Calling the engineers!

Please help me size this subminiature bolt. I need a few replacements to restore an old compass. The compass is German, probably pre WWII, but I am not convinced the hardware is metric.

Diameter of shaft: 1.12 mm (0.044")
ca 4 threads per mm (ca 100 threads per inch)

It is not size 00-90. I tried a 00-90 nut.

hotwheels

Okay, after repeated fiddling, I got the 00-90 nut on the bolt. Maybe the bolt is 00-90, but at least visually it seems to me the thread is a hair coarser than on a 00-90. Unfortunately I don't have a macro lens, or I could blow up a picture of the tiny bolt next to calipers and make sure.

Does anyone know of a chart with common and uncommon subminiature thread sizes?

You probably want someone who collects/repairs old watches rather than an engineering type.

Kit Walker said:

You probably want someone who collects/repairs old watches rather than an engineering type.

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Engineers tend to know where to find all sorts of technical charts for fasteners. And a watchmaker is an engineer.

mtnredhed said:

http://www.mcmaster.com/

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I wish, because I already have an account with them. They have nothing remotely in this size. Even Otto Frei, the best watchmaker supply store,m has a very limited selection of subminiature hardware.

Prewar Germany used DIN standards. This translates to modern ISO metric sizes. However, prewar, it would not have been unusual for a manufacturer to deviate from standards, especially if they manufactured everything in-house.

If the diameter is 1.12mm (measure the diameter on the threads), that falls within the tolerance of M1.2x0.25 screws (1.182 to 1.115). That pitch means 101.6 threads per inch (4 threads per mm).

Thank you Mr. Bob. I'll have to see if I can rustle up that size bolt. If my brother were around I could conveniently ask him to make me those screws. He's a hardcore mechanical watch nut and is generally into engineering. Alas he's left the country for the foreseeable future.