Hex nuts
Hex-nut forms, thread identity, dimensions, material and mechanical designations, with source-specific limits.
Tags: components, fasteners, threads
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Accu's HFN-M8-V1-A2 thin nut lists M8 × 1.25, 13 mm wrench size and 4 mm thickness. Its unilateral tolerances give 12.73–13.00 mm across flats and 3.70–4.00 mm thickness. The listing identifies A2 material and natural finish. It leaves thread tolerance class, bearing-face dimensions and mechanical property class unspecified. Accu technical specification.
Identity and dimensional vocabulary
A hex nut’s internal thread mates with the screw. Across-flats size determines wrench fit. Accu HFN-M8-V1-A2, ASME B18.2.2-2022 overview.
Specify each interface separately.
| Attribute | What it describes | What it does not establish |
|---|---|---|
| Nominal thread diameter and pitch | The thread's nominal size and axial spacing | Wrench size, nut height or mechanical capacity |
| Thread tolerance class | Permissible variation within the specified thread system | Body tolerances or material strength |
| Width across flats | Distance between opposite parallel wrenching flats | Thread diameter or clearance around a socket's outside |
| Height or thickness | Axial body dimension | An independently verified length of fully formed thread engagement |
| Bearing-face geometry | The surface contacting the assembly | A bearing area derived solely from the hexagon's outside dimensions |
ISO treats metric thread tolerances in ISO 965-1, product tolerances in ISO 4759-1 and nut mechanical properties in ISO 898-2 or ISO 3506-2. ASME's inch-nut overview separately identifies wrench openings and bearing-surface runout. Those distinct scopes support keeping fit, body geometry and mechanical performance separate. ISO 965-1:2026, ISO 4759-1:2000, ISO 898-2:2022, ISO 3506-2:2020, ASME overview.
Metric forms and inch nomenclature
ISO's public abstracts distinguish the following steel and stainless-steel forms. The ranges below are the stated abstract scopes, not reproduced dimensional tables or evidence that every size is stocked.
| Standard | Form and thread | Stated size scope | Product grades |
|---|---|---|---|
| ISO 4032:2023 | Regular, style 1; metric coarse pitch | M5–M39; abstract points outside sizes to Annex A | A and B |
| ISO 4033:2023 | High, style 2; metric coarse pitch | M5–M39 | A and B |
| ISO 4035:2023 | Thin, style 0; metric coarse pitch | M1.6–M64 | A and B |
| ISO 8673:2023 | Regular, style 1; metric fine pitch | Nominal diameter 8–39 mm; abstract points larger sizes to Annex A | A and B |
A thin nut is not simply a regular nut occupying less space with the same performance. ISO 4035's abstract explicitly describes reduced loadability and lack of design resistance to thread stripping; it describes jam-nut use together with a regular or high nut. This statement supplies no tightening sequence or assembly setting. ISO 4035:2023 abstract.
Metric pitch is axial thread spacing in millimetres; US thread count is expressed in threads per inch (TPI). A smaller pitch means closer spacing, whereas a larger TPI means closer spacing. These terminology statements are supported by Bolt Depot's indexed explanatory page; direct page retrieval was blocked during review. Bolt Depot, thread pitch and TPI.
Accu's catalog distinguishes UNC and UNF inch thin-nut offerings from its metric range. ASME B18.2.2-2022 covers inch-series nut body dimensions. Metric coarse/fine and inch UNC/UNF labels therefore identify different catalog/thread families; a similar wrench size does not establish a mating thread. No inch dimensional or thread-fit table was inspected for this article. Accu range description, ASME B18.2.2 overview.
Material, property class, product grade and finish
Material designation identifies the material category or grade. Property class addresses specified mechanical properties. ISO 3506-2 covers stainless-steel grades and property classes as distinct designations, including proof load; its abstract spans austenitic, martensitic, ferritic and duplex steels. An A2 material label alone does not supply a particular property class or proof-load value. ISO 3506-2:2020 abstract.
For non-alloy and alloy steel nuts, ISO 898-2:2022 lists classes 04, 05, 5, 6, 8, 10 and 12, including proof load. Its mechanical tests are scoped to 10–35 °C, and its abstract warns that properties may not be retained at other temperatures. The presence of a class number is not a torque specification: the abstract excludes torque/clamp-force, prevailing-torque and corrosion-resistance requirements. No numerical proof loads or universal nut/bolt class pairing are established here. ISO 898-2:2022 abstract.
Product grades A and B concern the product-tolerance framework, rather than chemical composition or a mechanical class. ISO 4759-1's title explicitly concerns fastener tolerances and product grades A, B and C. Exact tolerance limits and size-dependent grade assignments require the applicable product specification; the public metadata alone supplies neither. ISO 4759-1:2000.
Finish or coating is another specification layer. ISO 4042's public abstract distinguishes electroplated coating systems with optional conversion coating, sealant, top coat and lubricant, and includes dimensional requirements. Consequently, “zinc” alone is incomplete identification of a coating system. ISO lists ISO 4042:2022, fourth edition, published June 2022, with Amendment 1 published April 2026. Only the public scope and amendment metadata were reviewed; no coating thickness, corrosion lifetime, hydrogen-embrittlement treatment or amended technical requirement is prescribed here. ISO 4042:2022 abstract, Amendment 1 metadata.
A supplier-specific dimensional example
Accu's HTML listing for HFN-M8-V1-A2, described as an ISO 4035 thin nut, lists the following values. Its standard reference is undated, so these are supplier-listed product values, not verified ISO 4035:2023 table entries. Accu technical specification.
| Supplier field | Listed value |
|---|---|
| Thread size; pitch | M8 (8 mm); 1.25 mm |
| Socket size J | 13 mm, +0/−0.27 mm |
| Thickness T | 4 mm, +0/−0.3 mm |
| Material; finish | Stainless steel A2; natural |
Derived arithmetic from those stated unilateral tolerances gives 12.73–13.00 mm for J and 3.70–4.00 mm for T. The 8 mm nominal thread, 13 mm wrenching dimension and 4 mm thickness illustrate three different dimensions of one nut. The inspected HTML does not give a thread tolerance class, bearing-face dimensions or a mechanical property class. These remain unknown for this example; neither “A2” nor “ISO 4035” fills them in.
Source versions and coverage limits
Review and retrieval occurred 2026-10-30 PDT, in America/Los_Angeles. ISO publication dates are edition dates, not this review date: ISO 4032 and 4035 are fifth editions, and ISO 4033 and 8673 fourth editions, all dated August 2023. ISO 898-2 is fourth edition, September 2022; ISO 3506-2 is third edition, April 2020, with confirmation in 2025; ISO 4759-1 is second edition, November 2000, confirmed in 2022. ISO 965-1 is fifth edition, April 2026, replacing the withdrawn 2013 edition and its 2021 amendment. These facts come from the linked ISO catalog records above.
The sources are public HTML abstracts/catalog records and supplier HTML, accessed through web-tool representations; direct HTTP attempts to ISO and Accu returned 403. No PDF, full standard, dimensional drawing or proof-load table was relied upon. Bolt Depot terminology was available only as indexed text, with no publication/update date shown. Accu's indexed listing showed a specification update of October 19, 2026, while a later web-tool page extract showed October 31, 2026; no timezone or immutable revision was supplied. Those displayed source dates are retained as source provenance, not converted into the review date or treated as a validated product revision.
This generic reference does not establish DIN/ISO interchangeability, a qualified structural assembly, customer acceptance, installation torque, achieved preload, reuse suitability or corrosion life. Thread identity and dimensional evidence alone leave those application-specific conclusions unresolved. Related context: Hardware and component references.