A tool holder is a device that safely provides a critical interface between the cutting tool and the spindle of the CNC machine. The cutting tool is mounted into the holder and is tightened so it does not move or vibrate during machining; providing the stability you need to ensure precision cuts every time.

Collet Pocket, Collet, & Nut pocket collet Pull Studs (also called retention knobs) are extremely important because they keep the toolholder in the spindle.

A spindle is a rotating shaft with a fixture for holding a tool (in the case of a milling, grinding, or drilling spindle) or a workpiece (in the case of a turning spindle). The spindle shaft serves as a support, a positioner, and a rotary drive for the tool or workpiece.

Milling spindles, as the main spindle of tool machines, are responsible for machine cutting a workpiece. Various tool interfaces are used to accommodate the milling tool, such as, for example, HSK (hollow shaft taper) or SK (quick-release taper).