What are the Differences between Collets and Chucks?

Feb 27th 2014

What are the Differences between Collets and Chucks?

Diameter range is the most notable difference between collets and chucks. Generally collets are used on smaller work pieces than typical three-jaw chucks. The general range for collets are 1/16in to 2.5in whereas chucks can be used on work pieces that are larger. Though chucks can also be used for smaller work pieces, collets are much more useful and better grip the items being used.

Even though chucks may not be the best option for smaller work pieces, they can still be used for a variety of jobs. Currently, in the United States, CNC lathes are generally prepared with the wedge-style, three-jaw chuck. Chucks of this style are either hard or soft jaws that can be altered to generate an array of uses.

Major benefits of using a chuck are positive length as well as its gripping capability. The typical collets used for a CNC lathe move in the Z-axis based on how much the range of the diameter of the surface. Generally, the part will move 0.003in on the Z-axis for every 0.001in of variability. The most gripping power and contact can be completed by the typical collet which provides additional closing forces.

Increased firmness, precision, and roundness can be the result of using a collet as the working device. When using a collet work holding device, the machine can be gripped closer to the headstock bearings leaving less overhang which may negatively affect quality of production. Chuck work holding devices unfortunately do not allow the machine to be as closely gripped resulting in more overhang.

Expendable pads may be used for a variety of sizes on some collets. Although, these allow the device to be used for additional jobs which does decrease work holding costs, they may not be as precise. To provide a variety of sizes on chucks, hard jaws or several sets of jaws may be used instead of pads. These jaws can offer a larger range of sizes to work with.

Increased precision can be provided by hardened or ground collets more so than a standard chuck’s hard or soft jaws. The reasoning for this being that the location of the collet’s grip provides increased accuracy and tighter gripping. In addition, during secondary operations, collets grip the parts better than chucks. This allows collets to create more roundness in parts, whereas chucks would not be able to produce the same.

Lastly, collets are able to grip unusual shapes better than three-jaw chucks. Collets can be ordered based on specific measures which can increase precision whereas using the soft jaws for chucks has limited accuracy.