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DIN 934 hex nuts

DIN 934 hex nuts are metric fasteners with coarse thread designed according to the German standard DIN 934. They are commonly manufactured in steel with property classes 6, 8, 10 and 12, and can be supplied with zinc-plated, black, or stainless steel finish. This standard has been largely superseded by the international equivalents ISO 4032 (normal nut type 1) and ISO 8673 (high nut type 2), although it remains in common use in maintenance and legacy engineering applications.

Main Dimensions

Section titled “Main Dimensions”

The most relevant dimensions of a DIN 934 nut are the width across flats (s), which matches the wrench size, and the height (m). The following table lists the standard values for the most common sizes with coarse thread pitch.

Nominal Size Pitch s / Wrench Size Height m
M3 0,50 mm / 0.020 in 5,5 mm / 0.217 in 2,4 mm / 0.094 in
M4 0,70 mm / 0.028 in 7,0 mm / 0.276 in 3,2 mm / 0.126 in
M5 0,80 mm / 0.031 in 8,0 mm / 0.315 in 4,0 mm / 0.157 in
M6 1,00 mm / 0.039 in 10,0 mm / 0.394 in 5,0 mm / 0.197 in
M7 1,00 mm / 0.039 in 11,0 mm / 0.433 in 5,5 mm / 0.217 in
M8 1,25 mm / 0.049 in 13,0 mm / 0.512 in 6,5 mm / 0.256 in
M10 1,50 mm / 0.059 in 17,0 mm / 0.669 in 8,0 mm / 0.315 in
M12 1,75 mm / 0.069 in 19,0 mm / 0.748 in 10,0 mm / 0.394 in
M14 2,00 mm / 0.079 in 22,0 mm / 0.866 in 11,0 mm / 0.433 in
M16 2,00 mm / 0.079 in 24,0 mm / 0.945 in 13,0 mm / 0.512 in
M18 2,50 mm / 0.098 in 27,0 mm / 1.063 in 15,0 mm / 0.591 in
M20 2,50 mm / 0.098 in 30,0 mm / 1.181 in 16,0 mm / 0.630 in
M24 3,00 mm / 0.118 in 36,0 mm / 1.417 in 19,0 mm / 0.748 in
M27 3,00 mm / 0.118 in 41,0 mm / 1.614 in 22,0 mm / 0.866 in
M30 3,50 mm / 0.138 in 46,0 mm / 1.811 in 24,0 mm / 0.945 in
M33 3,50 mm / 0.138 in 50,0 mm / 1.969 in 26,0 mm / 1.024 in
M36 4,00 mm / 0.157 in 55,0 mm / 2.165 in 29,0 mm / 1.142 in

Allowable Loads and Property Classes

Section titled “Allowable Loads and Property Classes”

The load capacity of a DIN 934 nut is defined by the proof load, the value the nut must withstand without permanent deformation or thread failure. This load depends on the tensile area of the bolt and the property class of the nut. The common classes are 6, 8, 10 and 12, where the number indicates the nominal strength in MPa divided by 100 (e.g., class 8 equals 800 MPa).

Size Class 6 Class 8 Class 10 Class 12
M3 3,02 kN / 679 lbf 4,02 kN / 904 lbf 5,03 kN / 1131 lbf 6,04 kN / 1358 lbf
M4 5,27 kN / 1185 lbf 7,02 kN / 1578 lbf 8,78 kN / 1974 lbf 10,5 kN / 2361 lbf
M5 8,52 kN / 1915 lbf 11,4 kN / 2563 lbf 14,2 kN / 3192 lbf 17,0 kN / 3821 lbf
M6 12,1 kN / 2720 lbf 16,1 kN / 3620 lbf 20,1 kN / 4520 lbf 24,1 kN / 5420 lbf
M8 22,0 kN / 4946 lbf 29,3 kN / 6587 lbf 36,6 kN / 8228 lbf 43,9 kN / 9870 lbf
M10 34,8 kN / 7826 lbf 46,4 kN / 10431 lbf 58,0 kN / 13039 lbf 69,6 kN / 15647 lbf
M12 50,6 kN / 11381 lbf 67,4 kN / 15159 lbf 84,3 kN / 18955 lbf 101,2 kN / 22751 lbf
M14 69,0 kN / 15514 lbf 92,0 kN / 20684 lbf 115,0 kN / 25855 lbf 138,0 kN / 31025 lbf
M16 94,2 kN / 21180 lbf 126,0 kN / 28329 lbf 157,0 kN / 35301 lbf 188,4 kN / 42354 lbf
M20 147,0 kN / 33047 lbf 196,0 kN / 44062 lbf 245,0 kN / 55078 lbf 294,0 kN / 66093 lbf
M24 212,0 kN / 47661 lbf 282,0 kN / 63405 lbf 353,0 kN / 79356 lbf 424,0 kN / 95307 lbf
M30 337,0 kN / 75762 lbf 449,0 kN / 100931 lbf 561,0 kN / 126111 lbf 673,0 kN / 151291 lbf
M36 490,0 kN / 110152 lbf 654,0 kN / 146996 lbf 817,0 kN / 183657 lbf 980,0 kN / 220309 lbf
Section titled “Recommended Tightening Torques”

The torque values below apply to joints with steel bolts of grade 8.8, in dry condition (friction coefficient μ ≈ 0.125) and assume the nut works within its elastic limit. For other bolt grades or lubrication conditions, the torque must be adjusted; excessive lubrication can reduce the friction coefficient by half and cause dangerous overtightening.

