Expansion Segments/Shoes

Expansion segments, also known as expansion shoes, are critical components of expanding mandrels used in lathes, grinders, and other rotating machinery. These hardened steel segments mount on a tapered mandrel body and move radially outward when axial force is applied via a drawbar or hydraulic system. Their precisely machined outer surfaces contact the inner diameter of hollow workpieces (tubes, rings, sleeves) to provide concentric clamping with minimal distortion. The expansion mechanism ensures uniform pressure distribution for high-precision machining of cylindrical parts.

The expansion segments operate on a wedge principle: when axial force pushes the segments along a tapered mandrel surface, they translate this linear motion into radial expansion. Hydraulic or mechanical actuation forces the segments outward against the workpiece ID, creating friction-based clamping. Retraction springs return segments to their collapsed position when force is released.