ISO 3506-2 specifies mechanical and physical property requirements for corrosion-resistant stainless steel nuts (coarse and fine pitch), including defined grades and property classes used to match nuts with compatible stainless steel bolts, screws, and studs.
If you need help aligning an internal specification, drawing callout, or inspection plan to the correct ISO 3506-2 edition and nut property class, you can talk with our team about your application.
ISO 3506-2:2020 — Fasteners — Mechanical properties of corrosion-resistant stainless steel fasteners — Part 2: Nuts with specified grades and property classes
ISO 3506-2 is an International Standard focused on nuts manufactured from corrosion-resistant stainless steels. It is commonly used to define what “property class” markings and performance level a stainless steel nut must meet for a bolted joint, along with the related acceptance checks used by manufacturers, buyers, and QA/QC teams.
The requirements in ISO 3506-2 are evaluated at ambient temperature test conditions, and the standard notes that properties can differ outside typical service temperature ranges. For elevated- or low-temperature service, selection and verification should be handled carefully based on the exact joint conditions and the stainless steel grade/property class pairing.
Quick Definition
Document type: Product specification (mechanical/physical property requirements and property-class system for stainless steel nuts).
What it covers: Nuts with ISO metric threads (coarse and fine pitch) made from austenitic, ferritic, martensitic, and duplex stainless steel grades, with specified property classes (including proof load).
What it is not: It does not set functional performance requirements such as torque/clamp-force behavior, prevailing torque performance, or weldability.
What This Standard Covers
ISO 3506-2 defines property classes for stainless steel nuts and the associated requirements used to demonstrate conformity. It also ties applicability to common ISO metric thread systems and tolerance frameworks, and it is written to support nut/bolt compatibility within the ISO 3506 fastener property system.
The scope includes nuts intended to mate with bolts, screws, and studs that use property classes in accordance with ISO 3506-1, and it includes different nut styles (such as thin, regular, and high nuts) within the standard’s dimensional applicability limits.
Why This Standard Matters in Testing
When a purchase specification, drawing, or customer requirement calls out ISO 3506-2, it is usually establishing a minimum mechanical performance level for nuts used in corrosion-resistant bolted joints. In practice, this drives how incoming lots are accepted, how supplier certificates are reviewed, and what verification tests are selected when additional assurance is required.
Because this is a property-class standard (not a single bench test method), the most important practical step is ensuring the inspection plan matches the exact nut type, size range, and property class cited, and that the selected verification approach addresses the required mechanical/physical properties for that designation.
Common Materials, Product Types, or Applications Covered
Common product types: Stainless steel nuts with ISO metric coarse or fine pitch threads used in general industrial bolted joints.
Common stainless steel families referenced by the property-class system: Austenitic, ferritic, martensitic, and duplex (austenitic-ferritic) stainless steels.
Typical industries and use cases: Equipment builds and installations where corrosion resistance is important (industrial processing, marine/coastal exposure, infrastructure, OEM assemblies, maintenance/repair), and where the nut property class is specified to control joint integrity.
Common Test or Verification Workflow
ISO 3506-2 is most often used as the acceptance basis for a nut lot rather than as a standalone “run this test” document. A practical verification workflow typically includes selecting the correct nut designation and property class, confirming dimensional/thread system compatibility, and applying mechanical/physical verification appropriate to the callout.
Common verification elements: Review of supplier documentation for the stated grade/property class, dimensional/thread inspection aligned to the specified ISO metric thread framework, and mechanical checks that support the required property class (including proof load requirements where applicable).
Temperature note: Testing is evaluated at ambient temperature conditions, and additional engineering review is commonly needed when the bolted joint is intended for service outside typical temperature ranges.
Equipment Commonly Used for This Standard
Because ISO 3506-2 is a specification for nut performance classes, equipment selection usually follows the specific verification activities a buyer chooses (or a customer requires) for conformity assessment.
Common equipment families: Universal testing machines configured for fastener proof-load style checks (with appropriate fixtures), hardness testers for stainless steels (method and scale depending on the requirement), dimensional/thread inspection tools (thread gauges and metrology), and material identification tools when positive material identification is part of the receiving workflow.
If you are equipping a lab for stainless fastener acceptance testing (or upgrading fixturing for nut proof-load style checks), you can request a detailed quote for a configuration matched to your nut sizes, target loads, and reporting needs.
How to Read This Designation or Revision
ISO 3506-2 indicates the “Part 2” document within the ISO 3506 series and is specifically focused on nuts.
ISO 3506-2:2020 indicates the 2020 edition of the standard. For procurement and test planning, the cited year matters because requirements, tables, and the property-class framework can change between editions.
Related Standards, Methods, or Frameworks
ISO 3506-2 is commonly used alongside related ISO fastener and thread system references because nut acceptance depends on both the property class system and the thread/dimensional framework.
Commonly paired references within the ISO 3506-2 scope and notes: ISO 3506-1 (property classes for bolts/screws/studs to be mated with nuts), ISO 3506-6 (general rules and additional technical information), ISO 68-1 (ISO metric screw threads), ISO 261 and ISO 262 (metric thread diameter/pitch combinations), and ISO 965-1 and ISO 965-2 (thread tolerances).
Get help quoting equipment for ISO 3506-2 verification
If you share the nut sizes, target property class, and whether your plan includes proof-load verification, hardness checks, and/or dimensional inspection, we can help you scope an equipment package and lab workflow that fits the way ISO 3506-2 is typically applied. To discuss pricing and configurations, ask for a quote.