Need help identifying fastener metrics

[LEDcandle]

I have this shift knob that uses 5 allen-key head fasteners and 1 got lost. I'm hoping to find a replacement or perhaps replace all 5 if I can't find a match.

But from my noob measurements, I seem to get that these fasteners are M2 x 0.476 x 10mm, which is not a standard.

In fact, seems like M2 fasteners only come in 0.4mm diameter and 0.45mm is M3.

Here are some pics :-

I know the ruler isn't exactly accurate but it does appear to be a 2mm diameter x 10mm length x 21 threads (in 10mm) .Are my calculations correct? Or are these fasteners some other measurement? Are they a standard size?

Also, any idea where I may get this size online?

Any help is appreciated!

 

[Morelite]

That might be an M2.5, check this one out.

McMaster Carr item no. 91290A103, M2.5 are .45mm pitch x 2mm dia. Yours appears to be 22 threads in 10mm which = .45mm

 

[Anglepoise]

Any good bicycle shop should be able to help you out. Presuming you live near a town as opposed to deep in the country somewhere.

 

[snarfer]

I was surprised to find out recently that there are several other sizes available in this range. Not only is there M2.5, but also M2.2, and M2.6. To make things even more confusing, it might not even be metric. It could be a Nr. 2 or Nr. 3 as seen here (pdf). Probably you would be safe with M2.5 though. That's what I'd try. Even if it's not quite right you might be able to jam it in there.

 

[chimo]

You need a thread gauge tool (or go to a shop that has one).

 

[gadget_lover]

When you get the new one, hold it up against the known good sample with the threads interlocked. They should be a perfect fit, with no slop.

Holding them end to end will let you compare the outer size of the thread. The valleys shoudl be the same sice on both old and new.

What ever you do, don't try to force a new one that "almost fits". You will ruin the threads, possibly causing them to jam or strip out.


Daniel

 

[LEDcandle]

Thanks for the replies guys.

Hmm.. yeah, possibly its a 2.5 x 0.45 actually, after a 2nd look.

That would make it easier, being a standard size.

That tool looks useful! I'll look into it. Thanks again!