Tool made of tempered steel used for cutting ′cold′ metals.
The image to the left shows a flat chisel used to cut bars and rods, to reduce surfaces and to cut sheet metal which is too thick or difficult to cut with tin snips.
Chisels are used when the finsih is not critical or a part is being roughed out for further machining.
When grinding the cutting edge be careful not to over heat the chisel as it will lose its temper, best to cool the chisel frequenctly in water.
Some chisels are made from beryllium copper where it is important not to create sparks.
The are four common types of cold chisel:
- Flat chisel - used to cut bars and rods to reduce surfaces and to cut sheet metal which is too thick or difficult to cut with tin snips.
- Cross cut chisel - used for cutting grooves and slots. The blade narrows behind the cutting edge to provide clearance.
- Round nose chisel - used for cutting semi-circular grooves for oil ways in bearings.
- Diamond point chisel - used for cleaning out corners or difficult places and pulling over centre punch marks wrongly placed for drilling.
The cutting surfaces are best ground to a 60° angle. Note that the cutting edge is slightly curved to stop the corners digging into the workpiece.
The cross cut chisel is also known as the cape chisel.
Note that the nose is actually half-round with a flat upper surface.
The chisel is initially made square and then ground down to give the diamond shaped cutting edge.
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