8.

MACHINE TOOL TESTING

Sr. Alignment Test Performance Test
No.

01 Various geometrical checks Actual performance of job on

are carried out, called as machine tool is called
alignment test. performance test.
02 These tests are carried out at These tests are carried out at
static condition. working condition.

03 These tests are checking It is checking of jobs,

position of components and manufacturing on machine
displacement relative to one and its tolerance limits as per
another. design.
04 e.g. Alignment of axis of e.g. Manufacturing of job on
lathe spindle to saddle lathe.
movement.
 Parallelism Testing
• Two lines or planes are called
parallel to each other when the
distance between them, measured
in perpendicular plane remains
same or constant.
Parallelism of two planes
• Two planes are said to be parallel, when their
distance from each other is measured anywhere
on the surface and at least in two directions, and
the maximum error (the difference between the
maximum and the minimum dimensions obtained
when measuring) over a specified length does not
exceed an agreed value.
The test for parallelism of two planes is carried
out in two directions (generally
perpendicular to each other).
• The dial indicator, which is held on a support
with a flat base, is moved in one plane over a
given length, and the feeler is made to rest
against the second plane ; and the deviations
noted down
Parallelism of an axis to a plane
• An axis is said to be parallel to a plane, if the
maximum difference between the several readings
taken while measuring the distance of line from plane
at a number of points, does not exceed a
predetermined value. In testing, the feeler of the dial
indicator is made to touch the surface of the cylinder
representing the axis and thedial indicator (held on a
support with a flat base) is moved along the plane by
the specified amount (length over which the test is to
be performed) (Fig. 7.10). At each point of
measurement the shortest distance is found by slightly
moving the indicator in a direction perpendicular to
the axis.
Parallelism of two axes
• This test is made in two planes, first plane being the one
passing through one of the two axes and as near as
possible to the second axis, and the other plane is
perpendicular to the first one. In this test, the dial
indicator is held on a support with a base of suitable
shape, so that it slides along a cylinder representing one
of the two axes; and the dial indicator is adjusted so that
its feeler slides along the cylinder representing the
second axis. The maximum deviation between the axes
at any point may be determined be gently rocking the
dial indicator in a direction perpendicular to the axes. In
the same way the parallelism may be tested in the
perpendicular plane.
 Straightness Testing
• A line is to be straight for a given length
if variation of distance of its points from
two planes perpendicular to the plane of
point and parallel to the line remains
same within specified tolerance limit.
Straight Edge Method
Spirit Level Method
By Autocollimator
• In case of measurement by auto-collimator, the
instrument is placed at a distance of 0.5
to 0.75 meter from the surface to be tested on
any rigid support .
• The parallel beam from the instrument is
projected along the length of the surface to be
tested.
• A block fixed on two feet and fitted with a
plane vertical reflector is placed on the surface
and the reflector face is facing the instrument.
• The reflector and the instrument are set such
that the image of the cross wires of the
collimator appears nearer the centre of the
field and for the complete movement of
reflector along the surface straight line,
the image of cross-wires will appear in the
field of eyepiece.
• The reflector is then moved to the other end of
the surface in steps equal to the centre distance
between the feet and the tilt of the reflector is
noted down in second from the eyepiece.
• With the reflector set at a – b , the micrometer
reading is noted and this
line is treated as datum line.
• Successive readings at b – c, c — d, d – e etc.
are taken till the length of the surface to be
tested has been stepped along.
 Squareness Testing
• Two lines, two planes or a line and plane are
said to be perpendicular when the error of
parallelism in relation to a standard square
does not exceed a given value.
Squareness between axis & plane
• For this test the dial indicator is mounted on an arm which
is attached to the spindle representing the axis of rotation.
