Single Point Cutting Tool Geometry 1

Prof. S. S. Pande

Mechanical Engineering Department

Indian Institute of Technology, Bombay

Outline

• Tool Geometry, Tool Angles

• Systems for Tool nomenclature - ISO System - ORS/NRS - American Standards System - ASA

• Tool Angle Conversion: ISO ASA

- Mathematical Basis

Basic Tool Shape

2β

Work

Tool

P

Wedge angle : 2β

Cutting Efficiency

2β

Tool

P

R R

Cutting Efficiency =

P = 2R sinβ

Orthogonal Cutting Geometry

Orthogonal Cutting

Velocity V

Orthogonal Cutting

Characteristics

• Cutting edge Perpendicular to cutting Velocity Vector

• Plain Strain (2D) phenomenon

• No Spread of material across

Oblique Cutting

Tool

Chip

λ

Work piece V

Oblique Cutting

Characteristics

• Cutting edge at an angle(λ) to normal to velocity vector in the cutting plane

• Inclination angle λ - modifies Tool angles - governs Direction of chip flow

Stabler’s Law for Chip flow

nc = k. λ nc = chip flow angle K = 0.8 – 1.0

Free and Restricted Cutting

Feed Motion

Tool

Chip Flow

Free Restricted

Single Point Tool Geometry

Tool Nomenclature Systems

Tool in Hand

• ISO System : ORS/ NRS - Orthogonal/ Normal Reference System

• American Standards Association (ASA) system

Tool in Machine

• Tool /Insert setting in fixture

Tool Angle Reference Systems ORS and ASA

λ

γx

γy

γo

Tool Reference Planes

Feed

πB

πo πc Cutting Orthogonal

Basic

axis v

Orthogonal (ORS) Reference Planes

Trace of πo

Trace of πc

πB πB

πc πo

Reference Planes - ORS View in πo

View in πc

πc πB

πo

Reference Planes – ASA system

Y

X X

V πx

πy

πB

ASA Reference Planes

X X

Y

πy

πx

Y

Tool Angles – ASA System

Y

X

V View in πx Plane

View in πy Plane

Ø = Plan Approach angle Øs = Side cutting Edge angle Øe = End cutting Edge angle

Ø = 90 - Øs

Tool Angles

Feed

Ø

Øs

Øe X X

Tool Designation

ASA System

γy , γx , αy , αx , Øe , Øs , r

γy : Back rake angle γx : Side rake angle αy : Front clearance angle αx : Side clearance angle Øe : End cutting Edge angle Øs : Side cutting Edge angle

r : Nose radius (mm)

Tool Angle Conversion

ORS ASA (γo, λ) (γx , γy )

Ø = Plan Approach angle

Tool Angle Conversion

ASA ORS (γx , γy ) (γo, λ)

Ø = Plan Approach angle

Does Orthogonal Plane πo represent True rake angle?

Orthogonal and Normal Reference Planes

λ

πo πc πn

Tool Angle Conversion

ORS NRS γo γn

Tool in Machine System

Static angles on Tool/Insert change due to

• Setting in tool Holders/ Fixtures

• Tool/ Work relative motion.

Inserts in Tool Holder

Inserts and Tool Angles

Tool Setup on Machine