mma tool geometry

7/29/2019 MMA Tool Geometry

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a esse e resen et

AAU, Technology Faculty,

ma gsta esse ya oo.com

References:

1. Shaw .M.C., Metal cutting Principles , 2nd edition Oxford clarendon Press, 2005

2. Boothro d G. and Kni ht. W.A Fundamentals of Machinin and Machine tools 3rd edition Marcel

Dekker, New York, 2006.2. Bhattacharya. - Metal Cutting Theory and Practice , New central Book Agency(p) Ltd.,Calcutta, 1984.


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Methods of MachiningMethods of Machining

In the metal cutting operation, the tool is wedge-shaped and has a straightcutting edge. Basically, there are two methods of metal cutting, dependingupon the arrangement of the cutting edge with respect to the direction of

-

Orthogonal cutting or two dimensional cutting Oblique cutting or three dimensioning cutting.

Orthogonal Machining Oblique Machining

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Orthogonal CuttingOrthogonal Cutting

e cutt ng e ge o t e too rema ns atto the direction of feed (of the tool or the

work)

cutting edge of the tool The cutting edge of the tool has zero

inclination with the normal to the feed

The chip flows in the plane of the tool face.Therefore, it makes no angle with the

normal (in the plane of the tool face) to thecutting.

The shear force acts on a smaller area, soshear force per unit area is more.

The tool life is smaller than obtained in oblique cutting (for same conditions of

cutting)

There are only two mutually perpendicular components of cutting forces on the

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tool

The cutting edge is bigger than the width of cut.


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Oblique CuttingOblique Cutting The cuttin ed e of the tool remains inclined

at an acute angle to the direction of feed (ofthe work or tool)

The direction of the chip flow is not normalto the cutting edge. Rather it is at an angle

to the normal to the cutting edge.

The cutting edge is inclined at an angle to.

inclination angle.

The chip flows at an angle to the normalto the cuttin ed e. This an le is called chi

flow angle.

The chip flows at an angle to the normal to the cutting edge. This angle is called

.The shear force acts on a larger area, hence the shear force per area is smaller

The tool life is higher than obtained in orthogonal cutting

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tool

The cutting edge is smaller than the width of cut.


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Cutting Tool GeometryCutting Tool Geometry,

or finish. So a cutting tool must have at least a sharp edge. There are two types ofcutting tool. The tool having only one cutting edge is called single point cuttingtools. For example shaper tools, lathe tools, planer tools, etc. The tool havingmore than one cutting edge is called multipoint cutting tools. For example

drills, milling cutters, broaches, grinding wheel honing tool etc.

A single point cutting tool may be either right or left hand cut tool dependingon the direction of feed.

Primary Cutting Edge

Right hand cuttingLeft hand cutting

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tooltool


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ToolTool--inin--hand Nomenclaturehand Nomenclature The geometry of a cutting tool consists of the following elements: face or rake

surface, flank, cutting edges and the corner. Face or rake is the surface ofthe cutting tool along which the chips flow out. Flank surfaces are those facing the

work piece. There are two flank surfaces, principal and auxiliary flank surfaces.Principal cutting edge performs the major portion of cutting and is formed by the

.

(often called end cutting edge) is formed by the intersection of the rake surfacewith the auxiliary flank surface. Corner or cutting point is the meeting point of theprincipal cutting edge with the auxiliary cutting edge.

Shank of tool

Tool axis

Corner

Principal cutting edge

Rake or Face

Principal flank surface

Auxiliarycutting edge

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Auxiliary flank surface


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Single Point Cutting ToolSingle Point Cutting Tool

Side rake angle (x)

n cu ng e ge

angle (e)

Side clearance

angle (x)

Nose radius rSide cutting edgeangle (s)

Back rakeangle (y)

Endclearance

angle (y)Note: All the rake and clearance

angles are measured in normal

direction

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Side Cutting Edge Angle (s): The side cutting-edge angle (SCEA) is usuallyreferred to as the lead angle. It is the angle enclosed between the side cutting edge

.and 90, depending upon the machinability, rigidity, and, sometimes, the shape ofthe workpiece. As this angle increases from 0 to 15, the power consumptionduring cutting decreases. However, there is a limit for increasing the SCEA, beyond

which excessive vibrations take place because of the large tool-workpiece

interface. On the other hand, if the angle were taken as 0, the full cutting edgewould start to cut the workpiece at once, causing an initial shock. Usually, the

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Auxiliary or End Cutting Edge Angle (e): The end cutting-edge angle(ECEA) serves to eliminate rubbing between the end cutting edge and themac ne sur ace o t e wor p ece. t oug t s ang e ta es va ues n t e rangeof 5 to 30, commonly recommended values are 8 to 15.

Side Clearance Angle (x) and End Clearance Angle (y): Side and end

the side and end flank, respectively. Usually, the value of each of these anglesranges between 5 and 15.

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Back Rake Angle (y) and Side Rake Angle (X): Back and side rake anglesdetermine the direction of flow of the chips onto the face of the tool. Rake anglescan e pos t ve, negat ve, or zero. t s t e s e ra e ang e t at as t e om nantinfluence on cutting. Its value usually varies between 0 and 15, whereas the backrake angle is usually taken as 0.

.

A sharp point on the end of a tool is highly stressed, short lived and leaves agroove in the path of cut. There is an improvement in surface finish and permissiblecutting speed as nose radius is increased from zero value. Too large a nose radius

will induce chatter.

