Every milling cut is either climb (down) or conventional (up) milling, and picking the wrong one for your setup can ruin a finish or break a cutter.

Conventional milling (cutting up)

The cutter rotates against the direction of feed. The chip starts at zero thickness and grows as the tooth exits the cut, so the tooth rubs before it bites — more heat, a slightly rougher finish — but cutting forces pull the workpiece into the table, which is forgiving on manual machines with backlash in the table screws.

Climb milling (cutting down)

The cutter rotates with the direction of feed. The chip starts thick and thins out, so the tooth bites immediately — less rubbing, less heat, better finish, less work hardening. The catch: cutting forces pull the workpiece toward the cutter, which can yank the part into the tool on a machine with backlash. Climb milling is the default on rigid CNC machines with good backlash compensation.

Rule of thumb

  • CNC with good backlash comp: climb mill for finishing passes — better surface finish, less burr.
  • Manual mill or a machine with play in the table: conventional milling for safety, especially roughing.
  • Work-hardening materials (stainless, Inconel): climb milling reduces hardening of the surface you just cut.
💡 Many shops rough conventional and finish climb — best of both worlds when the machine allows it.