High speed spindle with adjustable tool

In a machine tool assembly having a spindle housing, a spindle shaft directed therethrough and a draw bar directed through the spindle shaft for adjusting the position of a cutting tool mounted on the output end of the spindle shaft the improvement comprising:

• first, second and third bearing means supported on said spindle housing for rotatably supporting said spindle shaft;
• said first and second bearing means each including a pair of bearing races located at opposite ends of said spindle housing;
• each of said bearing races having a plurality of roller elements thereon for radially supporting said spindle shaft;
• said third means being including a pair of bearing races located in said housing between said first and second bearing means and nearer said first bearing means than said second bearing means;
• said third bearing means including a plurality of ball bearing elements supported on each of said bearing races for axially supporting said spindle shaft;
• a motor housing directly connected to one end of said spindle housing electric motor means for driving said spindle shaft;
• said electric motor means including stator means supported on said motor housing and rotor means connected to said spindle shaft for rotating said spindle shaft with respect to said spindle housing in a range of 3600 to 7200 revolutions per minute;
• and
• fourth bearing means constituting the sole means for supporting said spindle shaft on said motor housing and said fourth bearing means being located near only one end of said motor housing;
• said first, second and third bearing means maintaining a rigidity at full operating speed of said spindle shaft to maintain the axis thereof within plus or minus 50 millionths of an inch.