This question was posted in my ad in the classifieds and the info should be in this thread also.
Was wondering what is the size of opening, is it correct size that it could be threaded for a smaller apature?
Thanks Don.
The I.D. is 3/16" or .1875"
The next size up is M6x1,00mm which uses a 5,00mm tap drill (.1969")
The next size smaller is 12x28 which uses a #15 tap drill (.1800")
However, the aperture (and windage screw) are 4140 steel heat treated to 35 Rc
You would have to anneal the aperture, which could cause problems with the hardness of the shank. It is heat treated so the set screw does not damage the flats on the sides of the thread.
A easier method would be to epoxy a reduced diameter sleeve in the hole.