Manufactured in accordance with standard JB3411.58-99, these screw jacks are used for supporting workpieces during component inspection. The products are available as either steel or cast iron castings, with external surfaces finished in either chrome plating or paint.

A fully-configured screw jack consists of: a screw, nut, base, setscrew, and hex nut. The screw is typically manufactured from medium carbon steel, with the top section locally hardened. These jacks are suitable for supporting workpieces during layout operations on rough castings or forgings.

During operation, the workpiece is supported on three screw jacks. The workpiece height can be adjusted via the nuts to establish the required datum. The support points selected should be spaced as far apart as possible. Pre-made center punch marks at the support locations can help ensure stable and reliable positioning.

When performing layout on large, heavy rough castings/forgings, several additional auxiliary screw jacks can be installed for safety. If the supporting surface is narrow and the workpiece is tall and slender, a slightly slack hoisting chain may be used as a safety precaution.

The tops of the jacks are also available in two variant configurations: a V-Block type and a Double Roller type. These are suited for supporting general-purpose or large stepped shaft-type components, respectively, during layout operations.