Hacksaw Blades – Sizes and Different Pitch for Different Materials in ITI Turner Trade

In the ITI Turner trade, hacksaw blades are widely used for cutting metals and other materials. The efficiency and quality of cutting depend largely on the correct selection of blade size and pitch. This chapter explains the different sizes of hacksaw blades and how to select the correct pitch for various materials.

Introduction to Hacksaw Blades

A hacksaw blade is a thin strip of steel with teeth on one edge, used for cutting workpieces. It is mounted on a hacksaw frame and operated manually. The blade removes material through a series of cutting teeth during the forward stroke.

Proper selection of blade size and pitch is important for efficient cutting and longer blade life.

Material of Hacksaw Blades

Hacksaw blades are made from:

• High carbon steel
• High-speed steel
• Bi-metal (combination of flexible back and hard teeth)

These materials provide strength, durability, and resistance to wear.

Sizes of Hacksaw Blades

Hacksaw blades are available in standard lengths. The size refers to the distance between the pin holes at both ends of the blade.

• 250 mm (10 inches)
• 300 mm (12 inches)

The 300 mm blade is most commonly used in workshops due to its versatility and efficiency.

Pitch of Hacksaw Blade

The pitch of a hacksaw blade refers to the distance between two consecutive teeth. It is commonly expressed as Teeth Per Inch (TPI).

The pitch determines how the blade cuts material and affects cutting speed, finish, and blade life.

Common Pitch Values (TPI)

• 14 TPI: Coarse pitch
• 18 TPI: Medium pitch
• 24 TPI: Fine pitch
• 32 TPI: Very fine pitch

Selection of Pitch for Different Materials

1. Soft Materials (Aluminium, Brass, Copper)

Soft materials require a coarse pitch blade (14–18 TPI). The larger teeth remove material quickly and prevent clogging.

2. Mild Steel and Medium Hard Materials

For materials like mild steel, a medium pitch blade (18–24 TPI) is suitable. It provides a balance between cutting speed and finish.

3. Hard Materials (High Carbon Steel, Alloy Steel)

Hard materials require fine pitch blades (24–32 TPI). Smaller teeth reduce the load on each tooth and prevent breakage.

4. Thin Materials (Sheets, Pipes)

Thin materials require very fine pitch blades (24–32 TPI). This ensures that multiple teeth are in contact with the material at all times, preventing tooth damage.

General Rule for Pitch Selection

At least two to three teeth of the blade should be in contact with the workpiece at any time. This ensures smooth cutting and prevents damage to the blade.

Importance of Correct Pitch Selection

• Improves cutting efficiency
• Prevents blade breakage
• Provides better surface finish
• Increases blade life

Tooth Set of Hacksaw Blade

The teeth of the blade are set alternately to both sides. This helps in:

• Reducing friction
• Preventing blade from jamming
• Providing a wider cut

Direction of Cutting

Hacksaw blades are designed to cut during the forward stroke. Therefore, the teeth should face forward, and pressure should be applied only in that direction.

Uses of Hacksaw Blades

• Cutting rods and bars
• Cutting pipes and tubes
• Cutting metal sheets
• Trimming and shaping workpieces

Advantages

• Versatile and widely available
• Suitable for various materials
• Easy to replace
• Low cost

Limitations

• Requires manual effort
• Slower than machine cutting
• Blade wear over time

Precautions While Using Hacksaw Blades

• Select correct blade size and pitch
• Ensure proper blade tension
• Do not apply excessive force
• Use steady and uniform strokes
• Replace worn or damaged blades

Maintenance of Hacksaw Blades

• Keep blades clean and dry
• Store properly to avoid damage
• Check teeth condition regularly

Application in Turner Workshop

In the Turner trade, hacksaw blades are used to cut raw materials into required sizes before machining. Correct selection of blade size and pitch ensures efficient cutting and reduces material wastage.

It also improves the accuracy and quality of workpieces.

Conclusion

Hacksaw blades are essential cutting tools in the ITI Turner trade. Understanding their sizes and selecting the correct pitch for different materials is important for efficient and accurate cutting.

By following proper techniques and precautions, trainees can improve their skills and extend the life of hacksaw blades.

In conclusion, correct blade selection plays a key role in achieving high-quality results in workshop operations.