Work supporting jack

A work supporting jack comprising a body having a bore therein, a work supporting plunger axially slideable in said bore and projecting out of said body at one end thereof for supporting engagement with a workpiece, a second bore in said body intersecting the first bore, a control plunger slideable axially in said second bore, said control plunger having an axially inclined surface thereon engaged by the work support plunger such that axial movement of the control plunger in one direction causes the work support plunger to be displaced axially outwardly of said body at said one end thereof, a plunger clamping member mounted in said body in a position fixed axially relative to said second bore, said clamping member having at least a portion thereof movable radially of said second bore into frictional clamping engagement with said control plunger to lock the control plunger against axial movement, a clamp actuating member mounted in said body for movement in a direction parallel to the axis of the second bore and having a surface thereon engageable with the movable portion of said clamping member to displace said portion of the clamping member radially into locking engagement with the control plunger when the clamp actuating member is displaced axially in one direction.