measuring machine

8/19/2019 Measuring Machine

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MEASURING MACHINE

Measuring machines are generally used formeasurement of length over the outer faces of

a length bar or any other long member with

ends that may be either rounded ,or flat andparallel.A number of measuring machines of various designs are available ,out of which

some are discussed here


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Length bar measuring

machine The general form of measuring machine called lengthbar measuring machine used to determine the length

consists of a long bed having vee and flat guide-ways

along the bed to allow suitable spacing of measuringhead, anvil and work supports. A fixed headstock and

a movable tailstock each with a measuring face or

anvil are carried on the bed. A micrometer screw fixed

on tailstock is used as a means of revealing difference

in length between a setting master and work piece.The machine can show the length of the work either

by the direct comparison with standard length bar or

by the use of an accurate built in scale .


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Length Bar Measuring Machine


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In either case the tailstock has to be moved to such a

position that the two anvils are just touching the end of

the work piece which is supported parallel to the bed ofthe machine. This is achieved by using a micrometer

screw in tailstock and sensitive indicator dial gauge ! in

the headstock. "ifference between the settings

re#uired for standard bar and work piece is measured

by the micrometer screw in the tailstock. The headstock

anvil is in such a way as to show when contact is made

with the work piece. This part of the machine is so

sensitive that the reading of the tailstock setting on any

work piece can be repeated to $.$%&mm. 'or correctmeasurement, the correct support in hori(ontal plane is

very essential and for this the two support points should

be spaced $.&)) * apart, * being the length of the work

piece .


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The supports used are of vee form and adjustable for

height, and spacing laterally across the bed.This

machine has two special features which are essentialin any set-up for fine measurement i.e. the piece to be

measured is positively located in relation to the

measuring faces and the contact between measuring

faces is proved mechanically without relying on any

personal element.

Work support


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Universal measuring

machine +This machine can be utilised to measure length anddiameters of both plain and threaded work tapers andpitch of the screw threads to a high degree of

accuracy. ome machines employ two and three co-ordinate measuring systems based on the use of linestandards. The scales are generally enclosed withinthe machine and thus not liable to damage byphysical contact. The basis of the accuracy of

measurement of these machines is an accuratelydivided scale viewed through a microscope. Themicroscope is used to determine the movement of themeasuring anvils of the machine. In order to satisfythe principle of alignment, the scale is positioned in

line with the line of measurement.


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Universal Measuring Machine


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TOOL MAKERS MICROSCOE

The instrument is used for checking the si(e of small

components, dia of holes, angles, profile of punch and

dies, profile of thread, form tool etc. It has a table

which is controlled by micrometer head and mountedover a base.Table can be rotated through $$. /ork

is kept over a glass disc and is illuminated by the

bulbs provided on a holder. Another illuminator is

provided in the base which gives a bright green background while checking. The magnified image of the

work is seen through the eyepiece. Inspection may be

done by eye in the normal way or the projection

attachment may be fitted to bring the magnified image

on the screen.


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Tool Makers Microscope


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0rotractor 1yepiece

0rotractor eyepiece or goniometric head of the

instrument has a disc with radial and cross setting

lines. The disc is provided with an angular scale

calibrated in degrees. "isc can be rotated by a knobfor setting any of the lines to the edge of the work.

Angle can be measured to an accuracy of 23. 'or

length measurement the line is made to coincide first

with one side of the component and then with theother end.The reading on the micrometer head is

noted and the distance is calculated.


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4adius measuring head

4adius measuring head has different radii arranged

around a disc which may be rotated to bring. The

re#uired radii my be bought into possible by rotating.The

other eye piece also contain a rotating glass disc. 4oundthe disc as a circle passing through the field of eyepiece

are engraved various thread profiles.


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The Thread Template Unit

The thread template unit of the instrument

has selected thread forms arranged round

the glass disc in the eye piece and this maybe rotated to bring any desired thread form

into position for comparison with the

magnified image of the work.The radius

measuring head has different radii arrangedaround a disc which may be rotated


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5easuring head 6 table


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Lighting Unit


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Coordinate measuring

machines [C M M]

These machines have precise movements in x-y-(

coordinates which can be easily controlled and

measured. 1ach slide in three directions is e#uipped

with a precision linear measurement transducer whichgives digital display and senses 7ve -ve direction.

These are manufactured in both manual and computer-

controlled models and come in a wide range of si(es to

accommodate a variety of applications.The measuring

head incorporates a probe tip, which can be of different

kinds like taper tip, ball tip etc.8arious type of 955s

are shown in figure.


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CMM


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The cantilever type is easiest to load and unload,but is

most susceptible to mechanical error because of sag or

deflection in y-axis beam. :ridge type is more difficultto load but less sensitive to mechanical errors.

;ori(ontal boring mill type is best suited for large heavy

work pieces. 8ertical bore mill type is highly accurate

but usually slower to operate.A floating bridge type

machine is also available in which the complete bridge

can slide in y-direction on the slides. It has the

compromises of both cantilever and bridge type, and is

thus fast to operate, simple in alignment, and rugged

construction affords consistent accuracy.


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'or measuring the distance between two holes,the work

piece is clamped to the worktable and aligned with the

machineand rotary axes

are incorporated.These machines can measure various

features of parts whose shapes are objects of revolutions like

cones,cylinders,and hemispheres.

measuring machine

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