In this article, you’ll learn what is a chisel and How it is used in the workshop. with its Parts, Methods, Precautions and Types of Chisel with PDF.
Chisel and Its Types
Chisel is used to cut flat, round or angle iron and thick metal sheets. It is also used to remove the unwanted metal from the surface of a job by cutting it in bits and small pieces. This act is known as chipping.
The cutting done by a chisel is rough. Therefore, there is need for finishing after chipping done by the chisel. It saves time. Chisels are used both on hot and cold metals. As such chisels have been divided into two categories.
Classifications of Chisel
- Hot chisel
- Cold Chisel
1. Hot Chisel
Hot chisel is used for cutting hot metals in blacksmith’s workshop. There is a hole in a chisel in which a wooden handle is fixed. Their cutting edge is made at an angle of 30°. While using this part, it is frequently dipped into water for making it cold so that its edges remain intact.
2. Cold Chisel
Cold chisels are generally used in sheet metal and fitter trade workshops. With cold chisel cutting or chipping of metal can be done when these metals are in cold condition.
This is available in 4 sides, 6 sides or 8 sides. These are made of high carbon steel, which contains 0.75% to 1.00% of carbon. Generally, chisel, of 150 mm length is used. Practically, chisels measurement is known from the width of chisels cutting edge.
Read Also: 9 Different Types of Sheet Metal Operations
Parts of a Chisel
Following are the different parts of a chisel:
- Forging angle
- Cutting edge
- Cutting angle
The topmost part of a chisel is called “Head”. It is a bit suck in the middle so that the blow of hammer strikes at the centre of the chisel. Thus, because of repeated blows, its head becomes mushroom as shown in fig.
In this case, the chisels head should be set right by grinding. While making head, the upper part of the body should be 10° to 20°.
That part of a chisel from which we hold it is called the body or stock. It is made of four, six or eight sides so that it is easy to hold. The body is made somewhat flat from the bottom.
3. Forging Angle
Some part of the flat position below a chisels body is tapered. This angle of taper is called forging angle. It is also known as Draw Angle.
4. Cutting Edge
That part of chisel that performs the function of cutting is called the cutting edge. Its width is taken as chisels measurement.
5. Cutting Angle
The angle at which a cutting edge of chisel is grinded is known as its cutting angle. For cutting hard metal, the cutting angle is more and for cutting soft metals the cutting angle is less. While grinding chisels for cutting various kinds of metals their angles should be as under:
- Mild steel – 55 °
- Cast iron – 60 °
- Tool steel – 65 ° to 70 °
- Copper – 45 °
- Aluminium – 30 °
- Brass – 50 °
Hardening and Tempering of Chisel
In order to make the cutting edge last longer even the tapered part of a chisel is made hard and the edge is tempered. For this purpose, chisel should be heated at an appropriate temperature up to half of its length and this edge part of the chisel should be cooled in clean water.
This would make that particular part of chisel hard. Then its edge part should be cleaned with a sand-paper. Again it should be heated at an appropriate temperature.
Now the colour of this part would start changing and when it turns into appropriate colour, it should be cooled down in lime-water. This would temper the longer period.
Types of Chisel
Following are the different types of chisel:
- Flat chisel
- Cross cut chisel
- Side cut chisel
- Round Nose Chisel
- Diamond point chisel
- Cow mouth chisel
1. Flat Chisel
In these types of chisel, It is an all-metal chisel used for obtaining a flat surface on metal by chipping. This chisel is used to cut wires, thin sheets and round rods etc.
The edge of this chisel is in “V” shape and is flat, which is raised from the centre. Because of this projected parts, it does not get stuck into the cut surface, while chipping.
2. Cross Cut Chisel
It is mainly used to cut square slots and channels. Keyway on a shaft is made with this chisel. Its cutting edge is from 3 mm to 12 mm in width.
In order to ensure that this chisel does not get stuck into the grooves and slits while using it in the grooves and slits, the part behind its edge is made comparatively thin.
3. Side Cut Chisel
Where other types of chisel cannot be used easily, side cut chisels are used. The keyway and cotter way is cleaned with this chisel.
It is almost similar to the flat chisel but the part which performs the function of cutting is turned to one side. It is turned at an angle and then forged. Its cutting angle is generally at and forging angle at an angle.
4. Round Nose Chisel
Its edge is round. It is used for making an oil groove in a bearing and for cutting slits at corners. Its forging angle is at and cutting angle is of 35 ° to 40 °. In such jobs where the drill is dislocated at the time of drilling and some substance is left, the leftover metal is set right with this chisel.
5. Diamond Point Chisel
This is made of good quality steel. Its shape is square and it is tapered. Its edge is pointed and of the shape of a diamond.
On the basis of its square ends, its measurement is determined. Square corners and triangle corners are cleaned with it. We can make a groove in plain surface with this chisel.
6. Cow Mouth Chisel
In these types of chisel, Its shape is like that of the broad mouth of a cow. That is why it is known as cow mouth chisel. Edges of the protruding parts of plain metal and rivet heads and big round holes are made with it. Its forging angle is at an angle.
Methods of Using Chisel
Chisel is used for cutting and chipping a thin metal sheet, plate, round rod and such other material. In fig cutting of a metal plate has been illustrated. The following points should be kept in mind while using a chisel:
- Accurate marking should be done on the metal to be cut.
- Always hold the chisel properly with your left hand and the hammer in your right hand.
- Set the chisel properly on the marked line then strike the hammer on its head. Before striking the second blow on the chisel, it should be set again.
- While cutting with a chisel we should concentrate on its cutting edge.
- Strike the hammer blow at the centre of the head of the chisel.
Precautions of Using Chisel
- At the time of chipping, we must always use safety goggles.
- Keep your face towards the wall, while chipping.
- If someone is working in your front, you should fix chipping guard at the rear of the vice so that chips do not hit him.
- The mushroom head chisel should never be used for chipping.
- There should not be any greasy substance on the chisel head and face of the hammer being used for chipping.
- An extraordinarily long chisel should not be used for chipping.
- While chipping we should keep on applying grease on the edge of the chisel.
That’s it, thanks for reading. If you have any questions about “Types of Chisel” you can ask in the comments.