2020-10-23 - screw it...

i'm working on a pet project. it actually already spinned off a couple more child projects. one of them i hope to cover shortly. as a part of this effort a needed to screw down one part. thread was M10. i'm always using metric screws, in couple different sizes (depending on length / strength / weight parameters): M2, M3, M5, sometimes M8… and do so for many years now. this time i needed M10, which is much bigger than i typically use, but still – the same standard. so i made a trip to the shop just to buy two nuts and washers – around 0.2EUR total. when i got home, it turned out that the nut does not match thread!

i suspected that it was not M10 but instead some imperial-rooted thread, that some1 accidentally rated as M10. but no – i checked multiple sources and all of them reported it as M10. so i did some reading and when i was finally able to “ask the right question” in the growser, it turned out that for standard metric system screws, you can have different thread pitches: coarse (“default” one, if not mentioned otherwise) and fine (that in turn can also come in a couple flavors).

the notion i was used to was eg. M10x50, which reads: M10 screw (i.e. 10mm diameter), 50mm long. this is the coarse pitch – default one. for M10 it is 1.5mm pitch, thus the full marking would be M10-1.5×50. for “fine” threads of M10 you can choose among M10-1.25 and M10-1.

“the good news about standards is that there are so many of them to choose from”

Andrew Tannenbaum

now i need to go back to the shop and look for more M10s, but with a (new measured), non-default pitch: M10-1.