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. CONTINUED ON PAGE 164
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