Fastener specifications often include markings DIN 933 and ISO 4017. Both standards describe hexagon head screws with full thread, therefore in practice they are very often used interchangeably.
The differences between these standards are minor, but there are dimensional changes in some diameters. The most important of these is screw head size, i.e. wrench size.
DIN 933 vs. ISO 4017
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Both standards describe fully threaded hexagonal screws.
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DIN 933 this is the German standard.
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ISO 4017 is its international equivalent.
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In most applications, the screws are interchangeable.
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In selected diameters it differs screw head wrench size.
The most important difference: screw head size (wrench size)
The most important difference between the standards concerns screw head dimensions – i.e. wrench width (s).
For several diameters the values may differ by approximately 1 mm.
Examples of differences
Diameter DIN 933 ISO 4017 M10 17 mm 16 mm M12 19 mm 18 mm M14 22 mm 21 mm M22 34 mm 32 mm In practice this means that an ISO standard screw may require a smaller key than the DIN screw.
Why is this difference important?
In most standard connections it does not matter much.
However, it may affect assembly in situations such as:
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serial assembly
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limited installation space
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use of specific sockets or wrenches
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structures designed very precisely.
Therefore, it is always worth mentioning a specific standard in technical documentation.
Where are DIN 933 / ISO 4017 screws used?
Fully threaded screws are very versatile and are used in many industries.
Most common uses:
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steel structures
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industrial machines
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technological installations
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mechanical devices
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supporting structures.
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FAQ – Frequently Asked Questions
Are DIN 933 and ISO 4017 the same screws?
The standards describe very similar fully threaded screws. In most applications, they are interchangeable.
Has DIN 933 been withdrawn?
Not entirely, but in new technical projects the ISO 4017 standard is more often used.
Does the difference in key size matter?
Most often, it does not affect the strength of the connection, but may be important when installing in tight spaces.
Why does ISO have a smaller head size?
The change results from the harmonization of standards and the optimization of the design of fasteners.
Check out Eurobolt's offer
Are you looking for screws that meet standards? DIN 933 or ISO 4017 for steel structures, machinery, or industrial installations? Eurobolt offers a wide selection of fasteners in various strength classes, materials, and anti-corrosion coatings.
Check out the available products in our offer or contact us if you need help choosing the right solution for your project.
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