Understanding Cutting Tool Geometry

| |

The selection of proper cutting tool geometry is of the utmost importance when doing an effective cutting. In this video, we will provide a clear explanation of the cutting process and tool geometry related to single point cutting tool.

A detailed webpage version of the video is given below.

The Basic Cutting Operation

To remove a metal chip from a work piece, you have to cut along at least 2 surfaces. Cutting along just one surface will not guarantee chip removal. This is clearly shown in the figure below.

power flow in automobile

Fig.1 To remove a piece of metal from the work piece you have cut through 2 surfaces

For this purpose, cutting tools are provided with 2 cutting edges, a main cutting edge and an auxiliary cutting edge. The main cutting edge cuts the main portion of the chip, while the auxiliary cutting edge cuts the second surface and removes the material.
power flow in automobile

Fig.2 A close-up view of main and auxiliary cutting edges

Single Point Cutting Tool – Tool Geometry Details

The single point cutting tool has many geometrical parameters to make the cutting process more smooth and efficient. These geometrical parameters also help to enhance the tool life by a great extent. All these details are discussed in this session.

Nose Radius

You can see the smooth corner between the main and auxiliary cutting edges; this corner is known as the nose of the tool. The radius of the nose greatly affects the surface finish of the operation and the strength of the tool. Sharp nose always produces scratches on the work piece. A blunt nose as shown in the figure eliminates these scratches and gives a good surface finish. Moreover the risk of nose breakage is greatly reduced in a tool with an appropriate nose radius.

power flow in automobile

Fig.3 Nose, Rake angle and relief angle make the cutting operation more efficient

Rake Angle

Material removal by the main cutting edge is easier when the material’s flowing surface is at an angle, as shown. This angle is known as the rake angle of the tool, more specifically as the back rake angle. The back rake angle greatly affects the chip thickness and the force of the cutting. The rake angle can be positive, zero or negative . A positive rake angle greatly reduces the cutting force . Due to this reason most of the cutting operations are done with a positive rake angle.

Relief Angle

To avoid the rubbing of the cutting tool with the work piece, a relief angle is provided as shown. The relief angle greatly reduces the tool wear. Please remember that the relief angle has to be positive always.

Side Rake and Relief Angle

Similar rake and relief angles are also given to the auxiliary cutting edge. To get a better view of the angles a cross-sectional shape is shown in the figure below.

power flow in automobile

Fig.4 Auxiliary cutting edge is also provided with rake and relief angles

End and Side Cutting Edge Angle

Now, let’s have a look at the tool’s initial position. You can see that the cutting edges form angles, as shown. They are called end and side cutting edge angles.

power flow in automobile

Fig.5 A view of side and end cutting edge angles

The Tool Signature

These 7 parameters together, completely define the geometry of a tool. These 7 parameters together known as the signature of a tool.

power flow in automobile

Fig.6 The 7 parameters discussed so far is known as tool signature

There are different international standards available to represent the the tool signature. However all those standards are interchangeable.

You may also like...

Read More

Is there something called Bernoulli's component of Lift ?, Have a concept check

| |

The theory under consideration is often called as 'Equal Transit' theory. It is true that, a high static pressure is created at the bottom of airfoil and low pressure on the top. But this pressure difference is not created by the so called 'Equal Transit' theory. The 2 big mistakes people did while applying Bernoulli's principle were

  1. Why should the 2 particles starting together, meet at the trailing edge at the same time. It is completely an absurd argument, there is no law in physics to support this. The 2 particles can leave for a completely different path and they may not even meet in their life time.
  2. You cannot apply Bernoulli's equation across 2 streamlines. It should applied strictly along a stream line.

Bernoulli's equation is completely true, it is conservation of energy along a streamline. Some people applied Bernoulli's equation without properly understanding what it is. That caused the whole confusion.

Scientist from NASA strogly disagree with 'Equal trasit theory'. Please read these valuable articles and paper. ARTICLE1

If you are interested in learn more about the lift generation (truth & myth), watch this excellent lecture from Dr Holger Babinsky of Cambridge university.
You can download the slides he used for the lecture from here SLIDES

Read More
Powered by Blogger.