mandrel

thumb|Old shop-made mandrel for turning hollow objects on an engine lathe

A mandrel, mandril or arbor is a tapered tool against which material can be forged, pressed, stretched or shaped (e.g., a ring mandrel – also called a triblet – used by jewellers to increase the diameter of a wedding ring), or a flanged or tapered or threaded bar that grips a workpiece to be machined in a lathe. A flanged mandrel is a parallel bar of a specific diameter with an integral flange towards one end, and threaded at the opposite end. Work is gripped between the flange and a nut on the thread. A tapered mandrel (often called a plain mandrel) has a taper of approximately 0.005 inches per foot and is designed to hold work by being driven into an accurate hole on the work, gripping the work by friction. A threaded mandrel may have a male or female thread, and work which has an opposing thread is screwed onto the mandrel.