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What is Dividing Head?
The dividing head is also known as the indexing head. Indexing is the process of evenly dividing the circumference of a circular workpiece into equally spaced divisions, such as in cutting splines, cutting gear teeth, milling grooves in taps and reamers, spacing holes on a circle. The indexing head of the indexing fixture is used for this purpose.
For indexing, the workpiece, this type of dividing head is very useful.
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| Fig. 1 Universal Dividing Head |
Types of Dividing Head
There are three types of dividing head
- Plain dividing head
- Universal dividing head
- Optical dividing head
Plain Dividing Head
Plain dividing head is the simplest of all types of dividing heads. Plain dividing head is classified into two types.
First type Plain Dividing Head
- The first type carries an indexing plate directly mounted on its spindle and there is no use of worm and worm wheel.
- The index plate carries 12-24 equispaced slots on its periphery.
- The workpiece is held between two centers i.e. one on the dividing head spindle and the other on the tailstock.
- For locking the spindle in its position hand lever is used.
- The plate, together with the spindle can be rotated by means of hand i.e. provided on the left-hand side of the dividing head.
Second Type Plain Dividing Head
- The second type of plain dividing head uses a worm and worm wheel mechanism.
- In this indexing, the plate movement is obtained by the worm which is rotated by hand.
Plain dividing head is commonly used in operations where average accuracy is required such as fluting taps, reamers, milling rectangles, squares, hexagons, etc.
Universal Dividing Head
Universal Dividing Head/Indexing Head consists of a robust body and a worm drive is enclosed in it. It is having a worm and worm wheel as shown in fig 2.
Fig 2 shows details of the internal mechanism of the Universal Dividing Head. In this, the dividing head spindle carries a worm wheel that meshes with the worm.
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| Fig. 2 Internal Mechanism of Universal Dividing Head |
This worm carries a crank at its outer end. The index pin works inside the spring-loaded plunger, which can slide radially along a slot provided in the crank.
This plunger can slide, adjust the pin position along a desired hole circle on the index plate.
The index plate is mounted on the same spindle as the crank, but on a sleeve, hence the crank and worm spindle can move independently on the index plate.
To set a definite distance along the desired hole circle, sector arms are used. Sector arms are of a detachable type and can be set at the desired angles with one another. The index plates are available in a set of two or three, with a number of hole circles generally on both sides.
Advantages of Universal Indexing Head
The universal indexing head or universal dividing head is used to perform the following operations :
- To set the workpiece in the desired position, in relation to the machine table.
- To rotate the workpiece through the desired angle, after each cut and hence, index the periphery of the workpiece.
- To provide continuous rotary motion to the workpiece while milling of helical grooves.
Optical Dividing Head
The optical dividing head is the most precise dividing head. An optical dividing head is used for the measurements and inspection of precision angles, measurements, and dimensions.
The angular dimensions can be read up to seconds of a degree with the help of optical lenses set in the head.
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