Just A Chuck?

Posted by: 21. October 2014

Every element of part processing, from machine, to cutting tools, to workholding, to program, to material handling and part loading and unloading, impact job quality, efficiency, and profit.  Each element may not be as important as the next, but any one piece of the puzzle can derail a job if it isn’t right for the job or doesn’t work the way it should.

Not every lathe job requires high quality chucking, but when it does, do you know all of the questions to ask?  Some may think—it’s just a chuck. And they might be right, while being dead wrong. Depending on the application do you ask these chuck-related questions? What’s the maximum RPM rating?  What’s the jaw stroke and chucking pressure at each point along the stroke?  Is gripping force or maximum speed different for ID and OD chucking conditions? Does grip force change with a change in RPM and by how much?  Are my parts delicate or thin-walled or prone to jaw marking and how will my parts respond to jaw force at different speeds? Are hard, soft, full wrap, insert, or special jaws required?  How much of the Z axis machine stroke is lost due to the length of the chuck body?  Is the chuck protected from swarf, coolant, dust, fine metal chips?  Is the chuck designed to avoid hanging up stringers?  Can the chuck and jaws be washed with the machine coolant and air pressure during the loading and unloading process automatically or will manual intervention be required? Is the chuck plumbed for interfacing air or coolant through the chuck? Can irregularly shaped parts be chucked without sacrificing speed or pressure? What base jaw interfaces (serration and pitch) are available? Can the chuck be used in horizontal, vertical or inverted vertical applications? Can the chuck handle through feed of round bar, tube, hex or other material shapes? Will the method of chuck actuation (open and close) be compatible with the machine design?  Are bearing and moving surfaces hardened and ground for long life? What is the repeatability and run-out of the chuck? Can the jaws be quick-changed? Is the chuck compatible with the machine spindle nose?

Sigh.  Surely there are more questions, but this should start the conversation.  As I’ve mentioned before, I read brochures for a living. One of the latest I read was about the Schunk ROTA NCO, wedge hook power chuck. It reminded me that there are actually some standard chucks designed for very difficult, close tolerance applications. Go down the check list of hypothetical questions while considering this SCHUNK product. This beautiful-to-look-at, piece of craftsmanship is likely to respond optimally in hundreds of applications.  Available in 6” to 40”, this is not a special design chucking system. It’s just another highly engineered, high-quality, off-the-shelf, SCHUNK product.  

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