A Quantitative Evaluation of Diamond and CBN Grains by Overcut Fly-Milling Test

Abstract

An overcut fly-milling test with inclined workpiece was performed to accurately evaluate the cutting and wear characteristics of diamond and CBN grains, Namely, a quantitative evaluation of the chipping and tip wear of a single grain was made by tracing across the grooves with a stylus instrument. The milling experiment was carried out on a surface grinder, in dry, at cutting speeds 12.7 and 38.0m/s, and feeds 1.3 and 4.0m/min. The work materials used were hardened SUJ 2 steel, P 20 carbide, alumina, Si3N4, and silicon. The test grains were natural diamond, CBN, green SiC, and fused alumina, where grit size was #12 with an exception of CBN grain (#14-20). The CBN grain had the most high resistance to chipping and attritious wear for cutting SUJ 2 steel. However, the CBN grain as well as A and GC grains could not cut the other work materials due to grain fracture. The high chipping probability of the diamond grains was found on a Si3N4 ceramic. Also, the most fine chipping appeared on this work material. The attritious wear of the diamond grain was most remarkable on the P20 carbide.