Taper Turning.

(d) A power feed of approximately 0.002 inch per revolution may be used,

although it is sometimes advisable to feed by hand, thereby retaining

control of the cutter bit in case of emergency. The cutting edge is set on

center when cutting off stock 1 inch or less in diameter and 1/16 inch above

center for each additional inch in diameter. The tool must be lowered as

the diameter is reduced, unless the center of the workpiece has been drilled

out.

Do not attempt to cut off work that is held between centers.

It

cannot be performed satisfactorily.

(3) Chattering. The rapid vibration of the tool and work, which is called

chattering, frequently takes place when using a parting tool or a cutting

off tool and may be due to one or more reasons: a tendency of the tool or

workpiece to spring, the tool is set too high, looseness of the cross-slide,

or looseness of the lathe spindle in its bearings.

j.

Taper Turning.

(1) General.

(a) In ordinary 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.

However, when cutting a taper, the tool moves at an

angle to the axis of the work, producing a taper.

Therefore, to turn a

taper, the work must either be mounted in a lathe so that the axis upon

which it turns is at an angle to the axis of the lathe, or cause the cutting

tool to move at an angle to the axis of the lathe.

(b) When the diameter of a piece changes uniformly, from one end to the

other, the piece is said to be tapered.

Taper turning as a machining

operation is the gradual reduction in diameter from one part of a

cylindrical workpiece to another part (figure 28 on the following page).

(c) Tapers can be either external or internal.

If a workpiece is

tapered on the outside, it has an external taper; if it is tapered on the

inside, it has an internal taper.

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