Types of drill bits and their uses,parts,defects

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Today I have talked about drill bits which is also known as a drill. 
In which we will know about types of drill bits and their uses as well as also discussed parts of a drill bit. 

Drill bits are performed in drilling process to making a hole in a workpiece or a job.

Basically, Drilling process is the part of a manufacturing process. This process is widely used in an industry for the purpose of mass production.

Drilling is an operation through which holes are produced in a metallic or non-metallic material by means of a resolving tool called drill bit. 

The complete process is done through a machine that is said to be a drilling machine.

This machine provides a rotatory motion to the drill bit and drill bit is directed towards the job or a workpiece, through which hole is to be made.

Before knowing Types of drill bits and their uses First of all, we have to know parts of drill bits, So that we can better understand the types of drill bits. 

So, let's start step by step drill bit parts and their types.

Definition of Drill Bit

It is a tool having a cutting points and make a hole in the solid materials. It is made up of high carbon steel or alloy steel.

For drilling, the drill bit is rotated with a downward press, which causing the tool to penetrate into the material.

It is also called as a drill. 

For holding the drill bit a work holding device used which is known as a drill chuck in a drilling machine.

Parts of Drill Bit

There are following parts of drill
  • Body
  • Point
  • Shank
  • Tang
  • Flutes
  • Land
  • Body Clearance
  • Web
  • Neck
See in figure parts of drill bit

Types of drill bits and their uses
Parts of Drill Bit

Body

The body between the shank and the point of the drill is called the body. 

Point

The end point of the drill is called point and it is cone shaped.

It is generally found at 180°.

Shank

The driving end of the drill which fits into the drilling machine is called a Shank. 

Tang

Tang is a part of shank that fits into the machine spindle. 

Flutes

Spiral grooves on the body of the drill are called flutes.

They mainly do three types of tasks: first, metal cutting as cutting edge, and secondly
Turning out the chips into curls and the third, coolant reaching the cutting edge. 

Land

The length of the body across the body between the flutes says land.

Its also known as a margin. 

Body Clearance

The part of the body whose diameter is slightly less than the diameter of the drill is called body clearance. 

Due to this the friction between the drill and the hole is reduced.

Web

The part separating the two flutes is called the web.

Neck

The part connecting the shank and the body of the drill is called a neck.

This part is found in a few drill bits.


Types of Drill Bits

According to the shape and size of a hole, there are many types of drill, which are as follows
  • Flat Drill Bit
  • Fluted Drill Bit
  • Taper Shank Drill Bit
  • Oil hole drill Bit
  • Centre Drill Bit
  • Counter Bore Drill Bit
  • Multi-diameter Drill Bit
  • Counter Sink Drill Bit
  • Size of Drill
  • Bit
See in figure different types of drill bits


Types of drill bits and their uses
Different Types of Drill Bits


Flat Drill Bit

It is usually made up of high carbon steel, which is forged to shape, and ground to size then hardened and tempered.

It is simple type of drill and has two cutting edges bevelled at 45°.

Clearly see in figure shown two cutting edges at 45°.

This type of drill bit is mainly used to drill wood or soft metal. 

Such drills are not capable of deep holes as there would be no management to remove chips or sawdust. 

Fluted Drill Bit

Flutes are made in the body of such a drill bit.

Types of fluted Drill bit

Fluted drill bit can be divided into two types which are following

  1. Straight Fluted Drill Bit
  2. Twist Drill Bit

Straight Fluted Drill
Bit

It is used for rough drilling and have two straight flutes cut, which are made up of high carbon steel.

It is hard tempered and works as twisted drill.

Their rack angle is zero

Twist Drill Bit

It is the most commonly used variety of a drill and made with two, three or four cutting lips.

The most advantage of using this type of drill the chips will be easily come out and also maintain easily cooling near its cutting point.

Twist drill is made through high carbon steel.
It has the taper or parallel shank. The main parts of twist drill are body, shank, neck, flutes, land, margin, body clearance and point.

Types of Twist Drill Bit

There are two types of twist drill such as
  1. Two Flutes Drill Bit
  2. Multi Flutes Drill Bit 

Two Flutes Drill Bit

It is a rigid and does not use for the deep holes.