The plunger of the dial indicator is adjusted parallel to the
axis of rotation and made to touch the plane. As the spindle
revolves, the dial gauge (or the end of plunger if revolving
freely into air) describes a circumstances, the plane of
which is perpendicular to the axis of rotation. When no
testing plane is specified the dial gauge is rotated by 360°
and the variation in the readings of instrument represents
the deviation of parallelism between the plane of the
circumstances and the plane to be tested. However, if planes
are specified (e.g. planes 1 and 2) then the difference of the
readings in the position of the dial gauge, 180° apart is
noted for each of these planes
• The deviation is expressed in relation to the
diameter of the circle of rotation of the
instrument.
The effect of periodical axial slip of the
spindle can be eliminated by repeating the
above test after moving the dial gauge through
180° relative to the spindle and average of two
sets taken. The effect of minimum axis play
can be eliminated by means of a suitable axial
pressure.
Between Two Planes
• Squareness of two planes 1 and 2 is checked
by placing the square on one plane and then
checking the parallelism of 2nd plane with the
free arm of the square by sliding the dial
indicator (mounted on a base) along 2nd plane
and its feeler moving against free arm of the
square.
Between Two Fixed Axes
• Fix typical type of square with proper base as
shown in figure.
• Arrange dial gauge with stand on another axis.
• Move dial, which touches the square edge
(blade).
• Note the readings.
• Zero variation shows squareness of two axes.
Between One Fixed axis and other Rotable Axes
fixed.
• The dial gauge mounted on arm and fixed on
the mandrel is brought into contact with the
cylinder representing fixed axis at two points 1
and 2,180° apart and deviation expressed
in relation to distance between 1 and 2.
 Out of Roundness
• It is defined as the radial distance between the
minimum circumscribing circle and the
maximum inscribing circle, which contain the
profile of the surface at a section perpendicular
to the axis of rotation.
 Sources of Out-of-Roundness
• Several reasons when machining parts can be
attributed to cause out-of-roundness. These are
clamping distortion, spindle run-out, presence
of dirt and chips on clamping surfaces,
imbalance, heat and vibration. The
characteristic roundness shape varies greatly
depending on the method of generation.
The tolerance on roundness is critical and it
should be much closer (usually five times)
than that of the other dimensional tolerance
which it effects.
 Run out
• It is defined related to running of a job.
• The job may be rotating with some another
centre than its geometrical centre, the distance
of such centres is run out.
Measurement of Run out using V-block
• The V-block is placed on a surface plate and the
work to be checked is placed upon it. A sensitive
dial indicator is firmly fixed in a stand and its feeler
made to rest against the surface of the work. The
work is rotated to measure the rise and fall of the
work-piece. For determining the number of lobes on
the work-piece, the work-piece is first tested in a
60° V-block and then in a 90° V-block. The number
of lobes is then equal to the number of
times the indicator pointer deflects during rotation
of the work piece through 360°.
• Following factors are to be considered while
doing experimentation.
1) Angle of V-block.
2) Position of instrument.
3) Number of lobes on the job.
For such measurements in laboratory, adjustable
V-block can be used.
• Ovality –
• When a job instead of circular, is having elliptical
shape with some major and minor diameters
called as Ovality error is present.
• Lobbing –
• Number of times, because of error in
manufacturing, such type of error is created in a
circular job. If a inspector measures a circular job
at 3-4 places then also, the diameters of such job
found to be some. For this only the job is to be
checked using proper method for avoiding
lobbing errors.
 Flatness Testing Using Optical Flat
• The essential equipment for measurement by
light wave interference is a monochromatic
light source and a set of optical flats.
• An optical flat is a circular piece of optical
glass or fused quartz having its two plane
faces flat and parallel and the surfaces
are finished to an optical degree of flatness.
• Optical flats vary in size from 25
mm diameter to about 300 mm diameter.
• If an optical flat is placed upon another flat
reflecting surface (without pressure) it will
not form an intimate contact, but will lie at some
angle 0 making an inclined plane.
• If the optical flat be now illuminated by
monochromatic source of light, the eye if placed
in proper position, will observe a number of
bands.
