Spannzange

Spannzange is a clamping device used in machine tools to hold cylindrical tools or workpieces by radial compression. The most common form is a collet, a slitted sleeve that surrounds the shank and is tightened by a nut to grip the item evenly.

Principle and advantages: When the collet is tightened, it contracts along its length and applies a uniform, concentric grip. This results in high runout accuracy, good surface finish, and efficient torque transmission. Spannzangen are favored for precise drilling, milling, and turning, especially with small-diameter tools or when minimal axial runout is required.

Construction and varieties: A Spannzange typically includes a collet, a collet nut, and a spindle interface or housing. Collets and nuts must match the tool diameter and the machine’s spindle standard. Common systems in practice include DIN/ISO collets and standardized tool-holding collets such as ER-type sets, which enable holding a range of diameters with a single nut. The interface to the spindle can be a specific taper or chuck-compatible seat, depending on the machine design.

Applications and maintenance: Spannzangen are used to hold drill bits, end mills, reamers, and other cylindrical tools, as well as small workpieces in compatible setups. Proper use requires clean collet slots, correct seating of the tool, and appropriate tightening with the correct wrench. Contamination, worn or damaged collets, or over-tightening can reduce precision and shorten tool life.

See also: Collet, Collet chuck, Tool holder, Spindle interface.