Print these out and see what size hole you need to add a steel nut to your design. Metal threads in plastic?!?!? MADNESS!!!! Each stick covers 2 mm in .2 mm steps. For example the 10 mm to 12 mm stick has 10, 10.2, 10.4, 10.6, 10.8, 11, 11.2, 11.4, 11.6, 11.8 and 12 mm diameter in it's range. This is enough to determine a loose fit, a snug fit and a force fit for anything you can jam in the hole. Write the range on it with a marker. Nut traps add a whole new level to your designs. Check out my other designs to see trapped nuts doing cool stuff.