4 1T Turning Theory

8/3/2019 4 1T Turning Theory

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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

CoroKey 2006 Products / Turning theory


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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


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


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


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.


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


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


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


T-Max P inserts CoroTurn 107 inserts

Medium/Roughing machining Roughing machining

ap x fn (cutting depth x feed)

Documents

4 1T Turning Theory