(updated 05/09/2020)

This improvement over my original design combines an imperial screw diameter sizer along with a ruler, so you can sort most of your loose imperial screws without needing a second tool. I know I should have included the ruler component when I was drafting the original version, but the idea didn't occur to me until quite later.

As with the original tool, use is simple. If the shaft of the screw doesn't easily swipe unimpeded through the gap--or alternately, if it doesn't readily fall into the circular hole--then the screw belongs to the next larger size. You can now also measure the length of the screw by placing it in the slot beneath the inch ruler.

The first STL file contains one ruler slot for measuring length. The v2 STL file contains two ruler slots to more conveniently measure both screws with flat shoulders and countersunk screws.

Print at 0.1 resolution for optimal precision.