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17:36

MAIN CHARACTERISTICS OF CUTTING TOOL MATERIALS

We have seen the basics of metal cutting tools i.e.metal cutting tool definition and classification, single point cutting tool nomenclature. Also, we have studied the difference between rake angle and clearance angle of cutting tool 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. main characteristics of cutting tool materials.

We will see here that what are the various important characteristics of metal cutting tool materials.

Main characteristics of cutting tool materials

According to the analysis of tool failure, there are following important characteristics of cutting tool material as mentioned below.

Sufficient strength

Metal cutting tool material must have sufficient strength to maintain a sharp cutting edge.

Resistance to wear

Metal cutting tool material must have sufficient resistance to withstand wear of cutting edge of metal cutting tool and metal cutting tool may provide better service life before the replacement of metal cutting tool.

Sufficient hardness

Metal cutting tool material must have sufficient hardness especially at elevated temperatures so that strength and hardness of cutting tool material may maintained at the temperature encountered in the machining operation.

Sufficient toughness

Metal cutting tool material must have sufficient toughness so that impact forces on the cutting tool in interrupted cutting operations e.g. milling or turning may not fracture the cutting tool.

Chemical stability

Metal cutting tool material must have sufficient chemical stability so that any adverse reactions that may contribute to tool wear could be avoided or reduced.

Proper heat treatment

Metal cutting tool material must be well heat treated to secure good mechanical and technological properties.

Accurate design

Metal cutting tool material must be precisely designed to meet basic requirements.

Therefore, we have seen here the various important characteristics of metal cutting tools. 


Do you have any suggestions? Please write in comment box and also drop your email id in the given mail box which is given at right hand side of page for further and continuous update from www.hkdivedi.com.  

We will find out now the concept of in our next post.   

Reference:  

Production engineering by K.C. Jain and A.K. Chitale

Image courtesy: Google     

Also read

Lever and its types with examples

Guidelines for solving friction problems in mechanics

Rolling resistance or rolling friction

Wedge friction and self-locking in engineering mechanics

Concept of force system in engineering mechanics

Difference between fan and blowers

Basics of centrifugal compressor 

Force exerted by a jet on vertical flat plate  

Force exerted by a jet on stationary inclined flat plate  

Force exerted by a jet on stationary curved plate  

Force exerted by a jet on a hinged plate  

Force exerted by a jet on a curved plate  

Force exerted by a jet of water on a series of vanes  

Force exerted by a jet of water on a series of radial curved vanes  

Basics of jet propulsion of ships

02:26

DIFFERENCE BETWEEN RAKE ANGLE AND CLEARANCE ANGLE OF CUTTING TOOL

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. VC is the cutting velocity and its direction i.e. velocity vector is also displayed in the figure. 

Rake angle and clearance angle of cutting tool

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


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. 

Rake angle and clearance angle of cutting tool

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. 

Rake angle and clearance angle of cutting tool

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. 


Do you have any suggestions? Please write in comment box and also drop your email id in the given mail box which is given at right hand side of page for further and continuous update from www.hkdivedi.com.  

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

Reference:  

Manufacturing Process, By Prof A. B. Chattopadhyay

Image courtesy: Google     

Also read

Lever and its types with examples

Guidelines for solving friction problems in mechanics

Rolling resistance or rolling friction

Wedge friction and self-locking in engineering mechanics

Concept of force system in engineering mechanics

Difference between fan and blowers

Basics of centrifugal compressor 

16:21

EXPLAIN THE GEOMETRY AND NOMENCLATURE OF A SINGLE POINT CUTTING TOOL

We have seen the basics of metal cutting tools with the help of our previous post i.e. metal cutting tools: definition and classification.

Today we are going to start a very important topic here with the help of this post i.e. explain the geometry and nomenclature of a single point cutting tool.   

So, let us understand here the single point cutting tool nomenclature and its geometry

Single point cutting tool nomenclature and its geometry

A single point cutting tool will have an effective cutting edge and it will remove the excess materials from the workpiece along the cutting edge. Single point cutting tools will be usually used on lathes, shapers, planers, etc.

We can see here the various important parts of a single point cutting tool as displayed here in following figure. 

