Heavy Hex Nut Sizes & A194 Chart

Quick Reference

Heavy hex nuts for stud bolts are per ASTM A194. Common grades: 2H (carbon steel, with A193 B7), 7/7M (alloy steel, low-temp), 8/8M (stainless 304/316). Dimensions per ASME B18.2.2.

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Need printable charts? Download the Stud Bolt Weight Chart or ASME B16.5 Bolt Dimensions for bolt and nut specifications.

Hex Nuts and Washers for Stud Bolts

Bolt and Nut Size Chart Overview

Nuts and washers directly affect the clamping force and service life of stud bolt connections. This is true across general construction and high-pressure, high-temperature piping systems in petrochemical plants.

nuts and washers for stud bolts

Nuts for Stud Bolts

Nuts thread onto the exposed ends of stud bolts and apply the clamping force that holds flanged joints together. Adjusting how far the nut is tightened controls the bolt tension. The three main types used in piping service are:

Nut Type	Description
Hex nuts	The standard choice for most applications. Typically installed in pairs, one on each end of the stud bolt. Good balance of size, bearing area, and wrenchability.
Heavy hex nuts	Larger and thicker than standard hex nuts. The wider bearing face spreads load over a greater area, which matters in high-pressure flanged connections. These are the default nut for ASME B16.5 flanges.
Lock nuts	Resist loosening under vibration and cyclic loading. Variants include nylon-insert (nyloc) nuts and distorted-thread types.

Washers for Stud Bolts

Washers spread the load from the nut across a wider area, preventing the nut from gouging or galling the flange face. They also protect finished surfaces during tightening and help maintain preload as the joint cycles through thermal expansion and contraction.

Washer Type	Description
Flat washers	The most basic type. They increase bearing area and protect the contact surface from damage.
Spring washers (Belleville)	Conical disc washers that act as springs, maintaining bolt tension in services subject to vibration or thermal cycling.
Lock washers	Split-ring (helical) or toothed designs that grip the nut and mounting surface to resist back-off.

Application Considerations

Selecting the right nut and washer combination depends on the mechanical load, operating temperature, corrosive environment, and vibration exposure of the joint. Carbon steel hardware suits most general-purpose service; stainless steel and specialty alloys are required where corrosion resistance or elevated temperature strength matters.

Key Takeaway: In high-stress or critical applications, such as flanged connections in the oil and gas industry, correct selection and installation of nuts, washers, and stud bolts directly governs joint integrity and safety. Routine inspection and maintenance extend service life and prevent in-service failures.

Dimensional Charts

The chart below shows the hex nuts’ width and thicknesses by diameter:

Heavy Hex Nuts Dimensions ASME B18.2.2

Diameter (inches)	F Basic	F Max	F Min	C Max	C Min
1/2	7/8	0.875	0.850	1.010	0.969
5/8	1.1/16	1.062	1.031	1.227	1.175
3/4	1.1/4	1.250	1.212	1.443	1.382
7/8	1.7/16	1.438	1.394	1.660	1.589
1	1.5/8	1.625	1.575	1.876	1.796
1⅛	1.13/16	1.812	1.756	2.093	2.002
1¼	2	2.000	1.938	2.309	2.209
1⅜	2.3/16	2.188	2.119	2.526	2.416
1½	2.3/8	2.375	2.300	2.742	2.622
1⅝	2.9/16	2.562	2.481	2.959	2.828
1¾	2.3/4	2.750	2.662	3.175	3.035
1⅞	2.15/16	2.938	2.844	3.392	3.242
2	3.1/8	3.125	3.025	3.608	3.449
2¼	3.1/2	3.500	3.388	4.041	3.862
2½	3.7/8	3.875	3.750	4.474	4.275
2¾	4.1/4	4.250	4.112	4.907	4.688
3	4.5/8	4.625	4.475	5.340	5.102
3¼	5	5.000	4.838	5.774	5.515
3½	5.3/8	5.375	5.200	6.207	5.928
3¾	5.3/4	5.750	5.562	6.640	6.341
4	6.1/8	6.125	5.925	7.073	6.755

