Method and apparatus for making holes in a pipe

摘要

First, a plurality of grooves (3) is formed by operating a grooving punch (2) along the length of each of slits (7) to be made. Then, each slit (7) is formed in the pipe (1) by operating a hole-making punch (5) having the ends formed at an acute angle and recessed from the ends toward the center thereof. In view of the fact that each groove (3) is formed beforehand in the surface of the pipe (1) to be machined and that the corresponding slit is made while moving the cutting positions of the hole-making punch (5) slowly from the ends, a large load is not exerted on the pipe (1) at one time and therefore the pipe (1) is not crushed, burrs are not generated and the cutting chip is removed.