Mandrel

A mandrel (/ˈmændrᵻl/; also mandril or arbor) is one of the following:

An example of one type of mandrel is a shaped bar of metal inserted in, or next to, an item to be machined or bent in a certain pattern, e.g. in tube drawing. Exhaust pipes for automobiles are frequently bent using a mandrel during manufacture. The mandrel allows the exhaust pipes to be bent into smooth curves without undesirable creasing, kinking, or collapsing. Molten glass may be shaped in this way as well. Another example of this type of mandrel is found in jewelry manufacturing, where ring and bracelet mandrels are used to shape metal into a desired size and shape, using a tiny hammer to beat the metal against the mandrel.

Another type of mandrel is the chuck that a lathe uses to hold pieces of wood, metal or plastic to be machined as they are turned. In this way, rods can be threaded, furniture legs are turned to have æsthetic patterns, and irregularly-shaped objects can be given a round shape. There are several types of mandrels used with lathes. Original expanding mandrels have a slightly tapered wedge that will expand to hold the item.

The Xpandrel method of expanding mandrels was introduced in the mid-1990s. This method uses basic mechanical principles of deformation to achieve expansion of a non-tapered mandrel. Using various methods of actuation, the body of the mandrel is deformed below the limit of elasticity to provide repeatable holding forces without typical deformation caused by pressing on tapered mandrels. Other commercial mandrels are very slightly tapered, and the hollow object slides down the taper until it "sticks". The shop-made mandrel shown in the photo is designed to clamp a hollow tube or gear between the two tapered plugs. There is little about such a mandrel that can't be made right on the lathe on which it is to be used, so it is not uncommon for machinists to make a mandrel to hold a particular item and then set the mandrel aside hoping to use it again some day. Mandrels of this type are usually set in the lathe on centers and turned with a lathe dog.

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