What is a Mandrel?

Mandrel is a term with three widely accepted meanings — a metal shaping form, the workpiece clamp on a lathe, and a post or shaft used to secure and support various power tool attachments. When describing a metal shaping tool, the term refers to solid or hollow metal forms that bend or distort materials ranging from sheet metal to blown glass into a desired shape. When applied to lathes, the term refers to a purpose built clamp used to secure a specific workpiece in the lathe chuck for machining. Power tool mandrels typically consist of solid metal posts with machined shoulders and locking nuts designed to secure sanding or grinding discs and buffing pads in drills and other power driven devices.

Metal shaping mandrels have been used for centuries as jigs or forms to shape metal or even blown glass items. These devices are typically made to shape a specific item or to impart a specific profile in several different workpieces. For example, a pipe bending mandrel will be machined to impart a bend of a set deflection into pipes of a specific diameter. Several mandrels will be necessary for the same task with different bend angles or pipe diameters. A mandrel designed to impart a flared or bell shape into the end of tubes will have a cone shaped end profile which can be used on a variety of tube sizes.

Shaping mandrels may be designed to be clamped into place, with the workpiece manipulated around them by machines or by hand, such as those used to produce decorative wrought iron work. Others, such as the previously mentioned flare mandrel, are inserted into or against a rotating workpiece to form it. Industries such as vehicle exhaust system manufacturers make extensive use of mandrels to form complex pipe runs.

Mandrels used as lathe clamp inserts are generally designed and built for a specific workpiece, typically those with a shape unsuitable for clamping in a standard chuck. Due to its limited application, the lathe mandrel is often used once and discarded. The power tool mandrel secures accessories such as grinding and sanding discs, polishing mops, and even lawn tractor blades in a machine or tool drive. It is often no more than a simple steel rod fitted with an accessory-specific locking attachment and designed for use in a range of power tool chucks. Others intended for use in a specific machine may be more complex with machined splines, profiles, or keys suited to a particular drive mechanism.