Tool Design and Geometry
Cutting tools.
THE HACKSAW
The hacksaw is used to cut steel and other metals. It can also be used to cut plastics, although it is not normally
used to cut woods. It is sometimes called an adjustable hacksaw because the length of the frame can be altered
to hold blades of different sizes. Blades are supplied in two lengths, 250mm and 300mm. If the adjusting screw is
unscrewed, the frame can be pushed into the handle so that the smaller blades fit the hacksaw.
Blades are also described by the number of teeth per inch (TPI). Blades have 14, 18, 24, 32 teeth per 25mm
(inch). A blade with 14 TPI is coarse whilst a blade with 32 TPI is very fine.
Methods of Using Hacksaw
Hacksaw blade should be installed on the frame very accurately. It should not be very firm
nor very loose.
The job which is to be cut should not be held in a vice much high otherwise there would be
vibrations in it.
Hacksaw blade should not be allowed to become slanting while using a hacksaw. There are
possibilities that it may break because of slating
If the blade starts cutting in a slanting manner we should start a fresh cut.
The new blade can break if it is operated in an old slot.
Types of Hacksaw Frame
A. KEPHA – CUTTING TOOLS 1
,Following are the main two types of hacksaw frame:
1. Fixed Hacksaw Frame
2. Adjustable Hacksaw
A. KEPHA – CUTTING TOOLS 2
,1. Fixed Hacksaw Frame
For making this type of hacksaw frame, one-piece flat iron strip or pipe is bent at a right angle. In these
types of hacksaw frame, only hacksaw blades of a specific size can be fixed, not of the short size or long
size. Two types of handles are used:
1. Straight handle
2. Pistol type handle
2. Adjustable Hacksaw
In these types of hacksaw frame, Its structure is a bit different from a fixed frame. The frame is made in
two parts. These parts can be adjusted at different distances. Therefore in this adjustable hacksaw, big
and small hacksaw blades of the different standard can be used.
There is adequate provision of pin and grooves to pull, adjust and set them. These types of handles are
used. in this hacksaw:
1. Straight handle
2. Pistol type handle
3. Tubular type handle
4. Flexible Blade
These frames are generally made of flat strip or thin pipes and their handle are made of wood or
aluminium.
2. Hacksaw Blade
On the basis of metal of the job, different types of hacksaw blades are used in a hacksaw. These are
made of tungsten steel, high-speed steel and they are hardened and tempered. Their classification
depends on three points:
1. Size of the blade.
2. The number of dents cut on the blade per inch.
3. Nature of the blade.
Length of hacksaw blade is generally 8″, 10″ or 12″. Dents of four different grades are cut on them.
Types of Hacksaw Blades
Following are the main types of hacksaw blades:
1. Course Grade Hacksaw Blade
2. Medium Grade Hacksaw Blade
3. Fine Grade Hacksaw Blade
4. Superfine Grade Hacksaw Blade
5. All Hard Blade
1. Course Grade Hacksaw Blade
Hacksaw blade of this grade is used for cutting thickness of mild steel, copper, aluminium and brass etc.
It contains 14 to 18 teeth per inch.
A. KEPHA – CUTTING TOOLS 3
, 2 .Medium Grade Hacksaw Blade
Hacksaw blade of this type is used for cutting all kinds of metals such as cast iron, tool steel, aluminium,
brass, high carbon steel etc. From 20 to 24 teeth per inch are cut in this hacksaw blade.
3. Fine Grade Hacksaw Blade
This type of hacksaw blade is mainly used to cut thin pipes, sheets, tubes etc. It has 24 to 30 dents per
inch.
4. Superfine Grade Hacksaw Blade
For cutting extraordinary solid metals and thin metal sheets, thin type of hacksaw blade is used. There
are 30 to 32 dents per inch in this type of hacksaw blade.
In all the hacksaw blades of various grades mentioned above, teeth are cut on one or both the edges.
These blades are hardened in two different processes and on these depend their nature.
5. Ail Hard Blade
Blades of this nature are hardened and tempered only except the ends having holes. These are used for
cutting articles cast iron or mould iron etc.
6. Flexible Blade
In blades of this nature only the cutting teeth and nearby part it hardened and tempered. But this
process they become elastic and there is less risk of their being broken in the event of a shock. These
blades are used for cutting thin sheets, pipes, curves etc.
Setting of Teeth
Teeth of hacksaw blade are also bent to left or right side as in the case of ordinary saw used for cutting
wood. Bending of teeth is known as the setting of teeth. With this setting of teeth the hacksaw blade
cuts a slot in the metal of slightly more thickness than that of the blade.
Therefore, because of this slot, the blade does not get stuck while operating it. If the setting is not done,
there is a great risk that the blade would get stuck in the metal and get broken. The setting of teeth in a
blade is done in three ways.
1. Regular or Single Setting
In this type of setting, one tooth is bent to the left and the next tooth to the right and every fifth tooth is
kept straight. This tooth helps in cleaning the metal particles from the slot. This type of setting has been
shown in fig.
2. Double Alternate Setting
In this type of setting, two teeth are turned to the right and two to the left and one dent between them
is left straight, which performs the function of clearing the metal particles from the slot.
3. Zig-Zag or Wave Setting
In this type of setting a few teeth are bent to the right and a few to the left. Thus it looks like a wave.
This type of setting is done on blades of fine grade and superfine grades. It has been shown in fig.
Methods of Using Hacksaw
For the efficient cutting the following points should be borne in mind:
1. Selection of hacksaw blade should be done according to the metal for which it is to be used.
2. While fixing the blade on the frame it should be ensured that its teeth should cut the metal
when they are driven forward.
A. KEPHA – CUTTING TOOLS 4
Cutting tools.
