University of Nevada Las Vegas

MEG426/626 Manufacturing Processes

Department of Mechanical Engineering

Fall Semester 2000

 

 

 

 

Turning and Related Operations

 

 

Turning is a machining process in which a single-point tool removes material from the surface of a rotating cylindrical workpiece; the tool is fed linearly in a direction parallel to the axis of rotation.

Lathe is the machine tool used for turning. It provides power to turn the part at a given rotational speed and to feed the tool at a specified rate and depth of cut.

 

Operations Related to Turning
 

a). Facing;

b). Taper turning;

c). Contour turning;
 

d). Cutoff;

e). Chamfering;

f). Form turning;
 

g). Threading;

h). Boring;

i). Drilling;
 

j). Knurling.

    

 

Methods of Holding the Work in a Lathe

(a). Mounting the work between centers;

For work with large length-to-diameter ratios

(b). Chuck;

For both long and short work

(c). Collet;

For cylindrically shaped work such as barstock

(d). Face plate.

For parts with irregular shapes.

 

Engine Lathe: a manually operated versatile machine tool. It usually contains a headstock, a tailstock, a tool post, a cross-slide, a carriage, a leadscrew, and a machine tool bed.

Toolroom Lathe: built for fabricating components for tools, fixtures, and other high-precision devices.

Higher accuracy, smaller in size, wider range of cutting speed and feed comparing with the engine lathe.

Turret Lathe: a manually operated lathe in which the tailstock is replaced by a turret that holds up to six cutting tools.

Chucking Machines: uses a chuck in its spindle to hold the workpart.

No tailstock; for lightweight parts; automatically controlled.

Automatic Bar Machine: uses a collet to hold long bar stock, which permits the bar to be fed through the headstock.

For producing screws and similar items.

NC Lathes: machine motions are controlled by computers.

 

 Boring Machines

 

Boring is an internal turning operation. It uses a single point tool against a rotating workpart to cut the inside diameter of an existing hole.

The machine tools are called boring machines or boring mills.

 

Horizontial boring mill

Work rotates,

Tool rotates.

Vertical boring mill

For large, heavy workparts with large diameters.

 

Cutting Conditions in Turning

 

v = p D0 N

where v = cutting speed, in./min (mm/min); D0 = original diameter of the part, in. (mm); and N = spindle revolution.

D0 – Df = 2 d

 

Where d = depth of cut, and df = the final diameter of the part.

 

fr = N f

 

fr = feed rate, in./min (mm/min); and f = feed in./rev (mm/rev).

 

Tm = L/fr

where Tm = time of actual machining, min; L = length of the cylindrical workpart, in. (mm).

 

MRR = v f d

where MRR = material removal rate, in.3/min (mm3/min)

 

 

Created by Dr. Wang