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Right now button bits are widely used in rock drilling. Considerable effort has been expended by manufactures to increase performance and durability of the button bits. However, most of them were conducted on try and error basis mainly because high level acceleration and vibration in rock drilling prevented accurate sensing and fundamental data collection concerning button bit performance.In this study, static penetration testing was carried out to clarify the performance of worn bits . Preliminary test was conducted on Sanjome andesite as a sample rock, and then Niihari sandstone was tested with one new bit and three worn bits. The testing results can be summarized as follows;

The paper describes a fundamental investigation of the abrasive wear in rock drilling and cutting. Three laboratory tests of rock abrasivity were carried out and the results were compared with those obtained in fullscale field drilling tests.The laboratory tests were comprised of drilling test, Taber abrasive test and turning-operation(facing) test developed in the study. The Taber abrasive test was found to be not feasible because of its difficulty in specimen preparation. The modified drilling test and the turning-operation test gave reasonable results. A correlation was demonstrated between abrasivity and unconfined compressive strength for more than fifty rock samples.There was also a rough correlation between the results of the modified drilling test and the turning-operation test.The field drilling tests were performed measuring height-loss and gauge-loss of a worn bit. The best correlation exists between results of the turning-operation test and the field drilling test.