Factors Affecting Machinability

Factors Affecting Machinability

Factors Affecting Machinability -

List I. Common Machine Variables Affecting Ease of Cutting:

1. Cutting speed

2. Dimensions of the cut (feed, depth, etc.)

3. Tool form (angles, radii, type, etc.)

4. Tool material

5. Cutting fluid (chemical and physical properties, temperature, etc,)

6. Rigidity and freedom from chatter of machine tool and work-holding device

7. Nature of engagement of tool with work (continuous or intermittent, entrance and exit conditions, etc.)

Likewise, for a given set of machine conditions, the ease of machining varies with the work material variables (the various quantities that are used in practice to specify the properties of the work material, are enumerated in List II).

List II. Common Work material variables affecting Ease of Cutting:

1. Hardness

2. Tensile properties

3. Chemical composition

4. Microstructure

5. Degree of cold work

6. Strain hardenability

7. Shape and dimensions of work

8. Rigidity of workpiece.

Further, the criteria for judging the ease of working a metal vary with the preference of the experimenter or the requirements of the job. Some of the more common of these criteria, used singly or jointly as a measure of the ease of working a metal, are given in List III.

List III. Common Criteria/or Judging Ease o/Cutting:

A. General criteria:

I. Life of the cutting tool between re sharpenings, expressed in various terms

2. Magnitude of the tool forces machining work or energy, or power consumption.

3. Quality of the surface finish produced on the work.

B. Specific criteria (generally used as quick tests for judging ease of machining):

1. Drilling torque or thrust

2. Drilling time or rate of penetration.

3. Energy absorbed in pendulum type milling cut.

4. Temperature of cutting tool or chip

5. Amount that chip is hardened during removal

6. Cutting ratio of chip

7. Combined values of the mechanical variables that control forces and chip geometry

8. Feed rate under constant feeding pressure in turning at a constant speed

9. Ease of chip disposal.