Machining heads and multiple spindle heads are specialized tool holders that mount on machine tool spindles. Multi-spindle heads carry multiple tools at the same time for performing simultaneous machining operations. Most machining and multiple spindle heads cannot be shared, except in the case of identical-hole patterns in a family of parts. Machining and multiple spindle heads are designed for use with most drilling machinery and can double or triple drilling operations by simultaneously drilling, countersinking, reaming or tapping two or more holes in one operation.

Machining heads and multiple spindle head systems provide high-speed hole making, drilling anywhere from a handful of holes to several thousand holes at a time. In milling systems, the machining head allows the operator to mount any size cutting tool, as long as the tool fits the tool holder. A multi-spindle head is a drill unit attachment with multiple drill or tap spindles in which the spindles are gear-driven from the drill unit spindle. Machining and multiple spindle heads allow drilling or tapping of multiple holes in closer proximity than is possible with drill units alone.

A multi-spindle machine creates parts quickly due to its design, which allows more than one cutting operation to be performed at a time. Because there are many variations of machining and multiple spindle heads, each spindle on a multi-spindle machine is intersected by two independent axes of tool movement. A multiple spindle screw machine is an automatic bar machine that contains more than one spindle, usually 4, 6, or 8. Multiple spindles allow multiple tools to cut multiple workpieces simultaneously. A right angle drill chuck is an adapter for hand drills, which attaches to a drill chuck and drives another chuck at 90 degrees. A right angle drill head allows an operator to drill in tight corners or at awkward angles.