PURPOSE: To perform the boring with quite high accuracy by performing the reciprocal motion of a drill through the cam mechanism of an inclined face.

CONSTITUTION: In a boring machine, the rotation of a motor 1 is transmitted to a shaft 2 thus to drive two gears 5, 6 where the gears 3, 4 having different number of teeth are provided on same axis with different rotation. The shafts 8 and 7 are collided to form an inclined face 10 at this portion. The drill 19 is fixed by a collet chuck 20 to the shaft 8 and rotated by the gear 6 while projected from the arm 18 through a cam of the inclined face 10. Said projection is adjusted through the rotation of an adjuster 16 thus to perform the boring of desired depth accurately.