Expanding Collets Offer Solutions To Difficult Machining Problems

Elmira, NY - Expanding collets and between center arbors (mandrels) grip the internal diameter of a part for turning, milling, grinding, assembly, inspection and automation applications. When the OD of the part is hard to grip, or cannot be gripped, internal gripping may be your answer if there is an internal diameter in the 1/8" to 4" (3.175 to 101.6mm) range.

During chucking operations parts can be located against the face of the arbor or against a machineable workstop. This provides exact part length control as well as improved part consistency. The expanding collet draws the part firmly against the stop producing an extremely stable part location. Longer parts can be easily machined due to this added stability. The results are heavier cuts, better surface finishes and closer tolerances when using a workstop. Workstops may not be necessary if you are only machining the OD of the part. Because the part is pulled back against the workstop, short grip lengths can be firmly held.

Common ID gripping solutions include:

• Parts that need to be machined on multiple surfaces which would otherwise require multiple operations
• Thin-wall parts that would crush or distort with OD gripping
• Parts with OD threading that would be damaged with OD gripping
• Parts too large to grip on the OD
• Parts with an odd-shape that would be costly to manufacture a custom fixture or collet for
• Multiple parts loaded in pneumatic or hydraulic fixtures
• Pickoff collets for sub-spindles
• Short parts with limited gripping surface
• Gripping parts in a rotary indexing system for part positioning
• Grinding machine spindle workhead applications both direct-mount and collet style
• Between center grinding applications
• Assembly processes
• Grippers for automation
• Inspection applications in which there is an internal datum requirement

Hardinge manufactures Sure-Grip Expanding Collet Systems (patented) with interchangeable collet heads that have an under-over capacity of -.001" to +.015" (.025mm to.38mm) from its specified size to accommodate a range of part diameters. A double-angle design assures true parallel gripping with maximum grip force. Parallel gripping means that the collet expands equally the entire length of the collet rather than just at one end of the collet for maximum bearing contact against the part. This results in greater stability and better part accuracy. Parts are instantly centered and located without adjustment. Higher rpm and greater feed rates give you more parts per hour. A built-in safety stop will prevent the collet from over-expanding. Machines with ANSI type-A spindles and machines with collet-ready spindles or collet adapters can use the Hardinge Sure-Grip Expanding Collet Systems.

5C, 16C and 3J collet-style expanding collet systems mount directly into the collet angle of the spindle or in fixtures such as collet blocks with instant centering. There are no spindle adapters needed. The one-piece spindle arbor construction and the closing mechanism hold the workpiece extremely rigid for superior surface finishes and concentricity. A2-5, A2-6 and A2-8 expanding collet systems mount directly on to the spindle. Hardinge precision manufacturing processes guarantee the Total Indicator Reading (TIR) of the arbor will be within .0002" (.00508mm). With the expanding collet mounted on the arbor, the TIR of the collet and arbor will not exceed .0005" (.0127mm), without the need for adjusting screws and indicating.

Hardinge also manufactures center arbors that use Sure-Grip Expanding Collets for grinding machines, lathes and other applications that can be held between centers, or chucked on one end and supported by a center on the other end. Sure-Grip Expanding Collet Systems can be manufactured for special applications for spindles, sub-spindles and mill tables for any brand of machine or fixture. Pickoff collets are frequently engineered for Swiss and multi-spindle machines. Splined or serrated surfaces can be made for special grips and shapes. A recessed draw plug can be used to let you grip all the way to the bottom of the bore when needed. Hex- and square-shaped expanding collets are also available. Hardinge manufacturing capabilities and applications expertise result in this product being unique in terms of accuracy, functionality and value.

Request brochure #2270 for additional information. Order Hardinge workholding products online at hardingetooling.com, or phone 800-843-8801 (fax 607-734-3886).

SOURCE: Hardinge Inc.