Spannpratzen

Spannpratzen are a class of clamping devices used in machining and woodworking to securely hold a workpiece by applying pressure with a set of jaws or gripping surfaces. The name derives from German spannen (to clamp) and Pratzen (pads or blocks), and in practice the term denotes several related mechanisms rather than a single standard design.

In German workshop literature from the 19th and 20th centuries, spannpratzen appear as components of fixtures and vises, often as replaceable jaws or wedges that bite into the workpiece to prevent movement during cutting, drilling or grinding.

Design variations include screw-operated clamps with threaded blocks, wedge-action clamps that expand gripping pads, and modular systems that fit into a fixture plate. Common features are serrated or shaped contact surfaces to increase friction and threaded fasteners for adjustable clamping force. Some designs are guillotine-like or slide-in components for quick changes.

Applications: They are used to secure metal or wooden workpieces during milling, drilling, grinding, or assembly work, particularly where repeatable, stable grip is required. They are often used in jigs and fixtures, toolholding setups, or benchwork.

See also: Vise, Clamping device, Jig (engineering).