High-speed drilling or milling spindle

A high-speed rotary spindle of a drilling or milling machine tool, comprising:

• a stator fixedly attached to a stationary portion of said machine tool and having first drive means;
• a rotor adapted to be rotated about an axis of rotation relative to said stator at high revolutional speeds, said rotor having second drive means cooperating with said first drive means on said stator for effecting rotation of said rotor, said rotor, further, having chucking means for chucking a milling or drilling tool therein;
• a first roller bearing arranged between said rotor and said stator adjacent said chucking means, said first roller bearing having a very small thrust angle for making said first roller bearing acting essentially as a radial bearing during operation of said spindle;
• a second roller bearing arranged between said rotor and said stator distant from said chucking means, said second roller bearing having a very small thrust angle for making said second roller bearing acting essentially as a radial bearing during operation of said spindle;
• said first and second bearings allowing limited axial movement of said spindle and providing substantially all of the radial support for said spindle;
• a magnetic bearing being arranged between said rotor and said stator, said magnetic bearing being adjustable with respect to an axial bearing force;
• detector means for detecting axial force (F.sub.a) exerted on said tool;
• and
• control means for adjusting said axial bearing force as a function of the detected axial force (F.sub.a).