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ASME B18.2.2 · A194 · A563

Heavy Hex Nuts Manufacturer in India

Wider across flats, thicker, made for high-strength bolts and flange studs. We make heavy hex nuts to ASME B18.2.2 and B18.2.4.6M in ASTM A194 2H, 2HM, 7, 7M, 8 and 8M and A563 C, DH and DH3. Below: the nut drawn to scale, inch and metric tables, heavy against regular hex, grades and proof loads, bolt pairing and a finder.

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  • ISO 9001:2015 certified manufacturer
  • Proof load & hardness by lot
  • 1/4 to 4 in, M12 to M100
  • EN 10204 3.1 / 3.2
Stainless steel heavy hex nuts
Inch 1/4 – 4 in Metric M12 – M100 Grades 2H · DH · 8M
Overview

ASTM A194 2H / A563 DH Nuts (Heavy Hex Nuts): Manufacturer & Exporter

A heavy hex nut is wider across flats and thicker than a regular hex nut on the same thread. The larger bearing face spreads the load over oversized or slotted holes, and the extra height and hardness let the nut match high-strength bolts and studs.

Exotic Alloy manufactures and exports heavy hex nuts from Mumbai, India, for refineries, petrochemical and power plants, steel structures, pipelines and EPC contractors. We supply across India and export to Malaysia, South-East Asia, the Gulf and Africa.

Where heavy hex nuts go

Two nuts on every stud of a pressure flange (see flange bolting), on structural bolts in steel connections, and on anchor rods. For the lighter nut on general bolts see hex nuts; for the studs, full threaded studs.

ASME B18.2.2 A194 2H / 2HM A563 DH 8 / 8M stainless Metric M12–M100
Heavy hex nuts at a glance
Inch
ASME B18.2.2, 1/4 to 4 in
Metric
ASME B18.2.4.6M, M12 to M100
Thread
UNC, UNF, 8UN, class 2B; metric coarse
Pressure bolting
ASTM A194 2H, 2HM, 7, 7M, 8, 8M
Structural
ASTM A563 A, C, DH, DH3
1 in nut
1-5/8 in across flats, 63/64 in thick
Related
Hex nuts, jam nuts, washers
ASME B18.2.2 heavy hex nut 1-8 UNC drawn to scale in top view and side view: width across flats F 1-5/8 inch (1.575 to 1.625), width across corners G 1.796 to 1.876 inch, thickness H 63/64 inch (0.956 to 1.012), chamfered on both faces F = 1-5/8 in (wrench) G 1.796 to 1.876 in across corners 1-8 UNC-2B Top view Side view across corners H = 63/64 in H 0.956 to 1.012 in: about one diameter a regular 1 in hex nut is 1-1/2 across flats, 55/64 thick ASME B18.2.2 heavy hex nut, 1-8 UNC, to scale EXOTIC ALLOY
A 1-8 UNC heavy hex nut to ASME B18.2.2, to scale. Nearly as thick as the thread is wide, with a 1-5/8 in wrench size.
Specification

Heavy Hex Nut Specification

The range we manufacture and export.

DimensionsASME B18.2.2 (inch), ASME B18.2.4.6M (metric)
Sizes1/4 to 4 in; M12 to M100
ThreadUNC, UNF, 8UN, class 2B; metric coarse; overtapped for galvanizing
Pressure gradesASTM A194 / A194M 2H, 2HM, 7, 7M, 8, 8M
Structural gradesASTM A563 / A563M A, C, DH, DH3
Special alloysDuplex, super duplex, Monel, Inconel, Hastelloy
FinishPlain, hot-dip galvanized, zinc plated, PTFE (fluoropolymer) coated
MarkingGrade symbol (2H, 2HM, DH ...) and maker's mark on one face
CertificationEN 10204 3.1; 3.2 on request; NACE MR0175 for 2HM / 7M
SupplyLoose, or as stud bolt sets packed per joint
Inch sizes

ASME B18.2.2 Heavy Hex Nut Dimensions

1/4 to 4 in; F is the wrench size.