• These are produced by the interference of the
light rays reflected from the lower surface of the
top flat and the top surface of the lower flat
through the very thin layer of air between the
flats.
• S is the source of monochromatic light. At
point A, the wave of incident beam from S is
partially reflected along AB and is partially
transmitted across the air gap along AC.
• At C, again the ray is reflected along CD and
passes out towards the eye along CDE.
• Thus the two reflected components, reflected
at A and C are collected and recombined by
the eye, having travelled paths whose lengths
differ by an amount ACD.
• If the path lengths of the two components differ by an
odd number of half wavelengths,
then condition for complete interference is achieved.
• If the surface is perfectly flat, then condition of
complete interference is satisfied in a straight line
across the surface as the surface at right-angles to the
plane of the paper is parallel to the optical flat.
• Therefore, a straight dark line will be seen passing
through point C. Consider another ray incident along
path SFH.
• Again this ray is also slpitted into two components. It is
obvious that the path difference of the two component
rays will keep on increasing along the surface due to
angle 9.
• Thus if the path difference FHI be 3X12 or the next odd
number of half wavelengths, then interference will
occur and a similar fringe will be seen.
• Next when path difference is 5K/2, again there will be
another dark fringe.
• At the intermediate point between the points C and H,
the path difference will be an even number of half
wavelengths and the two components will be in phase
producing a light band.
• Thus, in case of a perfectly flat surface, we will have
pattern of alternate light and dark straight lines on the
surface, as shown in Fig. 6.6. Any deviation from this
pattern will be a measure of the error in the flatness of
the surface being inspected.
 N.P.L. Flatness Interferometer
• This instrument, as the name suggests, is mainly
used for checking the flatness of flat surfaces.
• This interferometer was designed by National
Physical Laboratory and is commercially
manufactured by Hilger and Watts Ltd.
• The flatness of any surface is judged by
comparing with an optically flat surface which is
generally the base plate of the instrument.
• This instrument essentially consists of a mercury
vapour lamp
• As we are interested in having single
monochromatic source of light, the radiations
of the mercury lamp are passed through a
green filter.
• The wavelength of the resulting
monochromatic radiation is of the order or
0.0005 mm.
• This radiation is then brought to focus on
pinhole in order to obtain an intense point
source of light. A mirror is used in order to
deflect the light beam through 90°.
• The pinhole is placed in the focal plane of a collimating lens,
thus the radiations out of the lens will be parallel beam of
light.
• This beam is directed on the gauge to be tested via an optical
flat. The fringes formed are viewed directly above by means
of a thick glass plate semi-reflector set at 45° to the optical
axis.
• The gauge to be tested is wrung on the base plate whose
surface is finished to a degree comparable to that of the
highest quality gauge face.
• As the optical flat is placed above it in a little tilted position,
interference fringes are formed; one between rays reflected
from the under surface of the optical flat and those reflected
from the surface of the gauge, and the other between rays
reflected from the under surface of the optical flat and those
reflected from the
base plate.
• If the gauge face is flat and parallel to the base
plate, then the optical flat being equally
inclined on both the surfaces the fringe
pattern from both the gauge face and the
base plate will consist of straight, parallel and
equally spaced fringes as shown in Fig. a
• When the gauge is flat but not parallel to the
base plate, then straight and parallel fringes of
different pitch above the gauge face as
compared with those of the base plate are
seen (Fig. b)
Surface of gauge is inclined to base plate.
Gauge surface convex/concave.
Slight rounding off at corners.
 Leveling of the Machine
• The level of the machine bed in longitudinal and
transverse directions is generally tested by a
sensitive spirit level.
• The saddle is kept approximately in the centre of
the bed support feet.
• The spirit level is then placed at a-a (Fig. 16.1),
the ensure the level in the longitudinal direction.
It is then traversed along the length of bed and
readings at various places noted down.
