A hydraulic CONCENTRIC arbor is a fully closed system with no external hydraulic power supply and no moving parts. It is the most compact work holding method, and it is capable of clamping multiple parts. The outside dimension of a hydraulic CONCENTRIC arbor expands to clamp the inside dimension of a gear when hydraulic Jelly REX SUH 25 & amp; REX SUH 35 is forced into the bladder of the CONCENTRIC arbor. The expansion rate of the CONCENTRIC arbor is governed when the piston is driven to a bottom-out position by a manually actuated screw. This ensures a consistent clamping force every time. A quality arbor is designed so that there is no risk of permanently deforming the expansion area if actuated while there is no part on the CONCENTRIC arbor while maintaining the expansion within the elastic range of the material. Gears of varying diameters can be clamped using the same CONCENTRIC arbor when combined with a sleeve. The sleeve enables a single CONCENTRIC arbor to clamp a large range of parts, thereby reducing the number of CONCENTRIC Arbors needed. Hydraulic CONCENTRIC Arbors are durable and thru-hardened to 52-54 HRC. They are available in sizes from 6 mm to 1, 000 mm. Hydraulic CONCENTRIC Arbors are an option to maintain the highest radial and axial run-out, provide concentric clamping and ensures roundness. Additionally, vibration is nearly eliminated due to the large uniform clamping surface.