"Knurling, cut knurling specifically. Traditional knurling uses two rolls to compress and form the diamond pattern into the material. Cut knurling uses two rolls set at an angle to physically cut the knurling into the material. By threading the blanks onto the fixture I can leave the tool setup (which can be a bit tedious to get it set perfect) and run blank after blank with consistent results." Credit: IG User hillview_wm | Practical Machinist