The GERARDI DUO-DUX is a manual self-centering chuck designed for heavy-duty turning on engine lathes. Its defining feature is the double-guided integral jaw system — each jaw rides on two guide surfaces in the chuck body, providing greater stability and load distribution than conventional single-guide scroll chucks. The entire chuck is manufactured in Italy from a single-piece cast iron GJL 250 body with a fully ground scroll, pinion, and case-hardened Ni-Cr steel jaws.

DUO-DUX Model Range and Specifications

What is the advantage of double-guided jaws?

In a conventional single-guide scroll chuck, each jaw rides in a single slot machined into the chuck body. Under heavy radial cutting loads, the jaw can tilt slightly in its guide, reducing clamping accuracy and accelerating guide wear. The DUO-DUX double-guide design adds a second bearing surface per jaw, distributing the cutting force across twice the contact area. This suppresses jaw tilt under load — critical for interrupted cuts, large-diameter workpieces, and roughing operations where cutting forces are high and variable. The GMD-160 is the only single-guide model in the range, intended for small parts and light machining where the double-guide benefit is less pronounced.

What jaw configurations are available?

GERARDI supplies three jaw types for the DUO-DUX series. External clamping jaws grip workpieces from the inside — ideal for boring and cylinder work. Internal clamping jaws grip from the outside for shaft and disc turning. Both are supplied as case-hardened, fully ground Ni-Cr steel components. For irregular workpieces and dedicated production runs, machinable one-piece jaws can be bored or shaped to the customer's specific workpiece geometry. A special Ø270 variant with an enlarged Ø105 bar passage is available outside the standard size range for shops running larger-diameter bar stock.

How is the DUO-DUX mounted to the machine spindle?

The DUO-DUX uses GERARDI's semi-finished adapter plate system. Each plate is supplied fully finished on the machine side (matching the spindle nose standard) and left machinable on the chuck side, allowing the user to turn the register diameter to match their specific spindle faceplate or backplate configuration. This approach accommodates a wide range of lathe spindle standards — DIN, Camlock, A-type — without pre-configured inventory. Mounting bolt patterns vary by chuck size, from 3×M8 on the GMD-160 to 6×M14 on the GDD-430.