Mordern Grinding

1. Prepared by : Ts. Dr. Nik Mizamzul binti Mehat

3. Course Outcome (CO)
• CO1: Ability to evaluate the principles, terminologies and
development of grinding technology.
• CO2: Ability to evaluate the characteristics and performance of
grinding wheel
• CO3: Ability to evaluate the concepts of grinding machine, various
operation and problems related to grinding technology

4. Assessments
(i) Peperiksaan/ Examination: 40%
• Final Examination = 40%
(ii) Penilaian Berterusan/ Continual Assessment: 60%
• Quizzes = 10% (3 Quizzes)
• Assignment = 20% (Assignment 1 & 2)
• Project Based Learning (PBL) = 10%
• Test 1 = 10% (WEEK 6)
• Test 2 = 10% (WEEK 15)

5. Topics will be covered
• Introduction to grinding technology
• Grinding Wheels: Composition and Properties
• Grinding Geometry and Kinematics
• Wheel truing and dressing
• Wheel wear and lubrication
• Types of grinding machine and operation
• Grinding deflections and problems related

7. ▪Grinding is a process of removing
material by abrasive action of a
revolving wheel on the surface of a
work-piece in order to bring it to
required shape and size.
▪Grinding is machining process that's
used to remove material from a
workpiece via a grinding wheel. As the
grinding wheel turns, it cuts material off
the workpiece while creating a smooth
surface texture in the process

8. ▪ Grinding and polishing have a long history that can be
dated back to the primitive century, a time when grinding
was generally a manual work performed with natural
sandstones.
▪ Abrasive stones were used for sharpening early knives, tools
and weapons.
▪ From early times, abrasives have been used to cut and
shape rocks and stones for pottery such as to make an
eating utensil.
▪ This maybe the earliest used of grinding as a machining
operation to obtain a desired shape, rather than just for
sharpening.
▪ The huge stone blocks used in building the pyramids of
Egypt were cut to size by sawing with some crude type of
grinding machine and their surface was smoothed by
sandstone.

9. ▪ Grinding of metal begun in ancient Egypt in about 2000 BC
which corresponding to the beginning of metallurgy.
▪ During this period, grinding skills became highly valued in
the Middle East for sharpening tools and making
ornaments.
▪ Abrasives were also used for cutting and polishing gems.
One of the earliest recorded uses of diamond powder as an
abrasive from fifteenth century Belgium, for cutting
diamond and for delicate finishing operation in
watchmaking.
▪ During the Middle Ages and up until Industrial Revolution,
abrasive was used for sharpening and polishing of tools,
weapons and armour.
▪ Early concept of grinding machines appear in the drawings
of Leonardo Da Vinci dating from about the year 1500.

10. ▪ It was not until the 1850s that the initial concept of a grinding machine was
introduced. Such machine still needed intensive human involvement, making it a
semi-automated endeavour.
▪ With the increasing demand for precision parts, especially from 1900 onward,
multi-axis machines were developed with the aim of achieving higher accuracy.
▪ Grinding technology continued to be used in increasingly diverse applications
today and much of modern technology relies on the grinding industry for its
existence.

11. ▪ High surface finish and accuracy are produced.
▪ Ability to machine hard material.
▪ Less pressure can be applied to work.
▪ Ability to work at high temperature.
▪ Offers high accurate dimensions.
▪ Ability to cut any type of metal at a speed rate.
▪ It can produce a smooth surface.

15. ▪ Grinding isn’t particularly effective at removing large amounts of material
from a workpiece.
▪ In fact, the average depth at which workpieces are grinded is 0.25 to 50
millimeters.
▪ The primary advantage of grinding over other cutting processes is that it’s
able to product a smooth surface.