Size Torque
M3 1,2 N·m / 0,9 ft·lb
M4 2,5 N·m / 1,8 ft·lb
M5 5,0 N·m / 3,7 ft·lb
M6 10 N·m / 7,4 ft·lb
M8 25 N·m / 18 ft·lb
M10 50 N·m / 37 ft·lb
M12 85 N·m / 63 ft·lb
M14 135 N·m / 100 ft·lb
M16 210 N·m / 155 ft·lb
M18 290 N·m / 214 ft·lb
M20 410 N·m / 302 ft·lb
M24 710 N·m / 524 ft·lb
M30 1420 N·m / 1047 ft·lb
M36 2470 N·m / 1822 ft·lb

Tightening Formula

Section titled “Tightening Formula”

The basic relationship between tightening torque, generated preload, and bolt diameter is expressed by the torque wrench formula. The nut factor (K) accounts for the influence of friction and thread geometry.

T = K · F · d

Variable Description Typical Units
T Tightening torque N·m / ft·lb
K Nut factor (combined friction coefficient) Dimensionless (~0.20 for normal dry nut)
F Preload in the bolt kN / lbf
d Nominal thread diameter mm / in
Section titled “Recommended Drill Sizes”

When machining a threaded joint, it is necessary to know the clearance hole diameter for the bolt (clearance drill) and the tap drill diameter if an internal thread that receives the nut is to be cut. The following dimensions correspond to ISO metric coarse thread, which is used on DIN 934 nuts.

Size Clearance Drill (Standard Hole) Tap Drill
M3 3,4 mm / 0.134 in 2,5 mm / 0.098 in
M4 4,5 mm / 0.177 in 3,3 mm / 0.130 in
M5 5,5 mm / 0.217 in 4,2 mm / 0.165 in
M6 6,6 mm / 0.260 in 5,0 mm / 0.197 in
M8 9,0 mm / 0.354 in 6,8 mm / 0.268 in
M10 11,0 mm / 0.433 in 8,5 mm / 0.335 in
M12 13,5 mm / 0.531 in 10,2 mm / 0.402 in
M14 15,5 mm / 0.610 in 12,0 mm / 0.472 in
M16 17,5 mm / 0.689 in 14,0 mm / 0.551 in
M18 20,0 mm / 0.787 in 15,5 mm / 0.610 in
M20 22,0 mm / 0.866 in 17,5 mm / 0.689 in
M24 26,0 mm / 1.024 in 21,0 mm / 0.827 in
M30 33,0 mm / 1.299 in 26,5 mm / 1.043 in
M36 39,0 mm / 1.535 in 32,0 mm / 1.260 in

Standard Equivalences

Section titled “Standard Equivalences”

Although DIN 934 has been withdrawn and replaced, its geometry practically coincides with the international standards indicated below. The American equivalence is based on the unified metric system, adopted by ASME.

Original Standard Equivalent Standard Description
DIN 934 (Hex nut, coarse thread) ISO 4032 (Hexagon normal nut, style 1) Direct dimensional equivalent for sizes M1.6 to M64.
ISO 8673 (Hexagon high nut, style 2) For applications requiring a greater gripping height.
ASME B18.2.4.1M (Hex nut, metric) American specification for equivalent metric nuts.

Frequently Asked Questions (FAQ)

Section titled “Frequently Asked Questions (FAQ)”

What does the property class mean on a DIN 934 nut?

Section titled “What does the property class mean on a DIN 934 nut?”

The property class indicates the proof stress that the nut material can withstand without failure. For example, class 8 equals 800 MPa, which translates into a specific proof load depending on the diameter. A higher class offers a greater safety margin, but the nut must be correctly matched to the bolt.

What is the difference between a DIN 934 nut and an ISO 4032 nut?

Section titled “What is the difference between a DIN 934 nut and an ISO 4032 nut?”

Practically none in dimensions. DIN 934 is the former German standard for hex nuts with coarse thread; ISO 4032 is its international successor. Both share the same width across flats and height for diameters up to M64, so they are considered interchangeable.

Can I reuse a DIN 934 nut after disassembly?

Section titled “Can I reuse a DIN 934 nut after disassembly?”

In non-critical joints, it can be reused if the thread shows no damage and the height has not been reduced by deformation. In structural applications or where preload is a controlled parameter, it is recommended to replace the nut each time, since reuse alters the friction factor and can cause inaccurate tightening.

What tightening torque should I use for a joint with a DIN 934 nut?

Section titled “What tightening torque should I use for a joint with a DIN 934 nut?”

The torque depends on the diameter, the bolt grade, and lubrication. As a reference for grade 8.8 bolts in dry condition: M8 ~ 25 N·m, M10 ~ 50 N·m, M12 ~ 85 N·m, M16 ~ 210 N·m, M20 ~ 410 N·m. Always consult the manufacturer’s specification and use a calibrated torque wrench.

How is the height of a hex nut measured?

Section titled “How is the height of a hex nut measured?”

The height (m) is the distance between the flat bearing faces and the nut crown, measured in the central area without counting the chamfers. It is verified with a digital caliper on the bearing face, checking that there is no wear on the edges.

Is the DIN 934 nut suitable for high-temperature applications?

Section titled “Is the DIN 934 nut suitable for high-temperature applications?”

Standard zinc-plated carbon steel nuts lose up to 30% of their proof load above 250 °C / 480 °F. For higher temperatures, materials such as heat-resistant stainless steel or special alloys are required, and the tightening torque in hot conditions must be re-evaluated.

Sources Consulted

Section titled “Sources Consulted”