We have seen the basics of metal cutting tools i.e. metal cutting tool definition and classification and single point cutting tool nomenclature with the help of our previous posts.

Today we are going to start a very important topic here with the help of this post i.e. difference between rake angle and clearance angle of cutting tool.

We will also see here the significance of rake angle and clearance angle of cutting tool and we will come to know here that why rake angle and clearance angle of cutting tool are so much important in metal cutting process.

Rake angle and clearance angle of cutting tool

Rake angle and clearance angle of cutting tool are very significant for all the metal cutting tools.

Following figure shows the metal cutting process. V_C is the cutting velocity and its direction i.e. velocity vector is also displayed in the figure.

There is one reference plane also displayed here in the following figure which is perpendicular to the velocity vector and denoted by π_R. Rake angle will be measured with respect to this reference plane π_R.

Now let us understand here the meaning of rake angle of metal cutting tool

Rake angle is basically defined as the inclination of rake surface of the metal cutting tool with respect to the reference plane. Rake angle will be denoted by ϒ.

We must need to understand the importance of rake angle in metal cutting process or machining process.

Rake angle is provided in metal cutting tool for smooth chip flow and to facilitate the machining process. If rake angle will be provided, machining process will be smooth and easier. Hence, less amount of energy, force and effort will be required.

Now let us understand here the meaning of clearance angle of metal cutting tool

Clearance angle is basically defined as the inclination of flank surface or clearance surface of the metal cutting tool with respect to the machined or finished surface. Clearance angle will be denoted by α.

We must need to understand the importance of clearance angle in metal cutting process or machining process.

Clearance angle is provided in metal cutting tool to avoid the rubbing action between the flank surface of metal cutting tool and finished surface. If clearance angle will not be given, finished surface will be damaged due to rubbing action of flank surface of metal cutting tool with finished surface and in this situation tool will also be damaged.

Therefore, clearance angle is very important and it must be positive. Clearance angle could never be negative.

Clearance angle will be in the range of 3 to 15 degree depending on the tool-work materials and machining process type e.g. drilling, turning, boring etc.

Rake angle and clearance angle in case of turning operation are also displayed in the following figure.

Sign of rake angle and clearance angle

Rake angle of metal cutting tool might be positive, negative or zero too. Let us consider the following figure where a turning operation is displayed with positive rake angle, negative rake angle and with zero rake angle too.

Positive rake angle will reduce the effort or cutting force and hence will reduce the cutting power requirement too.

Negative rake angle will help to increase the edge strength and life of the tool.

Zero rake angle will help to simplify design and manufacture of the form tools.

Clearance angle is very important and it must be positive. Clearance angle could never be negative.

If clearance angle will not be given, finished surface will be damaged due to rubbing action of flank surface of metal cutting tool with finished surface and in this situation tool will also be damaged.

Therefore, we have seen here the difference between rake angle and clearance angle of cutting tool. We have also seen here the significance of rake angle and clearance angle of cutting tool. Finally, we have also seen that why rake angle and clearance angle of cutting tool are so much important in metal cutting process.

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We will find out now the main characteristics of cutting tool materials in our next post.