Climb vs. Conventional Milling

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See the entries in the Glossary.

Given typical clockwise tool rotation, tool movement will result in climb or conventional milling.

Clockwise Tool Rotation Clockwise Spindle Movement Counter-clockwise Spindle Movement
Enlarging a pocket conventional milling climb milling
Reducing a profile climb milling conventional milling

Please note that in MakerCAM Help it's advised that “If you're cutting an inside profile, choose counter clockwise. For an outside profile, choose clockwise.”

Contrariwise, "Unless your machine is very rigid... you should always do conventional cutting"[1] ... except on low surface energy plastics (HDPE, Polypropylene, etc).[2]

Another recommendation is to climb mill for roughing passes and conventional mill for finishing passes.[3][4]

Conventional milling versus climb milling

Conventional milling. Point A may become work hardened.
Chip formation during climb milling.

Milling cutters can cut in two directions, sometimes known as conventional or up and climb or down.

  • Conventional milling: The chip thickness starts at zero thickness, and increases up to the maximum. The cut is so light at the beginning that the tool does not cut, but slides across the surface of the material, until sufficient pressure is built up and the tooth suddenly bites and begins to cut. This deforms the material (at point A on the diagram, left), work hardening it, and dulling the tool. The sliding and biting behaviour leaves a poor finish on the material.
  • Climb milling: Each tooth engages the material at a definite point, and the width of the cut starts at the maximum and decreases to zero. The chips are disposed behind the cutter, leading to easier swarf removal. The tooth does not rub on the material, and so tool life may be longer. However, climb milling can apply larger loads to the machine, and so is not recommended for older milling machines, or machines which are not in good condition. This type of milling is used predominantly on mills with a backlash eliminator.

" the primary difference between climb and normal cutting seems to be the deflection that occurs, and the ramifications to the size of the part. The bit will deflect opposite the direction it is spinning into the material. Often when cutting mating pieces, reversing the cutting direction is all that is needed for a very nice fit." [5]


Discussions in the Forums

Approach Moves [6]