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Designation of Cutting ToolsDesignation of Cutting Tools

By designation or nomenclature of a cutting tool is meant thedesignation of the shape of the cutting part of the tool. Theo ow ng systems to es gnate t e cutt ng too s ape w c

are widely used are:

Tool in Hand S stem

Machine Reference System or American Standard Association(ASA) System

Orthogonal Rake System (ORS)

Normal Rake System (NRS)

Work Reference System (WRS)

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Tool Reference SystemTool Reference System

The references from which the tool angles are specified are the Reference plane (R)

Machine longitudinal plane (x)

Machine transverse lane

Principal cutting plane (

c) Orthogonal plane (o) and

n

The reference plane (R) is the plane perpendicular to the cutting velocity

(Vc). The machine longitudinal plane (x) is the plane perpendicular to R.

transverse plane (y) is the plane perpendicular to both R and X orplane perpendicular to R and taken in the direction of cross feed. Therinci al cuttin lane is the lane er endicular to and containin

the principal cutting edge. The orthogonal plane (o) is the planeperpendicular to R and c. The normal plane (n) is perpendicular to the

principal cutting edge.

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American Standard Association SystemAmerican Standard Association System

Xm

Zm

oo ar ac er

y x y x e s r

50 100 70 80 200 300 1/32Yx

XSection B-B

X

y Back rake angle

x Side rake angle

y Back or end clearance angle

m

Z

Y

m

B B

A

Xx

e Auxiliary or End cutting edge angle

s Side cutting edge angle (90o-)

r Nose radius (inch)

e

y y

Y

m

A

Section A-A

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Rs


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Orthogonal Rake System (ORSOrthogonal Rake System (ORS))

X Zo

YoZo

o o ar act er

0 0 0/ e r

50 100 70 80 200 3000.8

Section M-M

oO o

C

o

c/

o

Yomm

Inclination angle

0 Orthogonal rake angle

Orthogonal clearance

M Section N-NXo

ang e

0/ Auxiliary orthogonal

clearance angle

eAuxiliary or End cuttinged e an le

e

MN

Principal cutting edgeangle (90-s)

r Nose radius (mm)

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Rs


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InterconversionInterconversion Between ASA and ORSBetween ASA and ORS

Interrelations can be established between ASA and ORS andvice versa. Various methods are used for developing suchnterre at ons ps suc as

Method of slopes

Method of master line Circle diagram

Vector methods, etc.

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Methods of Master Line for RakeMethods of Master Line for Rake

AnglesAnglesOA=T cot

Xmx

Zm

= cot y

OC=T cot oOD=T cot xOM=T cot

T

x

Xo Zo

XD/

Y

For T=1

T=Depth of the cutting tool

m

s

OXYm

Xo

C/

oOYo

Xo

o

m

M

OA= cot

OB= cot yOC= cot o

C y

y

Y

CM

Zm

E

= co x

OM= cot m

RA

H

Setting angle for grinding rake surface

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Master linem


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for a single point cutting tool.

+=

+=

yx

yxo

sintan costan tan(ii)

cosan s nan an

+=

=

oy

ox

sintancostan tan(iv)

costan-sintan tan(iii)

+= 2o2

m tantantan(v)

= o

1

tanantan(vi)

etting ang e or grin ing ra e sur ace

m Maximum rake angle

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tan o

= tan x

sin + tan y

cos

From Figure OBD=OBC+OCD

OB.OD=OB.CE + OD.CF

Xm

Ym

D

Yo

F

XoOB.OD=OB.OC sin + OD.OC. cos

Dividing on both sides by OB.OC.ODcossin1

+=G

=

B

CM

Etan o = tan x sin + tan y cos

OB= cot yOC= cot oOD= cot x

A

Master

H

-x

y

From Figure OAD = OAB +OBD

OD. AG = OB. AH + OB.OD

OD. OA. sin =OB.OA COS + OB.OD

OM= cot mline. .

OA

1

OD

cos

OB

sin+=

tan = -tan x cos +tan y sin

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Methods of Master Line for Clearance AnglesMethods of Master Line for Clearance Angles

Xm

Zm

OA=T cot

D/

T

y

Xo Zo

X

Y

= tan y

OC=T tan oOD=T tan xOM=T an

m

s

OXm

Ym

Xo

C/o

OYo

Ym

o

m

T=Depth of the cutting tool

For T=1

C

B/

x

x

Y

B C

/

D

M

Zm OA= cot

OB= tan yOC= tan o

=

RA

xOM= tan m

Setting angle for grinding principal rake surface

Maximum rake an le

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Master line


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Prove the followings by master line methods for a single pointcutting tool.

+=

+=

sincotcoscottan(ii)

coscotsincotcot(i)

yx

yxo

+=

=

sintancoscotcot(iv)

costan-sincotcot(iii)

o

ox

+= tancotcot(v) 2o2

m

= cot

antan(vi) o1 Setting angle for grinding principal rake surfacem Maximum rake angle

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YmYoX

cot o

= cot x

sin + cot y

cos

From Figure OBD=OBC+OCD

OB.OD=OB.CE + OD.CF

F

E

GO D

C

Xm

OB.OD=OB.OC sin + OD.OC. cos

Dividing on both sides by OB.OC.ODcossin1

+=

B

A

Masterline

H

cot o = cot x sin + cot y cos

For T=1

OA= cot

OB= tan y

-x

y

From Figure OAD = OAB +OBD

OD. AG = OB. AH + OB.OD

OD. OA. sin =OB.OA COS + OB.OD

OC= tan oOD= tan xOM= tan m

. .

OA

1

OD

cos

OB

sin+=

tan = -cot x cos +cot y sin

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mma tool geometry

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