Work supporting jack

A work-supporting jack comprising a support member having a bore therein, first and second opposed plungers axially slideable in said bore toward and away from each other, the confronting ends of said plungers comprising a pair of confronting faces which are inclined to the axis of the bore at an acute angle and which are spaced apart transversely of said bore, a key disposed in the space between said confronting faces, said key being fixed axially of the bore and having opposed faces adapted to be abutted by said inclined end faces of the plungers, said key being movable transversely of the bore in response to abutment of either of said opposed faces with said end faces of the plungers, the first plunger having its other end projecting axially outward of said bore for supporting engagement with a workpiece, means biasing said first plunger axially outwardly of said bore, said end face of said first plunger being inclined to the axis of the bore at a wedge locking angle relative to the key so that movement of the key into abutting engagement with the inclined end face of the first plunger will not produce axial movement of the first plunger outwardly of the bore, means for moving the second plunger in a direction toward the first so that the inclined end face of the second plunger bodily moves the key transversely of the bore into abutting relation with the adjacent inclined end face of the first plunger, and means for locking the second plunger against axial movement in a direction away from the first plunger when said opposed faces of the key are in abutting engagement with the inclined end faces of both plungers, whereby, when the first plunger is moved axially inwardly of said bore against said biasing means by a workpiece positioned against the outer end of the first plunger and the second plunger is moved toward the first to interengage the opposed faces of the key with the inclined end faces of the two plungers, the wedge locking angle on the end face of the first plunger cooperates with the locking means for the second plunger to lock the first plunger in an axially fixed position in said bore.