A collet is a type of chuck that forms a collar around the tool or object being held clamping it securely in place. A collet chuck is best used for smaller items less than 2.5 inches where standard chucks are inefficient and unwieldy. At these sizes, collets have many advantages.
1. Collets are lower in price than standard chucks. Though collets have a narrow clamping range, some collets have internal pads that are replaceable and available in a variety of sizes which reduces the cost of workholding.
2. Collets grip the tool closer to the part being machined; therefore it is more secure and accurate. Standard chucks project the tool farther from the chuck which can affect rigidity. In secondary operations, a collet’s ability to grip around a parts periphery results in greater rotational concentricity producing a more rounded part than possible with a jaw chuck.
3. A collet chuck is a better choice for turning at high spindle rpms being it is less massive than a jaw chuck. Also centrifugal force tends to reduce clamping force on a jaw chuck but does not seriously affect a collet. Likewise, being less massive, acceleration is much faster for the collet. Where lathe spindle weight control is an issue, a collet will also be a better choice.
4. Changeover time is greatly reduced when using a collet type chuck. Jaw chucks may take as much as 20 minutes to change, while a collet can be changed in 20 seconds. The time savings is a great benefit with large lots of small sizes.
5. Collets used to hold workpieces on a lathe have a standardized hole in the center so long bar stock can pass through. (ToolingU.com)
Standard chucks are the choice for larger parts, those with inconsistent diameter, and larger axial dimensions. But when machining smaller parts, a collet chuck is the winner because of price, grip, weight, acceleration and changeover speed.