Patent ID: 7147595

Claim:
A machine tool including: a base having a front portion and a rear portion; a worktable unit on said front portion of said base adapted for mounting a workpiece thereon; a support post unit including a post member disposed fixedly on said rear portion of said base, two vertical Z-axis sliding rails disposed fixedly on said post member and parallel to each other, a vertical first threaded rod journalled in a middle portion of said post member, a first driving member for driving said first threaded rod to rotate in said post member, and a counterweight, said first threaded rod having a first threaded portion of a first hand thread and a second threaded portion of an opposite hand thread; a first horizontal rail unit including a first sliding seat driven by said first threaded rod to move along said Z-axis sliding rails, two horizontal X-axis sliding rails disposed fixedly on said first sliding seat and parallel to each other, a second threaded rod journalled on a middle portion of said first sliding seat, and a second driving member for driving said second threaded rod to rotate on said first sliding seat; a second horizontal rail unit including a second sliding seat driven by said second threaded rod to move along said X-axis sliding rails, two horizontal Y-axis sliding rails disposed fixedly on said second sliding seat and parallel to each other, a third threaded rod journalled on a middle portion of said second sliding seat, and a third driving member for driving said third threaded rod to rotate on said second sliding seat, said Y-axis sliding rails being perpendicular to said X-axis sliding rails; and a spindle head unit including a spindle seat driven by said third threaded rod to move along said Y-axis sliding rails, and a driving motor disposed on an upper end of said spindle seat; and wherein said first sliding seat is mounted threadedly on one of said first and second threaded portions, and wherein said counterweight is mounted on the other of said first and second threaded portions.