cutting speed for turning
TRANSCRIPT
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On the Lathe
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Cutting speedCutting speed for turning is the speed at
which the work rotates. This is also known as surface speed
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Rate at which point on work circumference travels past cutting tool
expressed in meters per minute (m/min)Important to use correct speed for material
Too high: cutting-tool breaks down rapidlyToo low: time lost, low production rates
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Cutting speed selectionThe softer the work material, the faster the
recommended cutting speed
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The hardness of the cutting tool material has a great deal to do with the recommended cutting speed. The harder the cutting tool material, the faster the cutting speed. The softer the cutting tool material, the slower the recommended cutting speed
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The depth of the cut and the feed rate will also affect the cutting speed, but not to as great an extent as the work hardness
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Factors that Determine cutting speedThe material being cutThe rigidity and condition of the
machineThe material of which the tool is
made fromThe depth of cut and the feed rateAvailability of coolant (cutting fluid)
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Setting Speeds on a LatheSpeeds measured in revolutions per minute
Changed by stepped pulleys or gear levers
Belt-driven latheVarious speeds obtained by changing flat
belt and back gear driveGeared-head lathe
Speeds changed by moving speed levers into proper positions according to r/min chart fastened to headstock
Safety Note!! NEVER change speeds when lathe is running.
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Setting Speeds on a Lathe
Speeds measured in revolutions per minuteChanged by stepped pulleys or gear levers
Belt-driven latheVarious speeds obtained by changing flat
belt and back gear driveGeared-head lathe
Speeds changed by moving speed levers into proper positions according to r/min chart fastened to headstock
9
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Lathe Cutting SpeedsMaterial being cut Cutting speed (metres/minute
Mild steel 20 to 28
Cast iron 18 to 25
High carbon steel 12 to 18
Brass 45 to 90
Bronze 15 to 21
Aluminium Upto 30047-10
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Calculating Lathe cutting speedGiven in metres per minutespindle speed of machine (N) and
diameter of work must be known
S (m/min)= πDN/1000Where π= 22/7 or 3.142 D= diameter of material N= Spindle speed(rev/min)
47-11
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Calculating Lathe Spindle speed (rev/min)
D xS1000 rev/min
S (m/min)= cutting speedWhere π= 22/7 or 3.142 D= diameter of material N= Spindle speed(rev/min
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ExerciseCalculate the spindle speed required to
turn 200mm diameter piece of high speed steel, if the cutting speed is 28 m/min.
Find the cutting speed of a 15mm diameter bar being turned with a spindle of 955 rev/min.
Determine the lathe speed to cut a 40mm diameter at 30 m/min