What is Collet Chuck | Types Of Collet Chucks
What is Collet Chuck
Collet chucks or collets are used mainly to hold bar stock, especially in the smaller sizes. A collet is a circular steel shell having three or four equally spaced slits extending the greater part of its length.
These slits impart springing action to the collet. That is why, collets are also known as “spring collets”. The collet nose is made thicker to form the jaws. The outside surface of the nose fits in the taper hole of the hood. The inside of the collet is made according to the shape of the work to be held. Collets are much more suitable than a self centering chuck in mass production work due to its quickness in action and accurate setting. The collets may be operated by hand or by power.
Types of collet Chuck :
The collets are classified by the methods used to close the jaws on the work.
Push out type Collet chuck
The push out type collet chuck is shown in Fig. 2.68 (a). In this type the taper of the collet nose and hood converge towards the right. To grip the work, the tapered portion of the spring collet is pushed into the mating taper of the hood. There is a tendency of the bar to be pushed slightly outward when the collet is pushed for gripping. If the bar is fed against a stop bar fitted on the turret head, this slight outward movement of the bar ensures accurate setting of the length for machining.
Draw back or Draw in type Collet chuck
The draw back type collet chuck is shown in Fig. 2.68 (b). In this type the taper of the collet nose and hood converge towards the left. To grip the work, the tapered portion of the spring collet is pulled back into the mating taper of the hood which causes the split end of the collet to close in and grip the bar. The machining length of the bar in this type of chuck cannot be accurately set as the collet while closing will draw the bar slightly inward towards the spindle.
Dead length type Collet chuck
The dead length type collet chuck is shown in Fig. 2.68 (c). For accurate positioning of the bar, both the push out and draw in type collet present some error due to the movement of the bar along with the collet while gripping. This difficulty is removed by using a stationary collet on the bar.
In this type the taper of the collet nose converge towards the left. A sliding sleeve is placed between the collet and the hood. This sliding sleeve has a tapered edge which fits on the taper of the collet nose. To grip the work, the sliding sleeve is pushed towards the right. This makes the collet to close in and grip the bar. The end movement of the collet is prevented by the shoulder stop
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