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- The Advantages of a 5C Collet Chuck vs. a 16C or a 3J
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.
- Why use a Spindle Work Stop
I received a call today from my customer, John, who needs a stop to locate in his drawtube of his lathe to position a 16” long part on his z-axis. John informed me that this is the first operation of this part and he has a 16C Pullback Style collet chuck. I recommended the following:
This Spindle Work Stop (Also known as a Drawbar Stop) is a tool that is used as a parts stop in a lathe spindle or draw tube for quick setups, enabling accuracy or consistency of linear dimensions. Place the workpiece in a chuck or collet and set the proper length. Insert the work stop into the rear of the spindle or draw tube. Expand the fingers using the supplied T-handle wrench until they touch the spindle, then back off the screw a quarter turn. Using the T-wrench, slide the work stop into the spindle until it contacts with the workpiece. Tighten the work stop and remove the wrench.
I explained to John that he needs to be aware that when using a Pullback Style collet chuck, linear dimension can change if the OD diameter of the part varies. For every .001” on the diameter, the linear position will move .003”. Being that he is doing the first operation, he will simply program the machine to face the part to establish his overall length of the part. If John was doing a second operation and the OD of the part varied (Lets say +/- .003”) and he also had to hold the linear within .002”, this style stop would not work. This is because the stop moves with the draw tube and he would be unable to hold the linear dimension of .002”. For that situation I would recommend that John make a fixed stop to fit his machine that is independent of moving with the draw tube. For more information on this product click here: Spindle Work Stop. As always, feel free to contact us for more info: 800-423-5145
- Using Collets on a 4th Axis Rotary Fixture
We get a whole lot of inquiries asking about using collets on a 4th axis rotary fixture. We offer several different type of fixtures which can be found by clicking on this link: Collet Fixtures/ Air and Manual
The first thing that you need to determine is whether you want your system to be manually operated or air operated. Then you have a choice of a True Length or Pullback system.
With a Pullback collet fixture, closing the collet is accomplished by pulling it back into the fixture body. The True Length fixture collet is different in that it is rigidly fixed to the fixture body and a tapered sleeve pushes forward over the collet to compress it. Using a Pullback collet fixture will result in a slight variation in the z-axis positioning of the workpiece. This happens due to the fact that as the collet draws back and closes down, it begins to grip the workpiece and pull it back too. Typically the movement is just a few thousandths of an inch and remains consistent as long as the part diameter doesn’t vary. This slight z-axis movement is often acceptable for first operation work and can be easily remedied with a facing cut. However, there are several situations where z-axis movement is not desirable. In these situations, we suggest that you use a True Length collet fixture.
Need more info? Do not hesitate to contact us to go over your specific applications. 800-423-5145