THE HACKSAW
The hacksaw is used to cut steel and other metals. It can also be used to cut plastics, although it is not normally
used to cut woods. It is sometimes called an adjustable hacksaw because the length of the frame can be altered
to hold blades of different sizes. Blades are supplied in two lengths, 250mm and 300mm. If the adjusting screw is
unscrewed, the frame can be pushed into the handle so that the smaller blades fit the hacksaw.
Blades are also described by the number of teeth per inch (TPI). Blades have 14, 18, 24, 32 teeth per 25mm
(inch). A blade with 14 TPI is coarse whilst a blade with 32 TPI is very fine.
Methods of Using Hacksaw
Hacksaw blade should be installed on the frame very accurately. It should not be very firm
nor very loose.
The job which is to be cut should not be held in a vice much high otherwise there would be
vibrations in it.
Hacksaw blade should not be allowed to become slanting while using a hacksaw. There are
possibilities that it may break because of slating
If the blade starts cutting in a slanting manner we should start a fresh cut.
The new blade can break if it is operated in an old slot.
Types of Hacksaw Frame
A. KEPHA – CUTTING TOOLS 1
,Following are the main two types of hacksaw frame:
1. Fixed Hacksaw Frame
2. Adjustable Hacksaw
A. KEPHA – CUTTING TOOLS 2
,1. Fixed Hacksaw Frame
For making this type of hacksaw frame, one-piece flat iron strip or pipe is bent at a right angle. In these
types of hacksaw frame, only hacksaw blades of a specific size can be fixed, not of the short size or long
size. Two types of handles are used:
1. Straight handle
2. Pistol type handle
2. Adjustable Hacksaw
In these types of hacksaw frame, Its structure is a bit different from a fixed frame. The frame is made in
two parts. These parts can be adjusted at different distances. Therefore in this adjustable hacksaw, big
and small hacksaw blades of the different standard can be used.
There is adequate provision of pin and grooves to pull, adjust and set them. These types of handles are
used. in this hacksaw:
1. Straight handle
2. Pistol type handle
3. Tubular type handle
4. Flexible Blade
These frames are generally made of flat strip or thin pipes and their handle are made of wood or
aluminium.
2. Hacksaw Blade
On the basis of metal of the job, different types of hacksaw blades are used in a hacksaw. These are
made of tungsten steel, high-speed steel and they are hardened and tempered. Their classification
depends on three points:
1. Size of the blade.
2. The number of dents cut on the blade per inch.
3. Nature of the blade.
Length of hacksaw blade is generally 8″, 10″ or 12″. Dents of four different grades are cut on them.
Types of Hacksaw Blades
Following are the main types of hacksaw blades:
1. Course Grade Hacksaw Blade
2. Medium Grade Hacksaw Blade
3. Fine Grade Hacksaw Blade
4. Superfine Grade Hacksaw Blade
5. All Hard Blade
1. Course Grade Hacksaw Blade
Hacksaw blade of this grade is used for cutting thickness of mild steel, copper, aluminium and brass etc.
It contains 14 to 18 teeth per inch.
A. KEPHA – CUTTING TOOLS 3
, 2 .Medium Grade Hacksaw Blade
Hacksaw blade of this type is used for cutting all kinds of metals such as cast iron, tool steel, aluminium,
brass, high carbon steel etc. From 20 to 24 teeth per inch are cut in this hacksaw blade.
3. Fine Grade Hacksaw Blade
This type of hacksaw blade is mainly used to cut thin pipes, sheets, tubes etc. It has 24 to 30 dents per
inch.
4. Superfine Grade Hacksaw Blade
For cutting extraordinary solid metals and thin metal sheets, thin type of hacksaw blade is used. There
are 30 to 32 dents per inch in this type of hacksaw blade.
In all the hacksaw blades of various grades mentioned above, teeth are cut on one or both the edges.
These blades are hardened in two different processes and on these depend their nature.
5. Ail Hard Blade
Blades of this nature are hardened and tempered only except the ends having holes. These are used for
cutting articles cast iron or mould iron etc.
6. Flexible Blade
In blades of this nature only the cutting teeth and nearby part it hardened and tempered. But this
process they become elastic and there is less risk of their being broken in the event of a shock. These
blades are used for cutting thin sheets, pipes, curves etc.
Setting of Teeth
Teeth of hacksaw blade are also bent to left or right side as in the case of ordinary saw used for cutting
wood. Bending of teeth is known as the setting of teeth. With this setting of teeth the hacksaw blade
cuts a slot in the metal of slightly more thickness than that of the blade.
Therefore, because of this slot, the blade does not get stuck while operating it. If the setting is not done,
there is a great risk that the blade would get stuck in the metal and get broken. The setting of teeth in a
blade is done in three ways.
1. Regular or Single Setting
In this type of setting, one tooth is bent to the left and the next tooth to the right and every fifth tooth is
kept straight. This tooth helps in cleaning the metal particles from the slot. This type of setting has been
shown in fig.
2. Double Alternate Setting
In this type of setting, two teeth are turned to the right and two to the left and one dent between them
is left straight, which performs the function of clearing the metal particles from the slot.
3. Zig-Zag or Wave Setting
In this type of setting a few teeth are bent to the right and a few to the left. Thus it looks like a wave.
This type of setting is done on blades of fine grade and superfine grades. It has been shown in fig.
Methods of Using Hacksaw
For the efficient cutting the following points should be borne in mind:
1. Selection of hacksaw blade should be done according to the metal for which it is to be used.
2. While fixing the blade on the frame it should be ensured that its teeth should cut the metal
when they are driven forward.
A. KEPHA – CUTTING TOOLS 4
