Hi, here's a tool for creating circles, a radius, or measuring a length - In 5mm increments.

You need a pivot at zero, as well as the marker or cutter at your desired length.

Unlike a standard compass, this allows you to use various widths of pens, pencils, drill bits, etc. Since only the tip of the item is in contact with the compass, the width of the body of your pen is irrelevant :-)

[Licensing: You can use this for any purpose you like, as long as you don't make a profit - let's face it, if your income relies on this design, you are not great at business! :-p ]