Boring deep holes in southern pine

Abstract

When holes 10-1/2 inches deep and I inch in diameter were made with either a ship auger or a double-spur, double-twist machine bit, clogging occurred at a shallower depth (avg. 6.5 inches) when boring across the grain than when boring along the grain (avg. 10.1 inches). In both boring directions, thrust force and torque demand for unclogged bits were less for the ship auger than for the machine bit. Generally, torque and thrust were positively correlated with chip thickness and specific gravitY; they were unrelated to spindle speed when the thickness of chips was held constant. For the machine bit, thrust was less in wet than in dry wood. Although the ship auger required less horsepower than the machine bit, it was slightly less efficient; ie., more energy was required to remove a unit volume of wood. In boring along the grain, the ship auger made better holes than the machine bit when the wood was dry; in wet wood hole quality did not differ between bit types. When boring across the grain, the machine bit made better holes in both wet and dry wood.

Citation

Woodson, G. E.; McMillin, C. W. 1972. Boring deep holes in southern pine. Forest Products Journal 22(4):49-53