	Workholders - Hydra-Grip Arbors and Chucks

Drawings (A) and (B) illustrate how the gripping surface of hydraulically expanded arbors and chucks conform to the chucking surface of the part. Uniform hydraulic pressure assures part positioning on the true centerline, compensating for allowable taper. For example a part with a .002 tolerance on the chucking diameter could have a possible .002 taper, and still be within the allowable part tolerance. Subsequent machining operations from this chucking surface using A.G. Davis - AA Gage hydraulic tools, eliminates possible stack up of "in-tolerance" part variations which could result in scrap or marginal quality.

To hold non-critical part chucking diameters completely free from taper, or to very close size limits to facilitate holding related concentricity and squareness require- ments, adds unnecessarily to production costs.

Maximum gripping power is always effective, irrespec- tive of taper within the allowable part tolerance.

OUT-MODED CHUCKING METHODS
Conventional mechanical type arbors and chucks depend on metal to metal line contact on the chucking surface of the part. The gripping or chucking surfaces of mechanical chucks do not compensate for "in-tolerance" part taper. In Examples (C) and (D) chucking on the true part centerline is restricted by the minor diameter of the taper in the case of an arbor, and the major diameter of the taper in the case of a chuck. Part movement and vibration is likely as maximum gripping force cannot be equalized on the full locating surface of the part.

It is not unusual that a large part of the manufacturing tolerance must be allowed for the inability of conventional mechanical chucking devices to consistently locate the part accurately.

Drawings (E) and (F) illustrate how Davis hydraulically expanded arbors and chucks conform to the chucking surface of the piece part to compensate for "in-tolerance" variations such as "bell-mouth" or "outr of-round" Where a sequence of operations are performed, locating from the same chucking surface, it is important to consistently locate the part on its true centerline. A.G. Davis/AA Gage hydraulic expanding tools meet this requirement.