Boring question about M3 nuts

Rattled a tiny M3 nut off the light of my new tail tidy yesterday. Should have used a locknut ho hum… Went and bought a couple of M3 nuts from hardware shop but they don’t fit. They seem to have flat thread whereas I think I need a slightly inclined thread to fit the bolt. Does anyone know how many different types of M3 nut there are out there (!) and even which one I should be buying?? Ta very much :slight_smile:

I am no expert on nuts but the answer is to measure the distance in millimeters between the thread so you know the advance given by 360 degrees. A standard M3 advances 0.5mm and anything other than that will be described by appending x then the pitch in mm after the M3 (so M3x0.3 would be a an M3 screw that advances 0.3mm in 360 degrees). It doesn’t appear that there is a standard tight thread version of M3 though.

Thanks Guiliano- amazed that anyone has even attempted to answer this for me! Sadly, the nut in question is miniscule (3mm across) so I wouldn’t be physically able to measure the pitch of the thread. I was hoping there was maybe a ‘universal’ nylon-type nut that might fit?

Only cos I was tracking down a screw the otherday and found that Wikipedia entry that made things much clearer!

As for measuring the thread of a screw - get somethign thick, black and sticky, get it on the thread, then press it onto a piece of flat quality paper. It will be easier to measure the “hard copy” with a ruler, caliper etc.

If possible I find a nut that fits and take it to a proper fixings and fasteners supplier and they’ll find one to fit, or they’ll just simply identify it from the bolt. Much more knowledgeable than hardware stores I find. I used to sell to both so tend to know the difference.

Forgetting the niceties of measuring the thread pitch for the moment, there are only 3 common variations in use. In the trade they are known as metric fine, metric and metric coarse.

In 3 mm size “metric coarse” sounds a bit daft so “mf” might be what you need .

In theory, it should be available as a “nyloc”. (There is a BS-EN for that).

You’ll need a proper supplier to find that.

Is the tail tidy to make room for the Akropvics?

Ahhh Akrapovics…I was only thinking yesterday that I really do want to get some…if only I could justify the cost :w00t:

Acording to my trusty Zeus Book there is only one ISO pitch for M3 and that is 0.5mm.

There is however an American ANSI M3x0.8 if your tail tidy came from the states.

My guess is that the original wasn’t ISO M3 or the shop has mixed their nuts up with BA ones:cool:


Much as I love the Zeus Book, it’s a ready reference and only lists a selection of information.

For most smaller sizes there is “fine” and “extra fine”, used in instruments, cameras and the like. Oh, and just to be perverse, tyre valves are an obscure fine pitch thread.

Back to the original question: Did a google and looks like 2 different pitches are readily available from suppliers.

If all alse fails, try Stagonset. Being Swiss, the products are beautiful and precise and they will even post a single nut. At a Swiss price, of course.

Better, try talking/writing to the manufacturers. Lots will send out small bits like that for free.

Dont forget to use thread lock on the new one.

Granted, the Zeus Book is a ready reference and for more in depth info I refer to my Machineries Handbook;)

With the risk of “stating the bleedin’ obvious” the chances of said tail tidy having an obscure pitched instrument screw are as slim as me riding non-stop through winter;):smiley:

You know as well as I do that the vast majority of jap bike threads are ISO until you reach M10 and above:cool:

Use some gaffer tape!!

Sticks most things back together!!

The M3 is definatly boring but hang in there it takes you some nice places.:slight_smile:


I don’t suppose for a moment that the “extra fine” is used on a motorcycle (though perhaps in the instrument binnacle?) nor did I suggest it. But both the standard, 0.5 pitch, and fine, 0.35 pitch are readily offered by decent fastening retailers which kind of suggests that both are in fairly common use.

The big problem is, down at this size, B.A. diameters and pitches are so close to the ISO metric standards that it’s a bu88er to tell them apart. A good example is electrical face plate screws. (Incidently, currently ISO metric “fine”)

I’d still stop faffing around and write to the manufacturers to beg some spares. Just seems so much easier.

“Bed time for Old Guy and Germany”:slight_smile:

Thanks for the amusing debate…:wink:

I went down to Screwfix but they just stood there admiring my bike! They had two types of M3 but they said they thought they wouldn’t fit and I’d be better off trying Halfords!!!

Going to call R&G on Monday and see if they can send more nuts…

Bet you didn’t expect all that from the “Boring question…”

OMG just realised I’ve won on Ebay…Looks like I’m getting the Akra’s after all…oh yes!