| 摘要 |
PURPOSE:To break a collar with a predetermined force to prevent a machine and a drill from breakaging by providing a notch between a main body and a collar while a drill holder is divided into three and the free end thereof can be opened and closed. CONSTITUTION:A drill holder 3 is mounted on a base 1 and provided with a tapered hole 7 flaring upward, a projection 8 on an end of this tapered hole and a large diameter hole 9. Also, the holder 6 is divided into three circumferentially so that the free end is liable to expand. Further, a main body 4 is provided with a small diameter hole 11 and a notch 10 between the hole 11 and a collar 5. Also, a collar 15 fitted in the hole 9 is press fitted onto a drill 14. Thus, when the drill 14 onto which the collar is press fitted is forced into the holder 3 and further forced therin until a spring is completely compressed, the collar 5 is broken down to drop the holder and prevent a machine and the drill from breakage. |
