Work Supports and Fixture Jacks Information
Work supports and fixture jacks are fixturing components used to locate and support workpieces during 
machining operations. Workpiece support is critical to producing precision, chatter-free parts. When combined with proper clamping, work supports and fixture jacks provide workpiece rigidity for reduced part deflection and vibration during the machining process. Proper care must be used when clamping workpieces to avoid deflection and hold the part securely. Clamps should be oriented directly over a supported surface for proper loading.
Work supports contain a spring-actuated or fluid-actuated plunger that automatically adjusts its height. When the workpiece is positioned over the work supports, the plunger is depressed to the proper height. Once the height has been set, the plunger is locked in place to provide rigidity.
Work supports are locked in place via several actuation methods.
- Mechanical (screw or cam)
- Hydraulic
- Pneumatic
The following video illustrates the operation of a hydraulically locked, spring-actuated work support.
Video credit: Fixtureworks
Fixture jacks, sometimes referred to as support jacks or jack screws, are also used for supporting workpieces during machining. Simpler in design and construction than work supports, support jacks do not have a spring-actuated or fluid-actuated plunger. They utilize a screw or threaded body for height adjustment, and are manually adjusted to the proper height. These fixturing products should not be confused with similarly named and constructed products used for lifting, electronics or other applications.
Specifying Considerations
Work supports and fixture jacks are rated for specified load capacities, an important consideration when selecting a work support. Do not use a support that is not rated for the application.
Several different mounting styles are available for work supports and support jacks.
- Threaded body - for mounting in an internally threaded hole
- Flanged body / mounting holes - for mounting to a flat surface with bolts
- Cylindrical stem body - for mounting in a machined hole