Machine tool with rest apparatus and machining method thereof

A machine tool with a rest apparatus comprising:

• a base;
• a spindle head mounted on said base and having a chuck to hold rotatably a first end of a workpiece, said workpiece being a camshaft having a plurality of ground cams and a plurality of journal portions;
• a tail stock mounted on said base so as to face said spindle head and to hold rotatably the other end of said workpiece;
• said spindle head and said tail stock are movable respectively against said base;
• a first steady rest apparatus mounted between said spindle head and said tail stock and fixed to said base un-movably to support a first journal portion of said workpiece during machining in cooperation with the workpiece being held by said spindle head and said tail stock;
• and
• a second steady rest apparatus mounted between said spindle head and said tail stock and movably mounted on said base to support a second journal portion of said workpiece during machining in cooperation with the workpiece being held by said spindle head and said tail stock,
• wherein said first steady rest apparatus is mounted at a side of said tail stock from said second rest apparatus, and
• wherein said second steady rest apparatus includes
• a rest base fixed to said base,
• a body positioned against said rest base at two places along approaching and departing directions from and to said spindle head and said tail stock,
• a first stopper mounted at a side of said spindle head to adjust a first positioned place of said body at a side of said spindle head, and
• a second stopper mounted at a side of said tail stock to adjust a second positioned place of said body at a side of said tail stock.

A positioning method of a machine tool with a rest apparatus including a spindle head and a tail stock holding respectively at least two kinds of workpieces selectively, and a first rest apparatus fixed to a base un-movably to support said workpiece, the positioning method comprising the following steps:

• first positioning step positioning a first workpiece of said two kinds of workpieces along an axial direction of said first workpiece in a way that a first supported position of said first workpiece coincides with said first rest apparatus;
• first holding step holding said first workpiece by said spindle head and said tail stock after at least one of said spindle head and said tail stock is adjusted along said axial direction to hold said first workpiece as positioned;
• second positioning step positioning a second workpiece of said two kinds of workpieces along an axial direction of said second workpiece in a way that the first supported position of said second workpiece coincides with said first rest apparatus;
• and
• second holding step holding said second workpiece by said spindle head and said tail stock after at least one of said spindle head and said tail stock is adjusted to hold said second workpiece as positioned along said axial direction at a different position from a position for said first workpiece.