Tool driving device and method of producing drilled product

A tool driving device comprising:

• a drill chuck for holding a drill;
• a motor configured to rotate the drill chuck;
• a casing housing the motor;
• and
• a vibrator configured to periodically reciprocate the drill chuck relatively to the casing in a tool axis direction during rotation of the drill chuck,
• wherein the vibrator is configured to distance the drill chuck from the casing at a first speed smaller than a second speed for bringing the drill chuck close to the casing,
• wherein the vibrator includes an amplitude adjuster configured to adjust amplitude of reciprocation of the drill chuck,
• wherein the amplitude adjuster allows adjusting the amplitude of the reciprocation to zero so that the drill chuck rotates without the reciprocation, and
• wherein the vibrator includes:
• balls rollingly disposed between the drill chuck and the casing, the balls being disposed away from each other at regular intervals on a same circle;
• and
• a sliding surface formed directly or indirectly on one of the drill chuck and the casing, the balls being contacted to the sliding surface while rolling during the rotation of the drill chuck,
• wherein the sliding surface has equally spaced level differences at which the balls fall simultaneously during normal rotation of the drill chuck, and
• the sliding surface changes smoothly from each level difference toward an adjacent level difference, no level differences at which the balls ascend during the normal rotation of the drill chuck being formed on the sliding surface by the smoothly changing sliding surface.