Hex nuts · Standard and style (DIN 934, ISO 4032, ASME B18.2.2 heavy hex), thread, property class or grade matched to the bolt, coating and overtapping, and nut grades for structural bolting
A hex nut is a six-sided internally threaded fastener that mates with a bolt, screw or threaded rod; standard hex nuts suit general assembly, while heavy hex nuts, larger and thicker, are used with structural and high-strength bolts. Ask three things first: which standard, style and thread the bolt needs, which nut grade or property class matches the bolt's strength and coating, and which finish suits the environment.
Standard and heavy hex nuts in carbon, alloy and stainless steel to metric and inch standards, plain or coated. Flange, lock, cap, coupling and wing nuts, and nuts sold only as part of bolting assemblies, are outside this page except where compared.
CNFX editorial research · Sources checked October 11, 2026 · 4 sources
Haiyan lists heavy hex nuts to ASTM A194 2H/DH and ANSI B18.2.2 with UNC or UNF threads, in medium-carbon, alloy or stainless steel (SS201, SS304, SS316), metric property classes 8 to 10, metric sizes M10–M33 and inch sizes 3/8 in to 2-1/4 in, with plain, black, black oxide, black zinc, hot-dip galvanised, zinc, yellow zinc, nickel and other finishes; it describes heavy hex nuts as larger and thicker than standard hex nuts for greater strength. [2]
Fastenwell lists DIN 934 metric hexagon nuts alongside hex bolts, structural bolts and nuts, and ASTM F436 hardened washers. [3]
Editorial note: name the standard (for example DIN 934, ISO 4032, ASME B18.2.2, ASTM A563 or A194), the thread and the grade on the order; specify the bolt grade too, so the supplier can match the nut grade to it under the governing standard.
Give the supplier the standard and style (regular or heavy hex), thread (metric coarse/fine, UNC/UNF) and size, property class or grade, material, finish and any overtapping, the bolt grade and coating it mates with, quantity and packaging, and test certificates (proof load, hardness, coating thickness).
02
Match nut grade and coating in structural bolting
The RCSC 2020 Specification for Structural Joints Using High-Strength Bolts requires heavy hex nuts to ASTM A563, with grades from its Table 2.2: for Group 120 bolts, plain C, C3, D, DH or DH3 nuts with plain bolts and DH nuts with coated bolts; for Group 144 and 150 bolts, DH or DH3 nuts with plain bolts and DH with coated bolts; Type 3 (weathering) bolts take C3 or DH3 (Group 120) or DH3 (Groups 144 and 150). ASTM A194 Grade 2H nuts may substitute for A563 Grade DH. Nuts coated to the specification's coating section must be overtapped in accordance with ASTM F3125 Table A1.2. [1]
Its commentary explains that galvanised bolts and nuts must be treated as a matched assembly because galvanising affects the mechanical properties, overtapping affects the nut's stripping strength, and coating and lubrication change the torque needed for pretensioning. [1]
Editorial note: buy galvanised nuts and bolts as a matched, lubricated set from one supplier or with a documented matching test, rather than combining coated nuts and bolts from different sources. [1]
03
Compare what suppliers offer
Suppliers linked to this page list hex nuts; each card links to the page reviewed.
The suppliers reviewed list hex and heavy hex nuts with bolts, washers and other fasteners; ask each for the standards and grades they make, proof-load and hardness test results, coating and overtapping data, and packaging.
04
Check proof-load stress and hardness against the nut grade
Fastenal's engineering table of internally threaded fasteners (revision dated 25 August 2009) gives proof-load stress and Rockwell hardness by nut grade. For ASTM A563 Grade DH heavy hex nuts in quenched and tempered carbon steel, sizes 1/4 to 4 in, it lists 175,000 psi proof-load stress when plain and 150,000 psi when galvanised, with hardness C24 to C38; A563 Grade C heavy hex nuts, 1/4 to 4 in, are listed at 144,000 psi and B78 to C38. [4]
The same table lists ASTM A194 Grade 2H heavy hex nuts at 175,000 psi, and A194 Grade 8 (AISI 304) and Grade 8M (AISI 316) heavy hex nuts, 1/4 to 1-1/2 in, at 80,000 psi with hardness B60 to C32. Its footnote defines galvanised nuts as nuts coated thickly enough to require overtapping, for example by hot-dip or mechanical galvanizing, and says a zinc-coated A194 2H nut takes the coating, overtapping, lubrication and rotational-capacity testing of ASTM A563, with its proof stress reduced accordingly. [4]
Editorial note: the table predates the current editions of A563 and A194; ask for proof-load and hardness results on the certificate, measured against the edition named in your order.
Fill the specification fields with values for your joint
A hex nut quotation needs values for your joint. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.
Field
What it means and published values
Ask the supplier for
Applicable Standard
E.g. DIN 934; ASME B18.2.2; ASTM A563, A194. [3][2][1]
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Published product pages show what a company offers, not tested performance. Confirm the legal seller, factory and scope for your order. How we source and review
· Page last updated 13 October 2026
Buyer questions
Which nut grade goes with A325 structural bolts?
Under RCSC 2020, Group 120 (A325) bolts take A563 C, C3, D, DH or DH3 nuts when plain and DH nuts when coated; A194 2H may replace DH. [1]
Why are galvanised nuts overtapped?
To fit the coated bolt thread; RCSC requires coated nuts to be overtapped per ASTM F3125 and treats galvanised bolts and nuts as matched assemblies. [1]
What is a heavy hex nut?
A larger, thicker hex nut, such as Haiyan's A194 2H/DH nuts to ANSI B18.2.2, used with structural and high-strength bolts. [2]
What proof-load stress does an A563 Grade DH heavy hex nut have?
Fastenal's engineering table lists 175,000 psi plain and 150,000 psi galvanised, with Rockwell hardness C24 to C38, for sizes 1/4 to 4 in. [4]
Sources and what still needs a direct check
Sources checked 2026-10-11. The RCSC specification is the consensus standard for US structural bolting; Haiyan and Fastenwell describe their own products.
