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Tool Design

Dr. Ramadan El gamsy Tool design

1-Cutting Tool Materials.2-Turning machining

3- Turning Form tools


Cutting tool materials

• Selection of cutting tool materials is very important

• What properties should cutting tools have– Hardness at elevated temperatures– Toughness so that impact forces on the tool can

be taken– Wear resistance– Chemical stability


Cutting Tool Construction


Types of tool materials

o Carbon steelo High speed steel (HSS)o Cemented Carbideso Cast alloyso Ceramicso Cubic boron nitride (CBN)o Diamond


Carbon Steel

• Oldest of tool materials• Used for drills taps,broaches ,reamers• Inexpensive ,easily shaped ,sharpened• No sufficient hardness and wear

resistance• Limited to low cutting speed

operation


Temperature effects


High speed steel

• Retains its hardness at high temperature• Red hardness….• Relatively good wear resistance


Tungsten Carbide

• Composite material consisting of tungsten-carbide particles bonded together

• Alternate name is cemented carbides

• Manufactured with powder metallurgy techniques

• Small particles are pressed & sintered to desired shape • Amount of cobalt present affects properties of carbide tools • As cobalt content increases – the tougher the tool


Cast alloys

• Commonly known as stellite tools• Composition ranges – 38% - 53 % cobalt

30%- 33% chromium10%-20%tungsten

• Good wear resistance ( higher hardness)• Less tough than high-speed steels and sensitive to impact forces• Less suitable than high-speed steels for interrupted cutting operations• Continuous roughing cuts – relatively high g=feeds & speeds• Finishing cuts are at lower feed and depth of cut


Insert Attachment

Fig : Methods of attaching inserts to toolholders : (a) Clamping and (b) Wing lockpins. (c) Examples of inserts attached to toolholders with threadless lockpins, which are secured with side screws. While (d) is brazed.


Ceramics

• Used as grinding wheels.

• as cutting tool inserts. These are used in a similar way to cemented carbide inserts.

• they can withstand extremely high machining temperatures.

• They also have a high resistance to abrasion.


Cubic boron Nitride ( CBN ) :

• Made by bonding ( 0.5-1.0 mm ( 0.02-0.04-in)• Layer of poly crystalline cubic boron nitride to a carbide substrate by

sintering under pressure• While carbide provides shock resistance CBN layer provides high

resistance and cutting edge strength• Cubic boron nitride tools are made in small sizes without substrate

Fig : (a) Construction of a polycrystalline cubic boron nitride or a diamond layer on a tungsten-carbide insert. (b) Inserts with polycrystalline cubic boron nitride tips (top row) and solid polycrystalline CBN inserts (bottom row).


Diamond :

• Hardest known substance • Low friction, high wear resistance• Ability to maintain sharp cutting edge• Single crystal diamond of various carats used

for special applications• Machining copper—front precision optical

mirrors for ( SDI)• Diamond is brittle , tool shape & sharpened is

important• Low rake angle used for string cutting edge


Single Point Cutting Tool


Single Point Cutting Tool


Know the Single Point Cutting Tool

• Shank: Main body of tool, it is part of tool which is gripped in tool holder

• Face: Top surface of tool b/w shankand point of tool. Chips flow along this surface

• Flank: Portion tool which faces the work. It is surface adjacent to & below the cutting edge when tool lies in a horizontal position.

• Point: Wedge shaped portion where face & flank of tool meet.• Base: Bearing surface of tool on which it is held in a tool holder.• Nose radius: Cutting tip, which carries a sharp cutting point.

Nose provided with radius to enable greater strength, increase tool life & surface life. Typical Value : 0.4 mm – 1.6 mm


SPC Tool Geometry

SIDE RELIEF

SIDE CLEARANCE


Cutting Speed

The Peripheral Speed of Workpiece past the Cutting Tool

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D – Diameter (mm)N – Revolutions per Minute (rpm)


Feedf – the distance the tool advances for every

rotation of workpiece (mm/rev)

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Depth of Cutperpendicular distance between machined

surface and uncut surface of the Workpiece d = (D1 – D2)/2 (mm)

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3 Operating Conditions


Operations on Lathe

• Turning• Facing• knurling• Grooving• Parting

• Chamfering• Taper turning• Drilling• Threading

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Turning ..

Cylindrical job

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FacingFlat Surface/Reduce length

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Eccentric TurningO

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KnurlingO

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Grooving ..O

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Parting ..O

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ChamferingO

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Chamfering

Beveling sharp machined edges Similar to form turning Chamfering tool – 45° To

• Avoid Sharp Edges• Make Assembly Easier

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Taper Turning..

MethodsMethods • Form Tool• Swiveling Compound Rest• Taper Turning Attachment• Simultaneous Longitudinal and

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Taper Turning ..By Form Tool

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Taper Turning ,,By Compound Rest

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Drilling

Drill – cutting tool – held in TS – feed from TS

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Form tools

• Types of form tools• 1- flat form tool


Form tools• Circular form tool


Form tools

• Circular form tool fixation.


Circular


• Take K chip space 3-12• M wall thickness 6-8• α clearance angle• γ rake angle

kk

Form tools

• Advantages of form tools.• Cross feed is reducing the machining time.• High accuracy in marching formed shapes.• The first product is the same as last one.• High production rate.


Form profile

• There are two ways for produce the tool form.1- Graphical method.2- Analytical method.

1- graphical method for flat tool


Flat form tool


Circular form tool



Analytical method.Flat type


Analytical



Z= Length of form measured on the tool fac

X = Depth of form measured perpendicular to the tool flank


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