17. ➢ Machining hard materials
➢ Accuracy
➢ Surface texture
➢ Surface quality
➢ Speed of production
➢ Cost
➢ Slitting and parting
➢ Descaling, deburring
➢ Stock removal (abrasive milling)
➢ Finishing of flat as well as cylindrical surface
➢ Grinding of tools and cutters and resharpening of the same

19. ▪ Work piece material: shape, hardness, stiffness, thermal and
chemical properties
▪ Grinding machine: type, control system, accuracy, stiffness,
temperature stability, vibrations
▪ Kinematics: the geometry and motion between grinding wheel
and motion
▪ Grinding wheel: abrasive, grain size, bond, structure, hardness,
speed, stiffness, thermal and chemical properties
▪ Dressing conditions: type of tool, speed and feed, cooling,
lubrication and maintenance.
▪ Grinding fluid: flow rate, velocity, pressure, physical, chemical
and thermal properties
▪ Atmosphere?

21. ▪ It is the only economical method of cutting hard material like hardened steel.
▪ It produces very smooth surface , suitable for bearing surface.
▪ Surface pressure is minimum in grinding.
▪ It is suitable for light work, which will spring away from the cutting tool in
the other machining processes.

24. • CO2: Ability to evaluate the characteristics and performance of
grinding wheel

25. ▪ The wheel used for performing the grinding operation is
known as grinding wheel.
▪ It consists of sharp crystal called abrasive held together by a
binding material or bond.
▪ The wheel may be a single piece or solid type or may be
composed of several segments of abrasive blocks joined
together
▪ Every grinding wheel has two constituents:
i. abrasive used for cutting.
ii. bond that holds abrasive grains.

27. ▪ Grinding wheel consist of
1. Abrasive
2. Bond
3. Grit / Grain Size
4. Grade
5. Structure of wheel

29. ▪ Abrasive: it is that material of grinding wheel which does the cutting action
▪ Abrasive is a hard, tough substance containing many sharp projecting cutting
edges or points
▪ the most important properties of abrasives is hardness.
▪ The hardness should be retained at high temperature
▪ Abrasive should not react chemically or diffuse onto workpiece material
▪ Hardness values of common abrasive measured in Knoop
▪ Friability - tendency of a grain to fracture under compression
▪ Grains with greater friability are better for low grinding forces
▪ Fracture produces sharp new edges and hence friability is an advantage for
maintaining wheel sharpness
▪ Bond is the substance that acts as a binder to hold the abrasive grains together

31. ▪ The common natural abrasives are sand stone, emery (50- 60% crystalline
AL2O3+iron oxide), corundum (75-90% crystalline aluminium oxide+iron oxide),
and diamond
▪ The sand stone is used only for sharpening some wood-working tool.
▪ Diamond is used for dressing the grinding wheel and acts as an abrasive material
for hard material
Artificial abrasive:
▪ These are manufactured under controlled conditions in closed electric furnaces in
order to avoid the introduction of impurities and to achieve the necessary
temperature for chemical reactions to take place
▪ Example: Silicon carbide(Sic), Aluminum oxide(Al2O3)
Artificial diamond:
▪ The diamond produced through artificial means are quite comparable to the
natural diamond in their grinding characteristics and give better result than the
latter.

32. The artificial abrasives have lately superseded the natural abrasive for
following reason
1. The controlled conditions in the electric furnace enable uniformly in the
product
2. The quality of production and supply can easily be varied according to the
demands
3. They have largely abolished the dependence on natural means to meet the
growing demand of more abrasive material in the modern manufacturing
process.

34. ▪ The size of an abrasive grain is identified by a grit number.
▪ The smaller the grain size, the larger the grit number
▪ For example. Grit number 10 as very course, 100 as fine and 500 as very
fine.
▪ Size of grain grit is determined by sorting or grading the material by passing
through screens with the no. of meshes per linear inch.
▪ The grain size influences stock removal rate and the generated surface finish.
▪ The selection of grain size is determined by-
i. Nature of grinding operation
ii. Material to be grinded
iii. Material removal rate
iv. Surface finish required

36. ▪ The grade of a bonded abrasive is a measure of its strength,
including both the type and the amount of bonding material in
the wheel
▪ A hard wheel has a stronger bond and/or a larger amount of
bonding material between the grains than a soft wheel
▪ The structure of a bonded abrasive is a measure of its porosity
(the spacing between the grains)
▪ The structure ranges from dense to open.

