Power milling machine

A milling apparatus comprising:

• a housing;
• a drive shaft extending along and rotatable about an axis in the housing and having an axially front end, an axially rear end, an axially extending central passage open at the front end, and a transversely throughgoing and axially elongated slot;
• an axially compressible and radially expansible washer stack on the front end of the drive shaft;
• a tool having a central hole with a diameter greater than a diameter of the washer stack when the washer stack is axially not compressed and radially expanded;
• a bolt projecting radially in the slot through the shaft and limitedly axially displaceable in the shaft;
• an actuator element shiftable axially in the passage and having a front end and an opposite rear end fixed in the bolt;
• clamping means on the front end of the drive shaft and connected to the actuator element for axially compressing and radially expanding the stack and thereby locking the tool to the drive shaft;
• a spring assembly braced axially forward against the housing and axially rearward against the bolt and urging the bolt and clamping means axially rearward to radially expand the washer stack and lock the tool on the drive shaft;
• a piston axially displaceable on the drive shaft in the housing and bearing axially forward on the bolt;
• and
• means for pressurizing a rear face of the piston and pressing the piston forward against the bolt to compress the spring assembly and relax the washer stack so that the tool can be taken on and off the drive shaft, whereby depressurization at the rear face allows the spring assembly to rearwardly shift the bolt and thereby lock the washer stack to the tool.