• For test in transverse direction the level is placed
on a bridge piece to span the front and rear
guideways and then reading is noted
• . It is preferable to take two readings in lon-
gitudinal and transverse directions simultaneously so
that the effect of adjustments in one direction may also
be observed in the other.
• The readings in transverse direction reveal any twist or
wind in the bed. It may be noted that the two guideways
may be perfectly leveled in longitudinal direction, but
might not be parallel to each other. This is revealed by
the test in transverse direction.
• The straightness of bed in longitudinal direction for the
long beds can also be determined by other methods,
e.g., using straight edges, autocollimators or by taut wire
method. But the test in transverse direction can be
carried out only by spirit level.
• It is desired that the front guide way should be
convex only as the cutting forces and the weight
of carriage act downward on it.
• If the front guide ways are concave, then the
effect will be cumulative.
• The tendency of the carriage, under cutting
forces is to lift upwards from the rear and this is
prevented by a gib placed underneath the guide
ways.
• With the result, an upward force acts on the rear
guide ways ; which must, therefore, be made
concave.
• Transverse level may be in any direction, but no
twist can be tolerated.
 True Running of Lathe Main Spindle
• Fig. shows the arrangement of test set up.
• The test can be carried out by using a dial
gauge and stand only.
• Fix the dial gauge to stand and to a carriage of
lathe machine.
• Confirm that the plunger pointer touches the
locating lathe spindle.
• The headstock is then rotated on its axis and
the indicator should not show any variation in
reading.
Parallelism of Main Spindle to Saddle Movement
• The dial gauge is to be mounted on the
saddle and the feeler of dial should touch
on the mandrel which is fixed in
headstock of the lathe machine.
• Move the saddle as shown in longitudinal
direction and note the variation in dial
gauge.
• If no variation is present, they can be
called as parallel to each other.
Parallelism of Guide ways with the movement of carriage
• Sometimes the job is held between head-
stock and tail stock centre for turning. In
that case the job axis must coincide with
the tailstock centre.
• If the tailstock guide ways are not parallel
with the carriage movement there will be
some offset of the tailstock centre and
this results in taper turning.
• To check the parallelism of tailstock guide
ways in both the planes i.e., horizontal and
vertical, a block is placed on the guide ways
as shown in Fig. and the feeler of the
indicator is touched on the horizontal and
vertical surfaces of the block.
• The dial indicator is held in the carriage and
carriage is moved.
• Any error is indicted by the pointer of dial
indicator.
Alignment of Both Centers in Vertical Plane
• A mandrel is fitted between the two
centers and dial gauge on the
carriage.
• The feeler of the dial gauge is
pressed against the mandrel in
vertical plane as shown in Fig. and
the carriage is moved and the error
noted down.
Alignment Test on
Milling Machine
 Cutter Spindle Axial Slip or Float
• Axial slip is defined as the axial spindle
movement which may repeat positively with
each revolution .
• When testing the axial slip of a spindle the
feeler of the dial gauge rests on the face of the
locating spindle shoulder and dial gauge holder
is clamped to the table.
• The locating spindle shoulder is rotated and
change in reading is noted.
• axial slip must always be tested at two points
180° apart on the collar of the spindle.
 True Running of Internal Taper
• The table is set in its main position
longitudinally and the mandrel 300 mm long is
fixed in the spindle taper.
• A dial gauge is set on the machine table and
feeler adjusted to touch the lower surface of
the mandrel.
• The mandrel is then turned and the dial
readings at two points are noted i.e., one at
the place nearest to spindle nose and other at
about 300 mm from it.
• For shifting the position of dial gauge from A
to B cross-slide of the machine is operated to bring
the dial gauge at the bottom of the end of mandrel.
• There are can be two errors :
(i) Axis of the spindle and the axis of taper may not
be parallel.
(ii) Eccentricity of the taper hole which, if present,
should indicate same error at both the places.
The error in first case will give different readings at
two places. Due to this error, cut will not be shared
equally between teeth of cutters, and therefore
vibrations and poor finish will result.