40. ▪ Aluminium oxide : carbon steels, ferrous alloys and alloy steels
▪ Silicon carbide: nonferrous metals, cast irons, carbide, ceramics,
glass and marble
▪ Cubic boron nitride: steels and cast irons above 50 HRC
hardness and high temperature alloys.
▪ Diamond : ceramics, carbides and some hardened steels where
the hardness of diamond is more significant than its reactivity
with the carbon in steel.

41. 1. Use silicon carbide wheel for low-tensile- strength material and
aluminum oxide wheel for high-tensile-strength materials
2. Use hard wheel on soft materials and soft wheel on hard
materials
3. If wheel too hard, increase speed of work or decrease speed of
wheel to make it act as softer wheel.
4. If wheel appears too soft or wears rapidly, decrease speed of
work or increase speed of wheel.

42. ▪ Define the following marking on the grinding wheel
55-C-36-D-9-S-28
51-A-36-L-5-V-31
69-C-180-W-10-M-70

44. ▪ Material removal by grinding occurs
mainly by a chip formation process,
similar to that of other machining
methods such as turning or milling, but
on a much finer scale.
▪ A grinding wheel cuts through the
workpiece material as the workpiece
passes underneath.
▪ Normal and tangential forces are
generated between the grinding wheel
and workpiece
▪ The forces cause abrasive grains of the
grinding wheel to penetrate the
workpiece.
Material removal as the
workpiece passes the grinding
wheel in a down-cut grinding

45. ▪ A grain that cuts deeply into the
workpiece carves out a chip whereas a
grain that rubs the workpiece very lightly
may fail to penetrate the surface.
▪ A grain that rubs the workpiece without
penetration causes mild wear of the
surface that may be hardly detectible.
▪ Rubbing, cutting and ploughing are three
stages of metal removal.
▪ Some grains plough without cutting and
some grains experience all three stages.
▪ The transition from rubbing to ploughing
and then from ploughing to cutting
depends on increasing depth of grain
penetration into the surface. Rubbing, ploughing and cutting at different
grain penetration through the arc of contact

46. ▪ Many aspects of grinding behavior depend on the extent of rubbing,
ploughing and cutting involved.
▪ Abrasive grains that are mainly rubbing wear differently from grains involved
mainly in heavy chip removal.
▪ As a consequence, grinding force, grinding energy, surface texture, and wheel
life are all affected, and grinding behavior can only be explained in terms of
the nature of the grain contact and effects on grain wear

47. Down-cut grinding Up-cut grinding
Abrasive grains penetrate to a maximum
depth immediately after contacting the
workpiece. Penetration reduces to zero as
the grains move through the contact
Wheel rotates in the opposite direction so
that grain penetration steadily increase as
the grains pass through the contact
Chip removal occurs at the beginning of
contact by an individual grain
An individual grain coming into contact
rubs against the workpiece initially and
chip removal is achieved later in the
passage through contact
Forces tend to be lower, and there are
advantages for surface roughness and
reduced wheel wear
The grains have a greater tendency to
become blunt leading to higher grinding
force and higher wheel wear
Greater initial impact between the grain
and the workpiece and a greater tendency
for grain micro-fracture. This help to
maintain wheel sharpness and reduces the
overall rate wheel wear.
Cooling is more efficient as fluid is carried
into the contact on the finished portion of
the workpiece

48. ▪ https://www.youtube.com/watch?v=tnwXmAor-Ow

49. ▪ The chip formation in abrasive processes defines the local interaction
between abrasive grains and workpiece material in combination with the
surrounding fluid media (cooling lubricant or air).
▪ It can mainly be distinguished between brittle and ductile removal
mechanisms.
▪ The common removal mechanisms in grinding can be divided into ductile
material removal and brittle material removal.

