Work Holding Devices of Turret Lathes

Work Holding Devices of Turret Lathes

Work Holding Devices of Turret Lathes - Turret is a mass production machine. In order to keep set up time to minimum, the work holding devices should be accurate, easy and quick to operate, and should ensure rigidity against heavy cuts. Commonly used work holding devices are:

(a) Collet chucks,

(b) Jaw chucks,

(c) Arbors, and

(d) Fixtures.

a) Collet chucks Collet chucks are widely used to clamp bar stock in machining on turret lathes. Their main feature is a collet, which is a steel sleeve with split tapered portion forming jaws, Clamps bar 3 when tube 4 together with collet 2 is shifted to the left until the jaws of the collet are contracted by inner tapered hole of spindle 1.

The drawback of this arrangement is an axial bar displacement in clamping, which decreases the accuracy of axial bar positioning. Illustrates a collet chuck in which, on clamping bar, collet 1 is moved to the right and the outer taper of collet is contracted under the action of the inner taper of stop nut 2. screwed on spindle 3. The conventional collet taper angle is 30°.

Collet chuck may be hand operated or air operated.

(b) Jaw Chucks Jaw chucks are used 10 bold irregular shaped individual work pieces. Various jaw chucks employed for the said purpose are:

(i) Three jaw self centering chuck,

(ii) Four jaw independent chuck,

(iii) Two jaw box chuck,

(iv)Power chucks.

Jaw chucks (i) and (ii) have been described in the chapter on Lathe. Two jaw box chucks is used for holding specially the work pieces having parallel flat sides.

Power chucks are operated by air pressure, or hydraulic pressure. Air chucks are commonly used because of easy availability of compressed air in the workshops, ease of their operation and proper grip strength.

 (c) Arbors.Arbors may be sometimes used for holding small workpieces having accurately drilled holes in them. Threaded type and expanding type arbors are in use.

(d) Fixtures. Special fixtures may be employed to hold jobs which cannot otherwise, be held in collets, jaw chucks or arbors.