Lathe chuck is one of the most important devices in the lathe machine it is used for holding and rotating piece of work while performing a lathe operation. The workpiece of short length and large diameter of irregular shape which cannot be conveniently mounted between centres are held quickly and rigidly in a chuck.

A chuck is attached to the lathe spindle by means of bolts with the backplate screwed onto the spindle nose. Accurate alignment of the chuck with the lathe axis is effected by spigot ting.

Lathe Chuck Types

Following are the different types of chucks used in lathe machine:

  1. Four jaws independent chuck
  2. Three jaws universal chuck OR Self Centering Chucks.
  3. Combination type chuck
  4. Magnetic type Chuck
  5. Collet chuck
  6. Air or hydraulic operated chuck
  7. Drill Chuck

 

Four-Jaw Independent Chuck

The figure shows a four jaw chuck diagram. The arrangement of four jaws independent chuck, which has four jaws, located at an angle of 90° to each other

Here all the four jaws are opened independently. Four screws are used in place of scroll disk, Hence it is called as four jaw independent chuck.

These chucks are majorly used in industry as it is cheap compared to Universal thru chucks and these chucks can hold square and offset jobs easily.

Each jaw made of tough steel has three inner and one outer gripping surface. The outer gripping surface is used for holding larger sizes of the workpiece by reversing the jaw.

 

Three jaws universal chuck OR Self Centering Chucks.

A three-jaw chuck is shown in the figure. This is the most commonly used types of chuck in the lathe machine. The three jaws are generally made of high

quality steel and are arrogated at an angle of 120° to each other.

During the operation, the jaw teeth are made to mesh with scrawl spiral teeth (Bevel teeth). The meshing causes a moment of all three jaws either towards or away from the chuck centre, depending upon the direction of rotation of the bevel pinion. The pinion is operated by square end key called “chuck key”.

The chuck suitable for holding round, or hexagonal, and other similar shaped workpieces. In three-jaw chuck, the job is centered automatically and quickly. But it has the less gripping capacity as only three jaws are used and centering accuracy is soon lost due to wear.

In Current Market four Jaw Thru Chuk is most used For Holding Square jobs,

These chucks are costly compared to Dog Chucks.

Combination Chuck

As the name implies, a combination of chuck, as shown in the figure. It is used both as a self-centering and an independent chuck to take advantage of both the types

The jaws are operated individually by separate screws or simultaneously by the scroll disc. The frame has teeth cut on its underside which meshes with the scroll and all the jaws together with the screws move radially when the scroll is made to rotate by a pinion.

 

Magnetic Chuck

The chuck is used for holding a very thin workpiece made of magnetic material which cannot be held in an ordinarily chuck. It is also used where any distortion of the workpiece due to the pressure of the jaws is undesirable.

The holding power of the chuck is obtained by the magnetic flux radiating either from the electromagnets or from the permanent magnets introduced within the chuck.

In the ON position, the flux passes through the workpiece and grips it. In OFF position the magnets are set aside bringing them in contact with high permeable ” keepers” which short-circuit the flux and prevent them from passing through the workpiece.

 

Collet Chuck

Collet chucks are used for holding bar stock in production work where quick setting and accurate centring is needed.

The chuck attached to the spindle by a nut consists of a thin cylindrical bushing known as collet having a slots cut lengthwise on its periphery. The inside bore of the collet is cylindrical, hexagonal, square, etc. Depending on the shape of the work that will pass through it.

The outside surface of the collet which is tapered fits in the taper hole on the body of the chuck, and the tail end which is threaded meshes with a key.

When the key is turned from outside, the collet is drawn in resulting in the split tapered end to be pushed inward due to the springy action. And the workpiece is securely and accurately held in the chuck. Different sizes of collectors are used for holding different sizes of the bar stock. These chucks are commonly used in capstan and turret lathes.

 

Air or Hydraulic Operated Chucks

This type of chuck shown in the figure. It is used in mass production work for its fast and effective gripping capacity. The mechanism incorporates a hydraulic or air cylinder mounted at the back end of the headstock spindle and rotates with it.

 

Drill Chuck

A drill chuck is sometimes used in a lathe for holding straight shank drill, reamer, or tap for drillingreaming, or tapping operation. The chuck is held either in headstock or tailstock spindle. It has centering jaws which have operated by rotating a key.