Chapter9 2different Types of Jigs Part2

8/12/2019 Chapter9 2different Types of Jigs Part2

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TABLE JIG


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TABLE JIG

This also called as turn over jig because the work

piece is located from the face that is to be drilled

and clamped in the jig

Then the jig is turned over for drilling

This jig is also known as open jig as the work piece

is not having an! enclousre of the jig bod! around

it"so it presents no problem in chip disposal


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#igure below shows a turn over jig or open jig"

The jig is seated on the four foot nuts when

locating and clamping the work piece " and

inverted to the position shown when maching

This t!pe is eas! to load and swarf clearence

is no problem


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$I%A$&A'TAGE

(ain disadvantage is the lack of support given

to work piece beneath the point of cutting

)nl! the surface be drilled" loading and drilling

forces are generall! directed towards the

clamping devices therefore clamping device

should be rigid enough to withstand drilling

force


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INDEXING JIGS

Inde*ing jigs are used to drill holes on peripher!of c!lindrical work at the re+uired angular

positions An inde*ing device is provided in the

jig


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The drill is fed through the bush to drill the first holeThen locking device is released" the inde*ing device is

pressed down The workpiece is inde*ed for drillingne*t hole The inde*ing is done with the help of arotating member and an inde*ing device


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The fig shows a simple inde*ing drill jig to produce fourradial holes in the workpiece shown The workpiece islocated and clamped to a movable member that can be

inde*ed to bring the workpiece to the re+uired positionrelative to the cutter or drill bush and then locked in thatposition untill the feature is being machined The lockingdevice must be separate from the workpiece clamp


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A,,LI-ATI)' )# I'$E.I'G

#ig shows LI'EA/ I'$E.I'G in which a longstrip that is drilled in several places along itslength )ne drill bush is re+uired


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#igure shows /)TATI)'AL I'$E.I'G in which

the workpiece is rotated about an a*is It isused when holes have to be drilled on a large

pitch circle


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A0T)(ATI- $/ILL JIG

In machining and assembl! operations" au*iliar!

time forms +uite a large percentage of standard

time per piece The au*iliar! operations have to

be done hundred of times per da! If donemanuall! it ma! cause considerable fatigue to

operator and reduces efficienc! else the time

spent


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B! automatic "it is economicall! justified b! the

rate of operation and assures high efficienc!

Automated jigs and fi*tures should e*clude

possibilit! for incorrect location of workpiece


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Drive mechanism in Automatic drill jigs

are :-

(echanical ,neumatic

1!draulic

,neumoh!draulic Electrical


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Pneumatic Drives

,neumatic drives essentiall! re+uire the air

c!linderAir operated devices are widel! used due to read!

availabilit! of the compressed air

Advantages of Pneumatic :- /elative simplicit! of low cost

2uick action and reliabilit! in service

-apable of withstanding overloads


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Air operated drilling jig


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Advantages of Hydraulic Drives:-

/elativel! small and compact due to high working

pressure34556755'8mm9:;


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1!draulic operated drive


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Mechanical Drives:-

(otor driven clamping devices are used in turret6lathegroup" and other automatic jigs

Tor+ue from the motor shaft is transferred through a

reducer and a clutch to a screw which drives a nut linked to

the rod of clamping devices Tor+ue is controlled b!adjusting the strength of the tor+ue6control spring


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Chapter9 2different Types of Jigs Part2

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