SizeUNC
tpi		Across flats F
basic / max / min, in		Across corners G
max / min, in		Thickness H
basic / max / min, in		F / H max
mm
1/4201/2 / 0.500 / 0.4880.577 / 0.55615/64 / 0.250 / 0.21812.7 / 6.3
5/16189/16 / 0.562 / 0.5460.650 / 0.62219/64 / 0.314 / 0.28014.3 / 8.0
3/81611/16 / 0.688 / 0.6690.794 / 0.76323/64 / 0.377 / 0.34117.5 / 9.6
7/16143/4 / 0.750 / 0.7280.866 / 0.83027/64 / 0.441 / 0.40319.0 / 11.2
1/2137/8 / 0.875 / 0.8501.010 / 0.96931/64 / 0.504 / 0.46422.2 / 12.8
9/161215/16 / 0.938 / 0.9091.083 / 1.03735/64 / 0.568 / 0.52623.8 / 14.4
5/8111-1/16 / 1.062 / 1.0311.227 / 1.17539/64 / 0.631 / 0.58727.0 / 16.0
3/4101-1/4 / 1.250 / 1.2121.443 / 1.38247/64 / 0.758 / 0.71031.8 / 19.3
7/891-7/16 / 1.438 / 1.3941.660 / 1.58955/64 / 0.885 / 0.83336.5 / 22.5
181-5/8 / 1.625 / 1.5751.876 / 1.79663/64 / 1.012 / 0.95641.3 / 25.7
1-1/871-13/16 / 1.812 / 1.7562.093 / 2.0021-7/64 / 1.139 / 1.07946.0 / 28.9
1-1/472 / 2.000 / 1.9382.309 / 2.2091-7/32 / 1.251 / 1.18750.8 / 31.8
1-3/862-3/16 / 2.188 / 2.1192.526 / 2.4161-11/32 / 1.378 / 1.31055.6 / 35.0
1-1/262-3/8 / 2.375 / 2.3002.742 / 2.6221-15/32 / 1.505 / 1.43360.3 / 38.2
1-5/8–2-9/16 / 2.562 / 2.4812.959 / 2.8281-19/32 / 1.632 / 1.55665.1 / 41.5
1-3/452-3/4 / 2.750 / 2.6623.175 / 3.0351-23/32 / 1.759 / 1.67969.8 / 44.7
1-7/8–2-15/16 / 2.938 / 2.8443.392 / 3.2421-27/32 / 1.886 / 1.80274.6 / 47.9
24½3-1/8 / 3.125 / 3.0253.608 / 3.4491-31/32 / 2.013 / 1.92579.4 / 51.1
2-1/44½3-1/2 / 3.500 / 3.3884.041 / 3.8622-13/64 / 2.251 / 2.15588.9 / 57.2
2-1/243-7/8 / 3.875 / 3.7504.474 / 4.2752-29/64 / 2.505 / 2.40198.4 / 63.6
2-3/444-1/4 / 4.250 / 4.1124.907 / 4.6882-45/64 / 2.759 / 2.647107.9 / 70.1
344-5/8 / 4.625 / 4.4755.340 / 5.1022-61/64 / 3.013 / 2.893117.5 / 76.5
3-1/445 / 5.000 / 4.8385.774 / 5.5153-3/16 / 3.252 / 3.124127.0 / 82.6
3-1/245-3/8 / 5.375 / 5.2006.207 / 5.9283-7/16 / 3.506 / 3.370136.5 / 89.1
3-3/445-3/4 / 5.750 / 5.5626.640 / 6.3413-11/16 / 3.760 / 3.616146.0 / 95.5
446-1/8 / 6.125 / 5.9257.073 / 6.7553-15/16 / 4.014 / 3.862155.6 / 102.0

ASME B18.2.2-2022 Table 11, inch; mm columns converted. UNF is standard to 1-1/2 in and 8UN from 1-1/8 in; nuts for flange studs above 1 in are usually 8UN. The 2015 edition printed 0.411 in as the 7/16 in maximum thickness, below its own 27/64 in basic size; the 2022 edition gives 0.441 in.

