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Practical hints

Chips and coolant - get rid of both!

Evacuating chips and eliminating coolant are key parts of the machining strategy related to the cutting tool.

Efficient chip evacuation avoids scratching the turned surface and prevents chips getting stuck inside the bore prior to the second cut. Chips interfering with part handling must also be eliminated. Chip flow is infl uenced by several factors. Gravity is one, so the mounting direction of the tool requires consideration.

Others include cutting data, insert radius and coolant or forced air. Changing feed rate changes the direction of chip flow. Likewise, changing cutting speed affects chip temperature and hardness, thereby redirecting its flow. Thin chips do not generally break. However, increasing feed will increase chip thickness and thus promote chip breaking.

A larger radius or wiper radius allows increased feed rate while still maintaining surface fi nish. Changing tool path can also give a completely different chip flow path.

	Insert selection - time for a geometry lesson
	Tool wear - when the insert reaches the end of its life
	Surface generation - is there a clear cut strategy?

‘Upside down’ tool mounting under the work-piece promotes free-flow chip evacuation away from the surface being turned.

Changing tool path can completely reverse the direction of chip evacuation.

1. fn = 0.05 mm/r
2. fn = 0.10 mm/r
3. fn = 0.20 mm/r

Chip evacuation flow direction changes with feed rate (video)

Continuous cut HPT without cooling is the ideal situation, and is entirely feasible. Both CBN and ceramic inserts tolerate high cutting temperatures, which eliminates the cost and bother of handling coolants, and allows easy and cost-effective chip removal.

Some applications may nevertheless require coolant, e.g. to control the thermal stability of the work-piece. In such cases, ensure a continuous flow of coolant throughout the entire turning operation.

Latest update: 10/26/2006 02:31:25 PM