| 摘要 |
PROBLEM TO BE SOLVED: To form a projection for forming a Braille guide board at the same time by drilling a base plate from the back by using a specific cutting tool. SOLUTION: In drilling a base plate 2 with a drill 1 consisting of a blade 3a of an outer peripheral part with a rake angle and a relief angle, and a blade 3b of a web 4 of which the rake angle is negative, the tip part 3a of the blade aggressively drills the base plate, and the web part 4 does not make advancement in drilling but the drill tip pressurizes the base plate, and just before a hole is bored through, a projection 5 is formed on the surface of the base plate 2 by the pressing force. Therefore, a Braille pattern prepared separately from the drilling conditions (drill advancement) for forming this projection 5 is inputted to a numerically controllable machine tool beforehand for drilling the base plate according to the input data, the projections are sequentially formed and a Braille guide board is manufactured.
|
