When to choose spring chuck

The advantages and disadvantages of spring chuck advantages and disadvantages light weight, fast acceleration, small concentricity and high speed clamping parts can be quickly replaced when replacing the clamping parts. The suitable size range of the chuck is limited, and the axial dimension is long, which is more suitable for small parts, and more suitable for the workpiece with the same diameter and size

The three jaw electric chuck is the standard workpiece clamping device for most lathe users. This chuck has enough generality and can be applied to a variety of turning processes. However, it is not the best fixture for all machining tasks. Spring chuck is a kind of spare workpiece holding device, similar to jaw chuck, it also uses mechanical force to fix the parts to be turned. Although the range of workpiece sizes offered by the spring collet is not as wide as that of a jaw chuck, the advantages it provides in relation to speed, accuracy and productivity may be extremely important for some machining tasks.

There are several factors that need to be considered when making a decision about which fixture works better. For a given lathe task, all of the following factors need to be considered to determine whether to choose a spring chuck or a jaw chuck.
Spindle load capacity the maximum allowable weight of the lathe spindle is based on the bearing load capacity. If the combined weight of the chuck and workpiece is too large, the bearing may be overloaded. For those processing tasks with excessive danger, this risk may determine the choice of workpiece fixture. The weight of jaw chuck is often larger than that of the same spring chuck. Therefore, when the weight needs to be controlled, the spring chuck is the appropriate choice.

Spindle speed spring chuck is often a good choice for turning at very high spindle speed
One reason is related to the quality of the chuck. Assuming that the jaw chuck and spring chuck are driven by the same main shaft horsepower, the thicker jaw chuck needs longer time to accelerate to the required speed, and the longer the acceleration time will prolong the working cycle and reduce the productivity.

Another reason is related to centrifugal force, because it increases with the square value of RPM, so this value is very important in high-speed cutting. For example, if the spindle speed is doubled, the centrifugal force will be four times the original. This force pulls the chuck claws away from the center, often reducing the clamping force. However, the centrifugal force will not cause obvious influence when using spring chuck. Therefore, the clamping force will be more stable in the whole range of processing speed.

The machining operation of the spring collet exerts a clamping force on the entire circumference of the part, rather than only in the selected contact area. Therefore, good concentricity can be obtained. This is particularly important for secondary processing projects. The accuracy related to the primary processing needs to be considered in the secondary processing, because the accurate clamping ability of the spring collet is strong, even when the jaw chuck is used for primary processing, the spring The chuck can also be used for secondary processing. The chuck with hollow soft jaws can achieve TIR (total reading) repetition accuracy in the range of 0.0006 to 0.0012 inch, while the typical repeatability accuracy of spring chuck is 0.0005 inch TIR or better. In order to further improve the secondary machining accuracy, the concentricity of spring chuck can be adjusted during installation.

Workpiece size spring chuck is very suitable for workpieces less than 3 inches in diameter. The spring collet limits the length of the workpiece. In particular, the collet limits the axial (Z-axis) travel range of the machine tool because it is longer than the jaw chuck. When the processing length of the workpiece is about the whole available stroke of the machine tool, it is necessary to use the jaw chuck.

The processing batch size, large batch and small batch processing tasks are suitable for spring chuck.
In small batch and multi task processing, the advantage of spring chuck is related to the product conversion time. It takes about 15 to 20 minutes to replace the standard jaw chuck, 1 minute to replace the special jaw chuck, and 15 to 20 seconds to replace the spring chuck quickly. When the product changes frequently, the time saved is considerable.
When the processing batch is large, the time saved related to clamping can also be accumulated. The opening and closing time of spring chuck is less than that of jaw chuck. By reducing the non cutting time from one workpiece to the next, the machining cycle time is reduced.

Part of the reason for the faster opening and closing of the spring chuck is that its driving stroke is shorter and the range of workpiece sizes suitable for the spring chuck is more limited than that for the jaw chuck.
In the case of secondary spindles, turning machines equipped with secondary spindles are often used for a variety of mass processing, in which the spring chuck can significantly save processing time. They can process all surfaces of parts in one working cycle. These machines are often combined with bar feeder to realize unattended production and continuous processing of workpieces. In these applications, for a workpiece, the saved chuck driving time may be very small, but in the whole production process, the saved time of each workpiece multiplied by the number of processed workpieces is considerable.

Chuck tool library it is also important to consider the third option when choosing the most suitable workpiece holding device between the jaw chuck and the spring chuck. Where permitted, retaining two types of fixtures and changing from one to the other may be the most cost-effective option. Changing from jaw chuck to spring chuck, or vice versa, usually does not take more than 20 minutes. The jaw chuck can be retained on the machine to deal with uncertainties in the range of parts. However, when the machine tool is used to process a large number of workpieces, or several batches of parts with the same size, the spring chuck is used to obtain the