Heavy Hex Nuts Dimensions ASME B18.2.2

Diameter (inches)	Thickness Basic	Thickness Max	Thickness Min
1/2	31/64	0.504	0.464
5/8	39/64	0.631	0.587
3/4	47/64	0.758	0.710
7/8	55/64	0.885	0.833
1	63/64	1.012	0.956
1⅛	1.7/64	1.139	1.079
1¼	1.7/32	1.251	1.187
1⅜	1.11/32	1.378	1.310
1½	1.15/32	1.505	1.433
1⅝	1.19/32	1.632	1.556
1¾	1.23/32	1.759	1.679
1⅞	1.27/32	1.886	1.802
2	1.31/32	2.013	1.925
2¼	2.13/64	2.251	2.155
2½	2.29/64	2.505	2.401
2¾	2.45/64	2.759	2.647
3	2.61/64	3.013	2.893
3¼	3.3/16	3.252	3.124
3½	3.7/16	3.506	3.370
3¾	3.11/16	3.760	3.616
4	3.15/16	4.014	3.862

Weights

Hex Nuts Weight in Lbs

Hex nuts weight in Lbs (pounds/ 100 pieces) by diameter:

Heavy Hex Nuts Diameter	Finished Hex	Heavy Hex	Finished Jam	Heavy Hex Jam	Square	Heavy Square
1/2″	3.75	6.54	2.62	4	5.78	7.87
5/8″	7.33	11.9	4.93	6.96	10.8	14.3
3/4″	11.9	19.3	7.7	11	15.4	23.5
7/8″	19	29.7	12	16.7	24.5	36.2
1″	28.3	42.5	17.6	23.5	36.3	51.5
1-1/8″	40.3	59.2	24.7	32.4	52.5	72.4
1-1/4″	54.3	78.6	36.1	45.8	70.6	95.5
1-3/8″	73	102	47.9	59.3	94.5	125
1-1/2″	94.3	131	60.9	74.8	122	161
1-5/8″		162		91.6
1-3/4″	151	204	100	114
1-7/8″		241		134
2″	224	299	140	165
2-1/4″		419		227
2-1/2″		564		332
2-3/4″		738		429
3″		950		545
3-1/4″		1194		651
3-1/2″		1526		851
3-3/4″		1812		1005
4″		2180		1200

The weight of heavy hexagonal steel nuts for stud bolts in lbs / 100 units - ASME B18.2.2

Hex Nuts Weight in Kilograms

Hex nuts weight in Kgs. (kg/100 pieces) by diameter:

Heavy Hex Nuts Diameter	Finished Hex	Heavy Hex	Finished Jam	Heavy Hex Jam	Square	Heavy Square
1/2″	1.70	2.97	1.19	1.81	2.62	3.57
5/8″	3.32	5.40	2.24	3.16	4.90	6.49
3/4″	5.40	8.75	3.49	4.99	6.98	10.66
7/8″	8.62	13.47	5.44	7.57	11.11	16.42
1″	12.83	19.27	7.98	10.66	16.46	23.36
1-1/8″	18.28	26.85	11.20	14.69	23.81	32.83
1-1/4″	24.63	35.65	16.37	20.77	32.02	43.31
1-3/8″	33.11	46.26	21.72	26.89	42.86	56.69
1-1/2″	42.77	59.41	27.62	33.92	55.33	73.01
1-5/8″	0.00	73.47	0.00	41.54
1-3/4″	68.48	92.51	45.35	51.70
1-7/8″	0.00	109.29	0.00	60.77		0.00
2″	101.58	135.60	63.49	74.83		0.00
2-1/4″		190.02	0.00	102.94		0.00
2-1/2″		255.77	0.00	150.56		0.00
2-3/4″		334.68	0.00	194.55		0.00
3″		430.83	0.00	247.16		0.00
3-1/4″		541.48	0.00	295.23		0.00
3-1/2″		692.04	0.00	385.93		0.00
3-3/4″		821.74	0.00	455.77		0.00
4″		988.63	0.00	544.20

