A Hardinge 5C Step Chuck is an oversized collet used in conjunction with a Hardinge Closing Ring. These step chucks are available from 2”- 6” diameter in either an emergency style (you bore the collet to size) or in a hardened & ground style (the step chuck is hardened and ground to your specific size).
A typical 5C collet closes on the taper of the collet which is located behind the work head. The 5C Step Chuck does not have this taper, but instead has a taper on the larger diameter of the collet head. A Step Chuck Closing ring is required (Hardinge threaded or tapered style). The closing ring has the matching taper of the collet head on the inside bore of the ring. When the collet is closed, it’s fully encapsulated, eliminating the possibility of the collet from opening up with high rpm turning and having the part come flying out. In addition, by holding the part more securely, you will see the benefits of both a better finish and a more concentric part!
Hardinge does offer the 5C closing angle on the Emergency Regular Depth Step Chucks for the 2” and 3” step chucks, but 4”-6” Step Chucks do not come standard with the 5C closing angle. They are available with the 5C closing angle, but the cost is about 30% more than the ones without that angle.
