ISO 898-2 specifies mechanical and physical property requirements for steel nuts with ISO metric threads, organized by nut property class and nut style.
It is commonly used to verify that production nuts (and incoming fasteners) meet required proof load performance and hardness limits for reliable bolt/nut assemblies. If you need help matching nut class, style, and diameter range to your project requirements, you can talk with our team.
ISO 898-2:2022 — Fasteners — Mechanical properties of fasteners made of carbon steel and alloy steel — Part 2: Nuts with specified property classes
ISO 898-2 is an ISO fastener requirements document focused on nuts made of non-alloy steel or alloy steel, evaluated at standard ambient laboratory temperatures.
Rather than defining a single “tensile test for nuts,” it sets performance requirements (including proof load) tied to nut property class and nut style, so nuts can be selected and checked to match mating bolts, screws, and studs used in service.
Quick Definition
Document type: Mechanical/physical property requirements (fastener specification) for steel nuts with ISO metric threads.
Primary focus: Nut property classes (including proof load) and how requirements vary by nut style and size range.
Common use: Manufacturing QA, incoming inspection, and technical procurement verification for nuts used in bolted joints.
What This Standard Covers
ISO 898-2 defines mechanical and physical property requirements for nuts with ISO metric thread and specified diameter/pitch combinations. It applies to coarse pitch and fine pitch threads within defined metric size ranges.
The standard includes requirements organized by:
- Nut property class (including proof load requirements)
- Nut style (regular, high, and thin nut styles)
- Thread series (coarse pitch and fine pitch)
ISO 898-2 is intended for nuts designed to mate with bolts, screws, and studs having property classes defined in ISO 898-1.
Why This Standard Matters in Testing
Nut performance is often limited by thread stripping or permanent deformation under load. ISO 898-2 addresses this by defining proof-load-based requirements that support consistent load-carrying capability in bolted joints.
For labs and QA/QC teams, ISO 898-2 is frequently the basis for acceptance testing and documentation when:
- qualifying a supplier’s nuts to a declared property class,
- verifying lot-to-lot consistency, or
- supporting contractual purchasing specifications for critical bolted assemblies.
Common Materials, Product Types, or Applications Covered
ISO 898-2 applies to nuts made of non-alloy steel or alloy steel with ISO metric threads in the covered size ranges.
Common product types: Hex nuts and similar nut forms produced to standardized widths across flats and heights associated with the nut styles addressed by the standard.
Common application areas: General industrial bolting, equipment assembly, structural and machinery joints, and other bolted connections where nut property class alignment with the mating bolt property class is part of the design and purchasing workflow.
Common Test or Verification Workflow
ISO 898-2 is typically used as a requirements reference inside a broader fastener control plan.
Common workflows:
- Define the requirement: Identify the nut property class, nut style, thread series, and size range specified on drawings, purchase orders, or quality plans.
- Sampling and inspection: Select samples from production lots or incoming shipments per internal quality procedures.
- Mechanical verification: Perform a proof load verification approach appropriate to the nut style/class and confirm acceptance criteria.
- Hardness/physical checks: Verify hardness or related physical property requirements as required for the nut class/style.
- Marking and documentation: Confirm required markings and record results for traceability and release.
If you are building a fastener verification plan and need help aligning your acceptance testing to the exact nut style and property class being purchased, you can contact our team to discuss the most practical lab workflow.
Equipment Commonly Used for This Standard
Because ISO 898-2 is requirements-driven, equipment selection is usually based on the proof load levels and the specific nut size/style being confirmed.
Common equipment families:
- Universal testing machines (UTMs) or calibrated force frames capable of applying and holding the required proof load with suitable resolution and control.
- Nut proof load tooling (fixtures, adapters, and hardened mandrels as applicable) sized for the nut’s thread and geometry.
- Hardness testing equipment suitable for the hardness method and ranges required for the nut property class.
- Gauging and inspection tools commonly used for fastener verification (e.g., dimensional checks and thread gauging as required by your quality plan).
When quoting a system, the most important practical inputs are nut size range, expected maximum proof loads, preferred fixturing approach, and whether hardness verification will be done in-house. If you are selecting a load frame and fixtures for ISO 898-2 nut verification, you can request a detailed quote based on your nut sizes and target proof load range.
How to Read This Designation or Revision
ISO 898-2 identifies Part 2 within the ISO 898 series covering mechanical properties of fasteners made of carbon steel and alloy steel.
ISO 898-2:2022 indicates the 2022 edition of the document. In procurement, QA plans, and test reports, the edition matters because property class tables, proof load values, test conditions, and acceptance rules can change between editions.
Practical tip: If a customer drawing or purchase order cites only “ISO 898-2” without a year, it is good practice to agree on the edition to be applied before testing and reporting.
Related Standards, Methods, or Frameworks
ISO 898-2 is often used alongside related fastener property standards in the same family.
- ISO 898-1: Mechanical and physical properties for bolts, screws, and studs with specified property classes.
- ISO 898-3: Mechanical and physical properties for flat washers with specified property classes, used in combination with bolts/screws/studs and nuts.
Where bolted-joint performance is sensitive to component matching, it is common to treat these documents as a coordinated set so nuts, bolts, and washers are specified and checked consistently.
Get help selecting equipment for ISO 898-2 nut verification
If you are setting up or upgrading proof load and hardness verification for ISO 898-2 nut property classes, we can help you size a testing system, choose fixtures, and define a practical lab workflow. Share your nut size range and target property classes and speak with our team.