cutting tool performance and quality of measurement

8/19/2019 Cutting tool performance and quality of measurement

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Introduction

Machining

Machining is the removal of material from a work piece. Machining is widely performed

in manufacturing engineering and production technology engineering. In present it is a

demanding field of expertise with the escalating competitive industry. Machining

variability’s include:

1. Intended purpose - ompatible with re!uirement

". #imensional accuracy - re!uired accuracy

$. %urface finish & rough or smooth

'. (ork ) power consumption

*. +uality of finish product

utting parameters

1. Machine parameters ,ontrolling parameters

utting speed /eed rate , Machining time #epth of cut metal removal rate

". 0eometric parameters

%ide rake angle learance angle learance ,relief angle elix angle 2ool

wedge angle %ide cutting edge angle 3nd cutting edge angle 4ose radius

Machining machine & 5athe

5athe is also known as the mother)father of the entire tool family. 6 lathe is a general

purpose machine that operates on the principle of rotating work piece and a fixed cutting

tool. 2he cutting tool is feed into work piece which rotates about its own axis causing

work piece to be formed to the desired shape. 5athe machine perform a number of

operations 7 facing, turning (rough and finish), taper turning, form turning, threading,

reaming, grooving, knurling, boring, drilling ,chamfering, necking, spinning, filing,

polishing, honing, buffing, profiling, cutting etc. 2o perform the mentioned operations

different types of lathe machines exits 7 Copy lathe machine, Automatic lathe machine,

Turret lathe machine, Engine lathe machine, Bench lathe machine and Computer

controlled lathe machine.!"

Theory

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utting parameters

1. Machine parameters , ontrolling parameters

a. Cutting speed

• %peed is the rate of rotation of the spindle where the tool is held. It is measured

in revolutions per minute ,89Ms."; 1;

• 2he higher the hardness of the material the higher the cutting force and the

higher the friction co-efficient produced hence poor surface is produced. o-

efficient of friction and cutting force both decreases when cutting speed is

increased leading to decrease in surface roughness.

• %pindle speed calculation & speed to be set on lathe $;

89M < ,utting %peed x $"= ) #iameter.

89M - %pindle %peed

utting %peed - utting %peed for the material being machined. ,meters)min

#iameter - #iameter of work piece ,mm

b. #eed rate

c. $achining time

d. %epth of cut

e. $etal removal rate

". 0eometric parameters

a. &ake angle

• 2he angle of the cutting face relative to the work.

• 2he purpose of the rake angle is to allow the pieces of metal ,chips being

removed to slide along this angle away from the cutting edge.

• 2he rake angle determine the !uality of the finished work piece. 2he

better the chips slide along this angle the better will be the finish on the

work piece.

• 2he larger the rake angle the smaller the cutting force on the tool

• 6 large rake angle will improve cutting action but would lead to early

tool failure since the tool wedge angle is relatively weak. 6 compromise

must therefore be made between ade!uate strength and good cutting

action.

b. Clearance ( relief) angle

c. 'eli angle

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d. Tool edge angle

e. *ide cutting edge angle

f. End cutting edge angle

g. +ose radius

Apparatus

1. 5athe machine

". (ork pieces , Mild %teel 6luminum >rass

3. 2ool , #rill bits #rill huck $ ?aw chuck huck key utting

tools

4. @ernier caliper

Procedure

1. (ear safety goggles and safety shoes.

". 2ake a rectangular extruded rod of dimensions "*mm x 1Amm x B=mm.$. Mount the work piece onto the headstock using a $-Caw chuck using a chuck

key.

'. %et the cutting speeds using the gears on the control panel of the lathe

machine.

*. %tart the lathe.

B. 2aper the work piece to remove material from the surface by moving the

cutting tool with * o rake angle using the cross slide rotate it clockwise to

move the tool left from the loose end of the work piece.

A. 8epeat using 1= o= o-1= o rake angle cutting tool use the gear on the tail

stock to use the 1==-1= rake angle cutting tools in that are already mounted

on the tailstock.

D. 8epeat using $D= rpm and B'= rpm cutting speeds

E. 8epeat using 6luminum and >rass work pieces.

1=. Fbserve and compare the machining surface !uality with material cutting

speed and rake angle.

Observations

Machining surfaces

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Figure 1 Material – mild steel (surface nish of machining 5o, 10 o , 0 o, -10 o, 270 rpm ,380 rpm,!0rpm from right to left"

Figure 2 Material – #luminum (surface nish of machining 5o, 10 o , 0 o, -10 o, 270 rpm ,380 rpm,!0rpm from right to left"

Figure 3 Material – $rass (surface nish of machining 5o, 10 o , 0 o, -10 o, 270 rpm ,380 rpm,!0 rpmfrom right to left"

Machining !uality with rake angle comparisons

Table 1 %ualit& of machining 'ith rae angle

Material Angle

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0 o 5 o 10 o

Mild steel More rough surface with

ripples

%moother than the = o

angle surface


and * o angle surface

!rass rough surface with

ripples


angle surface



Alu"inu" +uite rough surface

with ripples


angle surface



2he rake angle determine the !uality of the finished work piece. It allow the pieces of

metal ,chips being removed from the work piece the better the chips slide along this

angle the better will be the finish on the work piece.

2he larger the rake angle the

smaller the cutting force on the tool and better the surface finish.