53. ▪ Calculate the undeformed chip, l and thickness, t for the following
parameters : Let D = 200 mm, d = 0.05 mm, v = 30 m/min, and V = 1800
m/min. Assuming that C = 2 per mm2 and r = 15
▪ Undeformed chip length, l = 𝐷𝑑 = (200𝑚𝑚)(0.05𝑚𝑚) = 3.162 mm
▪ Undeformed chip thickness, t =
4𝑣
𝑉𝐶𝑟
𝑑
𝐷
=
4 𝑥 30 𝑚/𝑚𝑖𝑛
1800 𝑚/ min 𝑥 2 𝑚𝑚2
𝑥 15
0.05 𝑚𝑚
200 𝑚𝑚
▪ = 0.0022𝑚𝑚2 (0.0158)
▪ = 0.00003476 𝑚𝑚2
▪ = 0.0059 mm

54. ▪ The most basic grinding parameters is the real depth of cut ae
▪ The machine operator sets or programmes a depth of cut ap
▪ As every operator knows, in a single pass of the grinding wheel across the
workpiece, the real depth of material removed is much less than the
programmed depth of cut.
Effects of grinding forces on wheel deflection and real depth of cut

55. ▪ ap = set or programmed depth of cut
▪ x = the grinding wheel surface deflection
▪ as = grinding wheel reduction in radius
▪ xexp = workpiece expansion

56. ▪ The programmed depth of cut in horizontal surface grinding is set by the
machine operator first detecting contact between the wheel and the
workpiece. The machine operator then sets a down feed of 25 µm. At the
beginning of the pass, the grinding wheel surface deflects upwards by 15µm.
The wheel has not had time to wear and the workpiece has not had time to
expand. At the end of the pass in horizontal surface grind, the grinding wheel
has reduced in radius by 4µm, the grinding wheel surface is deflected
upwards by 13µm, and the workpiece has expanded by 1µm.
What is the difference in real depth of cut along the workpiece length?
▪ Start ae =25-15-0+0 =10µm
▪ End ae = 25-13-4+1 =9µm
▪ The difference in real depth of cut along the length is 10µm-9µm=1µm

57. ▪ The depth of material removed ae is very much larger than the thickness of the
layer emerging from the grinding zone at wheel speed.
▪ The material is speeded up from work speed to wheel speed, and if the material
emerged as solid extruded sheet it would have a thickness correspondingly
reduced to the value known as the equivalent chip thickness
▪ Equivalent chip thickness is often used as a proxy for actual chip thikness as the
latter cannot be easily defined or measured (Snoeys et al.1974)
▪ ae = real depth of cut
▪ vw = workpiece speed
▪ vs = grinding wheel speed

58. ▪ The real depth of cut after a number of revolutions of the workpiece in a
plunge cylindrical grinding operation is 10 µm. The grinding wheel speed is
60 m/s and the work speed is 0.3 m/s. What is the equivalent chip
thickness?
▪ heq = 10 µm x 0.3 m/s
60 m/s
= 0.05 µm
= 0.00005 mm

59. ▪ Material removal rate in grinding is usually quoted in terms of removal rate
per unit width of grinding contact.
▪ Removal rate per unit width is known as specific removal rate Q’
▪ A moderate removal rate of Q = 50 mm3/s over 25mm wide cut is quoted as
Q’ = 2 mm3/s per mm width
Removal rate Q and
specific removal rate Q’
bw = contact width
ae = depth of cut
vw = work speed

60. ▪ Such high removal rates create high stresses on the grinding wheel grains
and require appropriate grinding wheel design to avoid rapid wear
▪ Another way to increase removal rate without increasing the stress on the
grinding wheel grains is to increase the active surface area of the grinding
wheel in grinding contact
▪ Example: The width of grinding contact in a horizontal surface grinding
machine is 15 mm, the real depth of cut is 10 µm, and the work speed is 300
mm/s. what is the removal rate and the specific removal rate?
▪ Q = 15 mm x 0.010 mm x 300 mm/s = 45 mm3/s
▪ Q’ = 0.010 mm x 300 mm/s = 3 mm2/s

61. ▪ Grinding energy provides a further valuable measure of the ability of a
grinding wheel to remove material.
▪ Grinding energy depends on the sharpness of the grinding wheel and the
grindability of the workpiece material
▪ The grinding energy required to remove a volume of material is given by the
grinding power P divided by the removal rate Q.
▪ Example : The maximum grinding power in steady grinding after subtracting
the no load power and the power required to accelerate the grinding fluid has
a mean value of 2 kW. The removal rate is 50 mm3/s. What is the specific
grinding energy?
▪ ec = 2000 W /50 mm3/s = 40 J/mm3

62. ▪ Specific grinding energy will start decreasing with material
removal rate because rake angle of the grit becomes more
favourable with increase of grit depth of cut.
▪ However, if increase of material removal rate causes chip
accommodation problem in the available inter-grit space then
specific energy may increase.