The weight of heavy hexagonal steel nuts for stud bolts in kilograms / 100 units - ASME B18.2.2

Stud Bolt Weight in Kgs (Stud + 2 Hex Nuts)

Complete stud bolt assembly weight in Kgs. (kg/100 pieces) by metric size:

Heavy Hex Nuts Diameter (Metric)	Bolt Weight (kg)	Nut Weight (kg)	Total Weight (kg)
M12 x 35	0.049	0.013	0.062
M12 x 40	0.053	0.013	0.066
M12 x 45	0.058	0.013	0.071
M12 x 50	0.062	0.013	0.075
M12 x 55	0.067	0.013	0.080
M12 x 60	0.071	0.013	0.084
M12 x 65	0.072	0.013	0.085
M12 x 70	0.080	0.013	0.093
M12 x 75	0.085	0.013	0.098
M12 x 80	0.089	0.013	0.102
M12 x 85	0.094	0.013	0.107
M12 x 90	0.098	0.013	0.111
M12 x 95	0.103	0.013	0.116
M12 x 100	0.107	0.013	0.120
M12 x 105	0.111	0.013	0.124
M12 x 110	0.116	0.013	0.129
M 16X35	0.087	0.032	0.119
M 16X40	0.094	0.032	0.126
M 16X45	0.102	0.032	0.134
M 16X50	0.110	0.032	0.142
M 16X55	0.118	0.032	0.150
M 16X60	0.126	0.032	0.158
M 16X65	0.132	0.032	0.164
M 16X70	0.141	0.032	0.173
M 16X75	0.148	0.032	0.180
M 16X80	0.153	0.032	0.185
M 16X85	0.161	0.032	0.193
M 16X90	0.167	0.032	0.199
M 16X95	0.177	0.032	0.209
M 16X100	0.186	0.032	0.218
M 16X105	0.195	0.032	0.227
M 16X110	0.203	0.032	0.235
M 16X115	0.211	0.032	0.243
M 16X120	0.220	0.032	0.252
M 16X125	0.228	0.032	0.260
M 16X130	0.235	0.032	0.267
M 16X135	0.243	0.032	0.275
M 16X140	0.251	0.032	0.283
M 16X145	0.259	0.032	0.291
M 16X150	0.267	0.032	0.299
M 16X155	0.270	0.032	0.302
M 16X160	0.278	0.032	0.310
M 16X165	0.286	0.032	0.318
M 16X170	0.294	0.032	0.326
M 16X175	0.302	0.032	0.334
M 16X180	0.310	0.032	0.342
M 16X185	0.318	0.032	0.350
M 16X190	0.326	0.032	0.358
M 16X195	0.334	0.032	0.366
M 16X200	0.342	0.032	0.374
M 20X45	0.173	0.061	0.234
M 20X50	0.186	0.061	0.247
M 20X55	0.198	0.061	0.259
M 20X60	0.211	0.061	0.272
M 20X65	0.223	0.061	0.284
M 20X70	0.235	0.061	0.296
M 20X75	0.248	0.061	0.309
M 20X80	0.260	0.061	0.321
M 20X85	0.273	0.061	0.334
M 20X90	0.285	0.061	0.346
M 20X95	0.297	0.061	0.358
M 20X100	0.310	0.061	0.371
M 20X105	0.322	0.061	0.383
M 20X110	0.334	0.061	0.395
M 20X115	0.346	0.061	0.407
M 20X120	0.359	0.061	0.420
M 20X125	0.371	0.061	0.432
M 20X130	0.384	0.061	0.445
M 20X135	0.396	0.061	0.457
M 20X140	0.408	0.061	0.469
M 20X145	0.421	0.061	0.482
M 20X150	0.433	0.061	0.494
M 20X155	0.445	0.061	0.506
M 20X160	0.458	0.061	0.519
M 20X165	0.470	0.061	0.531
M 20X170	0.482	0.061	0.543
M 20X175	0.495	0.061	0.556
M 20X180	0.506	0.061	0.445
M 20X185	0.518	0.061	0.457
M 20X190	0.530	0.061	0.469
M 20X195	0.542	0.061	0.481
M 20X200	0.554	0.061	0.493
M 24X45	0.258	0.104	0.362
M 24X50	0.276	0.104	0.380
M 24X55	0.294	0.104	0.398
M 24X60	0.312	0.104	0.416
M 24X65	0.330	0.104	0.434
M 24X70	0.348	0.104	0.452
M 24X75	0.366	0.104	0.470
M 24X80	0.384	0.104	0.488
M 24X85	0.402	0.104	0.506
M 24X90	0.420	0.104	0.524
M 24X95	0.437	0.104	0.541
M 24X100	0.456	0.104	0.560
M 24X105	0.471	0.104	0.575
M 24X110	0.492	0.104	0.596
M 24X115	0.510	0.104	0.614
M 24X120	0.528	0.104	0.632
M 24X125	0.546	0.104	0.650
M 24X130	0.559	0.104	0.663
M 24X135	0.582	0.104	0.686
M 24X140	0.598	0.104	0.702
M 24X145	0.618	0.104	0.722
M 24X150	0.638	0.104	0.742
M 24X155	0.656	0.104	0.760
M 24X160	0.674	0.104	0.778
M 24X165	0.688	0.104	0.792
M 24X170	0.709	0.104	0.813
M 24X175	0.727	0.104	0.831
M 24X180	0.745	0.104	0.849
M 24X185	0.762	0.104	0.866
M 24X190	0.78	0.104	0.884
M 24X195	0.798	0.104	0.902
M 24X200	0.816	0.104	0.920

