Little helper to train your eye

I want to get a better feel for screw and bolt sizes, so made this screw & bolt display as a helper for designing parts for 3D printing. The idea is to train my eye for the different sizes so I can quickly decide which one to include in a part. I chose M3, M4, M5 and M6 as they are the sizes I mostly use.

10 mm offset for stability and accurate representation

The holes are 10 mm deep and I go up in 10 mm steps for the screw length. This means the first row of screws (10 mm) will completely disappear inside and only the head sticks out. The second row of screws (20mm) however sticks out exactly 10 mm from the surface. It looks like a 10 mm screw has been glued to the top (which was my first idea, but too unstable).

I found this to be a good combination of stability and accuracy, because you can move the thing around without screws breaking off and you can see the correct length of the screw. The table below shows the real size and the apparent size, I hope that makes it more clear.