In a straight turning operations the diameter of a workpiece is reduced from 50 mm 40 mm using a feed rate of 0.1 mm/rev. The cutting tool used for the process has a normal working rake angle of 15°, clearance angle of 4° and a lead angle of 90°. The cutting force of 1200 N and a thrust force of 660 N is measured during cutting operations. The workpiece material was stainless steel with a density of 7850 Kg/m³, thermal conductivity is 15 J/smK, specific heat is 480 J/kgK. The width of the secondary deformation zone divided by the chip thickness wo is assumed to be 0.2 for the above mentioned cutting conditions. The chip/tool contact length is measured as 1.5 mm. (a) Calculate the temperature rise in the primary deformation zone (b) Calculate the temperature rise in the secondary deformation zone (c) Calculate the maximum temperature if the room temperature is 24°C If the tool life for the average cutting velocity of 90 m/min is measured as 10 min. and for a cutting velocity of 160 m/min is measured as 6 min. estimate the tool life when machining at:

A turning operation is performed on C1008 steel (a ductile steel) using a tool with a nose radius= 1.3 mm. Cutting speed = 61 m/min and feed = 0.27 mm/rev. Compute an estimate of the surface roughness in this operation. (Hint: the ratio of actual to ideal roughness can be read on the figure below) Equations used; Ra Ri Actual Ratio Theoretical 32NR = rai Ri 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0 Ductile metals Cast irons Free machining alloys. 100 30.5 200 Cutting speed-ft/min 61 Cutting speed - m/min 300 91.5 400 122

A student is performing a turning operation with a workpiece with an initial diameter of 40 mm to produce a 30 mm diameter rod that is 100 mm long. The lathe power is 20 kW and is operating on 85% mechanical efficiency. If the student set the cutting speed to 0.5 m/min and the cutting tool is set to have a rake angle of 5 degrees:  a.) What material can we choose for the rod is the coefficient of friction is 0.5? b.) If we select 4130 normalized heat-treated steel for the rod, and coefficient of friction is 0.5, what will the maximum depth of cut we can achieve?