The milling of Titanium is a more difficult operation than that of turning. The cutter mills only part of each revolution, and chips tend adhere to the teeth during that portion of the revolution that each tooth does not cut. On the next contact, when the chip is knocked off, the tooth may be damaged.
This problem can be alleviated to a great extent by employing climb milling, instead of conventional milling. In this type of milling, the cutter is in contact with the thinnest portion of the chip as it leaves the cut, minimizing chip "welding".
For slab milling, the work should move in the same direction as the cutting teeth; and for face milling, the teeth should emerge from the cut in the same direction as the work is fed.
In milling Titanium, when the cutting edges fails, it is usually because of chipping. Thus the results with carbide tools are often less satisfactory than with cast-alloy tools. The increase in cutting speeds of 20-30% which is possible with carbide tools compared with cast-alloy tools does not always compensate for the additional tool grinding costs.Consequently, it is advisable to try both cast-alloy and carbide tools to determine the better of the two for each milling job. The use of a water base coolant is recommended.
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