ISO successors to withdrawn DIN standards

Drawings and orders often still state DIN 933, DIN 934 or DIN 125. In most cases, what applies today is an ISO standard with a different number and, in some places, with different dimensions as well. Four points matter here: width across flats, nut height, the designation of washers and the length of pins.

Why many DIN standards have an ISO successor

The standards for screws, nuts and washers were harmonised at European and international level. DIN standards used to be purely German regulations. Many ISO standards are modelled on them, and some standards only exist as ISO, for example ISO 7380.

In Germany, an adopted standard is published as DIN EN ISO with the ISO number, and the old DIN is withdrawn. DIN 933, for example, has been replaced, and today DIN EN ISO 4017, 2022-10 edition, applies.

In purchasing, the old number lives on. Anyone ordering DIN 933 almost always means a hexagon head screw threaded to the head and today receives one to ISO 4017. The Schrauben-Lexikon describes the changeover in the trade as gradual, with DIN and ISO items produced side by side.

The most important successor standards

The table maps the common old DIN numbers to the standard that applies today. The right-hand column shows what changes with the switch.

Sources: Schrauben-Lexikon, changeover from DIN to ISO; DIN Media; NORM+DREH standards directory. Accessed on 26 September 2026.

Width across flats comes up most often. It affects every hexagon screw and every hexagon nut in the list. For washers and pins the differences lie elsewhere, for DIN 1444 in the nominal lengths.

What changes when you switch

In most cases, DIN and ISO parts are interchangeable. The deviations are in a few places, but there they have consequences for assembly or design.

Width across flats for hexagon screws and nuts

For M10, M12, M14 and M22, the width across flats has changed, so you need different tools for assembly. Three sizes become one millimetre smaller, M22 becomes two millimetres larger.

Source: Würth, hexagon head screws to DIN 933/931 and ISO 4014/4017, accessed on 26 September 2026.

Nut height

Hexagon nuts to ISO 4032 have a different height from DIN 934 in sizes M5 to M39. If the nut sits in a recess or the length of thread engagement is tight, this should be part of the check.

Nominal size for washers

DIN 125 named washers after the hole diameter. ISO 7089 and 7090 name them after the thread diameter of the matching screw, so the washer for M10 is no longer named after its hole. The parts themselves are considered interchangeable. The same changeover applies to DIN 9021 and ISO 7093.

Length of pins

For parallel and taper pins, ISO measures the length including the ends, DIN without them. With the same designation, the pin to ISO can therefore turn out shorter.

Standards without a successor

Not every DIN has a successor. Among others, DIN 137 (spring washers, wave type), DIN 6798 (serrated lock washers) and DIN 2098 (cylindrical helical springs) have been withdrawn without replacement, as have the spring lock washers to DIN 127 and DIN 128.

For locking elements, there is a technical reason for this. Spring lock washers, spring washers and serrated lock washers are considered ineffective. If one of them is on your drawing, it is better not to look for a replacement but to reassess the joint. More on this in the article on screw locking.

Is a withdrawn DIN standard still available?

In some cases yes, but you should not rely on it. A withdrawn standard is no longer maintained, but remains listed at DIN Media with its replacement note. Parts to the old DIN are in some cases still offered by the trade, because DIN and ISO items are produced side by side. For new designs and new drawings, the valid successor standard is the safe choice.

How to find the successor

DIN Media provides the binding information. The standard's page states for every withdrawn standard which document replaced it. That gives you the new number, but not yet the differences.

These are shown in the DIN to ISO comparison tables published by manufacturers and distributors of fasteners. Check the deviations against your drawing and your assembly tools, that is width across flats, nut height, nominal size reference and length definition.

Take the material and property class from the old designation. The property classes are given in separate standards, for steel screws for example in DIN EN ISO 898-1, and belong in full in the new order designation.

How NORM+DREH handles this
In the NORM+DREH standards directory, every old DIN number shows what applies today: the successor standard with its edition, or the note that the standard was withdrawn without a successor. So you can continue to order DIN 933. Because both numbers are listed side by side, you do not have to look anything up beforehand. You can find the overview on the page Standard parts to DIN and ISO.

Frequently asked questions about DIN and ISO standards

What is the difference between DIN 933 and ISO 4017?

Both describe hexagon head screws threaded to the head, and ISO 4017 is the successor to the withdrawn DIN 933. The widths across flats differ for M10, M12, M14 and M22, otherwise the screws are considered interchangeable.

Which ISO standard replaces DIN 934?

DIN EN ISO 4032 for coarse thread, DIN EN ISO 8673 for fine thread. In addition to the widths across flats, the nut height changes for M5 to M39.

Is DIN 912 still valid?

No, DIN 912 has been replaced by DIN EN ISO 4762. The hexagon socket head cap screws are considered interchangeable, although fine thread is not standardised in ISO 4762.

Which ISO standard replaces DIN 125?

DIN EN ISO 7089 and DIN EN ISO 7090. There, the nominal size is based on the thread diameter of the screw, no longer on the hole diameter of the washer.