Screw sizes used in H0 Models.

For fastening trucks (bogies) 2-56 is the NMRA standard, but any size close to that will do. Not all mfrs follow the standard.
For engines, it depends where/when they made. Most nowadays are assembled with metric screws (made in China), but if you have some from the 70s or earlier, they are likely assembled with US screws.
I think you have two choices:
a) get some metric taps and drills, and an assortment of metric screws. Some will fit in any case. For an odd sized hole, if there's enough material around it, you can drill it out and tap it, o'wise plug, drill, and tap.
b) get assortments in all three customary types, and find the replacement size by eyeballing, and testing by _gently_ trying to start the screw.
HTH Wolf K.

On 2/27/2011 8:37 AM snipped-for-privacy@yahoo.co.uk spake thus:
The small SAE sizes of machine screws are 2-56, 1-72 and 0-80. (There's also 1-64, but I don't remember ever encountering that size.)
If it's a U.S. model, chances are the hardware is SAE instead of metric.
One online source for small fasteners is Dunno if they ship to the U.K., but worth perusing the site anyway. Or find a local supplier. (I'm guessing that since we can get metric stuff here in the U.S., you can probably get non-metric somewhere over there.)

The best online source for fasteners I have found is
and they ship worldwide.

On 2/28/2011 3:25 PM Robert Small spake thus:
Thanks for that link. I had it bookmarked from a long time ago but forgot about it.
Forgive me for picking a nit here, but it looks as if Micro Fasteners' selection is a lot more limited than Small Parts'. Compare Micro's selection of flat-head brass screws to Small Parts:
Micro only has one length of each of the 3 small sizes (0-80, 1-72 and 2-56: 1/2", 5/16" and 1/2" respectively), while Small Parts has multiple lengths for each size. Plus the only materials I could find screws in on Micro's site were stainless and brass, while Small Parts has lots more.
Maybe they have more stuff that isn't listed here?