Up-cut and climb milling
For efficient cutting, the cutting edge must arrive at the workpiece first. If not, it may still cut but excessive heat will be produced by the tool rubbing. In ‘up-cut’ milling (or conventional milling) the tool starts at the bottom and cuts upwards. The cutting edge rubs momentarily until it bites into the cut, which is no problem when the cutter is sharp. When the cutter dulls, the cutting edge rubs more. This becomes evident in the resulting poor surface finish.
In ‘climb’ milling, the cutter is trying to climb over or along the workpiece. As the cutting edge takes a full cut straight away, there is no rubbing and a better surface finish results. The size of the swarf chip is the same by both methods.
To get the benefits of climb milling you need higher spindle power and a very rigid set-up for your machine, component, and tool holding. Unless your machine is fitted with ball screws or backlash eliminators, you will have to up-cut mill. If you try to climb mill, the tool will continually grab the workpiece as it takes up the backlash in the machine lead screw as you feed the table. This will result in a poor finish or damage to the workpiece and possibly chipping of the cutting edges or breakage of the cutting tool.