Workholding apparatus

A workholding apparatus for mounting a workpiece for machining on a machine tool, said apparatus having an axis extending the length thereof and comprising a chuck portion and a tailstock portion, said chuck portion comprising:

• a generally disc-shaped base portion,
• a generally cup-shaped body portion mounted adjacent said base,
• a piston member positioned in said cup-shaped body portion, said piston comprising a disc-shaped base and narrower axially-extending portion having an end,
• a nose portion secured to said cup-shaped body portion, said nose portion comprising a central opening in which said axially-extending portion of said piston member extends,
• a diaphragm attached to said nose portion, said diaphragm having an outer surface from which a plurality of jaws protrude, said diaphragm including a central opening through which passes means to secure said diaphragm to said end of said axially-extending portion of said piston member whereby axial movement of said piston member in said cup-shaped body portion effects flexing of said diaphragm to open and/or close said jaws,
• a backing plate attached to said diaphragm, said backing plate having a face and including a plurality of openings on said face to permit passage of said jaws therethrough, said face also including a centering locator guide for centering and stopping a workpiece in said chuck,
• a damping and sealing means adjacent to said backing plate, said assembly including material located at the periphery thereof for contacting a workpiece for sealing the area between said chuck and said workpiece and dampening vibrations brought about by a machining process,
• said tailstock portion comprising:
• a rotatable tailstock support having a inner surface at least a portion of which comprises a radiused surface for tangentially contacting an end surface portion of a workpiece opposite that end which contacts said stop surface,
• a centering locator guide extending axially from said tailstock support in a direction toward said chuck, said locator having a generally curved outer surface for centering said workpiece in said chuck,
• a housing cover extending in a flared manner from said tailstock support along said axis, said cover including an end flange to which is attached a sealing means whereby relative axial movement of said tailstock toward said chuck provides for said cover to fit over a workpiece mounted in said chuck with said sealing means contacting a surface of said workpiece radially inward of that portion of said workpiece being machined, said sealing means preventing the introduction of contaminants into said workpiece and said chuck and also providing for dampening of vibrations from the machining process.