Introduction to Fixture Design
1 . Introduction
A fixture is a device for locating, holding and supporting a workpiece during a
manufacturing operation. Fixtures are essential elements of production processes as
they are required in most of the automated manufacturing, inspection, and assembly
Fixtures must correctly locate a workpiece in a given orientation with respect to
a cutting tool or measuring device, or with respect to another component, as for
instance in assembly or welding. Such location must be invariant in the sense that
the devices must clamp and secure the workpiece in that location for the particular
There are many standard workholding devices such as jaw chucks, machine
vises, drill chucks, collets, etc. which are widely used in workshops and are usually
kept in stock for general applications.
Fixtures are normally designed for a definite operation to process a specific
workpiece and are designed and manufactured individually. Jigs are similar to
fixtures, but they not only locate and hold the part but also guide the cutting tools in
drilling and boring operations. These workholding devices are collectively known
as jigs andfixtures. Figure 1.1 shows an example of a fixture commonly used on a
horizontal CNC milling machine.
1.1.1 Elements of Fixtures
Generally, all fixtures consist of the following elements:
A locator is usually a fixed component of a fixture. It is used to establish and
maintain the position of a part in the fixture by constraining the movement of the
part. For workpieces of greater variability in shapes and surface conditions, a
locator can also be adjustable.
An Advanced Treatise on Fixture Design and Planning
A clamp is a force-actuating mechanism of a fixture. The forces exerted by the
clamps hold a part securely in the fixture against all other external forces.
A support is a fixed or adjustable element of a fixture. When severe part
displacement/deflection is expecte