Classification of Lathe Machine Chucks ~ MECHTECH GURU

Chucks

A chuck is one of the most important device for holding and rotating a workpiece in a lathe. Workpieces of short length and large diameter or irregular shape which cannot be conveniently mounted between centers are held quickly and rigidly in a chuck. A chuck is attached to the lathe spindle by means of bolts with back plate screwed to the spindle nose.
The different types of chucks are:

Four jaw independent chuck, Three jaw universal chuck,
Combination chuck, Magnetic chuck, Collet Chuck, Air or hydraulic operated, Drill chuck

1. Four jaw independent chuck

Four jaw independent chuck has four jaws which may be made to slide within the slots provided in the body of chuck for gripping different size of the workpiece. Each jaw may be moved independently by rotating the screw. Each jaw made of tough steel has three inner and one outer gripping surface. Outer gripping surface is used for holding large size workpiece by reversing of the jaw. This chuck is particularly used in setting up of heavy and irregular shaped workpiece. The diameter of the body specifies the size of the chuck.

1 – Concentric circle, 2 – Chuck body, 3 – Jaw screw, 4 – jaw, 5 – Gripping surface,

6– Recess for back plate

Four Jaw Independent Chuck

2. Universal or self-centering chuck

In three jaw universal chuck all the jaws may be made to slide simultaneously by an equal amount within the slots provide on body. By rotating any one of them pinion which meshes with teeth cut on underside of the scroll disk. When the disc is rotate by any one of pinions, all the jaws move backward or forward by equal amount. The chuck is suitable for holding round, hexagonal and any other similar shaped workpieces and the job is centered automatically. It has less gripping capacity as only three jaws are used and centering accuracy is soon lost due to wear.

1 –Bevel pinion, 2 – Scroll disk, 3 – Bevel teeth on scroll disc, 4 – Chuck body, 5 – Jaw

Universal or self-centering chuck

3. Combination chuck

As the name implies a combination chuck may be used both as a self-centering and independent chuck to take advantages of both the types. The jaws may be operated individually by separate screws or simultaneously by scroll disc. The screws mounted on frame have teeth cut on its underside which meshes with scroll and all the jaws move radially.

1 – Chuck body, 2 – Frame, 3 – Screw, 4 – Jaw, 5 - Scroll

Combination chuck

4. Magnetic chuck

The chuck is used for holding a very thin workpiece made of magnetic material which cannot be held in an ordinary chuck. It is also used where any distortion of the workpiece due to high pressure of jaws is undesirable. The holding power is developed by magnetic flux radiating either from electromagnets or from the permanent magnets within the chuck. In the ON position the flux passes through the workpiece and grips it. In OFF position “keepers” short circuit the path of flux and cannot pass through the workpiece.

1 – Workpiece, 2 – Nonmagnetic material, 3 – Keepers, 4 –Face plate, 5 - Magnet

Magnetic Chuck

5 . Collet chuck

Collet chucks are used for holding bar stock in production work where quick setting and accurate centering is needed. The chuck is attached to the spindle by a nut consists of thin cylindrical bushing known as “collet”. The inside bore of collet may be cylindrical, hexagonal, square etc. depending on the shape of the workpiece. The outside surface of collet which is tapered fir in taper hole on the body of chuck. Different sizes of collets are used for holding different size of bar stock.

1 – Bearing, 2 – Spindle, 3 – Nut, 4 – Key, 5 – Chuck, 6 – Collet

Collet Chucks

6. Air or hydraulic operated chuck

This type of chuck is used in mass production work for its fast and effective gripping capacity. In mechanism, a hydraulic cylinder is mounted at the back end of headstock spindle and rotates with it. The movement of piston is transmitted to the jaws by a connecting rod and links and the jaws grip the workpiece securely.

1 – Cylinder, 2 – Air Passage, 3 – Headstock spindle, 4 – Piston, 5 – Valves, 6 – Piston rod, 7 – Link, 8 – Jaw, 9 – Guide, 10 – sliding unit

Air or hydraulic operated chuck

7. Drill chuck

Drill chuck is sometimes used in a lathe for holding straight shank drill, reamer and tap for drilling, reaming and tapping operation.
The chuck may be held either in headstock or tailstock spindle.
It has self-centering jaws which may be operated by a rotating key.

Drill chuck