Lathe machine operations- Turning (Process & Formula)

Turning

With turning operations, the workpiece rotates as the primary means of moving
metal against the cutting tool, in other words, the workpiece is rotated and the tool is
fixed. But milling machines are operations in which the cutting tool rotates relative to
the fixed workpiece. Drilling machines are operations in which holes are produced or
refined by bringing a rotating cutter called twist with cutting edges at the lower into
contact with the workpiece. Drilling operations are done primarily in drill presses but
sometimes on lathes or milling.

• Average cutting speed, Vavg = Π DavgN
– Davg is the average diameter of the workpiece
– N is the spindle speed in rpm
• Material removal rate, MRR = Vavgdf
d is the depth of cut
– f is the feed (units: mm/rev or in/rev)
• Cutting power, Pc = ucMRR=FcV
Fc =Cutting force
V = Cutting speed
• Machining time, tm = L/(fN) = L/F
– F is the feed rate (units: mm/min or in/min)

Relation between u and t0
• As the depth of cut decreases, the surface
area to volume ratio increases, hence friction
(energy) increases
• Since,    u ≈ us + uf
• Hence

u ∝ 1 / t0

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