Nomenclature of single point cutting tool

Geometry and nomenclature of a single point cutting tool 

explain the geometry and nomenclature of a single point cutting tool

Shank

Shank is basically defined as the main body of the tool. Cutting portion will be formed at one end of the shank of the metal cutting tool. The shank in turn will be supported on the tool post of the machine.

Neck

The portion of the cutting tool which is reduced in section in order to form the necessary cutting edges and angles will be termed as the neck of the single point metal cutting tool.

Face

The face of the metal cutting tool is basically defined as the surface over which the chip slides once it will be separated from the workpiece.

Base

It is the surface on which tool rests.

Heel or lower face

Heel is basically defined as the horizontal surface at the end of the base in the neck portion which does not participate in the metal cutting process.

Flank

Flank is basically defined as the surface below the cutting edge. There are basically two types of flanks in a metal cutting tool i.e. major flank and minor flank.

Cutting edge or lip

Cutting edge is basically defined as the portion of the face edge along which the chip will be separated from the workpiece.

Cutting edge of metal cutting tool will have the following main parts as mentioned below

  1. Nose
  2. Side cutting edge or major cutting edge
  3. End cutting edge or minor cutting edge

Nose of the metal cutting tool will be defined as the corner, arc or chamfer at the junction of major and minor cutting edges. 


Therefore, we have seen here the various important parts of a single metal cutting tool with the help of this post.


Do you have any suggestions? Please write in comment box and also drop your email id in the given mail box which is given at right hand side of page for further and continuous update from www.hkdivedi.com.  

We will find out now the difference between rake angle and clearance angle of cutting tool and main characteristics of cutting tool materials with the help of our next posts. 

in our next post.   

Reference:  

Production Engineering, By K.C. Jain and A.K. Chitale   

Image courtesy: Google     

Also read  

Positive and negative effects of friction 

Classifications of friction 

Coulomb's law of dry friction 

Some guidelines for solving frictional problems 

Concept of rolling resistance or rolling friction

Wedge friction and concept of self- locking 

Hook’s law  

Concept of eccentric loading  

Assumptions made in the Euler’s column theory  

Difference between long column and short column 

Euler’s formula and its limitations

20:36

METAL CUTTING TOOLS: DEFINITION AND CLASSIFICATION

Today we are going to start a very important topic here with the help of this post i.e. metal cutting tools: definition and classification. 

So, let us first understand here the basics of metal cutting tool  


Metal cutting tool: Definition

Metal cutting tool is basically defined as a device used in metal cutting processes on machine tools for removing the layers of materials from the workpiece or blank in order to secure the product of specified size and shape with specified surface finish and accuracy.

Now we will see here the classification of metal cutting tools

Classification of metal cutting tools

The metal cutting tools are classified on the basis of number of cutting edges as mentioned below.

  1. Single point cutting tools
  2. Multi point cutting tools
  3. Forms tools

Single point cutting tools

A single point cutting tool will have an effective cutting edge and it will remove the excess materials from the workpiece along the cutting edge.

Single point cutting tools will be usually used on lathes, shapers, planers, etc. 

Single point cutting tools are classified as mentioned below 

  1. Forged tool
  2. Mechanically fastened tipped tool
  3. Brazed tipped tool
  4. Solid tool
  5. Tool bit inserted in the tool holder
  6. Right hand tool
  7. Left hand tool
  8. Round nose tool

Forged tool

Forged tools are manufactured from high speed steel or high carbon steel. The required shape of the tool is given by forging the end of a solid tool shank and further the cutting edges will be grounded to shape to provide the required tool angles.

Following figure displayed here indicates the forged tool.

Forged Tools

Mechanically fastened tipped tool

To ensure rigidity, tips are sometimes clamped at the end of a tool shank by means of a clamp and bolt as displayed here in following figure.

Mechanically fastened tipped tool


Brazed tipped tool

In brazed tipped type cutting tool, the cutting edge will be in the form a small tip made up of stellite and cemented carbide tool materials, which will be welded to the end of a carbon steel shank by brazing operation.

Brazed tipped tool is displayed here in following figure.

Brazed tipped tool


Solid tool

Solid tools are made up of high carbon steel, forged and ground to the required shape. They are directly mounted on the tool post of a lathe.

A lathe tool post is used to hold the metal cutting tool.

