DIN 934 Hex Nut Selection Guide

Standard Overview

The DIN 934 standard was officially withdrawn in 1992, and its technical content has been superseded by ISO 4032 (coarse thread) and ISO 8673 (fine thread). In actual purchasing, DIN 934 is still widely used as a product name, but the latest design documents should preferentially reference ISO 4032/8673.

Critical compatibility warning: DIN 934 and ISO 4032 are not interchangeable. Würth product documentation explicitly states that ISO 4032 replacing DIN 934 has "no similarity," with main differences including: nominal diameters have changed, nut heights for some sizes have changed, and widths across flats for M10, M12, M14, and M22 have changed.

DIN 934 specifies metric hex nuts, covering thread sizes from M1 to M64, designed for use with DIN 933 (fully threaded hex bolts) and DIN 931 (partially threaded hex bolts). Bossard and multiple fastener databases confirm DIN 934's equivalent standards include ISO 4032, UNI 5588, and ČSN 021401.

Key Technical Features

Mating Logic with DIN 933/931

DIN 934 hex nuts are the standard mating nuts for DIN 933 and DIN 931 bolts. The three form the foundational combination of the metric fastener system:

Strength grade matching principle: Per Reyher technical documentation, the nut grade must always be equal to or higher than the bolt grade. The grade correspondence is as follows:

Never use a lower-grade nut. ISO 898-2 notes that under load conditions exceeding yield or proof load, higher-grade nuts should be used instead of lower-grade nuts.

Property Grades and Materials

DIN 934 covers a complete material and grade system:

Grade marking convention: DIN 934 uses a vertical bar on both sides of the grade marking (e.g., |8|, |10|) to distinguish it from ISO 898-2 grade markings. Reyher technical documentation explains: (8 = 1/100 der Prüfspannung in N/mm² – 1 l = Markierung für DIN-Muttern), meaning the bar marking indicates the nut follows the DIN 267-4 system proof load.

DIN 267-4 vs. ISO 898-2 load difference: The |10| grade nut under the DIN 267-4 system has a lower load capacity than the ISO 898-2 grade 10 nut. Mechanical overload may cause the nut or bolt threads to strip first.

≤M5 special limitation: Bossard product documentation explicitly marks "8 (≤M5 grade 6)," meaning sizes M5 and below can only guarantee grade 6 proof load.

Marking requirements: Per Bossard technical documentation, DIN 934 hex nuts with nominal thread diameter d ≥ 5 mm must have the property grade marked on the bearing surface or side. For DIN 934 nuts made from free-cutting steel (grades up to 6), the marking must also include a groove on one chamfer.

Dimensional Parameters (Common Sizes)

Per German fastener catalogs and Hubauer technical data, DIN 934 dimensions are as follows (ISO 4032 width across flats in parentheses):

Bolded sizes are those where width across flats differs from ISO 4032. Bossard product pages confirm that M10, M12, M14, and M22 wrench sizes can be supplied to ISO standard on request.

Fine Thread Sizes

DIN 934 fine thread versions (corresponding to ISO 8673) are available in the following sizes:

Tightening Torque Reference

Per RUD technical manual maximum tightening torque data (friction coefficient μ = 0.14):

Stainless steel A2/A4 torque considerations: Reyher technical documentation notes that stainless steel fasteners have a significantly higher friction coefficient than quenched and tempered steel bolts, and the scatter range can exceed 100%. Special lubricants can reduce the friction coefficient, but the scatter range remains large. Testing under actual service conditions is recommended to determine the correct torque value.

Surface Finish Options

Zinc flake coating advantage: Bossard's DIN 934 products use ISO 10683 flZnnc zinc flake coating. The zinc-aluminum combination provides better corrosion protection than pure zinc coatings of the same thickness and carries no hydrogen embrittlement risk. Bossard also offers CresaCoat® C 307 Black special coating options.

Application Areas

General Industrial Assembly

DIN 934 nuts are among the most fundamental fasteners in industrial assembly. Paired with DIN 933 fully threaded bolts for general machinery connections, and with DIN 931 partially threaded bolts for structural connections requiring shear bearing. Product documentation shows wide use in equipment manufacturing, construction machinery, agricultural machinery, power transmission and distribution, construction, and marine industries.

Structural Engineering

The DIN 934 and DIN 931 partially threaded bolt combination provides a shank locating + nut fastening connection in steel structures. However, note that DIN 934 nuts are not suitable for preloaded or dynamically loaded critical structural applications; such cases should use ISO 4032 nuts and EN 15048 certified assemblies.

Automotive and Agricultural Machinery

Automotive and agricultural machinery extensively use DIN 934 nuts with DIN 933/931 bolts. Product documentation confirms suitability for agricultural machinery applications.

Stainless Steel Applications

A2/A4 stainless steel DIN 934 nuts are used in chemical, marine, and food processing equipment. PGB documentation notes that stainless steel nuts are coated with a special wax layer to reduce cold welding (galling) risk. Impact tools should be avoided during installation, and low-speed uniform tightening should be maintained.

Selection Guide

Summary

DIN 934 specifies metric hex nuts, covering M1 to M64 sizes, designed for use with DIN 933 (fully threaded) and DIN 931 (partially threaded) bolts. The standard was withdrawn in 1992 and superseded by ISO 4032/8673, with M10/M12/M14/M22 width across flats differing and not interchangeable. Property grades cover 4, 5, 6, 8, 10, and 12 plus stainless steel A2/A4-70. The DIN 267-4 system |10| grade carries a lower load than ISO 898-2 grade 10. Sizes ≤M5 guarantee only grade 6. Surface finishes from black oxide to zinc flake coating cover different corrosion protection needs, with zinc flake coating providing a hydrogen-embrittlement-free protection solution. Selection must follow the nut grade ≥ bolt grade principle, and stainless steel applications require galling prevention. DIN 934 is the most fundamental mating nut in the metric fastener system, widely used in industrial assembly, structural engineering, automotive, and agricultural machinery.