DIN 931 vs DIN 933 — Bolt Differences, Thread Length and Selection Guide

DIN 931 and DIN 933 at a glance

DIN 931 is commonly used in catalogues and purchasing systems for hexagon head bolts with a shank and a partial-thread configuration. DIN 933 is commonly used for hexagon head screws with thread to the head, often described as a full-thread configuration. These are useful market labels, not a substitute for the exact governing standard and revision.

The historical DIN 931 and DIN 933 records are withdrawn in the DIN Media catalogue. Current ISO references include ISO 4014:2022 for hexagon head bolts with a shank and ISO 4017:2022 for hexagon head screws with thread to the head. Do not silently rewrite an older drawing or customer part number: state the requested designation and ask whether a current ISO reference is accepted.

DIN 931 vs DIN 933: what changes in the purchase decision

The main practical difference is the available unthreaded shank and the length of thread. A partial-thread requirement may be selected when the drawing or joint design needs a defined shank and grip length. A full-thread requirement may be selected when thread engagement along the available length is important. The application engineer and governing drawing control the decision; a buyer should not choose one solely because it is more familiar or more readily listed in a catalogue.

Check the clamped thickness, required thread engagement, clearance, washer and nut arrangement, installation access and any joint-specific requirements. For structural, pressure, safety-critical or engineered assemblies, the product family name is not sufficient evidence of suitability.

ISO 4014 and ISO 4017 are related, not automatically interchangeable

ISO 4014:2022 and ISO 4017:2022 are separate ISO documents. ISO 4014 specifies hexagon head bolts with a shank; ISO 4017 specifies hexagon head screws with thread to the head. Both current ISO pages describe metric coarse-pitch fasteners from M1,6 through M64 and product grades A and B, but that does not make the two documents the same or make every DIN reference interchangeable.

Edition matters. ISO lists ISO 4014:2022 and ISO 4017:2022 as published standards and lists earlier editions as withdrawn. A customer drawing may intentionally retain an older designation, a national adoption or a project-specific requirement. Quote against the stated document first, and list any proposed alternative separately for approval.

How to read a common metric bolt specification

A notation such as M12 × 1.75 × 60 is a compact dimensional prompt: M12 indicates the nominal thread diameter, 1.75 indicates the pitch in millimetres, and 60 indicates the nominal bolt length. This example is for explaining how to read a request; it is not a HEXVARO stock or availability statement.

The request should also state whether the thread is full or partial, the thread tolerance or fit where relevant, the head and bearing requirements, and how length is measured under the governing document. If the buyer uses a part number, attach or reference the controlled drawing rather than relying on a catalogue photograph.

• Metric or inch thread system and nominal diameter.
• Pitch or thread series, tolerance and thread length where relevant.
• Nominal length and the standard's length-measurement convention.
• Full-thread or partial-thread requirement and required shank/grip length.
• Head style, washer/nut pairing and any clearance or installation limit.

Material and property class are separate decisions

DIN 931, DIN 933, ISO 4014 and ISO 4017 primarily identify geometry and product characteristics; they do not by themselves answer every mechanical or corrosion question for an order. State the material specification, property class or stainless grade separately. ISO's current 4014 and 4017 descriptions point buyers to ISO 898-1 or ISO 3506-1 when property classes or stainless grades are required.

For carbon-steel examples such as 8.8 or 10.9, confirm the applicable mechanical-property standard, heat-treatment or testing requirements and marking/documentation expectations. For stainless fasteners, state the stainless designation and any environmental or galvanic-compatibility concern. Do not infer a grade from the bolt colour, image or familiar catalogue name.

Common buyer questions

• Can DIN 931 be replaced by ISO 4014? Only after the governing document, edition, dimensions, material/grade and customer approval are checked.
• Can DIN 933 be replaced by ISO 4017? The terms describe related full-thread configurations, but the exact document and revision still need to be confirmed; do not claim automatic equivalence.
• Is a full-thread bolt always better? No. Thread configuration should follow the drawing, joint design, grip and engagement requirement.
• Does the standard define grade 8.8 or 10.9? Not by the product label alone. State the mechanical-property requirement separately.
• Can a product photo confirm DIN 931 or DIN 933? No. A photo cannot verify thread length, tolerances, material, grade, finish or documentation.

What to include in the RFQ

Send the designation exactly as it appears on the drawing or purchasing system, including the edition or revision when known. Then identify any acceptable current ISO reference as a question rather than an assumed substitution. HEXVARO can coordinate the inquiry with independent manufacturing partners in China, but the selected source, buyer engineering approval and written quotation control the final requirement.

• DIN 931/DIN 933 or ISO 4014/ISO 4017 reference, edition and revision.
• Diameter, pitch, length, full/partial thread and required shank or grip length.
• Material, property class or stainless grade, plus any required tests or records.
• Finish/coating, service environment, marking, packaging and traceability.
• Quantity per size, destination, timing assumptions and any drawing or inspection plan.