A mandrel is one of the following:

• an object used to shape machined work.
• a tool component that grips or clamps materials to be machined.
• a tool component that can be used to grip other moving tool components.

Variants

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. Exhaust pipes in 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 clamp

Clamp (tool)

A clamp is a fastening device to hold or secure objects tightly together to prevent movement or separation through the application of inward pressure...

 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 beautiful patterns, and irregularly-shaped objects can be given a cylindrical or round shape. There are several types of mandrels used with lathes. An expanding mandrel is slightly tapered with a tapered wedge that will expand to hold the item. 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 nothing 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.

The third type of mandrel discussed here is that which is used to hold circular saw blades, buffing wheels (used for polishing), and sanding discs onto drill

Drill

A drill or drill motor is a tool fitted with a cutting tool attachment or driving tool attachment, usually a drill bit or driver bit, used for drilling holes in various materials or fastening various materials together with the use of fasteners. The attachment is gripped by a chuck at one end of...

s, circular saws, and similar power tools. A mandrel of this type generally consists of a cylinder, threaded on one end, with a washer

Washer (hardware)

A washer is a thin plate with a hole that is normally used to distribute the load of a threaded fastener, such as a screw or nut. Other uses are as a spacer, spring , wear pad, preload indicating device, locking device, and to reduce vibration...

 brazed onto the threaded end and an accompanying screw

Screw

A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...

 and second washer which are used to clamp the circular saw blade, sanding media, or other rotary tool onto the mandrel.

While most mandrels are driven by direct connection to an electric motor

Electric motor

An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...

 or engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

, other mandrels are driven by attachment to a bearing-supported, pulley

Pulley

A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present...

-driven shaft.

Uses

In fiber optics, an optical fiber is often wrapped

Mandrel wrapping

In multimode fiber optics, mandrel wrapping is a technique used to preferentially attenuate high-order mode power of a propagating optical signal...

 around a mandrel to alter the light traveling in the fiber.

Mandrels are also used in industrial composite fabrication such as in filament winding

Filament winding

Filament winding is a fabrication technique for manufacturing composite material, usually in the form of cylindrical structures. The process involves winding filaments under varying amounts of tension over a male mould or mandrel. The mandrel rotates while a carriage moves horizontally, laying...

. During the manufacturing process, resin-impregnated filaments are wound around a mandrel to create a composite material

Composite material

Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...

 structure or part. The structure is cured and the mandrel is removed. One problem with this type of process is that the mandrel can be very difficult to remove once the part has been cured. As a result, engineers have created a new type of mandrel that has the ability to change shape and be easily extracted. When heated above a certain temperature, the mandrel becomes elastic and can be manipulated into the desired shape and then cooled to become rigid again in the new shape. It can then be used in the filament winding process. Once the composite part is cured, the mandrel can be reheated until elastic and easily removed from the cured part. These types of mandrels can be used repeatedly.

In the production of steel core used for flexible drives, the centre wire upon which the subsequent layers are wound is referred to as a Mandrel. This 'centre wire' may itself be composed of either a single wire or layers depending on the sizing of the finished product.

History

Mandrels are not recent inventions. Metal machining utilizing the spinning

Metal spinning

Metal spinning, also known as spin forming or spinning, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe....

 process has been recorded as far back as ancient Egyptian times. In metal spinning, a wood or metal spinning mandrel is used, the form of which corresponds with the internal contour of the part to be produced. This method securely clamps the raw material and allows for accurate machining into the desired final form. Since the material is clamped internally, there is no interference to the operator from the lathe/mandrel assembly during production.

Also, the traversing mandrel was introduced around the year 1700 AD, and consisted of designing a lathe mandrel that would be able to slide axially in its bearing

Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can...

s under the control of the operator, so that components having short lengths of thread

Screw thread

A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...

 could be produced, such as screws. The traversing mandrel was primarily employed by clockmakers and ornamental turners during this era. Eventually this device was superseded by a mandrel-driven device called a leadscrew

Leadscrew

A leadscrew , also known as a power screw or translation screw, is a screw designed to translate turning motion into linear motion...

, which utilizes a train of gear

Gear

A gear is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine....

s that can be altered as required for the turning application.

External links

• Historical pictures of mandrels, lathes and leadscrews: http://www.historicgames.com/lathes/special.html
• http://www.turners.org/Articles/lathehistory.html