When the time comes where it is necessary to machine the outside diameter of a work piece and the material cannot be gripped solidly, a work piece cannot be mounted on a mandrel and turned between centers.
A mandrel is a slightly tapered, hardened steel shaft that supports work machined between centers. Mandrels come in three types, the Solid Mandrel, the Expansion Mandrel and the Gang Mandrel.
The solid mandrel is made from a section of hardened steel that has been machined with a taper approximately 0.0005” per inch. Solid Mandrels come in sizes starting at around 1/8” in diameter.
The expansion mandrel allows for work with openings that vary in size. The shaft and sleeve of the mandrel have corresponding tapers and are made of hardened steel. The sleeve is generally slotted so it can expand when force is applied.
The gang mandrel is helpful when many parts of the same configuration must be machined. Several pieces may be placed on the mandrel and separated by spacing collars.