Hex Nuts Materials

ASTM A194 Material Specification

The ASTM A194 specification covers carbon, alloy, martensitic, and austenitic stainless steel nuts. Hex-heavy nuts are components of boltings sets for flanges. These nuts are intended for high-pressure or high-temperature service or both, and the bars from which they are made must be hot-wrought.

Per ASTM A194, the material may be further processed by centerless grinding or cold drawing. Austenitic stainless steel may be solution annealed or annealed and strain-hardened. Each alloy must conform to its prescribed chemical composition requirements. Hardness tests, proof-of-load tests, and cone-proof-load tests are mandatory for all nuts.

Key ASTM A194 Parameters

Parameter	Detail
Size range	1/4” through 4” (metric: M6 to M100)
Unit systems	Inch-pound or SI (not interchangeable)
Threading standard	ANSI B 18.2.2 Heavy Hex Series
Thread fit (<=1”)	UNC Series Class 2B
Thread fit (>1”)	UNC Series Class 2B or 8 UN Series Class 2B
Most common grade	A194 2H (paired with A193 B7 studs)

The most common grades of ASTM A194 heavy hex steel nuts are:

Grade	Material Description
A194 2H	Quenched & tempered carbon steel
A194 2HM	Quenched & tempered carbon steel (controlled hardness)
A194 3	Chrome-moly alloy steel
A194 4	Quenched & tempered carbon-molybdenum
A194 6	Martensitic stainless steel
A194 7	Quenched & tempered alloy steel (AISI 4140)
A194 7M	Quenched & tempered alloy steel (controlled hardness)
A194 8	Stainless AISI 304
A194 8A	Stainless AISI 304 (solution annealed)
A194 8M	Stainless AISI 316
A194 8MA	Stainless AISI 316 (solution annealed)
A194 8C	Stainless AISI 347 (stabilized)
A194 8T	Stainless AISI 321 (stabilized)

