| 摘要 |
PROBLEM TO BE SOLVED: To drill a neat hole in a film by flatly spreading the film prior to drilling of the film, placing the blade edge of a trepanning bar to the flatly spread film and drilling the film. SOLUTION: A trepanning bar 1 axially moves a revolving shaft 19 which is freely attachably and detachably inserted thereto. When the revolving shaft is moved forward in the axial direction, the front end of the trepanning bar 1 projects by the prescribed amount from the front end of an external cylinder 2. When the shaft is retreated backward in the axial direction, the front end of the trepanning bar 1 retreats into the external cylinder 2 from the front end of the external cylinder 2. When the front end of the trepanning bar 1 protrudes from the front end of the external cylinder 2, the trepanning bar 1 is rotated to drill the film of a crystalline body. The inner peripheral wall of the external cylinder 2 and the outer peripheral wall of the trepanning bar 1 are airtightly and slidably formed. The external cylinder 2 is composed of double pipes by a coaxial external cylinder 3 having a desired spacing. The film is flatly spread on the front surface of the external cylinder 2 by sucking air from the front and of the double pipes through the gap G of the double pipes. |
