Metal Cutting Basics

Global Knowledge Center Outline

• Metal Cutting Process – Chip Formation and Three Deformation Areas • Cutting Tool Temperature Zone • Cutting Movement • Part Surface • Cutting Forces • Cutting Angles • Tooling Materials • Machine Tools • Cutting Tool

• The first deformation area – There is a change from shear slip to plastic deformation • The second deformation area – The cutting tool compress the chip bottom, which causes friction deformation • The third deformation area – The back of the tool compresses the area behind the cut surface, causing strain-hardening

In a metal cutting operation what really happens to the material being machined?

The material is plastically deformed and sheared away.

Temperature Shear Stress

What two things does it take to make a chip?

Pressure Heat

Heat in a metal cutting application is created by what?

Vc doc

feed

=Speed

Cutting Tool Temperature Changing Chart

Thermal conductivity: Temperature Chip, part, tooling and coolant or air

Chart character：：： • The hottest section of the tool isn’t at the tool point.

• The hottest section of the insert is at the cutting edge.

• There are three thermal regions and three deformation areas.

Pressure in a metal cutting operation is determined by what?

VC aP

Feed

Machining surface Machined surface aP

Feed

Unmachined surface

Rotational Movement Feed Movement

Turning Milling

What are the 3 primary forces generated in metal working or chip forming?

Ft = Tangential Force (60-70%)

Ff = Feed Force (20-30%)

Fr = Radial Force (10-20%)

What are the 3 primary angles that all cutting tools have?

Lead Angle

Positive Neutral Negative

Rake Angle

Positive Neutral Negative Relief Angle

Forces

Point Angle Lead Angle

Positive Neutral Negative

Radial Rake (+) (-)

Axial Rake

Negative Tools

Positive Tools

Diamond, (PCD & CVDD)

PCBN TiC Alumina CeramicTiC Alumina & Whisker Reinforced Ceramic

(Speed) (Speed) Sialon & Silicon Nitride Ceramic

Cermet CVD Alumina Coated Carbide

CVD Tri-Phase Coated Carbide PVD Coated Carbide Mech. & Thermal Wear Resistance Wear Mech. & Thermal

Uncoated Carbide

High Speed Steel

Strength Toughness (Feed)

What are the 3 basic elements in carbide?

Tungsten (W)

Carbon (C)

Cobalt (Co)

What 2 of the 3 elements of carbide make up the hard, wear resistant grains?

Tungsten (W)

Carbon (C)

Carbide likes to do what? Carbide does not like to do what?

What are the 3 main operating parameters of a metal cutting operations that impact both tool life and productivity? Vc

Feed

Factor Productivity Tool Life DOC 1:1 1:0 Feed 1:1 1:1 Speed 1:1 1:2

CNC Universal Lathes

Dual spindle turning center

Vertical Lathes

CNC Universal Milling Machines

5-axis Machining