| 摘要 |
PROBLEM TO BE SOLVED: To provide a core bit which is a core bit for anchor for perforating a hole for anchor and wherein a core is hardly broken during perforation and when the core is broken, it is easily taken out from a tube. SOLUTION: In a core bit with a diameter of at most 50 mm for a portable perforation device, a thick-walled part 1a whose outer peripheral face is approximately the same face as the outer peripheral face of a chip 2 is provided on one end of the tube 1. Parts except one end of the tube are constituted of a thin-walled part 1b and the outer diameter of the thin-walled part 1b is smaller than the thick-walled part 1a and the inner diameter is the same diameter as the thick-walled part 1a. When the sum of the length in the axial direction of the core bit of the thick-walled part 1a and the chip 2 is h and the total length of the core bit is L and the outer diameter of the thick-walled part 1a is d, the thick-walled part a is formed so as to be 2L/ d<=h<=L/2d. In addition, a spiral channel 1c is provided on the thick-walled part 1a and this channel is formed by providing an angle of at least 45 degree to at most 85 degree to the axis of the tube 1. In addition, the inner peripheral face of the chip 2 is projected more to the inside in the radial direction than the inner peripheral face of the tube 1 and the step difference between the chip 1 and the tube 2 is at least 0.5 mm and at most 1.0 mm.
|
