Tapping can increase the tensile strength of an internal thread up to twice the
tensile strength of a cut thread. Carbide taps will decrease the cycle time
required to thread by at least a factor of two.
a carbide nib form tap assembled on a steel shank to take advantage of the
speed potential while preserving overall tap strength to tangential forces. The
improved cycle times are sweetened by tap life that can be more than 10 times
the life of a steel tap.
Aluminum can be most cost effective with PCD inserts, however, insert cost is
very high. Most Aluminum is milled and turned with carbide inserts honed for
sharpness and polished to aid in chip flow. The best of both worlds is a
development by LMT Fette in Germany using a coating process defined as Plasma
CVD. The coating is applied to a honed insert and increases insert life while
maintaining the edge integrity. As an added benefit Milling speeds can be as
high as 6000sfm and turning speeds to 10,000 sfm. Speeds significantly improve
throughput and insert life can be 10 times longer than uncoated inserts. Insert
cost is comparable to uncoated polished inserts.