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Machining Chip Type
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Continuous Chip Discontinuous Chip Continuous Chip with Built Up Edge Test Your Knowledge

You may have noticed when machining on a lathe or drilling machine that the swarf comes away as a continuous strip like wire or as small broken chips. This difference is due to materials properties where continuous chip (strip) is produced from ductile materials like aluminium and discontinuous chip is produced from brittle materials such as cast iron. Some materials are alloyed with others to give discontinuous chip e.g. "Free Cutting" aluminium is alloyed with another metal so that discontinuous chip is produced. This is especially important with CNC machining where the operator can not intervene during the cycle.

 

Continuous Chip

A continuous chip is formed when machining ductile material and shearing takes place within the plastic range.

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  • The chip comes away as a continuous strip, like wire.

  • This is because the material is ductile and is still in its plastic state after the cutting/shearing action.

  • Care must be taken with the disposal of continuous chip as it is very sharp.

 

Discontinuous chip

A discontinuous chip is formed when machining brittle material and the shearing takes place outside the plastic range.

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  • The chip breaks up as it is machined

  • This is because the material is relatively and has gone beyond its elastic limit after the cutting/shearing action.

  • Brittle materials or free cutting materials produce a discontinuous chip.

 

Continuous chip with Built Up Edge.

A continuous chip with built up edge is formed when machining ductile material and the shearing takes place within the plastic range. During this time some of the chip becomes pressure welded to the face of the cutting tool which is known a built up edge.

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  • The chip becomes welded  to the top of the cutting tool and then gets dragged off, giving a very rough surface and chip.

  • The cutting tool is subjected to high levels of wear and frequent regrinds are required.

  • It is still in its plastic state after the cutting/shearing action.

 

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Paddy Keays Engineering Teacher

Cresent College Comprehensive Limerick Ireland
Last updated 10 February 2004.

email   paddykeays@eircom.net