What Are Lathe Collets?

The collet is called an elastic collet or collet. The utility model is a cylindrical fixture used for installing on a milling machine to restrain a drill bit or a milling cutter. It is also a fixing device for fixing and strengthening the parts that need to be modified.

Control the movement of machinery, such as valve springs in internal combustion engines, control springs in clutches, etc.

Elastic collet, also known as elastic collet, is a drill-milling collet mounted on a drill / milling machine. Its function is to clamp a drill or milling cutter. Currently the most used ER collet. Its stable performance and high accuracy are trusted by the majority of manufacturers.

There are many types of elastic chucks, and its characteristic is that the radial runout is only half that of the C-type collet, which greatly improves the accuracy guarantee of the product during processing.

Its specifications are roughly divided into the following eight blocks:

specification	d (H7)	D	D1	D2	L	L1	L2	L3	Elastic shrinkage
ER8	0.5-5.0	8	8.5	6.5	13.5	2.7	1.5	1.2	0.5
ER11	1.0-7.0	11	11.5	9.5	18.0	3.8	2.5	2.0	0.5
ER16	1.0-2.0	16	17	13.8	27.5	6.26	4.0	2.7	0.5
	> 2.0-10.0								1.0
ER20	1.0-2.5	20	twenty one	17.4	31.5	6.36	4.8	2.8	0.5
	> 2.5-13.0								1.0
ER25	1.0-2.5	25	26	22.0	34.0	6.66	5.0	3.1	0.5
	> 2.5-16.0								1.0
ER32	2.0-3.5	32	33	29.2	40.0	7.16	5.5	3.6	0.5
	> 3.5-20.0								1.0
ER40	3.0-26.0	40	41	36.2	46.0	7.66	7.0	4.1	1.0
ER50	6.0-10.0	50	52	46.0	60.0	12.6	8.5	5.5	1.0
	> 10.0-34.0								2.0

The utilization rate of elastic chucks has increased rapidly in the past two years, and has increased nearly a hundred times over two years ago. With the continuous rise of the small processing industry, the quality and accuracy of processing are undoubtedly the biggest competitors at present, and the emergence of such collets has, to some extent, become the key to the survival of small and medium-sized enterprises. ER collets are most commonly used in their normal use, ER11-ER25. They account for 9/10 of these collets and are easier to buy in the market. With an annual output of 350 million sets, it is second to none in the field of drill chucks. ^[2]

Collet chuck for CNC milling machine. Is a device used to install on a milling machine

Advantages and disadvantages of the collet chuck: the advantages are light weight, fast acceleration, little influence of centrifugal force, high concentricity, quick change of collet when fast clamping parts replacement. Suitable workpiece size range is limited. Long axial size is more suitable for small parts More suitable for workpieces with the same diameter and size. The three-jaw electric chuck is the standard workpiece clamping device for most lathe users. This chuck has sufficient versatility.

The three-jaw electric chuck is the standard workpiece clamping device for most lathe users. This chuck is versatile enough to be used in a variety of turning operations. However, it is not the best fixture for all machining tasks. Collet chuck is a kind of spare work piece clamping device, similar to the jaw chuck, and also uses mechanical force to fix the parts that need to be turned. Although the collet chuck offers a wider range of workpiece sizes than the jaw chuck, the speed, accuracy, and productivity advantages it provides for some machining tasks may be extremely important.

Which fixture is more effective requires several considerations when making a decision. For a given lathe machining task, whether to use a collet chuck or a jaw chuck, all the following factors need to be considered.

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 the workpiece is too large, the bearing may be overloaded. For those machining tasks with a dangerous limit, this danger may determine people's choice of workpiece clamps. The jaw chuck is often heavier than the equivalent collet chuck. Therefore, when the weight needs to be controlled, the spring clamp The head is the right choice.

Spindle speed collets are often a good choice for turning at very high spindle speeds for two main reasons:

One reason is related to the quality of the chuck. Assuming that the jaw chuck and collet are driven with the same spindle horsepower, the heavier jaw chuck takes longer to accelerate to the required speed, and the acceleration time will be longer. Work cycle reduces productivity.

Another reason is related to centrifugal force, because it increases with the square value of rpm, so this value is important in the case of high-speed cutting. For example, if you double the spindle speed, the centrifugal force will be four times the original. This force pulls the chuck jaws away from the center, often reducing the clamping force. However, with the collet chuck, the centrifugal force will not have a significant effect. As a result, the clamping force is more stable over the entire processing speed range.

Machining operation Collet chuck exerts clamping force on the entire circumference of the part, not only in the selected contact area. Therefore, good concentricity can be obtained. This is particularly important for secondary processing projects. Secondary processing requires Considering the accuracy related to the primary processing, because the collet chuck has a strong clamping ability, even if the jaw chuck is used for the primary processing, the collet can also be used for the secondary processing. Chucks with hollow soft jaws can achieve TIR (total reading) repeatability in the range of 0.0006 to 0.0012 inches, while the typical repeat accuracy of collet chucks is 0.0005 inches TIR or better. In order to further improve the secondary processing accuracy, During installation, the concentricity of the collet can also be adjusted.

Workpiece size collets are ideal for workpieces less than 3 inches in diameter. Collet chucks limit the length of the work piece. In particular, collet chucks limit the axial (Z-axis) travel range of a machine tool because its length is longer than the jaw chuck. When the machining length of the workpiece requires almost the entire available stroke of the machine tool, a claw chuck is probably used.

Processing batches Large and small batches are suitable for collet chucks.

In the case of small batches and multiple tasks, the advantages of the collet chuck are related to the product changeover time. The jaw exchange of the standard jaw chuck takes about 15 to 20 minutes, and the jaw chuck dedicated to fast replacement takes 1 minute. The quick change of the collet chuck only takes 15 to 20 seconds. When the product is changed frequently, the accumulated time saved is considerable.

When the processing batch is large, the saved time related to clamping can also be accumulated. The opening and closing time of the collet chuck is less than that of the jaw chuck. By reducing the non-cutting time of changing from one workpiece to the next To reduce processing cycle time.

Workpiece size range The collet chuck opens and closes faster in part because of its shorter drive stroke. Compared to jaw chucks, collet chucks have a more limited range of workpiece sizes. Sub-spindle conditions Turning machines equipped with sub-spindles are often used for a variety of high-volume machining operations. In these applications, collet chucks can significantly reduce machining time. They can process all sides of a part in one work cycle. These machines are often combined with bar feeders to achieve unattended production and continuous processing of workpieces. In these applications, the chuck drive time saved for a workpiece may be small, but in the entire production process, the time saved for each workpiece is multiplied by the number of processed workpieces, and the accumulated time is Considerable. ^[1]