Tool bit inserted in the tool holder

In case of tool bit inserted in the tool holder, metal cutting tool will be inserted in a forged carbon steel tool holder and will be clamped in a position by bolt or screw as displayed here in following figure.

There are various advantages of tool bit over solid tool such as tool bit will be cheaper as compared to solid tool, regrinding of tool will be quite easy.

A tool bit will be easily withdrawn and replaced in position without disturbing the setting. 

Tool bit inserted in the tool holder

Right-hand tool and left-hand tool

A metal cutting tool will be said to be a right-hand tool or left-hand tool, if its cutting edge is on the right-hand side or left-hand side respectively when viewing the tool from the point end.

Multi point cutting tools

A multi-point cutting tool will have two or more than two cutting edges. For example, metal cutting tools used in the operation of drilling, milling and broaching will be considered as multi-point cutting tools.

In multi-point cutting tools, all the cutting edges may either operate one by one or engage simultaneously.

Each cutting edge of a multi-point cutting tool will be considered as a separate single point cutting tool with almost all the features of single point cutting tool.

Form tools

A form tool is basically a metal cutting tool which is shaped in such a way that it imparts a prespecified profile to the workpiece.

Form tools are usually ground on cutting tool elements as a replica of the work profile. These tools are used to shape short jobs for turret lathes.

Classification of form tools are displayed here in following table 

Classification of form tools

Therefore, we have seen here the basics of metal cutting tool i.e. definition of metal cutting tool and also the classification of metal cutting tools with the help of this post.

Now, we will be interested further to understand a very important concept in manufacturing process i.e. nomenclature of single point cutting tool with the help of our next post.  

Do you have any suggestions? Please write in comment box and also drop your email id in the given mail box which is given at right hand side of page for further and continuous update from www.hkdivedi.com.  

Reference:  

Production Engineering, By K C Jain and A. K. Chitale   

Image courtesy: Google     

Also read  

Positive and negative effects of friction 

Classifications of friction 

Coulomb's law of dry friction 

Some guidelines for solving frictional problems 

Concept of rolling resistance or rolling friction

Wedge friction and concept of self- locking 

19:03

INSTANTANEOUS CENTER OF ZERO VELOCITY

We were discussing the importance of friction i.e. positive and negative effects of frictionclassifications of frictioncoulomb's law of dry frictionsome guidelines for solving frictional problemsconcept of rolling resistance or rolling friction, wedge friction and concept of self- locking and the minimum stopping distance for a vehicle in engineering mechanics with the help of our previous posts. 

Now, we will be interested further to understand here a very important concept in engineering mechanics i.e. Instantaneous center of zero velocity with the help of this post.  

Instantaneous center of zero velocity 

Instantaneous center of zero velocity is basically defined as the point about which a body appears to be rotating at any given instantaneous or instant. It will have zero velocity and there will be only one instantaneous center per body per instant of time. 

Instantaneous center of zero velocity acts like absolute center of rotation at the instant considered. we must note it here that it will not be a fixed point in a body nor a fixed point in a plane. 

Let us consider a rigid body having a plane motion. There will be one linear component of translation motion and also rotary motion as displayed here in following figure. 


VA is the absolute velocity of a point and ω is the rotational velocity of the body. We must note it here that these two quantities i.e. absolute velocity and rotational velocity will define the velocity of all other points in the body. 

Let us consider the two arbitrary points i.e. point A and point B and the absolute velocity VA and VB respectively. Now we will determine here the instantaneous center of zero velocity.  


Let us see here how we will determine the instantaneous center of zero velocity   

Instantaneous center of zero velocity could be found by drawing perpendiculars from these velocities. We have drawn the perpendiculars from these velocities and we can see in the following figure that these perpendiculars are meeting with each other at a point C. 

This point C will be known as instantaneous center of zero velocity.  


We can also determine the angular velocity from here with the help of following figure.

ω = VA / rA = VB / rB 


Let us see here how we will determine the instantaneous center of zero velocity when velocities are parallel, same in directions but not equal in magnitudes 

Let us consider the two arbitrary points i.e. point A and point B and their absolute velocity VA and VB respectively. Let us assume that these velocities are parallel, same in directions and not equal in magnitude as displayed here in following figure. 


