Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

NIOSHTIC-2 Publications Search

Search Results

Design of Anti-incendive Conical Cutting Bits.

Authors
Cheng-L
Source
Trans AIME/SME 1990 286:1863-1868
Link
NIOSHTIC No.
10008140
Abstract
Almost all modern cutting bits use a cemented tungsten carbide tip to provide adequate bit life against wear. Laboratory tests by the U.S. Bureau of Mines have indicated that the number of strikes for ignition increased by a factor of 3 with a new nonrotating bit impacting a sandstone block when the clearance angle was increased by 10 deg, and that carbide-tipped bits allowed more strikes before ignition than steel-tipped bits by a factor of 7 to 10. Recent field tests in an operating coal mine indicate a dramatic reduction in the frequency of frictional ignitions and improvement in bit life by using a mushroom-shaped bit cap and a larger initial clearance angle. The latter was achieved by increasing the bit attack angle. Improved bit performance through selection of the grade of tungsten carbide is a compromise between fracture resistance and wear resistance. A large clearance angle should be maintained by various techniques, such as a variable-attack-angle holder or a reusable bit that can be reground.
Publication Date
19900101
Document Type
OP;
Fiscal Year
1990
NTIS Accession No.
NTIS Price
Identifying No.
OP 148-90
NIOSH Division
PRC;
Source Name
Trans. AIME/SME, V. 286, 1990, PP. 1863-1868
TOP