Taper and Taper Turning Prepared By: Gp Capt Dr. Hamid Ullah Khan Niazi

Learning Objectives After completing this unit you will be able to learn: Identify and state the purpose of self-holding and self releasing tapers. Cut short. Steep tapers using the compound rest Calculate and cut tapers on work between centers by offsetting the tailstock. Calculate and machine tapers with a taper attachment.

Definition Gradual decrease in the diameter of the work piece resulting in a cone shape is taper. According to units of measurement tapers are classified as Inch Tapers and Metric Tapers Metric tapers are expressed as a ratio of 1mm per unit of length: for example 1:20 taper would have a 1-mm change in diameter in 20mm of length.

Taper Elements D= Large diameter, d=small diameter, l=length of the taper, L=length of the work piece

Types of Tapers According to American Standard Association there are two types of tapers Self-holding Tapers and Self-Releasing Tapers Self-Holding Tapers: These are those tapers which when seated properly remain in position because of the wedging action of the small taper angle. Self-releasing Tapers: These are those tapers which are used mainly for alignment. They are also known as Steep tapers.

Types of Tapers-continued Standard Tapers include Morse Taper, Brown & Sharpe, Jarno Taper and Standard Taper pins Morse Taper : They are available in 8 sizes ranging from #0 to # 7. tpf= 5/8’’. They are used mostly on lathe center shanks, reamers, drills. Brown & Sharpe: They are available in sizes from # 4 to # 12. tpf=0.502’’. Brown and sharpe tapers are used on Brown and Sharpe tapers. Jarno Taper: They are used on lathe and drill spindles and sizes vary from # 2 to # 20. They have a tpf of 0.600’’.

Taper Turning A taper may be turned in a lathe by feeding the tool at an angle to the axis of rotation of the work piece. Basically there are three methods of producing a taper: By off setting the tail stock By means of a taper attachment set to the proper “tpf” or the proper taper angle of the work piece. By adjusting the compound rest to the taper angle. Note: The method used to machine any taper depends on the work length, taper length, taper angle and number of pieces to be machined.

What is TPF Tapers are measured as Taper per foot and it is the ratio of the difference of the large diameter and small diameter to the taper length l such as shown in the formula

The Tailstock offset method Tailstock offset method is used to cut a taper when no taper attachment is used or available. This involves moving the tailstock center out of line with the headstock center. Method of off setting the tailstock By visual method By means of the graduated collar and feeler gauge By means of a dial indicator.

Taper Turning by offsetting tailstock

Principle of Taper Turning by Tailstock off set The principle of turning taper by this method is to shift the axis of rotation of the work piece at an angle to the lathe axis and feeding the tool parallel to the lathe axis. This is done when the body of the tailstock is made to slide on its base towards or away from the operator by a set over screw.

Taper Turning by Off Setting the Tailstock The tailstock center is dislocated from its position which disturbs the tailstock center and hence the offset is measured with the help of simple rule

Advantages and Disadvantages of Tail Stock Off set The main disadvantage of this method is that live and dead center are not equally stressed out and the wear is not uniform. This method is suitable for turning small taper on long jobs The advantage is that it is suitable for turning small tapers

Mathematical Method of Measuring tailstock Off set Explanation of the formula : D-d/2xL/lx12/12 TPIxL/2x12/12

Inch Taper Attachment - Plain Taper Attachment

Telescopic Taper Attachment

Principle of Taper Turning by Taper Attachment- Advantages/ Disadvantages The principle of turning taper by taper attachment is to guide the tool in a straight path set at an angle to the axis of rotation of the work piece while the work is being revolved between the centers or by a chuck aligned to the lathe axis. The alignment of live and dead center being not disturbed, both straight and taper turning may be performed on a work piece in one setting without any loss of time. Very Steep tapers on a long work piece may be turned which cannot be done by another method.

Difference between Plain and Telescopic Taper Attachment In plain taper attachment the cross feed screw is disengaged. The depth of cut is made by using the compound rest feed handle. In telescopic taper attachment the cross feed screw is engaged. The depth of cut can be set by the cross feed handle.

Mathematical Method of Measurement Taper Turning by Taper Attachment

Principle of Taper Turning by Compound Rest Method To produce short and steep tapers in degrees the compound rest method is used. It is not highly recommended on long length of work pieces. Holding of work piece between the centers is not necessary.

Metric Tapers Metric tapers are expressed in the form of a ratio. CONICITY: For metric tapers it is given as K=D-d /l

Final note “Checking Tapers” Tapers are mainly checked by the following methods: Using a simple Micrometer Using a Taper Micrometer Using a Sine Bar By chalking lines

Checking taper by Chalking lines

Assignment Solve problems on Metric and Inch tapers. How to calculate taper angle and TPF How to calculate tailstock offset and taper attachment.

Summary Taper turning is one of most important operation performed on the lathe machine. Most of the drill shanks, reamers, lathe centers and milling machine spindles are all tapered and help in holding and joining different parts together.

Questions and answers