Chisel

The cold chisel is a hand cutting tool used by fitters for chipping and cutting off operations.

Chipping is an operation of removing excess metal with the help of a chisel and hammer. Chipped surfaces being rough, they should be finished by filing.

Chisels are made from high carbon steel or chrome-vanadium
steel. The cross-section of chisels is usually hexagonal or octagonal. The cutting edge is hardened and tempered.

Parts of a chisel

  1. Head
  2. Body
  3. Point or Cutting Edge
Parts of Chisel
Parts of Chisel

Types of Chisels

  1. Flat chisel
  2. Cross-cut chisel
  3. Half-round nose chisel
  4. Diamond point chisel
  5. Web chisel

1. Flat chisel

Flat chisels are used to remove metal from large flat surfaces and chip-off excess metal of welded joints and castings.

Flat Chisel
Flat Chisel

2. Cross-cut chisel

Cross cut chisels are used for cutting key-ways, grooves and slots.

Cross Cut Chisel
Cross Cut Chisel

3. Half-round nose chisel

Half round nose chisels are used for cutting curved grooves (oil grooves).

Half Round Nose Chisel
Half Round Nose Chisel

4. Diamond point chisel

Diamond point chisels are used for squaring materials at the corners, joints.

Diamond Point Chisel
Diamond Point Chisel

5.Web chisel

Web chisels are used for separating metals after chain drilling.

Web Chisel
Web Chisel

Specification of Chisel

  1. Length
  2. Width of cutting edge
  3. Type
  4. Cross section of the body

Chisel Angles

  1. Point Angle or Cutting Angle
  2. Rake Angle
  3. Clearance Angle
Chisel Angles
Chisel Angles

1. Point Angle

The correct point/cutting angle of a chisel depends on the material to be chipped. Sharp angles are given for soft materials and wide angles for hard materials. The correct point and angle of inclination generate the correct rake and clearance angles.

2. Rake Angle

Rake angle is the angle between the top face of the cutting point and normal (90°) to the work surface at the cutting edge.

3. Clearance Angle

Clearance angle is the angle between the bottom face of the point and the tangent to the work surface originating at the cutting edge.

If the clearance angle is too low or zero, the rake angle increases. The cutting edge cannot penetrate into the work. The chisel will slip.

If the clearance angle is too great, the rake angle reduces. The cutting edge digs in and the cut will become deeper and deeper.