TURNING UP - IRON AND STEEL MACHINING

Cutting tool material technology is pushing up productivity and quality. There are 6 major tool life limiters: notching, machanical fatigue cracks, plastic deformation, slip stick, chipping, and crater wear. The most important of these to overcome is crater wear, which is done by using a TiN carbide coating. Multicoating with TiC and TiN using chemical vapor deposition [CVD] adds life to carbides. This technique increases the over all shop productivity and increases the tool life up to 2 times. Another type of multicoating is physical vapor deposition [PVD] which allows the insert to cut cleaner with less cutting force because it is formed at a lower temperature. Compoared to carbides, ceramics generally have lower transverse rupture strengths and higher hot hardnesses to allow it to run cutting speeds at a maximum. Unfortunately, ceramics tend to breakdown more. They are best used when running large batches, cutting hard materials, large parts, or at high speeds. Cermets offer many benefits over Tungsten carbides: good wear resistance, higher cutting speeds, and others. A certain shop switched from multicated carbide to a TiC and TiN cermet, cutting machining time by up to 85 percent. If one can harden, and machine all in one chucking, and then ship the part, the manufacturing cycle is considerably shortened. While grinding is still necessary, the new manufacturing method of hard turning can finish the part to within 16uin. This machine costs almost 90 percent less per spindle than a production grinder.