In order to understand taper turning, first you have to understand the general meaning of TAPER.
Meaning of Taper
- A gradual decrease in thickness or width of an elongated object
- Diminish or reduce in thickness towards one end
- धीरे धीरे कम हो जाना
- to become or cause to become narrower towards one end
Now you have a general idea what taper is. So, you can better understand the Taper Turning now.
When the diameter of a piece changes uniformly, from one end to the other, the job is said to be tapered. Taper turning is a machining operation in which the gradual reduction in diameter from one part of a cylindrical workpiece to another part is carried out. There can be external or internal tapers. If a workpiece is tapered on the outside, it is known as external taper; if it is tapered on the inside, it is known as internal taper.
In a straight turning, the cutting tool moves along a line parallel to the axis of the work, causing the finished job to be the same diameter throughout.
Standard Machine Tapers
Certain types of small tools and machine parts, such as twist drills, end mills, arbors, lathe centers, etc., are provided with taper shanks which fit into spindles or socket of corresponding tapers, thus providing not only accurate alignment between the tool or other part and its supporting member, but also more or less frictional resistance for driving the tool. American Standards Association has classified Tapers as self-holding tapers and steep or self-releasing tapers.
Self Holding Tapers
The name self-holding has been applied to the smaller tapers like Morse and the Brown & Sharpe; because, where the angle of the taper is only 2 or 3 degrees, the shank of a tool is so firmly seated in its socket that there is considerable frictional resistance to any force tending to turn or rotate the tool relative to the socket. The term “self–holding” is used to distinguish relatively small tapers from larger or self releasing taper.
These are classified as follows
- Morse Taper
- Used for drills, reamers, and lathe center shanks
- Brown & Sharpe Taper
- Used for taper shanks on tools (end mills, arbors, reamers, collets etc.) generally used on Brown and Sharpe machines
- Jarno Taper
- Used in lathe and drill spindles
- Standard taper pins (1/4 inch per foot)
- Used for positioning and holding parts together
Steep or Self Releasing Tapers
A steep taper is defined as “a taper having an angle sufficiently large to ensure the easy or self–releasing feature.” The term “gage line” indicates the basic diameter at or near the large end of the taper. Steep tapers have a 3½ inch taper per foot. Formerly it was called standard milling machine taper. It is used mainly for alignment of milling machine arbors and accessories. It has key drive and uses draw-in bolt to hold it securely in milling machine spindle.
It is expressed as ratio of 1 mm per unit of length.