抄録
An investigation was done using workpieces with an inclined front face drilled by a gun drill and long drill (with a diameter of l0 mm). The inclination angles are 0°, 15°, 30°and 45°. Another investigation was made for workpieces with a prebored hole, next to which was drilled a parallel hole by a gun drill. The wall thickness between the two holes and the diameters of the prebored hole and of the parallel hole were varied. As a result, the following are clarified. The direction of the cutting force during the cutting of an inclined front face influences the hole deviation. Regarding the gun drill, the hole deviates toward the positive direction of the X-axis, i. e., in the same direction as the front work face. Regarding the long drill, the hole deviates toward the negative direction. Parallel hole deviation increases with prebored hole diameter. Hole deviation sharply increases when the wall thickness between two holes reaches a certain value.
