<UPDATE Sep 20,2016>
There are knurling bolts and a nut that modeling on Autodesk Fusion 360.
I got a inspiration form Knurled surface finishing library by aubenc. Thanks!
I've prepared a bolt of various lengths.
So, print a bolt you want.
Bolts are M15, pitch 2.0, length 20, 30, 40, 50, 60mm, and Head OD 30mm, height 20mm.
A nut is M14, pitch 2.0, height 20mm.
See my YouTube about how to making a knurling on Fusion 360 Modeling a knurling on Autodesk Fusion 360