Heavy vs regular

Heavy Hex vs Regular Hex Nuts

Heavy hex and regular hex nuts overlaid to scale at 1/2 inch and 1-1/2 inch: the heavy nut is 1/8 inch wider across flats (7/8 against 3/4 inch, 2-3/8 against 2-1/4 inch) and thicker (31/64 against 7/16 inch, 1-15/32 against 1-9/32 inch) Heavy hex vs regular hex, overlaid to scale Heavy hex Regular hex 1/2 in 1/2 in heavy hex nut thickness 0.504 in max 0.504 heavy 1/2 in regular hex nut thickness 0.448 in max 0.448 regular H max, in F 0.875 in heavy vs 0.750 in regular 1-1/2 in 1-1/2 in heavy hex nut thickness 1.505 in max 1.505 heavy 1-1/2 in regular hex nut thickness 1.317 in max 1.317 regular H max, in F 2.375 in heavy vs 2.250 in regular Heavy hex is 1/8 in wider across flats at 3/8, 1/2 and from 5/8 in up; 1/16 in at 1/4, 5/16, 7/16 and 9/16; always thicker. EXOTIC ALLOY
One size up in the wrench. A 1/2 in heavy hex nut takes the 7/8 in wrench of a regular 9/16 in nut.
SizeRegular hex F / H max
in		Heavy hex F / H max
in		Wider byThicker by
1/40.438 / 0.2260.500 / 0.2500.062 in0.024 in
5/160.500 / 0.2730.562 / 0.3140.062 in0.041 in
3/80.563 / 0.3370.688 / 0.3770.125 in0.040 in
7/160.688 / 0.3850.750 / 0.4410.062 in0.056 in
1/20.750 / 0.4480.875 / 0.5040.125 in0.056 in
9/160.875 / 0.4960.938 / 0.5680.063 in0.072 in
5/80.938 / 0.5591.062 / 0.6310.124 in0.072 in
3/41.125 / 0.6651.250 / 0.7580.125 in0.093 in
7/81.312 / 0.7761.438 / 0.8850.126 in0.109 in
11.500 / 0.8871.625 / 1.0120.125 in0.125 in
1-1/81.688 / 0.9991.812 / 1.1390.124 in0.140 in
1-1/41.875 / 1.0942.000 / 1.2510.125 in0.157 in
1-3/82.062 / 1.2062.188 / 1.3780.126 in0.172 in
1-1/22.250 / 1.3172.375 / 1.5050.125 in0.188 in

ASME B18.2.2-2022 Tables 5 and 11, maximum sizes. The larger bearing face lowers the pressure under the nut and covers oversize holes; the extra height adds thread engagement.

