Taper turning is the turning process in which the cutting tool moves at an angle to the axis of the workpiece so that a tapered shape is obtained in the workpiece.
In a tapered piece, the diameter of the workpiece changes uniformly from one end to another. The workpiece can be tapered from inside or outside.
To create taper the workpiece must be installed in such a way that the axis of rotation is at an angle to the axis of turning.
While using any method to create a taper, the cutting edge of the tool must be placed on the center of the axis of the workpiece. If the cutting edge is not properly placed on the center of the axis of the workpiece then the workpiece will not be truly canonical and the rate of taper will vary with each cut out.
Different types Of Taper Turning methods:-
i) Form tool method:
Form tool method is one of the simplest methods to produce a short taper.
In this method, a broad form tool having a straight cutting edge is set onto the work at a half taper angle and is fed straight into the workpiece. The tool used in this method is called the taper turning form tool.
The tool used itself is of taper shape hence producing tapered workpiece.
In this method, taper length should be less than tool cutting edge length. As the whole cutting edge removes the metal, it will produce huge vibration and hence a large force is required. This method is performed at a slow speed to reduce vibration and force required.
ii) Tail Stock Set Over Method:
This method is generally used when the angle of the taper is very small.
In this method, the axis of rotation of the workpiece is shifted at half an angle of taper to the lathe axis.
The workpiece is kept between the live center and dead center. The tailstock is moved in a cross direction perpendicular to the direction of the lathe axis by the turning set over method. The tail stock is off-setted wither in upward or downward direction so that the workpiece comes in a tilted position and hence the taper turning can be carried out.
iii) Compound Rest Method:
This method is generally used to produce short and steep taper. In this method, compound rest is swiveled to the required angle and clamped in position. The compound rest can be swiveled to 45 degrees.
The workpiece is held in the chuck and will be rotated in the lathe axis.
Both external as well as internal taper can be produced using this method.
iv) Taper turning attachment method:
In this method, taper turning is done using an attachment.
This attachment has a guide bar and this guide bar is generally pivoted at the center.
Guide bar can swing at any required angle of the taper. The tool moves parallel to the guide bar.
The guide bar is used to guide the tool at a required angle. The guide bar has a scale of degrees. The guide bar can be swiveled at a maximum angle of 10° on either side.
The required angle for taper turning is achieved by swiveling the guide bar.
In this method, the workpiece is held in a chuck.
It has a guide block that connects to the rear end of the cross-slide and it moves on the guide bar.
In this method, the guide bar is set at an angle at which the workpiece is to be tapered.
Using the taper turning attachment method, taper turning of any size can be performed easily.
The job is held either in the chuck or in the centers i.e dead and
live center in the taper turning process.
The depth of cut is given by the compound rest handwheel.
Advantages of taper Taper turning attachment method:
a) The lathe remains in alignment and the center holes in the workpiece are not distorted.
b) In this method the alignment of the lathe is not needed to be disturbed and hence effort of the operator is reduced.
c) a very wide range of tapers can be produced using this method.
d) It can be used for mass production.
Some engine lathes have a prebuilt taper attachment and most of the manufacturers have taper attachment available.
v) Combining Feed Method:
It is an advanced taper turning method. In some of the lathe machines, both longitudinal and cross feed may be engaged simultaneously due to which the tool can be moved in a diagonal path and the taper turning can be done.
The diagonal path followed by the tool is the resultant of the two feeds. The direction of the tool can be altered by varying the feed rate of the longitudinal and the cross feeds.
This method can only be operated by a skillful operator because it is very easy to get wrong in this method.