| 摘要 |
PROBLEM TO BE SOLVED: To improve the positional accuracy in x-y direction and the positioned accuracy in z direction by arranging a rotary shaft of a drill bit in such a way that it coincides with a shaft of a drill holder and letting the drill holder perform the linear movement in the axial direction along a guide through a cross roller bearing. SOLUTION: Four first right-angled grooves in which two planes 823, 824;827, 828;831, 832;835, 836 form a 90 deg. angle respectively, are precision-machined on an outer face of a drill holder 8. All bisectors of an angle of 90 deg. formed by the first right-angled grooves pass a symmetrical axis P of the drill holder 8 and are arranged point-symmetrically at an interval of 90 deg. around the symmetrical axis P. After the assembly, since the first and second right-angled grooves oppose respectively to form a space like square pole and a cross roller bearing is arranged in this space, the assembled common axes coincide with each other naturally. Consequently, it is possible to keep high positional accuracy in x-y direction in hole drilling at all times.
|