Now we will determine here the instantaneous center of zero velocity for above mentioned case. 

Instantaneous center of zero velocity could be found by drawing the lines joining the tip and the base of these velocities. These lines will intersect or meet with each other at a point C which will be termed as instantaneous center of zero velocity.  


When the parallel velocities will become equal in magnitude, the instantaneous center will be pushed further and will approach to infinity and hence there will be a pure translation motion. 

Let us see here how we will determine the instantaneous center of zero velocity when velocities are parallel and opposite in directions 

Let us consider the two arbitrary points i.e. point A and point B and their absolute velocity VA and VB respectively. Let us assume that these velocities are parallel but opposite in directions as displayed here in following figure. 


Now we will determine here the instantaneous center of zero velocity for above mentioned case. 

Instantaneous center of zero velocity could be found by drawing the lines joining the tip and the base of these velocities. These lines will intersect or meet with each other at a point C which will be termed as instantaneous center of zero velocity. 


Therefore, we have seen here what is the basics of instantaneous center of zero velocity and we have also secured the information to determine the instantaneous center of zero velocity. 

Do you have any suggestions? Please write in comment box and also drop your email id in the given mail box which is given at right hand side of page for further and continuous update from www.hkdivedi.com.   

We will find out now the concept of in our next post.    

Reference:  

Engineering Mechanics, By Prof K. Ramesh  

Image courtesy: Google      

Also read  

00:21

HOW TO CALCULATE THE MINIMUM STOPPING DISTANCE OF A CAR

We were discussing the importance of friction i.e. positive and negative effects of frictionclassifications of frictioncoulomb's law of dry friction, some guidelines for solving frictional problems, concept of rolling resistance or rolling friction and wedge friction and concept of self- locking in engineering mechanics with the help of our previous posts. 

Now, we will be interested further to understand here a very important concept in engineering mechanics i.e. the minimum stopping distance for a vehicle with the help of this post.  

The minimum stopping distance for a car or a vehicle 

Let us consider that a vehicle of mass m is moving with a speed v along a level road as displayed here in following figure. 

As car or any vehicle is initially running with a speed of v. Now, we are applying the brake in order to stop the vehicle i.e. car.  

We want to determine here the minimum stopping distance d for a vehicle of mass m moving with speed v along a level road.  


Let us assume and write down here the following terms from above figure. 

Initial velocity of the vehicle, V0 = v 
Final velocity of the vehicle, Vf = 0 

Acceleration of the vehicle = - a 
We are taking negative sign here as there will be retardation or deceleration after application of brake to vehicle. 

Minimum stopping distance of the vehicle = d 
Mass of the vehicle = m 
Static coefficient of friction between the tyre and the road = µ
Maximum frictional force generated due to braking action between the tyre and road = fmax  

Vehicle will be stopped with minimum stopping distance when retardation will be maximum and it is only possible when frictional force generated will be maximum. Hence, we are considering here the maximum frictional force. 

Normal reaction = N = mg 

Let us write and use the following equation of motion as mentioned below

Vf2 = V02 + 2 a d  0 = v2 + 2 a d
d = - v2 / 2 a

The minimum stopping distance for a vehicle, d = - v2 / 2 a

Let us draw here the free body diagram of the vehicle and write here the equation of motion of the vehicle as mentioned below  

∑F = m x a
- fmax = m x a
- µs N = m x a
- µs mg = m x a
a = - µs g

The minimum stopping distance for a vehicle, d = - v2 / 2 (- µs g)
The minimum stopping distance for a vehicle, d = v2 / 2 µs g  


Therefore, we can see here that the minimum stopping distance for a vehicle will be dependent over the velocity of the vehicle and co-efficient of friction between the tyre and road. 

Usually, the static co-efficient of friction between the tyre and road is 0.8.  


Therefore, we have seen here the minimum stopping distance for a vehicle with the help of this post. 

Do you have any suggestions? Please write in comment box and also drop your email id in the given mail box which is given at right hand side of page for further and continuous update from www.hkdivedi.com.  

We will find out now the concept of instantaneous center of zero velocity in our next post.   

Reference:  

Engineering Mechanics, By Prof K. Ramesh  
Image courtesy: Google     

Also read