Chisels

A chisel is a hard steel cutting tool made from high carbon or nickel alloy steel with a soft chamfered head to prevent cracking under repeated hammer blows. It is used for shearing rivets, cutting and chipping any metal softer than the chisel itself. The nature of the task governs the size and shape whereas the material type governs the cutting angle. The cutting angle should be 60^o to 70^o for cutting wire, strapping iron and other general purposes.

The following are the types of chisels.

Flat Chisel: It is used for general chipping work such as parting metal sheets. The size of a flat chisel is determined by the width of the cutting edge.

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Crosscut/Cape Chisel: It resembles a flat chisel but with a narrow cutting. It has the same cutting angle and is used for cutting grooves in a flat surface.

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Diamond Point Chisel: It has a tapered square at the cutting end which is then ground at an angle to provide the sharp diamond point. It is used for cutting out corners and rectifying incorrect drill starts.

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Half Round Chisel: It is used for cutting half round bottomed grooves and also used for rectifying incorrect drill starts.

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Round Nose Chisel: It is used to re-center a drill that has moved away from its intended center.

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The following are the precautions and maintenance instructions that has to be followed when using chisels.

• Select the chisels based on the nature of the task and the material to be cut.
• During grinding, the cutting edge must be kept cool by frequently dipping in water.
• The end of the chisel should be kept free from ragged ends and burrs.