CUTTING OF DIFFICULT-TO-CUT WOOD-BASED MA TERIALS WITH DIAMOND-COATEDCEMENTED CARBIDE TOOLS .1. DIFFERENCE OF CUTTING PERFORMANCE BY THE FILAMENT POWER IN THE SYNTHESIS OF DIAMOND FILM

In this study, diamond films whose thicknesses were 20 mu m were synth esized on both rake and clearance faces of throw-away cemented carbide milling tips by the hot-filament chemical vapor deposition (CVD) meth od with varying filament powers. Continual milling tests of wood-chip cement board with three kinds of diamond coated tools with filament po wers of 2.2, 2.3, 2.4 kW and a non-coated one were conducted until the total cutting length reached approximately 116.5 m, and then the cutt ing performances were examined. Although diamond films of coated tools peeled off in the early stage of cutting, edge recessions and surface roughness of these tools in the middle stage of cutting became extrem ely small compared with that of the non-coated one. In the last stage of cutting, the tool edge of a filament power of 2.4 kW fractured, and its edge receded extremely. However, this type of fracture was not se en for the filament powers of 2.2 kW and 2.3 kW. For cutting power con sumption and cutting noise, these values for the non-coated tool were the smallest among all tools tested in the early stage of cutting, but those for coated tools became almost equal to that for the non-coated one with the continuation of cutting. As a result, diamond coated too ls she-wed excellent cutting performances compared with the non-coated one for edge recession and surface roughness, and the cutting perform ance depended on the filament power in the hot-filament CVD method.