Chad A. Swope

Full scale linear cutting experiment to examine conical bit rotation

Conical bits are very common in excavation of soft to medium rocks in a great deal of mining and construction applications. Bit rotation allows the conical bits to maintain their tip shape and allows them to work more efficiently for extended period of time. This paper discusses the importance of bit rotation and the research work of measuring bit rotation and the impact of various parameters on this phenomenon. To find the relevant factors contributing to bit rotation, a few dominant parameters such as bit type, cut spacing, depth of cut, attack angle, and skew angle were considered. The paper described full scale linear cutting tests which were performed at Kennametal rock cutting lab in Latrobe PA. This linear cutting test is a prototype experiment to verify the direct measurement of bit rotation, to evaluate the impact of related parameters before performing rotary cutting tests. This paper offers the review of the linear cutting test results and outlines the observed bit rotation during experiments and their practical implications.

Study of conical bit rotation using full-scale rotary cutting experiments

Conical bits are very common in the excavation of soft to medium rock in many mining and construction applications. These bits are claimed to rotate as they cut the rock, allowing for uniform wear of their tip and body that helps maintain the tip shape, and works efficiently for an extended period of time. This paper will present an extensive study of bit rotation, including full scale cutting tests performed to measure bit rotation using different cutting geometry to evaluate the mechanism and extent of bit rotations relative to the controlling parameters. This includes bit type, depth of cut, cut spacing, skew angle, and sequence of cuts. The testing started with linear cutting tests, which indicated limited to no bit rotation when the bit was fully engaged with rock. As a follow-up study, full-scale rotary cutting tests, the impact of cutting parameters, as well as cutting speeds on bit rotation were studied. Full-scale rotary cutting tests were conducted using a test drum laced with an instrumented bit. Bit rotation was measured under the rotary motion of the cutter-head with several variables. The results of rotary cutting tests showed that bit rotation occurs when the bit enters and exits the rock. The results of rotary cutting tests and the impact of various parameters on measured bit rotation; especially skew angle will be summarized in this paper.