SQUARE PIERCING DRILL BIT

摘要

PROBLEM TO BE SOLVED: To generate a square hole by using a rotary drill device.SOLUTION: A rotary arbor 2 having a drill 8 and an umbrella gear 4 is attached to an electric drill 1. At the same time to rotation of the rotary arbor 2, a plane trunk 3 rotates around a non-rotary shaft 5 by the umbrella gear 4. The non-rotary shaft 5 does not fall because of a falling prevention receptor 7 attached to the arbor 2. Both sides of a round hole generated by rotation of the drill 8 are cut by the plane trunk 3 for forming a square hole. Uncut parts remaining on front and rear positions are cut by rotating the plane trunk 3 by 90 degree and inserting a drill bit again.