Surface Parallel with Longitudinal Movement
• For this test the dial gauge is fixed to the spindle.
• Feeler is directed upon the surface the machine table
and latter moved longitudinally.
• The deviations from parallelism between the table
surface and longitudinal motion are noted down.
• If the table is uneven, a straight edge may be placed
on the surface.
• Due to this error the surface of the table will fluctuate
up and down and cutter will not take equal cuts on the
job which is clamped on the table and the milled
surface will not be parallel to the base.
 Traverse Movement Parallel with Spindle Axis
(a) in horizontal plane;
(b) in vertical plane.
• The table is set in its mean position and dial
gauge fixed on the table.
• The table is moved crosswise and any deviation
on reading of dial gauge is noted with feeler on
one side of mandrel in horizontal plane and
under the mandrel for error in vertical plane.
• Due to this error, depth of cut will vary when
cross slide is moved.
Alignment Test on
Drilling machine
Flatness of clamping surface of base
• To perform this test, gauge block and straight
edge are used.
• Keep the gauge blocks on the base on which
the straight edge is to be kept.
• See the gap present between straight edge and
base and check it by inserting slip gauges or
feeler gauges.
• The error should not exceed 0.1 mm per 1000
mm clamping surface.
Perpendicularity of drill head guide to the base plate
• The squareness (perpendicularity) of drill head guide to
the base plate is tested :
(a) in a vertical plane passing through the axes of both
spindle and column, and
(b) in a plane at 90° to the plane at (a).
The test is performed by placing the frame level (with
graduations from 0.03 to 0.05 mm/m) on guide column
and base plate and the error is noted by noting the
difference between the readings of the two levels.
• This error should not exceed 0.25/1000 mm guide
column for (a) and the guide column should be inclined
at the upper end towards the front only, and 0.15/1000
mm for (b).
Parallelism of the spindle axis with its vertical
movement
• This test is performed into two planes (A) and
(B) at right angles to each other.
• The test mandrel is fitted in the tapered hole of
the spindle and the dial indicator is fixed on
the table with its feeler touching the mandrel.
• The spindle is adjusted in the middle position
of its travel.
• The readings of the dial indicator are noted
when the spindle is moved in upper and lower
directions of the middle position with slow
vertical feed mechanism.
True running of spindle taper
• For this test, the test mandrel is placed in the
tapered hole of spindle and a dial indicator is
fixed on the table and its feeler made to scan
the mandrel.
• The spindle is rotated slowly and readings of
indicator noted down.
• The error should not exceed 0.03/100 mm for
machines with taper up to Morse No. 2 and
0.04/300 mm for machines with taper larger
than Morse No. 2.
Squareness of clamping surface of table to its axis
• For performing this test, the dial
indicator is mounted in the tapered
hole of the spindle and its feeler is
made to touch the surface of table
(Refer Fig.).
• Table is slowly rotated and the
readings of dial gauge noted down,
which should not exceed 0.05/300
mm diameter.
Squareness of spindle axis with table
• For this test a straight edge is placed in positions AA’ and
BB’.
• Work table is arranged in the middle position of its
vertical travel.
• The dial indicator is mounted in the spindle tapered hole
and its feeler made to touch the straight edge first say at
A and reading noted down.
• The spindle is rotated by 180° so that the feeler touches
at point A’ and again reading is noted down.
• The difference of two readings gives the error in
squareness of spindle axis with table.
• Similar readings are noted down by placing the straight
edge in position BB’.
• Calculate the alignment error for the headstock
and tailstock for the following data.
• Initial reading of dial indicator = 0.1 mm
• Final reading of dial indicator = 0.2 mm
• Movement of carriage along longitudinal
direction = 100 mm
Solution -
H  0.2  0.1  0.1 mm
Alignment error is 0.1 mm per 100 mm of
carriage movement along horizontal axis of lathe
H 0.1 mm
 tan   
L 100 mm
  0.0572
  0 3 26.26
0 ' "