When this program runs, a CNC lathe puts a knurled grip surface on a rotating metal cylinder with no knurling tool in the turret. The result is a fine diamond cross-hatch, and the finished parts become knobs that need grip so a person can turn them by hand.
The approach is essentially a fancy threading cycle. Jake Hazlewood wrote the code about a year before sharing it, and it is all single line code rather than a canned cycle. A right hand multi-start thread pass is followed by a left hand multi-start thread pass, and the reversed half of the pattern is that left handed thread. The spindle puts out a signal once per rotation, and the start point for each pass is worked out from it. The code has to bring the tool back to its start point before working out the next move, and if it arrives just after the signal it sits out one rotation. That timing is why the gaps between tool moves are not all identical. Coolant is sprayed on the cutting zone throughout.
Details that stand out: the workpiece is held in a chuck, the OD threading tool sits in a holder, and the tool makes a run of precise rhythmic passes before retracting at the end. Since the threading tool is nearly always already in the machine, no extra setup is needed.
One open point: standard single point threading inserts may lack flank clearance for big wide knurls. The maker wonders whether the light cut hides any interference. Also worth noting the feed rates are high, so proving the program out in fresh air first is advised.
Project by Jake Hazlewood. Watch it on their YouTube channel: