Spindle (tool)


In machine tools, a spindle is a rotating axis of the machine, which often has a shaft at its heart. The shaft itself is called a spindle, but also, in shop-floor practice, the word often is used metonymically to refer to the entire rotary unit, including not only the shaft itself, but its bearings and anything attached to it.
A machine tool may have several spindles, such as the headstock and tailstock spindles on a bench lathe. The main spindle is usually the biggest one. References to "the spindle" without further qualification imply the main spindle. Some machine tools that specialize in high-volume mass production have a group of 4, 6, or even more main spindles. These are called multispindle machines. For example, gang drills and many screw machines are multispindle machines. Although a bench lathe has more than one spindle, it is not called a multispindle machine; it has one main spindle.
Examples of spindles include

High speed spindle

High speed spindles are used strictly in machines, like CNC mills, designed for metal work. There are two types of high speed spindles, each with different designs:

Belt-driven spindle

Consisting of spindle and bearing shafts held within the spindle housing, the belt-driven spindle is powered by an external motor connected via a belt-pulley system.
A main component of this spindle is the motor, stored internally.
Both types, the belt-driven and the integral motor spindles, have advantages and disadvantages according to their design. Which one is more desirable depends on the purpose of the machine and product being produced.