Today I have talked about drill bits which are 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 the drilling process to make a hole in a workpiece or a job.
Basically, the drilling process is 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 revolving tool called a 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 the drill bit is directed towards the job or a workpiece, through which a hole is to be made.
Before knowing the 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 point and making 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 causes the tool to penetrate into the material.
It is also called a drill.
For holding the drill bit a work holding device is used which is known as a drill chuck in a drilling machine.
Parts of Drill Bit
There are the following parts of a drill:
- Body
- Point
- Shank
- Tang
- Flutes
- Land
- Body Clearance
- Web
- Neck
See in figure parts of drill bit which are described below in detail.
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| 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 the 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.
It's 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 which are described below in detail.
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| 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 a simple type of drill and has two cutting edges beveled at 45°.
Clearly see in the 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
The fluted drill bit can be divided into two types which are following:
- Straight Fluted Drill Bit
- Twist Drill Bit
Straight Fluted Drill Bit
It is used for rough drilling and has two straight flutes cut, which are made up of high carbon steel.
It is hard tempered and works as a twisted drill.
Their rack angle is zero
Twist Drill Bit
It is the most commonly used variety of a drill and is 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.
A twist drill is made through high carbon steel.
It has the taper or parallel shank.
The main parts of the 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:
- Two Flutes Drill Bit
- Multi Flutes Drill Bit
Two Flutes Drill Bit
It is rigid and does not use deep holes.
Multi Flutes Drill Bit
It is used for drilling 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 center 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 of the cutting chips.
Center Drill Bit
It is used for drilling a conical shape on both ends of a job or workpiece at the lathe machine or the milling machine.
Counter Bore Drill Bit
It is used for drilling and boring operations.
Multi-diameter Drill Bit
It has the property to make the different diameters of a hole at a time.
It has drilled the taper and straight shank.
It is used in step drilling so it is also called a 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 the size of a drill bit, It can be classified into three categories which are as follows:
- Millimetre Size Drill
- Number Size Drill
- 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 a straight shank and above 16 mm in the form of a taper shank.
Number Size Drill
According to the number system, there are available 1- 80 drills.
1 number drill is the biggest drill number and 80 is the lowest drill number.
Letter Size Drill
In the letter size drill, there are numbers having English alphabets from A to Z.
In the 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 the Drilling Process
Cutting Speed
In the cutting operation, drill rounds on its axis speed depend 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 a feed.
It is denoted in hundredths of a millimeter.
Mathematically,
Feed = L/TN mm/revolution
Where,
L= Travelled distance by drill.
T= Time in minute
If adding the height of the 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 a 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 lengths or angles of cutting edges of a drill.
Remedy
At the grinding time, always kept in mind the right alignment of cutting edges and their length and angle.
Breakage of Drill
Causes
The relief angle is too small, and the 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 the smaller clearance angle and high cutting speed.
Remedy
Check the rigidity of the 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 chucked 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 types of drill bits and their uses, parts, and also know about some defect which is found during Drilling Process.
So, I hope you are all satisfied if any queries you can comment to me.
FAQ for Drill Bit
What is a drill bit?
A drill bit is a tool that has cutting points that are used to make a hole in any solid material.
Which of the following is the driving end of the drill?
The driving end of the drill which fits into the drilling machine is called a Shank.
What are the most common types of drill bits?
The most common types of drill bits are twist drill bits which are made with two, three, or four cutting lips.
What is the strongest drill bit?
Drill bits made from carbide material are the strongest drill bits.
Which color drill bit is for metal?
Black colored drill bits are for metal.
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