Napkin Ring and Knurled Knob Customizer

EDIT (17 Dec 2015): Clarified 'twist' and made it easier to get the right values

You want to create a knurled ring or knob for your rotary dial? This is the solution for you!

or

You want to snazz-up that dining experience? Get the wife-acceptance factor (WAF)? Print out some of your own design twisted and knurled napkin rings! Maybe even try one of those nice pastel colours that she likes so much.

This customiser allows you to create knurled and modern looking rings and caps, I hav