Four tips of RD 92 were tested at 600 fpm cutting speed, 0.010 in./rev. feed and 0.10 in. depth of cut to 0.030 in. flankwear. Two tips gave a tool life of 56 min., but with severe crater wear. The other two tips gave a shorter life - one failing after 30 min. cutting as a result of the breakdown of the crater lip.