Hacksaws

Hacksaws are used to cut metals and hard materials. They usually consist of a frame, blade and a handle.

• Frame: It is made of mild steel and its length may be fixed or adjustable depending upon the blade length.
• Blade: It is mounted on two pins located at end each end of the frame. High carbon steel blades are flexible and high speed tungsten blades are shape but fragile. Blades are classified based on their length, material and pitch (number of teeth per inch). The number of teeth per inch varies from 14 to 32. The more the teeth number, the finer the blade. The blade lengths are available from 6 – 16 inches. Soft metals require coarse pitch blades and vice versa. The flexible blades are usually best for sawing hollow shapes and metals having a thin cross section.
• Handle: The two styles in the handle are pistol grip and straight. When installing a blade in a frame, the blade has to be mounted away from the handle with the teeth pointing forward.

The types of commonly used hacksaws are discussed below.

Junior Hacksaw: It has a small flexible blade and is used to carryout simple tasks. The blade pitch is usually 32 in this type of hacksaws. Tension is applied by the elasticity of the frame.

FIGURE

Piercing Saw: It has a very fine blade and is used for cutting intricate shapes in sheet metal.

FIGURE

Coping Saw: It uses a 14tpi coarse blade that can be swivelled to any angle. These saws are used for cutting shapes in soft materials.

FIGURE

The following are the precautions that has to be taken when using hacksaws.

• Select an appropriate blade for the task.
• Select the correct blade length with the correct pitch.
• The blade has to be assembled in the frame so that the teeth points away from the handle.
• Correctly adjust the tension of the blade in the frame in order to prevent the saw from buckling and drifting.
• Make sure that the work is clamped securely in the vice.
• Mark the starting point by nicking the surface that will aid in starting the saw at the right place.
• Hold the saw at an angle that will keep at least two teeth in contact with the work at all times.
• Use long steady strokes using the whole length of the blade releasing the pressure on the back stroke.
• After completing the cut, remove chips from the blade, loosen tension on the blade and return the hacksaw to its proper place.