Screws are actually pretty complicated. They have major diameters, minor diameters, pitch circles, and different thread profiles. They also have various number of "starts" etc. And also different tolerances of fit as well. The list goes on and on. The screws you buy at the hardware store are either standardized metric or imperial. The long and short of it is that cuemakers don't follow standard ASME or Metric guidelines. There could be a thousand different ways to make a 3/8 - 10 thread profile. Cuemakers may or may not have a good reason why they chose one style of 3/8 -10 over another.