ASTM A194 Chemical Composition

ASTM A194 NUTS	Carbon	Manganese	Phosphorous, max	Sulfur, max	Silicon	Chromium	Nickel	Molybdenum	Other Elements
ASTM A194 grade 2, 2H and 2 HM	0.40% min.	1.00% max.	0.04%	0.05%	0.40% max
ASTM A194 grade 3	0.10% min.	1.00% max.	0.04%	0.03%	1.00%	4.0-6.0%		0.20-0.30%
ASTM A194 grade 4	0.40 -0.50%	0.70-0.90%	0.035%	0.04%	0.15-0.35%			0.20-0.30%
ASTM A194 grade 6	0.15%	1.00%	0.04%	0.03%	1.00%	11.5-13.5%
ASTM A194 grade 6F	0.15%	1.25%	0.06%	0.06%	1.00%	12.0-14.0%			Selenium-0.15% min
ASTM A194 grade 7 and 7M (AISI 4140)	0.37-0.49%	0.65-1.10%	0.04%	0.04%	0.15-0.035%	0.75-1.20%		0.15-0.25%
ASTM A194 grade 8 (AISI 304)	0.08%	2.00% max	0.05%	0.03%	1.00% max	18.0-20.0%	8.0-11.0%
ASTM A194 grade 8M (AISI 316)	0.08%	2.00% max	0.05%	0.30%	1.00% max	16.0-18.0%	10.0-14.0%	2.00-3.00%
ASTM A194 grade 8C	0.08%	2.00%	0.045%	0.03%	1.00%	17.0-19.0%	9.0-12.0%		Columbium and Tantalum - 10x carbon content, min
ASTM A194 grade 8T	0.80%	2.00%	0.045%	0.30%	1.00%	17.0-19.0%	9.0-12.0%		Titanium-0.70%max, Nitrogen-0.10%
ASTM A194 grade 8F	0.15%	2.00%	0.20%	0.15%min	1.00%	17.0-19.0%	8.0-10.0%
ASTM A194 grade 8R	0.06%	4.0-6.0%	0.045%	0.03%	1.00%	20.5-23.5%	11.5-13.5%	1.50-3.00%	Columbium and Tantalum-0.10-0.30%, Nirogen-0.20-0.40%, Vanadium-0.10-0.30%
ASTM A194 grade 8S	0.10%	7.0-9.0%	0.060%	0.03%	3.5-4.5%	16.0-18.0%	8.0-9.0%		Nitrogen-0.08-0.18%
ASTM A194 grade 16	0.36-0.47%	0.45-0.70%	0.035%	0.40%	0.15-0.35%	0.80-1.15%		0.50-0.65%

ASTM A194 Mechanical Properties

Grade Marking	Specification	Material	Nominal Size (In.)	Tempering Temp (°F)	Proof Load Stress (ksi)	Hardness Min	Hardness Max	See Note
	ASTM A194 Grade 2	Medium Carbon Steel	1/4 - 4	0	150	159	352	1,2,3
	ASTM A194 Grade 2H	Medium Carbon Steel, Quenched and Tempered	1/4 - 4	850	175	C24	C38	1,2
	ASTM A194 Grade 2HM	Medium Carbon Steel, Quenched and Tempered	1/4 - 4	1150	150	159	237	1,2,3
	ASTM A194 Grade 4	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1100	175	C24	C38	1,2
	ASTM A194 Grade 7	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1100	175	C24	C38	1,2
	ASTM A194 Grade 7M	Medium Carbon Alloy Steel, Quenched and Tempered	1/4 - 4	1150	150	159	237	1,2,3
	ASTM A194 Grade 8	Stainless AISI 304	1/4 - 4	-	80	126	300	4
	ASTM A194 Grade 8M	Stainless AISI 316	1/4 - 4	-	80	126	300	4

Other ASTM Grades for Hex Nuts

Beyond A194, several other ASTM specifications cover hex nuts for different materials and service conditions.

ASTM A563

This specification covers carbon and alloy steel nuts for general structural and mechanical use. Grades range from Grade A (mild carbon steel) through Grade C (medium carbon, quenched and tempered) to Grade DH (carbon steel, quenched and tempered for high-strength bolting).

ASTM F594

Covers stainless steel nuts for general engineering applications. Nuts are classified by alloy group (304, 316, 321) with condition designators indicating strength level: CW for cold worked, A for annealed.

ASTM F467

Covers nonferrous nuts made from aluminum, copper, and nickel alloys for general use. Grades are categorized by base material and temper, for example Aluminum Alloy 6061-T6.

