WINTER 2021

110
THE DISTRIBUTOR’S LINK
EUROLINK THINGS TO CONSIDER WHEN CONVERTING BETWEEN METRIC FASTENER STANDARDS from page 28
If a fastener standard is not fully interchangeable,
then it can be mostly interchangeable if it can be used as
an alternate at most sizes and/or in most applications,
limited interchangeability if they can be used as an
alternate at some sizes and/or in some applications
and no interchangeability if it is not recommended to be
used as an alternative for whatever reason. Generally, no
interchangeability is either due to dimensional differences
so great that the fastener standard cannot be used as an
alternate in most applications, or because the dimensional
difference actually effects mechanical properties.
¤ Exact dimensional match (fully
interchangeable): In the case of socket head cap
screw DIN 912 and its counterpart ISO 4762, the
dimensions are exactly the same. The new standard
only changed the nominal size range covered in the
standard and added a fine thread pitch option (ISO
12474), whereas previously the sourcing agent would
have needed to specify if they want a fine thread DIN
912. There is no effect on any other variable, therefore
converting between these parts is of no concern.
¤ Mostly exact dimensional match (mostly
interchangeable): In the case of full thread and partial
thread hex head cap screws, DIN 933/DIN 931 and ISO
4017/4014, the DIN and ISO dimensions are the same
at all sizes except for M10, M12, M14 and M22. If a
customer is looking for an M8 X 40 hex head cap screw,
there is no concern as to whether or not the item is DIN
933 or ISO 4017, they will have the same dimensions,
but if the item is M10 X 40, then the standard will be of
concern because the M10 diameter DIN 933 does not
have the exact same dimensions as the M10 diameter
ISO 4017. The difference is in the width across the flats
(WAF), with the M10 ISO 4017 having a 16mm WAF,
whereas the M10 DIN 933 has a 17mm WAF. This 1mm
difference may not be of concern for some applications,
but for many applications, the difference can affect
output significantly.
¤ Similar dimensions (limited interchangeability):
To illustrate a case in which the dimensions are of
greater concern, we should review DIN 84 slotted cheese
head screws versus the ISO 1207 counterpart.
With DIN 84 and ISO 1207, though there are some
consistent dimensional differences, due to the typical
applications for these parts, they are considered to have
limited interchangeability. In this case, it may be pertinent
to have an engineer review the differences between the
standards should one be favored as a replacement for
the other. Between these two standards, head heights
and head diameters have changed, thread lengths have
changed, and some slot dimensions have changed. This
is in addition to some other relatively ineffective changes
such as a the M1.8 diameter and some nominal lengths
being deleted. Though when designing for this part, it
may be worth noting that property class 8.8 has been
omitted, therefore if the application calls for ISO 1207
specifically, it should be designed for a material that the
standard readily covers (such as 4.8 steel or A1.4305,
A2 or A4 stainless steel).
¤ Similar dimensions (little to no
interchangeability): This may be surprising for some,
as this is probably the part mentioned so far that people
would assume is most interchangeable, but ISO 4032
hex nuts are not considered interchangeable with DIN
934 hex nuts. Anecdotally, it seems people are getting
that point, as I believe we’ve seen an uptick in people
specifying that they need ISO 4032, rather than accepting
DIN 934 (which is more commonly stocked stateside). I
choose this fastener to highlight this section, because
the dimension themselves are not drastically different
though there are some potentially significant dimensional
differences, rather it is the mechanical property that
actually allows the ISO standard to consider itself noninterchangeable
with the DIN standard.
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