Shops are realizing significant advantages in using collet blocks rather than standard vises or 3-jaw chucks to grip round, hex, square or odd-shaped parts.
A collet automatically centers the workpiece, so it can reduce setup time.
A collet provides equal gripping pressure around the circumference of a part, unlike a standard vise or a 3-point contact jaw chuck, and collets will not crush or distort thin-wall parts or delicate materials, as a standard vise or jaw chuck could.
Collets that have serrations can add additional gripping power to prevent push-back and radial slipping, and extended-nose collets can provide additional tool clearance. Some collet blocks accept expanding collets to grip a part at the internal diameter.
With collets, centers remain fixed when the fixture is removed from the machine table, and collet blocks can be used horizontally or vertically on mill tables, or flat or angled for fixture plates, tombstones and rotary trunnions.
A hydraulic quickdisconnect handle can allow parts to remain clamped for preloading, loading and unloading pallets.
“When people hear the word ‘collet’, they tend to think of small, round-part gripping; however, hex, square and custom-shaped collets will hold a variety of shapes,” Cal Macomber, director of sales and marketing for the Hardinge Workholding Division (www.hardingeworkholding.com), said .
We see collet block applications in job shops doing milling, drilling and grinding, and also in the crimping, inspection, testing and assembly environments,” Macomber said.
Collet blocks from Hardinge range from 1C units for the micro-medical machining industry to 35J units that are designed to grip a 3.5-in. (88.9 mm) diameter for mid-range parts used in the automotive and aerospace industries.
Hardinge collet blocks are available in lightweight aircraft-grade aluminum or with heavy steel construction. Double-acting pneumatic or hydraulic models are available in dead-length style or pullback style. Hardinge’s failsafe 5C pneumatic collet block are designed for applications that frequently lose shop air, or those that are off-loading pallets. Air is required during setup to open the workholding.
In addition to collets, step chucks and expanding collets for use in collet blocks, Hardinge manufactures quick-change collets.
The company said its new HQC Quick-Change Collet Systems offer long life, can accommodate variations in barstock, provide the opportunity for increased federates and spindle speeds, allow for faster changeover than standard collets and are more flexible than master collets and pads. The company’s flexible collet head offers true parallel gripping with collet segments that run parallel to the stock, even when there are variations in the stock size. Collet heads have a working range of ±0.0156 in. Parallel clamping minimizes stock “push back” and requires less draw bar force than conventional collets.
The system can be changed from one size collet to another size in less than 20 seconds. This is accomplished by using a manual or hydraulic changing wrench. The wrench compresses the collet, allowing for quick and easy removal, and quick installation of a different size collet head.
Because the system requires less draw bar force to adequately grip the bar, it reduces the the potential for breaking the closing fingers and pins, which is common when the bar varies beyond the range of a standard solid collet or master collet with pads. HQC collets are available for multi-spindle automatic screw machines, Hardinge collet-ready CNC lathes and chuck-style lathes.
