WINTER 2021

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THE DISTRIBUTOR’S LINK
EUROLINK THINGS TO CONSIDER WHEN CONVERTING BETWEEN METRIC FASTENER STANDARDS from page 110
DIN 934 and ISO 4032 has equivalent dimensions
up to M4. For the majority of the nominal range of sizes
for both standards (at least up to M39), the height is
different, with the ISO hex nuts from M5 to M39 having a
height that ranges from 0.4 – 2.7 mm greater height than
their DIN 934 counterparts, depending on the nominal
diameter of the hex nut.
The WAF is the same for all of the sizes, with the
exception of the four sizes that were different for the hex
bolts: M10, M12, M14, and M22 with the WAF being
approx. 1 mm smaller for the M10, M12, and M14 ISO
4032 hex nuts, and 2mm larger for the M22 ISO 4032
hex nut (this is the exact same size differences in WAF
found in the DIN 933/931 to ISO 4017/4014 WAF
conversions).
As you can see, the dimensional difference is not that
vast. Based on dimensions alone, a purchasing agent
may be tempted to replace their M30 ISO 4032 hex nuts
with DIN 934, especially since the DIN 934 hex nuts are
available off the shelf stateside, whereas the ISO 4032s
might need to be imported, but this could be misguided.
Even though that height is slightly smaller, therefore it
might fit the application and the tool used for gripping
the nut may be able to account for the 1mm difference,
the key is that the proof loads for the ISO 4032 hex nut
are greater than the proof loads for the DIN 934 hex
nut, therefore an engineer would need to be consulted
to ensure that requirements for the application are being
met.
With the greater proof load of ISO 4032, the
dimensional differences and the DIN 934 standard being
formally withdrawn, the application may not be able to
use the DIN hex nut, therefore sourcing ISO 4032 is
essential.
Material Differences
As we saw with DIN 934 and ISO 4032, sometimes it
is not the dimensions alone that effects whether or not
two similar standards are considered interchangeable.
Sometimes it can be that the materials conforming to
a standard have been changed. This can be due to the
removal or addition of steel types, grades or classes.
This can also be due to new mechanical property
requirements of the fastener. A perfect example of this
is with DIN 125 flat washers versus the ISO 7089/7090
counterparts.
To clarify, DIN 125 has two types: A and B. DIN 125
A is without chamfer and correlates with ISO 7089,
whereas DIN 125 B has the chamfer and correlates
with ISO 7090. I refer to that as standards clarification,
and this splitting or combining of standards (though
usually splitting when going from DIN to ISO) is another
factor worth considering when making interchangeability
decisions, but it’s usually not a critical factor, it might
just make sourcing a bit easier though by means of using
correct nomenclature.
While many sourcing agents often consider DIN 125 to
be interchangeable with its ISO counterparts due to the
dimensional differences generally not being significant to
their applications, they may be mistaken, because there
is a material difference at play that very well may affect
sourcing decisions. DIN 125 washers have a hardness
class of 140 HV, whereas the ISO standard removed
the 140HV hardness class and replaced it with 200 HV
and 300 HV, therefore the lowest acceptable hardness
is 200HV, which is necessary for use with higher carbon
steels like class 8.8 steel, and a higher hardness class
is available at 300HV, which is typically recommended
for class 10.9 and 12.9 steels (absolutely necessary at
12.9). For sake of convenience and/or cost savings, or
possibly due to ignorance, these recommendations are
often ignored in practice.
Nominal Size Differences
Similar to standard clarification or splitting, differences
in nominal sizes are not normally an issue that affects
procurement, but it may be worth considering, especially
when making recommendations or designing products.
Nominal size differences can consist of excluding specific
sizes (usually second or third class diameters), adjusting
the nominal range, or changing the nomenclature of the
size identification.
CONTINUED ON PAGE 165