:P--> QUOTE(the big B @ Nov 24 2005, 12:47 AM) ←
its just a really deep grind.
Good luck doing that to your rim with a f**king grinder :P
Anywho, basically the tool shown up there has 2 super hard rollers on it.
These rollers have tiny knobbles in them.
You put the object you want knurling between the 2 rollers, and use the vice action to put them together onto your object.
So you've got 2 pointy rollers of a very hard material tight against your softer object (i.e a rim). You then turn the object/rim in the rollers so they make little indentations onto the surface.
You keep applying pressure to the vice part to push the indentations deeper into your rim.
And you basically roll the whole rim through the rollers until the whole rim is done.
The indentations on the rollers push in the material of the soft rim, leaving a series of tiny mounds and depressions.
Any D+T department worth their salt will have one.