Workholders

Description

Workholders are holding or clamping devices designed to support, hold and locate the workpiece for processing or for any machining operation and also to resist any force applied during operation. Holding force to a workholder can be applied hydraulically, pneumatically or electrically.

Types 

Workholders can be widely classified as follows:

• Fixtures - Fixtures to support hold and locate the workpiece during machining, joining, or assembly operation. Fixtures do not steer the cutting tool, but only provide a means of reference and aligns the cutting tool with the workpiece.
• Jigs - Jigs not only support, hold and locate the workpiece, but also steer the cutting tool fully through its cutting cycle. Drill jigs are the most common type of jig. They are used for drilling, tapping, reaming, countersinking, counterboring, chamfering, and spot-lacing.

Fixtures can withstand higher tool forces and stresses than jigs and are also more securely clamped on to the machine.

Design characteristics of a good workholder

The design or selection of a workholder is governed by many factors, the first being the physical characteristics of the workpiece.

• Workholders must position or locate a workpiece in a definite relation to the cutting tool, and must persist with the holding function and withstand cutting forces while maintaining a precise location
• Workholders must be strong enough to support the workpiece without deflection or deviation
• Good workholders maximize the number of operations performed in one go without removing and refixing the workpiece after each operation
• Workholders are designed in such a manner to prevent incorrect clamping and placements

Application

• Workholders are widely used in the manufacturing industries and in metalworking operations
• Workholders are also used for assembly, welding, and inspection operations