Vertical Machining Centers (VMC) are versatile CNC mills with a vertically oriented spindle on the Z-Axis over the work table. One of the most common types of CNC machines, they are used in the production of a wide variety of parts. Automatic tool changers allow for the use of different types of tooling while in operation. Some machines are better suited to machining certain materials- Cutting soft metal like aluminum may call for a machining center that features a higher speed (RPM) spindle, while harder metals may be suited for a geared machine running with lower RPM and higher torque, and possibly with a larger spindle taper (CAT 50 or BT 50 instead of CAT 40 or BT 40, for example). Many vertical machining centers are also equipped with 4th Axis and even 5th Axis capability in the form of add on rotary tables and trunnions for positioning purposes. Other common features include probes to increase accuracy and efficiency and through the spindle coolant (TSC) to better handle removal of chips in deep holes than flood coolant.