Comparison of Respirable Dust Generation by New Polycrystalline Diamond Compact and Tungsten Carbide Drill Bits in Wet and Dry Drilling


U.S. Bureau of Mines field test results show that polycrystalline diamond compact bits used for coal-mine roof bolting, can last 200 to 600 times longer than tungsten carbide bits. During these tests it was also noted that the cutting edges of polycrystalline diamond compact bits remained sharp, they did not show any decrease in penetration rate, and it appeared that they generated less airborne dust. During these tests, however, it was not possible to measure the amount of respirable dust generated under controlled conditions. Laboratory tests were subsequently conducted to compare the respirable dust generated by new tungsten carbide and polycrystalline diamond compact bits. These tests were performed using a rotary drill test facility at the Rock Mechanics and Explosives Research Center, University of Missouri at Rolla. Respirable dust, as defined by a lognormal particle penetration curve with 50 percent penetration of 3.5-µm aerodynamic diameter, and a geometric standard deviation of [sgrave][subscript g] = 1.5. Respirable dust generated by drilling was measured using a Bureau-designed, real-time continuous respirable dust monitor and a concurrent filter sampler. One tungsten carbide and three polycrystalline diamond compact bits were tested under identical test conditions with air and water used as bit- cooling and dust-removal agents. Results show that when drilling dry the polycrystalline diamond compact bits produced 71 to 88 percent less dust than the tungsten carbide bit. There was also a reduction of up to 95 percent in respirable airborne dust generation for all bit types when water was used during drilling.


Mining Engineering

International Standard Serial Number (ISSN)

1047-322X; 1521-0898

Document Type

Article - Journal

Document Version


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© 1996 Taylor & Francis, All rights reserved.

Publication Date

01 Jan 1996