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I need set screws for the gears of some of my old slot cars; Atlas, Revell and Monogram.
Does anyone know the correct dimensions for these set screws and where to find spares?

You'll be able to get replacements from anyone that deals in small screws etc. It's merely a matter of knowing what size they are. How do they compare in size to the Slot.it ones, which are M2 or the NSR, which are M2.5? Of course, chances are they will be small gauge imperial sizes rather than metric.

Right - the thing is I'm not familiar with the imperial sizes. If someone could suggest what might the right size(s) I can get some screws to try out.

I have the same set up and gearing. Just pulled a screw and checked they are 2-56 NC. Don't know where you are located but if you need help getting them let me know.

Nice try Shotgun but 4-40 is toooooo large.

Hey Balsa,

N.C. = Numerical Control




Phil

On the screws there are two common designations, NC (or UNC) and NF (or UNF)
NC / UNC - Unified National Course
NF / UNF - Unified National Fine
I have never really thought about why they add the suffix since the threads per inch are listed - but I would guess it is just a quick ref.
Also for ref:
#4 screws - 40 threads per inch is NC, 48 threads per inch is NF
#2 screws - 56 threads per inch is NC, 64 threads per inch is the NF
:)

I purchased some set screws and thought I might as well get a selection of various sizes while I was at it. They're quite cheap, from several sources on the net. It turned out that the Atlas car that I started with required 2-56 screws as expected, but then chassis no. 2 needed 3-48. It may be that someone re-drilled and tapped that gear. In any case I'm now armed to tackle my fleet of vintage cars and that feels great!

Allen head socket set screws are SO MUCH easier to work with over the flat blade grubs found in some of the old gears. They were always available in the old days and I for one changed fasteners at my own will. The sizes were never as consistent as they are in modern parts.