| 摘要 |
A board holder in a printed board boring machine and the holder has upper board holders (33, 41, 45, 52, 56) whose tip surfaces project from the contact surface with a printed board (1) towards a table (6) are disposed outside the contact surface in such a manner as to be movable in axial direction and biasing devices (31, 40, 50, 55) for biasing the upper holder (33, 41, 45, 52, 56) with a force greater than attraction generated in the board holder (18) towards the table (6) are disposed. According to this construction, floating of an upper plate (2) at the time of boring of the printed board (1) can be prevented and boring efficiency can be improved by minimising a wasteful moving distance of a drill (16). |
