Here’s the advantages of a 5C Collet Chuck vs. a 16C or a 3J: The through hole capacity of a 5C collet chuck is 1-1/16”, whereas a 16C is 1-5/8” and a 3J is 1-3/4”. Now, this may sound like the 16C and 3J may be a better choice due to the larger through hole, but these chucks do not give you nearly as many collet options as the 5C.
The key difference between the 5C and the other chucks is that the 5C has a 2-3/16-10 thread nose, otherwise known as the Hardinge Thread. With this thread, you have the ability to use the Step Chucks that are manufactured by Hardinge. These step chucks are available in sizes from 2”– 6” in diameter. These step chucks require a ring (Step chuck closer) that screws onto the 2-3/16-10 thread nose of the collet chuck. The purpose of these rings is to encapsulate the collet so that you can run your lathe at a higher rpm without needing to worry about the collet opening up due to centrifugal force. Step chucks, unlike standard collets that u
se the taper of the 5C to close the collet, have an ID taper at the opening of the ring. This is what causes the collet to close when you activate your draw bar. The additional benefit is more rigidity which results in better finishes and tighter tolerances of the part that you are machining!
The 3J collet chuck does not support this type of tooling, however you can purchase OD collets (Hardinge) that go up to 5” in diameter. The 3J OD collets do not require a closing ring, but they will cost you! Even though 16C step chucks are available in the same size range as the 5C, your collet chuck would need to have an A5 spindle mount on the front face in order to bolt the closing rings on. Hardinge only makes these rings with an A5 spindle mount configuration. Point being, if you’re going to be purchasing a collet chuck and you want to have your cake and eat it too, the 5C collet chuck is your most versatile choice.