Metric

Metric Heavy Hex Nuts, ASME B18.2.4.6M

Metric heavy hex nuts to ASME B18.2.4.6M compared with ISO 4032 regular nuts from M12 to M36: across flats 21 against 18 mm at M12 rising to 60 against 55 mm at M36, and height 12.3 against 10.8 mm at M12 rising to 36.6 against 31 mm at M36 Metric heavy hex (ASME B18.2.4.6M) vs ISO 4032, mm Heavy hex ISO 4032 Across flats s 0 20 40 60 M12 Heavy hex: s 21 mm M14 Heavy hex: s 24 mm M16 Heavy hex: s 27 mm M20 Heavy hex: s 34 mm M22 Heavy hex: s 36 mm M24 Heavy hex: s 41 mm M27 Heavy hex: s 46 mm M30 Heavy hex: s 50 mm M36 Heavy hex: s 60 mm M12 ISO 4032: s 18 mm M14 ISO 4032: s 21 mm M16 ISO 4032: s 24 mm M20 ISO 4032: s 30 mm M22 ISO 4032: s 34 mm M24 ISO 4032: s 36 mm M27 ISO 4032: s 41 mm M30 ISO 4032: s 46 mm M36 ISO 4032: s 55 mm 60 55 Height m max 0 10 20 30 40 M12 Heavy hex: m 12.3 mm M14 Heavy hex: m 14.3 mm M16 Heavy hex: m 17.1 mm M20 Heavy hex: m 20.7 mm M22 Heavy hex: m 23.6 mm M24 Heavy hex: m 24.2 mm M27 Heavy hex: m 27.5 mm M30 Heavy hex: m 30.7 mm M36 Heavy hex: m 36.6 mm M12 ISO 4032: m 10.8 mm M14 ISO 4032: m 12.8 mm M16 ISO 4032: m 14.8 mm M20 ISO 4032: m 18 mm M22 ISO 4032: m 19.4 mm M24 ISO 4032: m 21.5 mm M27 ISO 4032: m 23.8 mm M30 ISO 4032: m 25.6 mm M36 ISO 4032: m 31 mm M12 M14 M16 M20 M22 M24 M27 M30 M36 36.6 31 EXOTIC ALLOY
Metric heavy hex nuts are wider and taller than ISO 4032 nuts at every size. Hover a dot for the value.
SizePitch Ps
max / min		e
max / min		m
max / min		dw minc
min / max		ISO 4032
s / m max
M121.7521 / 20.1624.25 / 22.7812.3 / 11.919.20.4 / 0.818 / 10.8
M14224 / 23.1627.71 / 26.1714.3 / 13.6220.4 / 0.821 / 12.8
M16227 / 26.1631.18 / 29.5617.1 / 16.424.90.4 / 0.824 / 14.8
M202.534 / 3339.26 / 37.2920.7 / 19.431.40.4 / 0.830 / 18
M222.536 / 3541.57 / 39.5523.6 / 22.333.30.4 / 0.834 / 19.4
M24341 / 4047.34 / 45.224.2 / 22.9380.4 / 0.836 / 21.5
M27346 / 4553.12 / 50.8527.5 / 26.342.80.4 / 0.841 / 23.8
M303.550 / 4957.74 / 55.3730.7 / 29.145.60.4 / 0.846 / 25.6
M36460 / 58.869.28 / 66.4436.6 / 3555.90.4 / 0.855 / 31
M424.570 / 67.980.83 / 77.4142 / 40.464.50.5 / 165 / 34
M48580 / 77.692.38 / 88.4648 / 46.473.70.5 / 175 / 38
M565.590 / 87.2103.92 / 99.4156 / 54.182.80.5 / 185 / 45
M646100 / 96.8115.47 / 110.3564 / 62.1920.5 / 195 / 51
M726110 / 106.4127.02 / 121.372 / 70.1101.10.6 / 1.2–
M806120 / 116138.56 / 132.2480 / 78.1110.20.6 / 1.2–
M906135 / 130.5155.88 / 148.7790 / 87.81240.6 / 1.2–
M1006150 / 145173.21 / 165.3100 / 97.8137.80.6 / 1.2–

ASME B18.2.4.6M-2010, mm, for nuts to ASTM A194M, A563M, F836M and F467M. dw bearing face, c washer face thickness. Last column: ISO 4032 regular nut for comparison (sizes to M39).

Grades

ASTM A194 & A563 Grades and Proof Loads

Minimum proof stress of heavy hex nuts by grade, plain finish: ASTM A563 grade A 100 ksi, grade C 144 ksi, grade DH 175 ksi; ASTM A194 2HM and 7M 150 ksi, 2H and 7 175 ksi, stainless 8 and 8M 80 ksi Proof stress of heavy hex nuts, plain finish, ksi 0 50 100 150 200 A563 A A563 A: 100 ksi (689 MPa) 100 ksi A563 C A563 C: 144 ksi (993 MPa) 144 ksi A563 DH A563 DH: 175 ksi (1207 MPa) 175 ksi A194 2HM / 7M A194 2HM / 7M: 150 ksi (1034 MPa) 150 ksi A194 2H / 7 A194 2H / 7: 175 ksi (1207 MPa) 175 ksi A194 8 / 8M A194 8 / 8M: 80 ksi (552 MPa) 80 ksi Galvanized (overtapped) A563 nuts: A 75 ksi, DH 150 ksi. A194 2H may replace A563 DH. EXOTIC ALLOY
2H and DH are the strongest common grades. Stainless 8 and 8M nuts carry less than half their proof stress.

