In order to find the method by which the chips are effectively broken, it is necessary to observe in detail the chip breaking phenomena . In this report, the chip breaking phenomena are photographed by the high speed camera, and the relations between the chip breaking types and the cutting conditions are investigated by them. The following results are made clear. (1) The chip breaking types are able to be classified into three types: the type in which the chip hits the workpiece, the type in

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... ch the chip hits the tool flank, and the type in which the chip is broken at the point of tool tip. (2) As the cutting speed increases gradually, the chip breaking type generally transfers from the type in which the chip is broken at the point of tool tip to the type in which the chip hits the workpiece and finally to the type in which the chip hits the tool flank, or it transfers from the type in which the chip hits the workpiece to the type in which the chip hits the tool flank . (3) The chip breaking types change according to the kinds of workpieces. (4) The chip breakability is decided by the frequency in occurrence of the above three types.