63. ▪ It is desired to off set the adverse effect of very high negative
rake angle of the working grit, to reduce the force per grit as well
as the overall grinding force.

65. ▪ Wheel truing is defined as act of restoring the cutting face of a grinding wheel
by removing the abrasive material from the cutting face and sides of the
wheel, so that it will run true with respect to the axis of rotation and produce
perfect round or flat work.
▪ It also includes the altering of the cutting face shape to produce special
contours.
▪ As soon as a fresh wheel is fitted, it becomes necessary to true its face.
▪ It also produces concentricity or parallelism of faces.
▪ It prepares the wheel to perform a forming operation.

66. ▪ It is the process of changing the shape of the grinding wheel as it becomes
worn from an original shape, owing to the breaking away of the abrasive and
bond.
▪ This is done to make the wheel true and concentric with a bore or to change a
face contour for form grinding.
▪ Truing and dressing is done with the same tools, but not for the same
purpose.
▪ The only satisfactory method of truing a wheel is by the use of a diamond
tool.
▪ In truing a wheel with a diamond, the feed must not exceed 0.02mm
otherwise grooves may be cut on the grinding wheel.

67. ▪ No matter how precisely manufactured, once a grinding wheel is mounted on
a spindle there will be some eccentricity.
▪ Even if it's less than 0.001”•
it's going to affect the final size and finish of the
workpiece, so to produce high-quality work the wheel must be trued.
▪ Grinding wheels lose their geometry with use, truing restores the original
shape.
▪ Truing grinds a small amount of material to expose new grinding media, and
new cutting edges on worn glazed grains.

70. ▪ Wheel dressing is defined as the act of improving the cutting action.
▪ It can also be described as sharpening operation.
▪ It becomes necessary from time to time during the course of working to
correct uneven wear and to open up the face of the wheel so as to obtain
efficient cutting conditions.
▪ Dressing a wheel does not necessarily true it.
▪ The wheel may be out of round or parallel even after dressing as it only
removes the outside layer of dulled abrasive grains and the foreign material.
▪ As grinding wheels are used then tend to become loaded with lodged metal
chips in the cavities.
▪ Dressing is used to remove the lodged metal chips.

71. ▪ Dressing may be accomplished by using metal
crushers, abrasive sticks, abrasive wheels,
single-point diamonds, single set and matrix
diamond dressers, rotary and stationary
diamond rolls, and crushing rolls.
▪ Metal crushers are used to dress wheels meant
for roughing operations.
▪ Abrasive sticks are used to dress the wheels
and to remove loading or glazing from diamond
wheels.
▪ Crushers are used for profile dressing.

78. ▪ Grinding wheel wear is an important consideration, because it adversely
affects the shape and dimensional accuracy of ground surfaces.
▪ Wear of grinding wheels is caused by three different mechanism: attritious
grain wear, grain fracture and bond fracture.
▪ The quality, characteristics, and rate of grinding wheel wear can be affected
by contributions of the characteristics of the material of the workpiece, the
temperature increase of the workpiece, and the rate of wear of the grinding
wheel itself.
▪ Moderate wear rate allows for more consistent material size.
▪ Maintaining stable grinding forces is preferred rather than high wheel wear
rate which can decrease the effectiveness of material removal from the
workpiece.

80. ▪ Bond fracture occurs when high
stresses are applied to a grain
and also when bond retention of a
grain is weak
▪ Grain micro-fracture is a
favourable type of wear that
maintains a sharp grain with a
slow rate of wear under
conditions of high stress. Micro
fracture depends on the
crystalline nature of the grain
▪ Grain macro-fracture is where the
grain fractures into large
fragments. Macro fracture
depends on the crystalline
structure of the grain and the
grinding stress levels.