Multi Flutes Drill Bit

It is used for drilling the deep holes because there is a maximum space for chips to exit from the hole.

Taper Shank Drill Bit

It is similar to the twist drill, but it is used for boring. It has a small cutting edge, not filled up to the centre, so that it is not used in a new drill.

Oil Hole Drill Bit

It has an oil hole in the shank and body.This Oil Hole Drill provides the oil for the cutting edge. It protects the cutting edge from the heating during the going out the cutting chips.

Center Drill Bit

It is used for drilling a conical shape on the both ends of a job or workpiece at lathe machine or the milling machine.

Counter Bore Drill Bit

It is used for drilling and boring operation.

Multi-diameter Drill Bit

It has a property to make the different diameters of a hole in a time. It has drilled the taper and straight shank. It is used in step drilling, so that it is also called step drill.

Counter Sink Drill Bit

It is used to change the shape of a hole.

It has a show length of a body with flutes.

Its cutting point grinded from 60° to 82° angle.

Size of Drill
Bit

According to size of drill can be classified into three categories  which is as follows

  1. Millimetre Size Drill
  2. Number Size Drill
  3. Letter Size Drill

Millimetre Size Drill

According to the Metric system, the sizes of the drill are up to 16 mm in the form of straight shank and above 16 mm in the form of taper shank.

Number Size Drill

According to the number system, there are available 1- 80 drills. 1 number drill is biggest drill number and 80 is the lowest drill number.

Letter Size Drill

In letter size drill, there are numbers having English alphabets from A to Z. In letter size drill, A represents the smallest size of a drill  that Diameter 0.234"or 5.994 mm and Z is the biggest size of a drill i.e., diameter 0.413" or 10.490 mm.

Cutting Speed and Feeding in Drilling process


Cutting Speed

In the cutting operation, drill rounds on its axis speed depends on its per minute revolution and It is denoted by revolution per minute.

Mathematically,

Cutting speed =  πDN /1000 m/min

 Where,

D = Diameter of drill in mm.

N = Drill's revolution per minute.


If drill size is in the inch, then

Cutting speed   πDN /1000 ft/min

where,

D= Diameter of a drill in fit

N= Drill's revolution per minute.


Feed

The penetrated distance by a drill into the workpiece in one complete revolution is called feed.

It is denoted in hundredths of a millimetre.

Mathematically,

Feed = L/TN mm/revolution

Where,

 L= Travelled distance by drill.

T= Time in minute

 If adding the height of cone, then

Feed = L+B/ Tx N

 Where,

 B = Height of a cone.


Defects in Drill Bit During Drilling Process

The drilling process creates some defects in performing an operation, so in order to know the remedies of those defects. Some defects and their remedies are discussed below

Following defects found in drill bits during performing drilling operation

•Making a Hole Bigger than Size

•Breakage of Drill

•Overheating of a Drill

•Receiving the Rough Surface of Hole

•Decrease the feed rate and Continuous Breaking of Drill


Making a Hole Bigger than Size

Causes

Due to different length or angle of cutting edges of a drill.

Remedy

At the grinding time, always kept in mind its right alignment of cutting edges and its length and angle.

Breakage of Drill

Causes

The relief angle is too small, and drill is blunt.

Remedy

Increase the rigidity of a machine, drill and workpiece clamping, reduce the cutting speed or feed and change the coolant.

Overheating of a Drill

Causes

Due to smaller clearance angle and high cutting speed.

Remedy

Check the rigidity of drill and grind the drill.

Receiving the Rough Surface of Hole

Causes

Too high drill feed and high vibration in the job.

Remedy

Completely fixed the job and chuck and change the lubrication method.


Decrease the feed rate and Continuous Breaking of Drill

Causes

Low accuracy of regrinding and bed chip ejection.

Remedy

Select the correct bush diameter and always use the proper lubrication.



In this topic I discussed about types of drill bits and their uses, parts and also know about that some defect which is found during Drilling Process.
So, I hope you all satisfied if any query you can comment me.

Thank You

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