Geometry of Single Point Cutting Tool

DEEPAK KUMAR
Assistant Professor,
Department of Mechanical Engineering,
Dr. B. C. Roy Engineering College, Durgapur
 Introduction
• Production, Manufacturing and Machining

Casting Turning Milling Joining

MACHINING

Grinding Drilling
Powder
Forming Metallurgy

PRODUCTION Manufacturing 2
 Introduction
• What is Manufacturing?
Value Addition
Processes

Raw materials Finished Product

• Primary manufacturing processes convert raw material or scrap to a basic

primary shaped and sized product.

• Secondary manufacturing processes further improve the properties, surface

quality, dimensional accuracy, tolerance, etc.
3
 Introduction
• Machining
• One of the secondary manufacturing processes.
• Excess material is removed (by shearing) from the preformed blank in the form of chips.
• Uses a wedge shaped cutting tool in order to get product having desired shape, size and
tolerance.
• Machining to high accuracy and finish essentially enables a product to
• Fulfill its functional requirements
• Improve its performance
• Prolong its service

• Tools necessary for machining

• Machine Tools
• Cutting Tools
4
 Cutting Tools
• Both material and geometry of the cutting tools play very important roles on
their performances in achieving effectiveness, efficiency and overall economy
of machining.
• Classified according to the number of major cutting edges (points) involved in
cutting:
• Single point: only one cutting tip is available.
e.g., turning tools, shaping, planning and slotting tools and
boring tools
• Multipoint: more than one tip is available.
e.g., drills, milling cutters, broaching tools, hobs,
gear shaping cutters etc.

5
 Salient features of cutting tool point
1. Nose
2. Rake surface
3. Principal Flank
4. Auxiliary Flank
5. Principal Cutting Edge
6. Auxiliary Cutting Edge

Tool-in-Hand System
6
 Systems of description of tool geometry
• Tool-in-Hand System – Only the salient features of the cutting tool point are
identified or visualized such as
• Nose (Cutting Tip)
• Rake surface, Principal Flank, Auxiliary Flank
• Principal Cutting Edge, Auxiliary Cutting Edge.
• There is no quantitative information, i.e., value of the angles.
• Machine Reference System – ASA system
• Tool Reference Systems 6
• Orthogonal Rake System – ORS
• Normal Rake System – NRS 2
• Work Reference System – WRS
1 3
4 5 7
 Systems of description of tool geometry

Reference planes and Axes in ASA system

Top view of Lathe Machine
8
 ASA and ORS systems

Reference planes and Axes in ASA system Reference planes and Axes in ORS system

9
 ORS and NRS systems

Reference planes and Axes in ORS system Reference planes and Axes in NRS system

10
 Machine Reference System – ASA system
• The planes of reference and the coordinates used in ASA system for tool geometry are :

• =Reference plane; plane perpendicular to the velocity vector,

• =Machine longitudinal plane; plane perpendicular to and taken in the direction of assumed
longitudinal feed.
• =Machine Transverse plane; plane perpendicular to both and , in the direction of assumed
cross feed.
• The axes are:
• =in the direction of longitudinal feed,
• =in the direction of cross feed.
• =in the direction of cutting velocity (vector).

11
Tool Signature of SPTT in ASA system

12
Tool Signature of SPTT in ASA system

13
 Tool Signature of SPTT in ASA system
Angle Made by With Measured
on
Back Rake rake surface reference πY
angle,γY plane
Side Rake rake surface reference πX
angle,γX plane
Back principal VC (or Zm) πY
Clearance,αY flank
Side principal VC (or Zm) πX
clearance,αX flank
End Cutting end cutting πX πR
Edge edge
angle,φe
Approach Side cutting πY πR
angle,φs edge 14
 Tool Reference Systems- ORS System
• The planes of reference and the co-ordinate axes used for expressing the tool
angles in ORS are: πR – πC – πO and X0 – Y0 – Z0
• πR = Reference plane perpendicular to the cutting velocity vector,
πC = cutting plane; plane perpendicular to πR and taken along the principal cutting edge
πO = Orthogonal plane; plane perpendicular to both πR and πC and the axes;
Xo = along the line of intersection of πR and πO
Yo = along the line of intersection of πR and πC
Zo = along the velocity vector, i.e., normal to both Xo and Yo axes

15
Tool Signature of SPTT in ORS system

16
 Tool Signature of SPTT in ORS system
Angle Made by With Measured
on
Inclination rake principal πC
angle, λ surface cutting edge
Orthogonal rake reference πo
rake angle,γ0 surface plane
Orthogonal principal πC πo
clearance,αo flank
Auxiliary Auxiliary πC’ πo’
orthogonal flank
clearance αo’
φ 1= φ e end cutting πX πR
edge

φ=90- φs Side cutting πX πR

edge 17
Auxiliary orthogonal clearance angle
18
 Summery of SPTT geometry
• ASA system-convenience of inspection
• ORS system- for analysis and research
in machining and tool performance
• ORS does not reveal the true picture of
the tool geometry when λ≠0.
• sharpening or resharpening of the tool
by grinding in ORS requires some
additional calculations for correction
of angles.
• In NRS, rake and clearance angles are
visualized in the normal plane, πN.
19
 QUIZ
• Select the correct answer from the given four options :
1. Back rake of a turning tool is measured on its
(a) machine longitudinal plane
(b) machine transverse plane
(c) orthogonal plane
(d) normal plane

