Top jaw assembly with replaceable work holding pads

A top jaw assembly comprising:

• (a) a top jaw adapted to be mounted on a master jaw of a chuck rotatable about a central axis, including:
• (1) a support block having a first support surface lying in an axial plane with respect to the central axis;
• and
• (2) a clamping block having a second support surface concentric with the central axis removably mounted to the support block;
• (b) an arcuate shaped work holding pad releasably secured to the top jaw and having concentric inner and outer surfaces, the outer surface of the pad being adapted to seat against the second support surface of the top jaw assembly and the inner surface being adapted to grip a work piece;
• (c) clamping means contained within the clamping block for releasably securing the work holding pad to the top jaw, the clamping means including a locking element for engaging the work holding pad so as to urge the work holding pad downwardly against the first support surface to axially locate the pad and rearwardly against the second support surface to maintain the inner surface of the pad concentric with the central axis;
• and
• (d) locating means for indexing the work holding pad on the top jaw assembly.