machining operations

advantages of machining

• variety of work materials

• variety of part shapes

• dimensional accuracy

• good surface finish

disadvantages of machining

• wasteful of material

• time consuming

material removal

excess material removed from starting workpart so that remains is desired geometry

types of machining

conventiona, abrasive processes, non-traditional machining

conventional machining

cutting tools remove material

abrasive processes

hard abrasives used

non traditional machining

uses other forms of energy

• mechanical, electrochemical, thermal and chemical

factors of geometry produced

• motions between tool and workpart

• shape of cutting tool

generating operations

geometry of workpart is determined by cutting tool feed trajectory

forming

shape of part determined by geometry of cutting tool

turning operations

point tool removes material from surface of rotating workpiece

• tool fed in direction parallel to axis of rotation

• carried out on machine tool called lathe

lathe

tool on which turning operations occur

three jaw chuck

turning: lathe: holds workpiece with three jaws

faceplate

turning: lathe : workpart placed on spindle which rotates on faceplate

turning operations: facing

tool fed radially onto rotating work on one end to create flat surface (generating)

turning operations: form turning

tool has shape that has imparted to work (forming)

taper turning

tool fed at angle creating tapered look by generation

chamfering

generating: cuts angle on corner of cylinfer

contour turning

generative

cutoff

cuts at some location of part to cut off end of part

boring

scrapes OUT material, single point tool fed linearly inside

threading

turning operation that creates threads in cylinder (screw)

thread

indentations like screw

drilling

can be perfomerd on lathe by feeding drill into rotating work

knurling

NOT machining operation as it does not remove metal. metal forming operation used to produce crosshatches

drilling vs boring

drilling creates round hole, boring enlarges existing hole, performed on drill press

blind hole

does not go straight thru

through hole

goes straight through

reaming

enlarges hole, giving better tolerance on diameter and improves surface finish

tapping

creates screw threads in existing hole

counterboring

larger diameter follows smaller diamerer

countersinking

drilling operation where the step is cone shaped

centring

drilling operation where a blind hole is created to centre actual one

spot facing

similar to milling, creates flat part on work

milling

machining operation where workpart is fed past rotating cylindrical tool with multiple cutting edges

machine that performs milling

milling machine, axis of rotation is PERPENDICULAR to direction of feed

types of milling operations

peripheral milling and face milling

cutting edges in milling

teeth

interrupted cutting operation

milling: after rotation of each milling teeth, they exit

face milling

face is in contact w material

peripheral milling

side of teeth are in contact with workpart

conventional face milling

• diameter of cutter is greater than workpart width

• cutter overhangs work on both sides

partial face milling

cutter overhangs work on one side

end milling

cutter diameter less than work width

profile milling

end milling where outside is cut

pocket milling

used to mill shallow pockets

surface contouring

creates 3D surface form