Basic Operation of the Milling Machine - by Glacern Machine Tools

The spindle of a manual milling machine is supported by ball bearings inside of a quill - and the quill is contained within the milling head. A long threaded drawbar is fitted through the hollow center of the spindle shaft, and screws onto the back end of the tool bullet. Tightening the drawbar with the wrench securely holds the tool holder within the tapered spindle socket. Some machines have pneumatic-powered drawbars which allow push-button tool changes.

The head on a manual milling machine has several levers and knobs for various functions. The power knob has forward, reverse and off - and delivers power to the spindle motor. Spindle motors come in single phase and three phase - both of which are readily available. Three phase motors may require phase converters in residential shops but offer benefits such as low vibration and instant spindle reversal.

The spindle brake lever can be used for rapidly stopping the rotating spindle, or to lock the spindle in place when changing tools. Step pulley heads require changing the belt position to adjust spindle speed. Variable speed heads are simpler to operate - only requiring the turning of a small hand wheel.

The high/low gear lever engages the backgear which is necessary when slow spindle speeds down to 70 RPM are required.

Another feature found on many conventional machines is the power quill feed. With the power off, the power downfeed transmission can be engaged. The speed selector gives you a choice of three different feed rates. The power can then be turned on and the feed direction knob can be pushed forward for downwards feeding. Finally, the clutch lever is pulled to the left for quill engagement. The quill stop can be set at a desired depth, and the overload clutch will automatically disengage the quill at the proper depth.