screw size of an old style rear sight, N frame

[m37ral]

I need the actual thread size of the rear sight attachment screw.(the small old style one) Just picked up a 29-3 8 3/8 that had a scope on it. The scope mount was attached by drilling and tapping the sight screw hole oversize.
Sure hope there is such a thing as a helicoil that small.

 

[armorer951]

The correct OEM tang screw is 4-48.

 

[Protocall_Design]

In the picture it looks like they got that hole off center. Best bet on that one would be to tig weld it and drill and tap a new hole.

 

[m37ral]

I got a screw from a local source, it fits the sight perfectly. It is 3-56. I found some helicoils for it too.I got the sight for the 29 used, with the square front- supposed to be correct, is it possible the proper sight uses a larger screw, and the one I got was for something different using the smaller screw? Just trying to get it right.

 

[steelslaver]

I think they all use the same size screw, but the new sights use a screw that is rounded under the head and the older ones the bottom of the head is squared.

 

[toad67]

It can be a real pain to figure out what the thread count is on small fasteners. If you are fortunate enough to have the screw, these gauges come in really handy. I have both the US and metric one...

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