4″
1-1/4
47/64
1-1/4
27/64

7/8″
1-7/16
55/64
1-7/16
31/64

1″
1-5/8
63/64
1-5/8
35/64

1-1/8″
1-13/16
1-7/64
1-13/16
39/64

1-1/4″
2
1-7/32
2
23/32

1-3/8″
2-3/16
1-11/32
2-3/16
25/32

1-1/2″
2-3/8
1-15/32
2-3/8
27/32

1-5/8″
2-9/16
1-19/32
2-9/16
29/32

1-3/4″
2-3/4
1-23/32
2-3/4
31/32

1-7/8″
2-15/16
1-27/32
2-15/16
1-1/32

2″
3-1/8
1-31/32
3-1/8
1-3/32

2-1/4″
3-1/2
2-13/64
3-1/2
1-13/64

2-1/2″
3-7/8
2-29/64
3-7/8
1-29/64

2-3/4″
4-1/4
2-45/64
4-1/4
1-37/64

3″
4-5/8
2-61/64
4-5/8
1-45/64

3-1/4″
5
3-3/16
5
1-13/16

3-1/2″
5-3/8
3-7/16
5-3/8
1-15/16

3-3/4″
5-3/4
3-11/16
5-3/4
2-1/16

4″
6-1/8
3-15/16
6-1/8
2-3/16

HEX NUT DIMENSIONS
Nut Size	Heavy Hex Nut	Heavy Hex Jam Nut
A	B	A	C
1/4″	1/2	15/64	1/2	11/64
5/16″	9/16	19/64	9/16	13/64
3/8″	11/16	23/64	11/16	15/64
7/16″	3/4	27/64	3/4	17/64
1/2″	7/8	31/64	7/8	19/64
9/16″	15/16	35/64	15/16	21/64
5/8″	1-1/6	39/64	1-1/16	23/64
3/4″	1-1/4	47/64	1-1/4	27/64
7/8″	1-7/16	55/64	1-7/16	31/64
1″	1-5/8	63/64	1-5/8	35/64
1-1/8″	1-13/16	1-7/64	1-13/16	39/64
1-1/4″	2	1-7/32	2	23/32
1-3/8″	2-3/16	1-11/32	2-3/16	25/32
1-1/2″	2-3/8	1-15/32	2-3/8	27/32
1-5/8″	2-9/16	1-19/32	2-9/16	29/32
1-3/4″	2-3/4	1-23/32	2-3/4	31/32
1-7/8″	2-15/16	1-27/32	2-15/16	1-1/32
2″	3-1/8	1-31/32	3-1/8	1-3/32
2-1/4″	3-1/2	2-13/64	3-1/2	1-13/64
2-1/2″	3-7/8	2-29/64	3-7/8	1-29/64
2-3/4″	4-1/4	2-45/64	4-1/4	1-37/64
3″	4-5/8	2-61/64	4-5/8	1-45/64
3-1/4″	5	3-3/16	5	1-13/16
3-1/2″	5-3/8	3-7/16	5-3/8	1-15/16
3-3/4″	5-3/4	3-11/16	5-3/4	2-1/16
4″	6-1/8	3-15/16	6-1/8	2-3/16

THREAD DIMENSIONS & OVERSIZING ALLOWANCES FOR HOT-DIPPED GALVANIZED NUTS
Size & Thread Pitch	Diametral Allowance	Pitch Diameter
Size & Thread Pitch	Diametral Allowance	min	max
1/4″-20	0.016	0.2335	0.2384
5/16″-18	0.017	0.2934	0.2987
3/8″-16	0.017	0.3514	0.3571
7/16″-14	0.018	0.4091	0.4152
1/2″-13	0.018	0.4680	0.4745
9/16″-12	0.020	0.5284	0.5352
5/8″-11	0.020	0.5860	0.5932
3/4″-10	0.020	0.7050	0.7127
7/8″-9	0.022	0.8248	0.8330
1″-8	0.024	0.9428	0.9516
1-1/8″-8	0.024	1.0678	1.0768
1-1/8″-7	0.024	1.0562	1.0656
1-1/4″-8	0.024	1.1928	1.2020
1-1/4″-7	0.024	1.1812	1.1908
1-3/8″-8	0.027	1.3208	1.3301
1-3/8″-6	0.027	1.2937	1.3041
1-1/2″-8	0.027	1.4458	1.4553
1-1/2″-6	0.027	1.4187	1.4292
1-3/4″-5	0.050	1.6701	1.6817
2″-4.5	0.050	1.9057	1.9181
2-1/4″-4.5	0.050	2.1557	2.1683
2-1/2″-4	0.050	2.3876	2.4011
2-3/4″-4	0.050	2.6376	2.6513
3″-4	0.050	2.8876	2.9015
3-1/4″-4	0.050	3.1376	3.1517
3-1/2″-4	0.050	3.3876	3.4019
3-3/4″-4	0.050	3.6376	3.6521
4″-4	0.050	3.8876	3.9023

ASTM A194

ASTM A194

A194 is a ASTM International specification for nuts

A194 Grades

A194 MECHANICAL PROPERTIES

A194 CHEMICAL PROPERTIES

HEX NUT DIMENSIONS

THREAD DIMENSIONS & OVERSIZING ALLOWANCES