This paper describes on the failure process of carbide tool, and the effect of chip breaker on it; that is, how the failure of carbide tool progresses as the cutting proceeds, what kind of appearance of failure the tool shows at the end of its life, how the failure process of carbide tool with chip breaker differs from that without chip breaker, and so on.
The kind of carbide tool used in the experiment is S 1 and the cutting material is 0.4% carbon steel (Rockwell hardness B 64). Cutting conditions are as follows: cutting velocity 100 and 150m/min, depth of cut 2mm, and feed 0.3mm/rev.
From the results obtained from the observation by using microphotographs, universal measuring machine, and so on, the following facts were recognized:
(1) The kinds and processes of failure of carbide tool at cutting of steel were clarified.
(2) It was ascertained how the final damage of tool occurs.
(3) The effect of grooved flank wear on tool life should not be neglected.
(4) The distance between the centre of crater and the cutting edge is not constant contrary to the conclusion by Opitz.
(5) The chipping of end cutting edge induced by the development of cratering on tool face often determines the life of tool.
(6) The existence of chip breaker gives a slight change of the development of cratering, especially in the early stage of cutting.
(7) Generally speaking, chip breaker does not affect on tool life.
(8) The values of the radius of chip-curl calculated by Henriksen's formula fairly disagree with those obtained in the experiment.
