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n = RPM
(revolutions per minute)
vc = Cutting speed
(meter per minute)
Dc = Workpiece diameter
(millimeter)
ap = Depth of cut
(millimeter)
Turning definitions
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Definition of terms
vc
fn
ap
nvc = Cutting speed
(m/min.)
ap = Depth of cut
(mm)
n = Spindle speed(rpm)
Fn = Feed
(mm/rev.)
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D2 100 mm diameter = 300 mm (3 x 100)
D1 50 mm diameter = 150 mm (3 x 50)
Circumference = x diameter = 3.14 (approx. = 3)
Cutting data calculation
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Given vc = 400 m/min
Dc = 100 mm
vc x 1000 x Dc
400 x 10003.14 x 100
= 1275 rev/min
Calculating cutting data
n=
n=
RPM (n) from cutting speed (vc)
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Utilize the potential ofap -to reduce number or cutsfn -for shorter cutting timevc -for best tool life
Effect on tool life
ap - little effect ontool life
fn - less effect ontool life than vc
vc - large effect ontool life.Adjust vc forbest economy
How do cutting data parameters effect toollife?
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Effects of feed rate (fn)
Too light
Stringers
Uneconomical
Too heavy
Loss of chip control
Poor surface finish
Cratering-plastic deformation
High power consumption
Chip welding
Chip hammering
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Effects of depth of cut (ap)
Too small
Loss of chip control
Vibrations
Excessive heat
Uneconomical
Too deep
High power consumption
Insert breakage
Increased cutting forces
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Lead angle-5 degrees
Entering angle95 degrees
ANSI ISO
Lead angle - entering angle (r)
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Effect of entering angle on radialcutting forces
Fcn = radial
Fcn = radial
Ff = axial Ff = axial
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Features / benefits:Small entering angle
Cutting forces directed towardschuck
Turn against a shoulder
Higher cutting forces at entranceand exit
Tendency to notch in HRSA andhard materials
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Features / benefits:Large entering angle
Produces a thinner chip
increased productivity
Reduced notch wear
Cannot turn against a shoulder
Forces are directed both axially
and radially vibration tendencies
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Insert shape
Large insert shape
Stronger cutting edge Higher feed rates
Increase cutting forces
Increase vibration
Small insert shape
Increase accessibility Decrease vibration
Decrease cutting forces
Weaker cutting edge
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Selecting the insert size
CoroKey 2006 Products / Turning theory
la = effective cutting edge
l = cutting edge length
ap
la
l
r
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Note: As a general rule of thumb, the depth of cut should be no less than 2/3 of thenose radius.
Effect of nose radius
Small nose radius Ideal for small cutting depth
Reduces vibration
Insert breakage
Large nose radius Heavy feed rates
Large depths of cut
Strong edge security
Increased radial pressures
CoroKey 2006 Products / Turning theory
r= 0.2r= 0.8
r= 1.6
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Rmax = fn2 x 1000
8 x r
In a turning operation, surfacefinish is a function of nose
radius and feed per revolution
fn
ra
p
Surface finish, m Insert nose radius, mmRa Rt 0.4 0.8 1.2
0.6 1.6 0.07 0.10 0.12
1.6 4.0 0.11 0.15 0.193.2 10.0 0.17 0.24 0.29
6.3 16.0 0.22 0.30 0.37
Surface finish: negative T-MaxP inserts
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In a turning operation, surfacefinish is a function of nose
radius and feed per revolution
Surface finish, m Insert nose radius, mmRa Rt 0.2 0.4 0.8 1.2 1.6
0.6 1.6 0.05 0.07 0.10 0.12 0.14
1.6 4.0 0.08 0.11 0.15 0.19 0.223.2 10.0 0.10 0.17 0.24 0.29 0.34
6.3 16.0 0.13 0.22 0.30 0.37 0.43
Surface finish: positive CoroTurn107inserts
Page A376
fn
ra
p
Rmax = fn2 x 1000
8 x r
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High feed turning with Wiper inserts
CoroKey 2006 Products / Turning theory
Wiper insertTwice the feed, same Ra
Traditional insert
Wiper insertHalf Ra, same feed
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Cutting forces effect on internal turning
Tangential force Frforces tool downand away from centre line
Radial forceF
t will attempt to pushthe tool away from workpiece.
CoroKey 2006 Products / Turning theory
Fr
Ft
Ft
Fr
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Internal turning factors
Tool geometry
Chip evacuation
Tool requirements
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Tool geometry:Entering angle
Close to 90
Less force in radial direction = less deflection
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90 75
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Tool geometry:Insert geometry
Positive insert geometries generate less cutting forces
PositiveNegative
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Tool geometry:Nose radius
Depth of cut at least the nose radius
Less force in radial direction = less deflection
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DH7
Ra 32
Tool requirements:Clamping
Maximum contact between tool and tool holder(design, dimensional tolerance)
Clamping length 3 to 4 times bar diameter
(to balance cutting forces)
Holder strength and stability
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Factors that affect vibration tendenciesVibration tendencies grow towards the right
CoroKey 2006 Products / Turning theory
90 75 45
0.2 0.4 0.8 1.2 mm
r
+
ER GC VB
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Power requirement for T-MaxPand CoroTurn107 inserts
CoroKey 2006 Products / Turning theory
T-Max P inserts CoroTurn 107 inserts
Medium/Roughing machining Roughing machining
ap x fn (cutting depth x feed)