Machine tool having a C-shaped frame

A machine tool comprising:

• a machine frame including a base seat, and a hollow upright mounting frame disposed fixedly on said base seat;
• a worktable device including
• a worktable-carrying member movable vertically on said machine frame and including a housing, and a supporting block connected fixedly to said housing,
• a lower driving unit including a guiding unit for guiding vertical movement of said worktable-carrying member on said machine frame, a threaded seat disposed fixedly on said base seat and formed with a threaded hole, a lower vertical threaded rod engaging said threaded hole in said threaded seat, and a driven gear connected fixedly to said lower vertical threaded rod, said supporting block being sleeved rotatably on and movable synchronously with said lower vertical threaded rod,
• an operating unit including a first driving rod journalled on and extending into said housing of said worktable-carrying member, a first driving gear connected fixedly to said first driving rod and meshing with said driven gear, and a swing lever connected to said first driving rod and operable to rotate said first driving rod, and
• a worktable attached to said housing of said worktable-carrying member;
• a spindle unit including an upper vertical threaded rod journalled on said upright mounting frame of said machine frame, an upper driving unit operable to rotate said upper vertical threaded rod, a spindle seat connected to said upper vertical threaded rod such that rotation of said upper vertical threaded rod results in vertical movement of said spindle seat, a main spindle journalled on said spindle seat, and a motor for rotating said main spindle;
• and
• a balancing unit including an upright guiding rod disposed fixedly in said upright mounting frame of said machine frame, a counterweight block sleeved movably on said guiding rod, a guiding wheel assembly disposed on a top end portion of said upright mounting frame, and a driving belt extending around said guiding wheel assembly and having two ends fastened respectively to said spindle seat and said counterweight block.