Conventional Milling (AKA: "up-milling") the end mill meets the work piece at the bottom of the cut.
- The cutter rotates against the direction of feed as the work-piece advances toward it, from the side where the teeth are moving in an upward motion.
- The thickness of the chip increases consistently to the top of the cut.
- If the work-piece has a highly abrasive surface, conventional milling will usually produce better cutter life since the cutting edge engages the work below the abrasive surface.
- Conventional milling, also protects the edge by chipping off the surface ahead of the cutting edge.
However, in horizontal conventional milling, the cutting action has a tendency to lift the work piece fixture and the table from their bearings. Conventional milling is recommended when the system is not rigid because the cutting forces oppose the feed, thereby tightening the system. A positive rake angle cutter is preferred because the edges will more easily dig in at the beginning of the cut where the chip thickness is zero. All of CGS carbide end mills can be used for this type of milling.
Climb milling (aka: "down-milling") the tooth meets the work-piece at the top cut.
- The cutter rotates in the direction of the feed and the work-piece advances toward the cutter, from the side where the teeth are moving downward, producing a wedge shaped chip.
- The rubbing action is eliminated, allowing the gradual disengagement of the teeth and work piece with the feed, diminishing any marks.
- Climb milling often produces a better finish, allowing for a greater feed per tooth and prolonging the tool life.
- The downward pressure caused by climb milling has an advantage as it tends to hold the work and fixtures against the table.
- The use of climb milling is only limited by the condition of the machine and the firmness at which the work is clamped and supported.
Since there is a tendency for the cutter to climb up on the work, the work-piece fixture must be rigid enough to handle this. While it is beneficial to climb mill heat treated alloys and non-free machining grades of stainless steel, climb milling may cause chipping due to the hardened layer on the surface and a hard scale. Climb milling will not work with every application and should not be used if the material and machine set-up are not adapted for this type of milling. All of CGS carbide end mills can be used for this type of milling.