Larger Diameter Chucks Today …
Larger Workholding Capabilities Tomorrow!
Today, the vast majority of chucks range in sizes from 4” to 24” in diameter and usually are an off-the-shelf commodity item. Most manually operated machines in this range use a Manual Scroll Type Chuck and production type machines use either Air Operated or Hydraulic Operated Chucks with 8” to 15” size models predominantly being used in the turning industry. Speed is the most important issue relating to smaller chucks…these chucks usually having a stroke between 5/16” to 3/8” per jaw, with smaller sizes running as high as 4,000 rpm and a 24” diameter chuck in the neighborhood of 1,500 maximum rpm.
Royal Machine & Tool technician Dave Turek inspects a newly produced Steel Bodied Large Diameter, Manually Operated 3-Jaw Chuck with wedge and gear actuation
When referring to Large Diameter Chucks, they range in size from 24” to 72” in diameter. In addition to rpm’s and being similar in overall design, there can be many internal differences relating to Large Diameter Chucks. Obviously, speed is still a main concern and requires changes in the design of chucks. For instance, a large chuck will require open cavities to reduce the chuck’s weight or to introduce counterweights. Only so much weight can be removed before taking away from the integrity of the chuck. Many manufacturers make the chuck body out of a casting with cavities being part of their pattern. Although it requires additional machining and cost to the manufacturing process, making the chuck body out of solid steel and machining out the cavities provides a more balanced machine body and extended chuck life.
Because larger work pieces require more room to load/unload, Large Diameter Chuck’s require strokes that can range from ½” to 1 ½” per jaw. If the work piece is loaded on a horizontal lathe, a load/unload assist device is usually employed for handling. Larger horizontal lathes are mostly for shaft work…and vertical lathes are used where less space is required as well as for ease in loading/unloading of large parts. The weight of larger parts makes it difficult for the operator to load in a small area. However, in cases where a longer stroke per jaw is possible, loading is made easier.
Power Actuation on larger chucks is usually not an issue. Some parts can take hours, possibly days to machine and, therefore it is not critical to have power actuation. Since cycle time is not an issue, a manual clamping using a torque wrench is usually sufficient. Also, many large aerospace parts or bearings are very thinned walled and clamping has to be manual to insure that there are no markings or distortions during the clamping process.
Manual Large Diameter Chucks prevail in larger chucks because chucking cylinders take up too much room which is limited on vertical lathes. In addition, vertical lathes normally require much longer cylinder strokes because of the large jaw movements. Also, a great amount of pressure is required to pass through the system to actuate the jaws…producing a very slow motion to actuate the jaws. Flow control valving usually helps this process. Because manual clamping is dependent upon the operator, a hydraulic clamp is advantageous in that it will always consistently clamp a part with the same pressure.
Solid Steel Manual Large Diameter VTL Chucks are the Next Generation of LDC’s. Unlike older designs, using Cast Iron Bodies and Scrolls with limited wear ability, solid steel’s design boasts superior solid strength, induced wear resistant body, hardened and precision ground Master Jaws and Wedge. Together they will produce increased accuracies and wedge style gripping forces. This next generation design uses a readily replaceable pinion gear for added torque and coupled with the wedge offer a more sensitive grip of the work piece. Also, chip protection is improved with the next generation designs which reduces maintenance down time.
Possible uses and applications for large diameter chucks are found in the aerospace, bearings and turbine engine industries where close tolerances are necessary on critical thin-walled parts.
Karol Ziecina, Machine Specialist at Atlas Precision Manufacturing in South Windsor, CT prepares chuck top tooling on a 32” diameter 3-jaw manual chuck
With economic times quickly improving, these new Solid Steel Manual Large Diameter VTL Chucks will provide the ideal solution for American industries to meet their ever-increasing demands to manufacture quality, high volume, uniquely shaped, varying sized products in the USA on time… and still be competitively priced.