ASTM A194 (pressure and high-temperature bolting)

GradeMaterialProof stress
heavy hex, ksi		Hardness
HB
2HMedium carbon steel, quenched & tempered175248–327 to 1-1/2 in; 212–327 above
2HMAs 2H, hardness limited (sour service)150159–235
7Cr-Mo alloy steel (AISI 4140 type), Q&T175248–327
7MAs 7, hardness limited150159–235
8Stainless 30480126–300
8MStainless 31680126–300

Grade 4 was removed from ASTM A194 in 2017; grade 7 replaces it.

ASTM A563 (structural and general bolting)

GradeMaterialProof stress
plain, ksi		Proof stress
galvanized, ksi		Hardness
Rockwell
ACarbon steel10075B68–C32
CCarbon steel, may be Q&T144–B78–C38
DHCarbon steel, quenched & tempered175150C24–C38
DH3Weathering steel, quenched & tempered175–C24–C38

Heavy hex nuts, 1/4 to 4 in. Galvanized values apply to nuts tapped oversize for hot-dip galvanized bolts.

A194 heavy hex nut proof loads

SizeStress area
in²		2H, 7
lbf		2HM, 7M
lbf		8, 8M
lbf
1/40.03185,5704,7702,540
5/160.05249,1707,8604,190
3/80.077513,56011,6206,200
7/160.106318,60015,9408,500
1/20.141924,83021,28011,350
9/160.181931,85027,30014,560
5/80.226039,55033,90018,080
3/40.334558,45050,10026,720
7/80.461780,85069,30036,960
10.6057106,00090,90048,480
1-1/8 (8UN)0.7905138,200118,50063,200
1-1/4 (8UN)0.9997175,000150,00080,000
1-3/8 (8UN)1.2335215,800185,00098,640
1-1/2 (8UN)1.4918261,100223,800119,360

ASTM A194 proof loads, heavy hex, 1/4 to 1-1/2 in: UNC to 1 in, 8UN above. Each equals the proof stress (175, 150 or 80 ksi) times the stress area.

Finder

Heavy Hex Nut Finder: Wrench, Thickness & Proof Load

Pick the size, grade and finish; get the dimensions, the load and the order line.

Nut & order

Dimensions from the tables on this page. Proof load = proof stress of the grade × stress area of the thread (inch); “Standard” thread is UNC to 1 in and 8UN above, as for flange studs. A194 proof loads are tabulated to 1-1/2 in; metric proof loads are not shown. Mass: our calculation for steel (hexagon minus the thread hole).

Result
1-5/8
in wrench (F max 1.625)
63/64
in thick (0.956 to 1.012)
Thread:1-8 UNC-2B
Across corners:1.796 to 1.876 in
Proof load:106,000 lbf (472 kN)
Goes with:A193 B7 studs
Mass (approx.):209 g each, 209 kg
Designation:1000 pcs heavy hex nut 1-8 UNC-2B, ASME B18.2.2, ASTM A194 2H

Bolt pairing

Which Heavy Hex Nut for Which Bolt

Bolt or studHeavy hex nutTypical use
ASTM A193 B7A194 2HFlange bolting, pressure piping
ASTM A193 B7MA194 2HMSour service (hardness limited)
ASTM A193 B16A194 7Higher-temperature joints
ASTM A320 L7A194 7Low-temperature service
ASTM A193 B8 / B8MA194 8 / 8MStainless joints
ASTM A307 Grade BA563 AGeneral and flanged joints
ASTM A325 / F3125 Gr. A325, plainA563 C (or DH)Structural steel
ASTM A325 / F3125 Gr. A325, galvanizedA563 DHStructural, hot-dip galvanized
ASTM A490 / F3125 Gr. A490A563 DHHigh-strength structural
ASTM A354 BDA563 DHHigh-strength studs and bolts

A194 pairings as used for flange bolting; A563 pairings from the A563 bolt and nut compatibility table. An A194 2H nut may replace an A563 DH nut; DH nuts from 3/4 in up are often made only to large orders. ASTM F3125 now covers A325 and A490 bolts.

