Abstract
The aim of this experimental research is to clarify the effect of longitudinal pitch, lateral pitch and direction of rotation of cutting drum of point attack bit on the impact cutability for mortar, and to find the optimum longitudinal pitch, lateral pitch and direction of rotation of cutting drum that the amount of debris per unit cutting work takes a maximum value. As the result, it was observed that the amount of debris per unit cutting work increases with longitudinal pitch, the optimum lateral pitch exists at the case of shallow cutting depth, and the optimum direction of rotation of cutting drum is the reverse direction of down cut.
