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Measurement of Coal-cutting Forces Underground With the In-seam Tester.

MISSING :16 pages
The Bureau of Mines designed, fabricated, and is using an in-seam tester for in situ determination of coal cutting forces. This report describes the results of field tests conducted in the Pocahontas No. 3 and Upper Freeport seams to obtain peak and mean cutting forces during coal cutting with several bit geometries, including radial and point attack bits currently used on drum-type machines. Comparisons were also made between new and worn bits, and by using data obtained from a Bureau-modified chisel bit. The test results show that longwall plough cutting (horizontal cuts) in bony coal bands (shale) requires greater than three times the cutting force for the same cuts in a vertical direction. When no bony coal is present, the cutting forces required to make horizontal and vertical cuts are equal. Worn bits require four to five times more cutting and normal force than new or undamaged bits. Normal force increased drastically for the worn chisel bit. Peak force encountered in making independent cuts was found to be approximately three times higher than that required to make interactive cuts using a spacing-to-depth-of-cut ratio of 2. Both rake and clearance angles were found to have a significant effect on normal and cutting force.
Publication Date
Document Type
IH; Report of Investigations
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
RI 9033
NIOSH Division
Source Name