4mm Thread Pitch, custom thread design that I used to better understand threads and bolting. 
 

Rather than try to copy a thread pitch optimized for other manufacturing methods I put some thought into optimizing for FDM printers. When I designed this model for printing the technology wasn’t nearly as good as it is today but the result is that this print turns out wonderfully.

The 4mm thread pitch is optimized for 3D printing and uses my 3 rules for great prints.

1. No feature smaller than 2mm
2. 45 degree or less overhang 
3. Simple is always better 

I printed the first version a long time ago and it's been sitting on my office desk for some time, I usually fidget with it while on conference calls.