ASTM A563M (Metric)

The metric counterpart to ASTM A563, covering carbon and alloy steel nuts in metric sizes. Grades and property classes parallel those of A563 but use metric dimensions and SI strength units.

ASTM F836M

The metric version of ASTM F594, specifying stainless steel nuts in metric sizes for general engineering use. Classified by alloy group and condition, following the same framework as F594 but with metric measurements.

European Material Grades Specs for Nuts

European standards for hex nuts used in flanged connections serve the industrial, construction, and energy sectors. The key specifications are summarized below.

EN ISO 4032

Covers style-1 hexagonal nuts in threads from M1.6 through M64. Product grade A applies to threads up to M16; product grade B applies above M16. These are the general-purpose nuts used across most flanged connections.

EN ISO 4033

Similar scope to EN ISO 4032 but specifies hexagonal high nuts (taller profile). Used where longer thread engagement is needed or where the assembly calls for a thicker nut body.

EN ISO 4034

Covers style-1 hexagonal nuts in threads from M5 through M39, product grade C. Intended for less critical applications where coarser dimensional tolerances are acceptable.

EN ISO 4035

Covers hexagon thin nuts (chamfered) with metric fine-pitch thread, product grades A and B. Used where axial space is limited, including certain flange connections.

EN ISO 4036

Covers hexagon thin nuts (unchamfered) with metric fine-pitch thread, product grades A and B. Similar application range to EN ISO 4035, for thin-nut service without a chamfer.

EN 1092-1

Primarily a flange standard, but EN 1092-1 indirectly sets requirements for bolts and nuts in flanged connections by specifying flange types, dimensions, and materials for various pressure-temperature combinations.

Common ISO Grades for Nuts

Steel nuts in Europe follow ISO classification, which provides a uniform framework for mechanical properties across international borders.

ISO 898-2 for Carbon Steel and Alloy Steel Nuts

ISO 898-2 groups nuts into property classes based on proof load capacity:

Property Class	Strength Level	Typical Use
Class 6	Low strength	Light-duty assemblies where high tensile load is not a factor
Class 8	Medium strength	General engineering and structural applications
Class 10	High strength	Applications requiring good tensile strength and hardness
Class 12	Very high strength	Demanding structural and mechanical joints

ISO 3506-2 for Stainless Steel Nuts

The two primary stainless grades are A2 and A4:

Grade	Equivalent	Corrosion Resistance	Typical Service
A2	AISI 304	Good in standard atmospheric and mild chemical environments	Indoor and outdoor general-purpose applications
A4	AISI 316	Superior, especially in chloride and marine exposure, due to molybdenum content	Marine, offshore, and chemical process environments

Tensile/Yield Strength Classification (8.8/10.9 Nuts)

The ISO 898 grading system uses a two-number code to describe mechanical properties of hex nuts:

• The first number multiplied by 100 gives the approximate minimum ultimate tensile strength in MPa.
• The second number, multiplied by the first, gives the ratio of yield strength to tensile strength.

8.8 Grade nuts have a minimum tensile strength of 800 MPa and a yield strength of approximately 640 MPa (0.8 x 800). They are made from medium carbon steel or alloy steel and can be heat-treated. Zinc or other protective coatings are common. Grade 8.8 sees wide use in automotive, construction, and manufacturing assemblies that require moderate strength and toughness.

10.9 Grade nuts have a minimum tensile strength of 1000 MPa and a yield strength of approximately 900 MPa (0.9 x 1000). These are typically alloy steel, heat-treated to reach the higher strength range. Like 8.8 hardware, they accept corrosion-resistant coatings. Grade 10.9 is specified for heavy machinery, structural steelwork, and any joint under high static or dynamic loading.

Selection Factors

When choosing a hex nut grade, three factors drive the decision. First, the mechanical loading and environmental conditions of the joint (temperature extremes, cyclic stress, vibration) determine the minimum property class. Second, corrosion resistance requirements dictate whether carbon steel, A2 stainless, or A4 stainless is needed; A4 is the standard choice for marine and chemical-plant service. Third, the required proof load and hardness range must match the stud bolt grade to avoid galling or under-clamping the joint.