an auxiliary - function hydraulic system is provided for a computerized numerical control machine tooling unit . hydraulic power is provided for locking collet or chuck to an open or closed position and providing an affirmative collet - open and / or collet - closed signal to communicate the collet position to the host computer . the tailstock can be brought gently forward to contact a workpiece and can be returned rapidly to the home position , with a break - away pressure feature being employed to overcome initial static friction . a pressure switch indicates that the tailstock is in position against the workpiece . a spindle brake applies braking to the spindle to stop the same from high speed either on command or in the event of system failure . in the latter case , braking occurs prior to loss of pressure to the collet closer cylinder . also , a turret clamp locks and unlocks a tool changer turret .