fluted knobs

This code is a development of the ideas in https://www.thingiverse.com/thing:2163938.
Openscad source that can be used to generate several types of nice looking knobs for electronic projects. Knobs with both 6-32 setscrews using an embedded nut or the D shape push on shaft style are configurable. These knobs resemble the style used on Icom HF radios. The knobs include a tapered skirt that hides the control mounting nut.

// Change History from original:
// - reformatted for easier readability
// - commented code to help with modification
// - added option to add/delete filler for shafts with flats
// - added option for 6-32 set screw using trapped 6-32 nut
// - number of flutes scales with knob size
// - Mar 14 2019 - made knob taper adjustable + or -

// Sept 2019 added photo of printed knobs, usb plug mount, and 22mm bezel all on my A/C and D/C power supply projects.