Oblique cutting

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Orthogonal cutting1- Cutting tool travel in the direction perpendicular to the cutting edge.2-The cutting edge clear either end of work piece.3- Chip flows in the direction perpendicular to the cutting edge.4-Two mutually perpendicular cutting forces act on the work piece.

Oblique cutting1-cutting edge travels, making an angle with the normal of cutting edge.2-The cutting edge may or may not clear either end of work piece.3- chip flows, making an angle with normal of cutting edge.4-Three mutually perpendicular forces are involved.

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Ff

FrFt

Z

X

Y

Fc

Orthogonal plane

R

Turning tool

Cylindrical job

Rake face

Forces acting during oblique turning

ζ

Cutting forces acting during oblique turning operation

• Feed force, Ff - along z-axis• Radial force, Fr - along x-axis, radial direction• Cutting force, Fc- along y-axis perpendicular to

x-z plane

• Merchant circle diagram is drawn for the forces acting in orthogonal plane, i.e. the plane containing cutting force Fc and Ft ( resultant of Ff and Fr)

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Normal rake angle (αn)

Where αb and αs = back and side rake anglesΨ =side cutting edge angle

Shear angle (φn)

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nc

ncn

sinr1cosrtan

α−α

=φ

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Z

X

Y

Turning tool

Cylindrical job

Rake face

Forces acting during oblique turning

Dept

h of

cut

=

d

Feed = f

Chip

ψ

ψ

15De

pth

of c

ut =

d

Feed = f

ψ

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ψcosdwcut.of.Width ==

ψcosftthickness.chip.Uncut 1 ==

cc1 fdvvwtmrrrate.removal.Metal ===Where,Cutting velocity = vc = πDND = Average diameter of the

workN = RPM

ψ = side cutting edge angled, f = depth of cut, feed/

revolution

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volume.unit/consumed.Energy..........)U(energy.Specific c

=

fdF

mrrvFU ccc

c ==

ccvFWWnconsumptio.Power

==

Machining time (tc)(for a single cut)

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fNt L

c =

Where,L = Length of the work along the axisF = feed/ revolutionN = rpm of the work

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ProblemThe following data are available from a turning operation:

* s stands for (4-second digit of serial number)

Determine the (a) shear angle (b) friction coefficient (c) shear stress and shear strainon shear plane(d) chip velocity and shear velocity and (e) energies uf, us and ut.

Work material Aluminium Steel

Tool signature 9,s*,6,7,10,15,9 mm 9,s*,6,7,10,15,9 mm

Depth of cut, mm 2.5 2.5

Cutting speed, m/s 2 2

Chip thickness, mm 0.23 0.58

Cutting force, Fc, N 430 890

Thrust force, Ft, N 280 800

Thanks

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