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I am working on a project that requires:

3pcs M5x30-50 bolts and nuts

I assume the M5-30 is the size and length. What is the 50 specify?

Tony Giaccone
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2 Answers2

5

I think your project instructions left out the thread pitch because M5 bolts and nuts come only in 0.8mm pitch in ordinary commerce. So in my opinion, the project calls for:

M5-0.8 bolts that are any length between 30 and 50 mm long

MTA
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I'm assuming you know how bolt threads work, are measured, and are cut.

M5 means the nominal diameter of the machine screw.

x30 is nonsensical. It sounds like someone is trying to say "30 threads per inch" as SAE fasteners are specified... but that is absurd in a metric fastener. However, 1/30 of an inch is very close to 0.8mm, and that is the most common thread pitch for M5.

-50 means the length of the bolt is 50mm (about 2 inches).

Harper - Reinstate Monica
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    There are (at least) ISO and DIN standards for such things, in fact. And your standard "imperial" screws might be Witworth threads or SAE, so... – Ecnerwal Oct 11 '21 at 00:06
  • @Ecnerwal No, metric is a hot mess. There are as many as 4 thread pitches for a given diameter, i.e. stuff between 8mm and 14mm. You'll have 3 on the same car! A standard with this many variations is no standard at all. Whereas in SAE there are only 2. 1 fine 1 coarse. Whitworth is functionally obsolete and I work on some pretty old stuff. – Harper - Reinstate Monica Oct 11 '21 at 00:21
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    You haven't met UNEF threads, evidently. The "US-Automaker" business of randomly mixing metric and SAE on the same car is far more annoying in my experience. – Ecnerwal Oct 11 '21 at 01:16
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    @Ecnerwal Right, but UNEF gets used rarely in very unique applications. I see the 3 pitches of 8mm and 10mm used randomly and haphazardly on my cars, for no good reason and on the same car! GM did an orderly switch to metric in the 80s, first they switched bodies at generation change (e.g. 1982 for F-body). Then they changed engines at generation change (e.g. LT1 for the Chevy small block). If you know the generations, you know which socket set to grab. Yet a GM car will use a 13mm hex head, where Japan uses a 12mm. SMH... more standards fail... – Harper - Reinstate Monica Oct 11 '21 at 21:51
  • @DanMašek then I'll drop it from the answer. Please reconsider any DV. (and please don't DV for comment content). – Harper - Reinstate Monica Oct 13 '21 at 01:27