Mandriles

A scroll chuck is a self-centering workholding device that mounts on the lathe headstock spindle. Turning a key or tommy bar drives all jaws simultaneously inward or outward via a scroll mechanism, gripping a tenon or expanding into a mortise cut into the base of the workpiece. It allows quick, repeatable workpiece mounting and removal with consistent concentricity.

Lathe chucks mount via a threaded spindle nose. You must match the chuck's internal thread to your lathe headstock's spindle thread — common sizes include 1 inch x 8 TPI for many American lathes and M33 x 3.5 mm for metric machines. Check your lathe's owner's manual for the exact spindle thread specification before purchasing a chuck.

Gripping mode closes the jaws around a cylindrical tenon cut proud of the workpiece base — the most common method for bowl turning. Expansion mode opens the jaws outward inside a shallow recess (mortise) cut into the workpiece. Both approaches provide secure holding; the choice depends on the workpiece design and which face needs to be accessible during turning.

Yes, if the chuck accepts interchangeable jaw sets. Larger dovetail jaws handle bowl-blank tenons, while smaller pin or spigot jaws grip narrow spindle stock. Most quality scroll chucks are designed around an interchangeable jaw system, making a single chuck body the foundation for the full range of woodturning work.

Tenon diameter should match the gripping range of your specific chuck jaws — typically the midpoint of the jaws' stated range produces the strongest, most centered grip. Tenon depth should be approximately half the tenon diameter, with a slight undercut at the shoulder so the jaws seat fully. Refer to your chuck manufacturer's guidelines for precise tenon dimensions.

Both methods are safe when used correctly. A faceplate provides an extremely secure mount for heavy or off-center blanks and is preferred for initial rough-turning. A scroll chuck offers the convenience of quick mounting and repositioning for subsequent passes. Many turners rough-turn on a faceplate and switch to a chuck for finish-turning once the blank is balanced.

Runout is the degree to which the gripped workpiece deviates from the true rotational axis of the lathe. Lower runout means the workpiece spins more concentrically, which produces rounder forms, reduces vibration, and extends tool life. A precision-machined scroll chuck with tight jaw tolerances minimizes runout compared to lower-quality alternatives.

Most scroll chucks use either a dedicated chuck key (a T-handled tool that engages a square drive socket) or a tommy bar (a round rod inserted through holes in the chuck body). The style depends on the chuck manufacturer. Both methods turn the scroll mechanism to open and close the jaws. Always remove the key or bar before starting the lathe.

The Infinity Tools learning blog is a useful starting point for woodturning and general woodworking technique content. Many woodturning guilds and regional turning associations also offer hands-on courses where chuck technique is taught in person.

The Infinity Tools team can help match a chuck to your lathe and turning style. Reach out through the contact page and include your lathe make, model, and spindle thread size for the most accurate recommendation.