2. Normal rake and orthogonal rake of a turning tool will be same when its
(a) φ = 0
(b) φ1 = 0
(c) λ = 0
(d) φ1 = 90o
20
 QUIZ
3. Normal plane of a turning tool is always perpendicular to its
(a) πX plane
(b) πY plane
(c) πC plane
(d) none of them
4. Principal cutting edge angle of any turning tool is measured on its
(a) πR
(b) πY
(c) πX
21
(d) πo
 QUIZ
5. A cutting tool can never have its
(a) rake angle – positive
(b) rake angle – negative
(c) clearance angle – positive
(d) clearance angle – negative

6. Orthogonal clearance and side clearance of a turning tool will be same if

its perpendicular cutting edge angle is
(a) φ = 30 o

(b) φ = 45 o

(c) φ = 60 o

(d) φ = 90 o
22
 QUIZ
7. Inclination angle of a turning tool is measured on its
(a) reference plane
(b) cutting plane
(c) orthogonal plane
(d) normal plane

8. Normal rake and side rake of a turning tool will be same if its
(a) φ = 0 and λ = 0
o o

(b) φ = 90 and λ = 0
o o

(c) φ = 90 and λ = 90
o o

(d) φ = 0 and λ = 9
o
23
 Conversion of tool angles
• Purposes of conversion of tool angles from one system to another
• To understand the actual tool geometry in any system of choice or convenience from the
geometry of a tool expressed in any other systems.

• To derive the benefits of the various systems of tool designation as and when required

• Communication of the same tool geometry between people following different tool
designation systems.
• Methods of conversion of tool angles from one system to another
• Analytical (geometrical) method: simple but tedious
• Graphical method – Master line principle: simple, quick and popular
• Transformation matrix method: suitable for complex tool geometry
• Vector method: very easy and quick but needs concept of vectors
24
 Conversion of tool angles
• From ASA to ORS

• From ORS to NRS

25
 QUIZ
1. If the approach angle of a turning tool be 30o, the value of its principal cutting edge angle will be
(a) O deg.
(b) 30o deg.
(c) 60o deg.
(d) 90o deg.
2. The values of orthogonal clearance and normal clearance of a turning tool will be same if,
(a) φ=0
(b) αX = αY
(c) λ = 0
(d) none of the above
3. Determine the values of normal rake of the turning tool whose
geometry is designated as : 10o, - 10o, 8o, 6o, 15o, 30o, 0 (inch)?
4. Determine the value of side clearance of the turning tool whose
geometry is specified as 0o, - 10o, 8o, 6o, 20o, 60o, 0 (mm) ? 26
 Effect of tool Geometry on machining
• Back Rake angle
• Guides the direction of the chip flow.
• The size of the angle depends upon the material to be machined
Softer the material greater the positive rake angle.
• Rake angle (Al) > Rake angle (C.I.)
• With increase in back rake angle, the strength, forces and
power consumption of tool will decrease and tool life will be increased.
• Positive rakes are used when cutting low
tensile strength and non-ferrous materials
• Zero back rake is used during machining
of brass work pieces and also during
thread cutting operations.
• The negative rake angles are used with
tools which are weak in tension. (Carbide 27
cutting tools)
 Effect of tool Geometry on machining
• Back Rake angle
• Higher value of rake angle weakens the cutting edge of tool.
• the maximum value of positive rake angle is 45◦.
• Cutting tools with negative rake angle are stronger and are used to cut high strength alloys.
• the uses of an increased negative rake angle leads to increase cutting force during
machining.
• maximum negative back rake angle used = 10°

28
• Side Rake angle (5°-15°)
• guides the direction of the chip away from the job.
• With increase in side rake angle, the amount of chip bend in width direction decreases.
• Larger side rake angle produces smooth surface finish.
• As it increases, strength decreases, forces decreases, Power consumption decreases
and Tool life increases.
• Clearance Angles
• If this angle is very large, the cutting edge of the tool will be unsupported and will break.
• If this angle is very small, the tool will rub on the job, cutting will not proper and poor
finish will be obtained on the job.
• Its values varies from 5 to 15°.

29
• End cutting edge angle:
• It acts as a relief angle that it allows only small section of the end cutting edge to contact with the
machine surface and prevents chatter and vibration.
• Normally it varies from 8 to 20°.
• Approach angle:
• Avoids the formation of built up edge, controls the direction of chip flow and distributes the cutting
force and heat produce over larger cutting edge.
• Normally Cs = 0 to 90°
• The cutting edge angles are mainly influencing surface finish produced on the work
piece.
Let Rt = Maximum peak to valley height (mm)
• If the value of s increases then Rt decreases. Thus better surface finish will be
obtained.

30
 Quiz
• For cutting of brass with single‐point cutting tool on a lathe, tool should have
• Negative rake angle
• Positive rake angle
• Zero rake angle
• Zero side relief angle
• The following tool signature is specified for a single point cutting tool in American
system:10, 12, 8, 6, 15, 20, 3. What does the angle 12 represent?
• Side cutting‐edge angle
• Side rake angle
• Back rake angle
• Side clearance angle
• Normal rake and side rake of a turning tool will be same if its Principal cutting edge
angle and inclination angle respectively are (in degree)
• 0,0
• 90,0
• 90,90
• 0,90
31
Thank you

32