mandrel

A mandrel (pronounced IPA: /ˈmændrɨl/, and also spelled mandril; in American English also called an arbor) is either an object used to shape machined work; a tool component that grips or clamps materials to be machined; or a tool component that can be used to grip other moving tool components.

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.

Old shop made mandrel for turning hollow objects on an engine lathe.

Another type of mandrel is the clamp 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 drills, circular saws, and similar power tools. A mandrel of this type generally consists of a cylinder, threaded on one end, with a washer brazed onto the threaded end and an accompanying screw 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 or engine, other mandrels are driven by attachment to a bearing-supported, pulley-driven shaft.

In fiber optics, an optical fiber is often wrapped around a mandrel to alter the light traveling in the fiber.

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 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 bearings under the control of the operator, so that components having short lengths of 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, which utilizes a train of gears that can be altered as required for the turning application.

Images

Rotary tool mandrel with an accompanying grinding wheel.

Pulley-driven mandrel used to hold lawn tractor cutting blades.

External links

Historical pictures of mandrels, lathes and leadscrews: http://www.historicgames.com/lathes/special.html

References

The Ornamental Turning Center: http://www.turners.org/Articles/lathehistory.html
Verschoyle Patent Mandrel

See also

• Operation Mandrel

Metalworking
Machine tooling	Angle plate • Chuck • Collet • Fixture • Indexing head • Lathe center • Machine taper • Magnetic base • Mandrel • Rotary table • Wiggler
Metalworking topics	Casting • CNC • Cutting tools • Drilling and threading • Fabrication • Finishing • Grinding • Jewellery • Lathe • Machining • Machine tooling • Measuring • Metalworking • Hand tools • Metallurgy • Milling • Occupations • Press tools • Smithing • Terminology • Welding

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