Machining !uality with speed comparisons

Table 2 uality of machining ith speed

Material #peed

$%0 rp" 3&0 rp" '40 rp"

Mild steel More 8ough surface %mother than "A= rpm

surface

%moothest surface with

best surface finish

!rass 8ough surface %mother than "A= rpm

surface


best surface finish

Alu"inu" /airly rough surface %mother than "A= rpm

surface


best surface finish

. 2he higher the hardness of the material the higher the cutting force and the higher the

friction co-efficient produced hence poor surface is produced. o-efficient of friction

and cutting force both decreases when cutting speed is increased leading to decrease in

surface roughness. 2he surface roughness increases from aluminum brass to mild steel.

(iscussion

#ifferent work holding methods

(ork pieces can be held by various methods: $;

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• (ork piece mounted between centers

• (ork piece mounted within a chuck

• (ork piece mounted within a collet

• (ork piece mounted on a faceplate

(ork holding devices:

1. hucks

• May have " $ ' or B Caws to hold work by external or internal surfaces

• Indexing chucks can index to different positions to present multiple surfaces

of a work piece to the cutting tool

• /or longer parts a tailstock support is used with the chuck or other lathe work

holding

". ollets

• 6ccurately and tightly hold the smooth surfaces of round bar and cylindrical

slug work pieces

• %pecial collets can grip s!uare and hex shapes

$. /ace plates

• Gsed for irregularly shaped work pieces

• /or work pieces that cannot be successfully held by chucks or mounted

between centers

'. Mandrels

• /or work pieces which cannot be held between centers because its axis has

been drilled or bored

• (ork pieces which are not suitable for holding in a chuck or against a

faceplate is usually machined on a mandrel.

*. #rive plates

B. 5athe centers

)eed rates and depth o* cut + geo"etric cutting para"eters

/eed rates

• /eed is the rate at which the tool is moved into the part or the part into the

tool. /eed is measured in feet inches or millimeters per time period.";

• /eed rate calculation $;

/8 < 89M x 2 x 5.

(here:

/8 - the calculated feed rate ,inches per minute or mm per minute

89M - is the calculated speed for the cutter.

2 - 4umber of teeth on the cutter.

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5 - 2he chip load or feed per tooth.

#epth of cut ,#F

• 2he measurement ,normally in inches or millimeters of how wide and deep

the tool cuts into the work piece.";

• #epth of cut calculation

# < 8,outside & 8,inside.

(here:

# & depth of cut ,mm

8 ,outside & outside radius of the work piece

8 ,inside & inside radius of the cut in work piece

,athe "achine co"ponents

5athe bed

• 2he bed is the base of the lathe and supports all the maCor components of lathe.

• 5athe bed material made of grey cast iron to resist deflection and absorb vibrations

during cutting

arriage /eed

• %lides along the ays and consists of the cross-slide tool post apron

• 9urpose of supporting guiding and feeding the tool against the Cob during operation.

eadstock

• olds the Caws for the work piece supplies power to the Caws and has various

drive speeds

• %erves as housing for the driving pulleys back gears headstock spindle live

center and the feed reverse gear.

2ail %tock

• Movable casting located opposite the headstock on the ways of the bed

• an slide along the bed to accommodate different lengths of work piece

between the centers.

• 2he tailstock spindle has an internal taper to hold the dead center and the

tapered shank tools such as reamers and drills.

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Figure 4 )chematic of lathe machine

Operations o* a center lathe "achine

• 2urning & produces straight conical curved or grooved work pieces

• /acing & produces a flat surface at the end of the part

• >oring & to enlarge a hole

• #rilling - to produce a hole

• utting off & to cut off a work piece

•2hreading & to produce threads

• Fther: Hnurling 2aper 2urning /orm 2urning 2hreading 8eaming 0rooving

hamfering 4ecking %pinning /iling 9olishing etc.$;

Procedure to "achine co"ponent depicted on *igure 5 ( *ee Appendi- A for % sketch)

Figure 5 *omponent to +e machined

1. 2ake a rectangular extruded rod of dimensions "*mm x 1Amm x B=mm.

". %et the cutting speeds using the gears on the control panel of the lathe machine

$. %lightly drill the ends of the rod and mount one end of the work piece onto the

headstock using a '-Caw chuck and the other end to the tailstock.

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4. 6s shown on figure B use straight turning to the whole part to remove material

from the surface until the radii of the arcs formed are 1=mm each.

Figure 6 urning operation in a lathe

*. Mount the work piece onto the headstock using a $-Caw chuck using a chuck key.

B. /ace *mm from both ends so that the length of the rod is *=mm. Fnly a small

amount of material should be removed each pass of the cross slide. 6fter each

pass of the cutting tool the rotate the top slide clockwise to move the tool

forward.

Figure 7 acing operation in a lathe

A. /ace of the left and right rod surface with a distance of D.*mm from the center of

work piece as schematically shown on 6ppendix 6.

D. #rill the center of one side with a 1)" drill bit till the depth of the hole is 1*mm

and drill the other center of one side with the a $)* drill bit till the depth of the

hole is "=mm. 2he tailstock of a lathe can be used for drilling with the aid of a

drill chuck attachment as shown on figure D. 1; Gse the scale next to the drill

chuck to track the depth of cut.

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SECTION A - A

Dimensions in millimeter

Figure 9 *omponent to +e machined

#imensions

3.g.: 1)"’’- "= G4/ 1*

,MaCor diameter of the thread & ,threads per inch ,describes the thread form here

G4/ < unified fine ,depth of cut

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1/2’’-20 UNF 15

3/8’’-24 UNF-25

1 X

8.5 8.5

20

5 0

!!

cutting tool performance and quality of measurement

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