Abstract
To establish the cutting performance and tool wear characteristics of a cemented carbide tool with clearance faces coated with CrN (UP), edge grain surfaces of spruce were milled with a 134 mm diameter cutter at a spindle speed of 6000 rpm and a feed speed of 1 m/min. The sectional profile and wear of the cutting edge were measured at feed lengths of up to 50 m to be compared with those of two uncoated tools of high speed steel (HSS) and cemented carbide (UH). Furthermore, in order to clarify the effect of cutting edge sharpness on chip formation for up-milling, edge grain surfaces of spruce, which were inclined by 0.14 degrees along the grain direction to gradually increase chip thickness, were orthogonally cut by tools at different feed lengths and a feed speed of 3 m/min. Tools of UP maintained sharp cutting edges in milling tests and its edge radius was six and two times smaller than that of HSS and UH, respectively, at a feed length of 50 m. The process of chip formation in orthogonal cutting was divided into three phases on the basis of the behavior of cutting forces. Tools of UP showed a shorter length between the points that the cutting edge came into contact with the work surface and they began to produce continuous chips. There was a good correlation between the undeformed chip thickness at the beginning of production of continuous chips and the tool edge radius.
