Variable rake mine tool insert and method of use
AssigneeGTE Products Corporation
InventorRandall W. Ojanen
Life of this patent
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Abstract
A mine tool roof bit insert having a leading face inclined at a constant angle of 0.degree.-3.degree. with respect to the axis of rotation, and a frontal face with a variable relief angle decreasing with increasing radial distance from the axis from 25.degree.-55.degree. at the axis to 15.degree.-25.degree. at its radially distal edge, the rate of decrease being at least 10.degree./in. A method of drilling a hole in a mine roof involves positioning a mine tool including the variable rake bit, insert, or the like, and rotating the bit, insert or the like at about 250-600 rpm and about 1000-8000 lb thrust for a time sufficient to drill the hole in the mine roof.
Claims7
A mine tool roof bit insert comprising a flat elongated body rotatable about a central axis and having two halves symmetrical about the axis, each symmetrical half comprising:
- a planar leading face inclined at a constant angle of 0.degree.-3.degree. with respect to the axis;
- a frontal face inclined with respect to a radial line intersecting and normal to the axis and inclined with respect to a second line normal to both the radial line and the axis;
- and
- a cutting edge defined by the intersection of the leading face and the frontal face;
- and wherein
- the angle of inclination of the frontal face with respect to the second line decreases with radial distance from the axis, decreasing from 25.degree.-55.degree. at the axis to 15.degree.-25.degree. at its radially distal edge, the rate of angle decrease being at least 10.degree./in.
A method of drilling a hole in a mine roof comprising the steps of:
- positioning a mine tool including a mine tool roof bit insert comprising a flat elongated body rotatable about a central axis and having two halves symmetrical about the axis, each symmetrical half comprising:
- a planar leading face inclined at a constant angle of 0.degree.-3.degree. with respect to the axis;
- a frontal face inclined with respect to a radial line intersecting and normal to the axis and inclined with respect to a second line normal to both the radial line and the axis;
- and
- a cutting edge defined by the intersection of the leading face and the frontal face;
- and wherein
- the angle of inclination of the frontal face with respect to the second line decreases with radial distance from the axis, decreasing from 25.degree.-55.degree. at the axis to 15.degree.-25.degree. at its radially distal edge, the rate of angle decrease being at least 10.degree./in;
- and
- rotating the mine tool roof bit, insert, or the like at about 250-600 rpm and about 1000-8000 lb thrust for a time sufficient to drill the hole in the mine roof.
Dependencies are inferred from the claim text.