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Question 4. Why does the temperature in cutting depends on the cutting speed, feed and depth of cut? Explain in term of the relevant process variable.

Temperature in cutting refers to the temperature at the tool/chip interface. It consists of the temperature rise in the body of the chip due to shear at the interfaces as the hot chip rubs on the tool faces, and the workpiece temperature. Those rises varies with cutting speed, in general, decreasing with an increasing in cutting speed.

Most of the mechanical energy expanded in metalcutting is transformed into heat. About 75%-80% of this heat is carried away by the chip; the remainder is divided between the workpiece and the tool.

An increase in speed or feed decreases the proportion of the heat transferred to the tool and workpiece. The relationship of cutting temperature to cutting speed is shown below:

Slide 13

θf = CV^n

where,
θf = tool/chip interface temperature
V = cutting speed
C = constant (dependent on tool/workpiece combination and cutting variables other than cutting speed)
n = exponent

An empirical equation of similar from relates cutting temperature to feed. It is seen that the increase in feed is less hazardous as far as temperature is concerned than a corresponding increase in speed. The depth-of-cut influences the cutting temperature in a limited manner.

If the depth-of-cut is more than twice the nose radius, a further increase in depth will have little effect on the cutting temperature. Basically, a depth of cut of 10 times of the feed rate creates a little temperature effect.

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