Single Point Cutting Tool Geometry - Mechanical Engineering

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 - Mathematical Basis

ASA

Basic Tool Shape P Tool 2β

Work

Wedge angle : 2β

Cutting Efficiency P Tool

2β

R

R P = 2R sinβ

Cutting Efficiency =

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 λ Chip V

Work piece

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 γx

γo λ

γy

Tool Reference Planes πc

πo

Cutting

Orthogonal

v

axis

Feed

πB Basic

Orthogonal (ORS) Reference Planes Trace of πo

Trace of πc πo

πc πB

πB

Reference Planes - ORS View in πo

View in πc

πc

πo πB

Reference Planes – ASA system πx

Y X

X

V

πy πB

ASA Reference Planes Y X

πx

X

πy Y

Tool Angles – ASA System V

Y

X

View in πx Plane

View in πy Plane

Tool Angles Feed

X

Øe

Ø Øs

Ø = Plan Approach angle Øs = Side cutting Edge angle Øe = End cutting Edge angle Ø = 90 - Øs

X

Tool Designation ASA System γy , γx , αy , αx , Øe , Øs , r γy γx αy αx Øe Øs

: : : : : :

r

:

Back rake angle Side rake angle Front clearance angle Side clearance angle End cutting Edge angle Side cutting Edge angle Nose radius (mm)

Tool Angle Conversion ORS (γo, λ)

ASA (γx , γy )

Ø = Plan Approach angle

Tool Angle Conversion ASA (γx , γy )

ORS (γo, λ)

Ø = Plan Approach angle

Does Orthogonal Plane πo represent True rake angle?

Orthogonal and Normal Reference Planes π πn o

πc λ

Tool Angle Conversion ORS γo

NRS 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