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Workholding

Fixture Body Construction 200

This class discusses common tool body forms and the material and cost considerations associated with their construction.

Difficulty Intermediate
Format Online
Number of Lessons 12
Language English

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Objectives
The Role of a Fixture Body
Strength
The Weight Factor
Reducing Costs
Cast Fixture Bodies
Welded Fixture Bodies
Built-Up Fixture Bodies
Precision Ground Materials
Cast Brackets and Structural Sections
Selecting the Fixture Body Material
Summary

Define the role of a fixture body.
Describe the importance of fixture body strength.
Describe the importance of fixture body weight.
Describe ways to reduce costs of workholding devices.
Describe cast fixture bodies.
Describe welded fixture bodies.
Describe built-up fixture bodies.
Describe precision ground materials.
Describe cast brackets.
Describe structural sections.
Distinguish among the characteristics of different fixture body materials.

Vocabulary Term

Definition

6061 aluminum

A wrought aluminum alloy containing small percentages of silicon, copper, magnesium, and chromium.

aluminum

A silvery white metal that is soft, light, and has a high strength-to-weight ratio.

aluminum tooling plates

A pre-formed tooling material made of aluminum that is ground to highly accurate dimensions.

brace

A device that steadies or supports other components.

built-up fixture bodies

A fixture body created by adding components to a standard tooling plate. The pieces are assembled with dowels and pins and are used for precision machining operations, inspection, and some assembly tools.

cast aluminum

Aluminum that is fabricated by allowing it to cool in a mold.

cast bracket

Brackets available in cast iron and cast aluminum in lengths of 25 in. (63.5 cm). They are designed as structural elements of a workholding device.

cast fixture bodies

A fixture body that is produced as a casting. Cast fixture bodies provide excellent dimensional stability and vibration dampening. They are used for permanent workholding devices that will not be drastically changed.

cast iron

A type of steel that is formed into its final shape from the molten state. It contains at least two percent carbon, as well as percentages of silicon and sulfur.

chuck

A device that holds a workpiece in place as it rotates. The chuck commonly has three or four jaws that can be adjusted to fit various sizes.

clamping

In workholding, the operation which holds the workpiece against the locators. Clamping resists secondary tool forces.

collet

A slitted device that holds a workpiece in place as it rotates. A collet has a hole through which the workpiece passes, and it is designed to hold specific dimensions.

doweled

Held together by small metal rods called dowels.

fixture

A workholding device used on machine tools to position and hold a part during various machining operations.

fixture body

The foundation of the workholding device. Various components, such as locators and clamps, are fastened to the fixture body to create a custom workholding device.

inertia

The tendency of a body to move in a straight line or remain at rest. On a machining center, it is very difficult to overcome the inertia of large workpieces.

locating

In workholding, the process of positioning the workpiece in a designated location. Locating is also used to describe a step in the process that corresponds to positioning the workpiece in the horizontal plane.

mechanical fastener

A fastener that is held in place by force. A screw or bolt is a mechanical fastener.

precision ground materials

Stock that is finished by very accurate grinding.

rib

A structural component that provides shape and support.

steel

A metal consisting of iron and carbon, usuallly with small amounts of manganese, phosphorus, sulfur, and silicon as well.

structural sections

A pre-formed tooling material made of steel, aluminum, or magnesium that is available in standard shapes and is used to save weight.

subassemblies

Semi-assembled pieces that will be attached to a larger piece in another assembly operation.

supporting

The process of locating from underneath the workpiece. Supports generally restrict motion down along the Z-axis.

tool steel

A type of steel designed with high wear resistance, toughness, and strength.

vise

A workholding device with one fixed jaw and one moveable jaw. Vises are often used to hold simple rectangular or cubic workpieces on a mill or machining center.

web

A structural component providing support through its web-like pattern of sections.

welded fixture bodies

A fixture body that is created by welding pieces together. They are used for roughing rather than finishing operations. Welded fixture bodies run the risk of heat distortion during welding.