Here's a bit of useful information that will save you money and may solve your problem. 7/32-40 is a special thread that is hard to find and costly, #12-40 on the other hand is a common fine thread size that is commonly employed with lock hardware. It is commonly available and is not a costly item. There is only .002" difference in the major diameter (outside diameter) of the two threads, not enough to make any difference. I learned this lesson several years ago when I was considering making sight aperture discs. Hope you find this little kernel of information interesting and of use. MSC Industrial Supply and McMaster-Carr both carry #12-40 taps & dies, you would want a bottom tap to go in the shallow hole in the Williams sight. Inexpensive carbon steel tap & die will work fine for a one time job, no need for High Speed Steel.
Last edited by gunswizard; 06/12/19.
