Ruger Old Army Grip Frame Screws - thread and pitch?

[Dark Skies]

Took the new (to me) Ruger Old Army to the range today. Shoots very well.

There's just one niggle - when I stripped it down for cleaning I discovered the previous owner had slightly stripped one of the two screws retaining the back of the grip frame (the ones either side of the hammer). I have some screws on order but I'd like to run a finishing tap through the affected thread just to tidy up any burrs that may be lurking there. As far as I can see the thread looks pretty good but if I gently screw the non-buggered screw in I can feel it tightening up a bit and I don't want to push my luck. It may just be some residual retainer down there - I gather the screws originally come with a blob of it on the threads. But like I say, I'd rather not push my luck when I can just run a tap through. Anyone know what tap I'll need?

[Sim G]

#6, 40tpi.

[Dark Skies]

#6, 40tpi.

That's UNF, then?

[Sim G]

Don't know. That's just what it says in my schematic parts list...

[Dark Skies]

Cheers.

[Pippin89]

#6, 40tpi.

That's UNF, then?

Yes #6 - 40 is UNF.

This site is a great help if you need to check something like that:

https://mdmetric.com/thddata.htm

[Dark Skies]

#6, 40tpi.

That's UNF, then?

Yes #6 - 40 is UNF.

This site is a great help if you need to check something like that:

https://mdmetric.com/thddata.htm

Awesome. Very useful for future reference. Cheers.