CHISELLING Basic Cutting Process Defination Chiselling can be

CHISELLING Basic Cutting Process

Defination Chiselling can be defined as working materials with a sharpened wedge-shaped tool (chisel). The cutting effect is achieved by striking the head of the chisel with the hammer. Chisels can be used either to separate work (to split or divide workpieces) without removing chips (chipless), or to make rough cuts (chip removal).

Types of chisels 1. Shearing chisel Lip angle 600

Types of chisels Flat chisel - Used to cut flat surfaces, to separate and to deburr. Cross-cut chisel - Used for chiseling keyways.

Types of chisels Drift punch - Used for driving through remainders after chain drilling. Punching chisel - Used for chiselling out convec curved or rounded parts.

Types of chisels Grooving chisel - Used for chiselling out channels in bearing bushes.

Cutting angle For soft materials such as copper (Cu) and aluminum (AI): 30 -50°. For structural and tool steel: 50 -70°. For hard materials such as very hard brass: 70 -80°.

Chisel operation Separation - dividing chiselling Holding and guiding the chisel. Guiding the hammer. The centre line through the chisel and the hammer must form one straight line (common line of application) Body position: - Keep your eyes on the cutting edge.

Chisel operation Separation - shearing chiseling During shearing chiselling, the cutting line (marking line) must be flush with the top edge of the vice. The chisel cut should be made at under 45º to the sheet. If the chisel is held correctly, the shaving rolls up into a spiral.

Chisel operation The formation of a chip - chip-removing chiselling

Chisel sharpening (grinding) v v Maintain the correct cutting angle and shape of cutting edge Always hold the chisel so that the cutting edge points in the opposite direction to the direction in which the wheel is turning. The cutting edge must be cooled continuously otherwise it will be overheated and become soft. Apply light pressure only, and move the chisel uniformly back and f 9 rth across the wheel. Always hold the chisel so that the cutting edge points in the opposite direction to the direction of rotation of the wheel.

Work safety v v v Be sure the hammer is in perfect condition (free from burrs and grease) Use a protection screen to protect other people and goggles to protect yourself Keep the hammer face and the chisel head clean Do not allow a "mushroom head" to develop; grind down rough edges from time to time. When sharpening a chisel, do not apply constant pressure on the grinding wheel; keep the cutting edge cool. Keep the tool rest at the-Correct distance from the grinding wheel; and make sure that the tool rest is in good condition.