An Overview of the Jaw Chuck

Posted on Dec 10, 2020

Jaw Chuck

The jaw chucks can be applied in either the lathes, which can be operated manually or in combination with the CNC (computer numerical control) system, or the conventional milling machine. In these two kinds of machines, the works that the jaw chucks hold are different, as the operation methods between the lathes and the milling machines are different as well.

What Is a Jaw Chuck?

A jaw chuck is a work-holding device, which clamps the works, either the machine tools or the workpieces, and facilitates the works it holds to rotate along with the rotating spindle behind during the process of the machining works. There are various work-holding devices for the machining works in the industries, each type of the work-holding devices is specialized in different machine tools or workpieces that they clamp depending on the requirements of the machining works.

The jaw chucks can be applied in either the lathes, which can be operated manually or in combination with the CNC (computer numerical control) system, or the conventional milling machine. In these two kinds of machines, the works that the jaw chucks hold are different, as the operation methods between the lathes and the milling machines are different as well. The lathes are operated with the workpieces rotated, and the machine tools are kept stationary. In contrast, the milling machine is operated with the machine tools moves, and the workpieces stay stationary.

Jaw chucks are used to help workpieces and machine tools rotate. In other words, in the working of lathes, the jaw chucks hold the workpieces, whereas, in the machining works of milling machines, the machine tools are held by the jaw chucks instead.
 

Vises vs. Jaw Chucks

To broadly differentiate these work-holding devices, the two common categories can be the vises and the chucks. Both vises and chucks are used to secure the workpieces or the machine tools they hold during the high pressure or high speed of machining works. They are actually different in the construction and the number of available jaws.

No matter what types of vises, there are two jaws on the device. One is the front jaw, which is the one that is closer to the operator, and the other is the rear jaw in the opposite position. These two jaws are set parallel to each other and are used in conventional drilling, milling, or grinding works. These vises usually work axially on horizontal, vertical, or angled surfaces, and are mainly used to hold workpieces and keep the workpieces stationary for the machine tools to cut on them.

In contrast, the chucks are relatively more versatile than the vises, since the jaws that the chucks have can range from one jaw to six jaws on the device, and each one of them is applied for different forms or shapes workpieces or machine tools. Since there are several jaws, which can be more than two jaws, on the chucks, they can also be called jaw chucks. Each of these jaw chucks is mounted on a circular scroll plate, and the entire device works by rotating itself with the rotating of the spindle of the machine. These two factors make the differences between the vises and the jaw chucks.
 

How Many Jaws Are There on a Jaw Chuck?

A jaw chuck consists of a main body that is made of cast iron or semi-steel with one or multiple pinions on the edges of the body, a cover, a scroll plate, and one or more jaws. The opinions on the edges of the main body are used for fastening or loosening the jaws with an additional wrench that is equipped with the jaw chuck. The cover is set behind the back of the main body, while the scroll plate is in the front, and the jaws would be attached and fastened or loosened right on the scroll plate.

When it comes to the jaws of the jaw chucks, there can be least to one and up to six jaws on the chuck, and each one of them is applied for different forms or shapes of works, which there are more details below:
 

One-jaw Chuck

The one jaw chuck is also known as the collet chuck, which is used to hold thinner works in the shapes of round, square, or hexagon. The works the one jaw chuck holds are usually more delicate than the works that are held by multiple jaws of chucks.
 

Two-jaw Chuck

The two-jaw chuck is usually used to clamp rectangular-shaped works on the lateral sides of the works.
 

Three-jaw Chuck

The three-jaw chuck is the most common and versatile type of jaw chucks, and it is used to hold round or hexagonal works. The three-jaw chucks can be in various sizes from 1/8-16 inch in diameter, and hold works with an accuracy level of around 0.010.
 

Four-jaw Chuck

The four-jaw chuck is the second commonly applied jaw chuck after the three-jaw chuck. It is used to secure square, hexagonal, and irregular-shaped works, and is required to be aligned with a dial-indicator.
 

Six-jaw Chuck

The six-jaw chuck is used for holding thin-walled parts of works. Since the works formed by thin walls would be more delicate, which means that they may be easily deformed or distorted during the machining works, they need the six-jaw chucks in order to allow for evenly distributing clamping forces by the jaws.
 

What Types of Jaw Chucks Are There?

According to the clamping forces of the jaw chucks, they can be differentiated into manual jaw chucks and power jaw chucks. The former requires the operators to fasten or loosen the jaws by manual force, while the latter relies on pneumatic or hydraulic pressure to automatically secure the works.

In addition to the variation of the clamping forces, the jaw chucks can also be differentiated by the clamping methods, including the universal jaw chucks, independent jaw chucks, and combination jaw chucks.
 

Universal Jaw Chucks

Unlike the jaws on the vises, which are set parallel on a horizontal surface, the jaw chucks clamp the works on a round plate with several jaws securely set radially around the works, the alignment of the jaws determines how the works perform their duties. Some of the jaw chucks, usually the three-jaw ones, are universal jaw chucks, which are also known as the self-centering chucks. The self-centering chucks can align the jaws on the chuck automatically, and each one of the jaws works is fastened or loosened together.
 

Independent Jaw Chucks

The independent jaw chucks, as the name suggests, are the chucks that each jaw can be moved independently, which allow these jaw chucks to be applied for the irregularly-shaped works, as in the four-jaw chucks. However, as the independent jaw chucks do not have the ability to center the jaws like the universal chucks, the dial-indicators are required for the purpose of aligning the jaws on the right track before the machining works. Therefore, the setup time of the independent jaw chucks would take longer than the universal jaw chucks accordingly.
 

Combination Jaw Chucks

The combination jaw chucks are the combination of the universal jaw chucks and the independent jaw chucks. In other words, this type of jaw chucks allows for either self-centering or independent adjustment of each jaw before the machining works. This feature makes the combination jaw chucks more versatile in the applications of jaw chucks, as they provide the flexibility for the operators to adjust the jaws or set the jaw chucks aside for self-centering depending on the requirements of the works or the preference of the operators.

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