Mandrel

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Old shop-made mandrel for turning hollow objects on an engine lathe Mandrel3.jpg
Old shop-made mandrel for turning hollow objects on an engine lathe

A mandrel, mandril, or arbor is a gently tapered cylinder against which material can be forged or shaped (e.g., a ring mandrel used by jewelers 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 identical thread is screwed onto the mandrel.

Contents

On a lathe, mandrels are commonly mounted between centres and driven by a lathe dog (typically the flanged or tapered mandrels), but may also be gripped in a chuck (typically the threaded mandrels, where the outer face of work is to be machined. Threaded mandrels may also be mounted between centres.

In addition to lathes, arbors are used to hold buffing wheels, circular saws, and sanding discs. Typically, these mandrels consist of a cylinder that is threaded on one end. There are many different types of mandrels for specialized applications. Examples include live chuck mandrels, live bull ring mandrels, and dead bull ring mandrels.

Variants

Rotary tool mandrel with an accompanying grinding wheel Mandrel 001.jpg
Rotary tool mandrel with an accompanying grinding wheel

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. A type of mandrel is also used in making reeds for double reed instruments such as the bassoon or oboe. [1]

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 aesthetic 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 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 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.

Uses

Pulley-driven mandrel used to hold lawn tractor cutting blades Mandrel 002.jpg
Pulley-driven mandrel used to hold lawn tractor cutting blades

Mandrels are also used in industrial composite fabrication such as in filament winding. During the manufacturing process, resin-impregnated filaments are wound around a mandrel to create a composite material 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. [2] 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. [3]

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.

A hole saw usually attaches to a mandrel, the latter being basically a drill bit with threads to secure the saw.

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.

The traversing mandrel was introduced[ where? ] around 1700, and instantiated the design of a lathe mandrel 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 the device was superseded by a mandrel-driven device called a leadscrew , which uses a train of gears that can be altered as required for the turning application.

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Collet

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Screw thread A helical structure used to convert between rotational and linear movement or force

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Chuck (engineering) Clamp used to hold an object with radial symmetry, especially a cylinder

A chuck is a specialized type of clamp used to hold an object with radial symmetry, especially a cylinder. In a drill or a mill, a chuck holds the rotating tool; in a lathe, it holds the rotating workpiece.

Machine taper

A machine taper is a system for securing cutting tools or toolholders in the spindle of a machine tool or power tool. A male member of conical form fits into the female socket, which has a matching taper of equal angle.

Grinding wheel

A grinding wheel is a wheel used for grinding. Grinding wheels are composed of abrasive compounds and are used for various grinding and abrasive machining operations. Such wheels are used in grinding machines.

Turning Machining process

Turning is a machining process in which a cutting tool, typically a non-rotary tool bit, describes a helix toolpath by moving more or less linearly while the workpiece rotates.

Vise Device to secure an object to be worked on

A vice or vise is a mechanical apparatus used to secure an object to allow work to be performed on it. Vises have two parallel jaws, one fixed and the other movable, threaded in and out by a screw and lever.

Lathe center

A lathe center, often shortened to center, is a tool that has been ground to a point to accurately position a workpiece on an axis. They usually have an included angle of 60°, but in heavy machining situations an angle of 75° is used.

Metal lathe

A metal lathe or metalworking lathe is a large class of lathes designed for precisely machining relatively hard materials. They were originally designed to machine metals; however, with the advent of plastics and other materials, and with their inherent versatility, they are used in a wide range of applications, and a broad range of materials. In machining jargon, where the larger context is already understood, they are usually simply called lathes, or else referred to by more-specific subtype names. These rigid machine tools remove material from a rotating workpiece via the movements of various cutting tools, such as tool bits and drill bits.

Rotary table

A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed axis. Some rotary tables allow the use of index plates for indexing operations, and some can also be fitted with dividing plates that enable regular work positioning at divisions for which indexing plates are not available. A rotary fixture used in this fashion is more appropriately called a dividing head.

Marman clamp

A Marman clamp is a type of heavy-duty band clamp; it allows two cylindrical objects to be clamped together end-to-end with a ring clamp. It is sometimes also known as a "Marman ring". It consists of a circular strap with an interior V-shaped groove. Tension is applied to the strap with a threaded bolt and nuts connecting to the ends of the strap. As the tension increases, the V-groove wedges over flanges on the circular parts to be assembled, providing the force that holds the ends of the two cylinders together. The Marman clamp is an alternative to a bolted flange connection which would be heavier and require more labor to connect. Another variety uses a flat strap, used where systems carry low pressure or to hold a cylindrical object in position.

Lathe faceplate Workholding accessory

A lathe faceplate is a basic workholding accessory for a wood or metal turning lathe. It is a circular metal plate which fixes to the end of the lathe spindle. The workpiece is then clamped to the faceplate, typically using t-nuts in slots in the faceplate, or less commonly threaded holes in the faceplate itself.

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Screw-cutting lathe

A screw-cutting lathe is a machine capable of cutting very accurate screw threads via single-point screw-cutting, which is the process of guiding the linear motion of the tool bit in a precisely known ratio to the rotating motion of the workpiece. This is accomplished by gearing the leadscrew to the spindle with a certain gear ratio for each thread pitch. Every degree of spindle rotation is matched by a certain distance of linear tool travel, depending on the desired thread pitch.

In mechanical engineering, a key is a machine element used to connect a rotating machine element to a shaft. The key prevents relative rotation between the two parts and may enable torque transmission. For a key to function, the shaft and rotating machine element must have a keyway and a keyseat, which is a slot and pocket in which the key fits. The whole system is called a keyed joint. A keyed joint may allow relative axial movement between the parts.

Screw Type of fastener characterized by a thread wrapped around a cylinder core

A screw and a bolt are similar types of fastener typically made of metal and characterized by a helical ridge, called a male thread. Screws and bolts are used to fasten materials by the engagement of the screw thread with a similar female thread in the matching part.

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Bolt (fastener)

A bolt is a form of threaded fastener with an external male thread requiring a matching pre-formed female thread such as a nut. Bolts are very closely related to screws.

References

  1. "Reed Making: how I do it, part 1. | Trent Jacobs, bassoonist". Tjbassoon.com. 2011-02-13. Retrieved 2019-10-01.
  2. "Smart Mandrels". Cornerstone Research Group. Retrieved 2009-09-30.
  3. "The Smart Mandrels Trapped Tooling Process". Cornerstone Research Group. Retrieved 2009-09-30.