Penetration Test with Worn Button Bits for Rock Drilling

Seisuke OKUBO, Akinori OTA, Toshio MATSUDA, Katsunori FUKUI and Masao AKIYAMA

J. fo MMIJ, No.9, pp.663-668 (1997)

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;

1. Penetration rate decreases linearly with height loss of face chips. Slopes of penetration curve both in loading and unloading portions linearly increase with height loss of face chips. Specific energy, or energy required for unit excavated volume, also linearly increases with height loss of face chips.

2. Linear relations also exist against height loss and gauge loss of side chips. For example, penetration rate decreases linearly with height loss/gauge loss of side chips.

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