Carbon & alloy steel
2H · 2HM · 7 · DH

Pressure and structural bolting.

10454140
Stainless
8 · 8M

As in the photo.

304316
Special alloys
Duplex · Monel · Inconel

Offshore and sour lines.

2205Monel 400625
Manufacturing

How Our Heavy Hex Nuts Are Made

1

Bar

Steel to the A194 or A563 chemistry, by heat.

2

Forge

Hot or cold forged, or machined from hex bar.

3

Tap

UNC, UNF or 8UN class 2B; oversize for galvanizing.

4

Heat treat

Quenched and tempered for 2H, 2HM, 7, DH.

5

Mark

Grade symbol and maker's mark.

6

Test

Proof load and hardness per lot.

Applications

Where Our Heavy Hex Nuts Are Used

Refineries

2H and 2HM nuts on flange and exchanger studs.

Steel structures

A563 DH nuts on structural bolts.

Power plants

Grade 7 nuts on high-temperature studs.

Oil & gas

Wellheads, manifolds and sour service (2HM).

Anchor rods

Galvanized heavy hex nuts on foundation bolts.

Offshore

PTFE-coated and duplex nuts.

Quality & testing

Heavy Hex Nut Inspection & Certification

CheckMethodApplied to
ThreadGO / NOT GO plug gauges, 2B or 6HEvery lot
F, G, HCalipers, height gaugeEvery lot
Proof loadHardened mandrel, A194 / A563Every lot
HardnessBrinell or RockwellEvery lot; every nut for 2HM
ChemistryHeat certificate, PMI on requestEvery heat
CoatingThickness gaugeCoated lots

Every shipment includes

  • EN 10204 3.1 certificate
  • Grade and maker's mark on every nut
  • Lot number on every box

On request

  • EN 10204 3.2 with third-party inspection
  • NACE MR0175 / ISO 15156 compliance
  • Impact tests for low-temperature nuts
FAQ

Heavy Hex Nut Questions, Answered

A hex nut that is wider across flats and thicker than a regular hex nut for the same thread. A 1 in heavy hex nut is 1-5/8 in across flats and 63/64 in thick; a regular 1 in hex nut is 1-1/2 in across flats and 55/64 in thick. Heavy hex nuts go on structural bolts and on the studs of pressure flanges.

To ASME B18.2.2 it is 1/8 in wider across flats at 3/8 and 1/2 in and from 5/8 in upward, and 1/16 in wider at 1/4, 5/16, 7/16 and 9/16 in. It is always thicker, by 0.024 in at 1/4 in up to 0.469 in at 4 in.

1-5/8 in. A 1/2 in heavy hex nut takes 7/8 in, a 3/4 in nut 1-1/4 in and a 2 in nut 3-1/8 in.

Both are quenched and tempered medium carbon steel heavy hex nuts. 2H has a proof stress of 175 ksi and a hardness of 248 to 327 HB up to 1-1/2 in; 2HM is limited to 159 to 235 HB for sour service and has a proof stress of 150 ksi.

ASTM A563 recommends a grade C heavy hex nut for plain A325 bolts and grade DH for galvanized A325 and for A490 bolts. An A194 2H heavy hex nut may be used in place of an A563 DH nut.

A194 2H heavy hex nuts. B7M studs take 2HM nuts, B16 studs grade 7 nuts and stainless B8 or B8M studs grade 8 or 8M nuts. Grade 4 was removed from ASTM A194 in 2017; grade 7 is used instead.

106,000 lbf for a 1-8 UNC nut, which is 175 ksi on the 0.606 square inch stress area. A 2HM nut of the same size is proof tested at 90,900 lbf.

Hot-dip galvanized nuts are tapped oversize so they run onto the coated bolt, and their proof stress is lower: 150 ksi instead of 175 ksi for A563 DH and 75 ksi instead of 100 ksi for A563 A.

Yes, ASME B18.2.4.6M covers metric heavy hex nuts from M12 to M100 for ASTM A194M and A563M. An M20 heavy hex nut is 34 mm across flats and 20.7 mm high, against 30 mm and 18 mm for an ISO 4032 nut.
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