81. ▪ Some common attributing factors to wheel can be caused by grain fracture, which can be
advantages, is the results of a portion of each of the individual grains on the wheel surface
breaking apart and leaving the remaining grain bonded to the wheel.
▪ The fractured grain is left with newly exposed sharp edges which attribute the self-
sharpening characteristic of grinding wheels and cutting tools in general.
▪ Attritious wear or progressive wear which is typically undesirable leads to the grains
dulling by developing flat spots and rounded edges on the wheel which can deteriorate the
wheels ability to remove material.
▪ Flat spots also can lead to excessive heat generation with the added surface contact which
and in turn enable bond fractures or the brittle fracture of the adhesive bonds between the
grains.
▪ The removal of these worn grains from the adhesive bonds restores the wheels cutting
ability once more.
▪ Grinding wheels can also be characterized by the grains increased capacity to fracture
according to a level of higher value of friability.
▪ Different bonding materials are used depending on the intended use of the grinding wheel.
The bonding material is classified by its individual strength called its wheel grade.

82. ▪ There is another type of wheel wear phenomenon that has disastrous effect on
grinding performance
▪ This is wheel loading or wheel clogging
▪ Loading occurs when the workpiece material adhere to the tips of the abrasive
grains and is brought into repeated contact with the material.
▪ Loading also occurs if long workpiece chips fill the pores of the abrasive and are
retained there.
▪ The consequences of loading and clogging are extremely poor surface texture of
the workpiece, increased grinding forces and increased grinding wheel wear.
▪ To avoid loading, it is important to use ample coolant with effective lubrication
properties.
▪ Other measures that can help include increasing wheel speed or reducing depth
of cut.

83. ▪ A high rate of wheel wear reduces workpiece material removal rate and
reduces redress life.
▪ Abrasive grains tend to be disloged increasing surface roughness
▪ If a grinding wheel wears too slowly, the abrasive grains become blunt,
grinding forces increase, size errors increase, temperature rise increase and
there is an increased risk of thermal damage to the workpiece.
▪ A moderate rate of wheel wear is usually preferred especially if grinding with
conventional abrasive as this allows the wheel to remain sharp, thus
maintaining stable grinding forces and minimising size variations.
▪ With super-abrasives, wheel sharpness may be maintained for long periods in
spite of minimal wheel wear.
▪ This has the benefit of reducing size variations and increasing wheel life.

84. ▪ A measure of the ability of a grinding wheel to remove material is given by G
Ratio.
▪ An efficient hard wearing grinding wheel will grind an easy-togrind material for a
long time with only a small amount of wheel wear
▪ The grinding ratio, G is defined as the volume of material removed divided by the
volume of wheel wear.
G = Volume of material removed
Volume of wheel wear
▪ In conventional grinding, the G ratio is in the range 20: 1 to 80: 1.
▪ As the wheel losses material, it must be reset or repositioned to maintain
workpiece size.
▪ Higher the force, greater the tendency for the grains to fracture
▪ Higher the wheel wear, lower the grinding ratio

85. ▪ Due to the nature of the grinding process, a great deal of heat is generated.
▪ Heat is generated due to the friction between the grinding wheel and the part
as well as during removal of chips from the part.
▪ This heat presents a major challenge during grinding, as it can lead in the
worst case to part damage (e.g. grinding burn) and thus to scrap, as the part
can no longer fulfil its load requirements.
▪ The most severe damage that usually occurs on the grinded work-piece is the
‘work-piece burn,' where discoloration and blemishes can be observed on the
work-piece.
▪ Also, during the grinding process the surface microstructure of the material
expected to change due to the increase in the working temperature. These
microstructure changes eventually vary the hardness of the material and
subsequently results in detrimental internal stresses.

86. ▪ This internal stress creates a higher tensile stress on the workpiece surface
that leads to a reduced fatigue life. As a result, it decreases the service life,
reliability of the produced parts and the precision of the grinding wheels.
▪ Also, while machining a high strength material, the working temperature
rises with the speed and load of the cutting tool used, this decreases the tool
strength leading to a quicker tool wear.
▪ Besides, the dulling (removal of the worn grains to develop the new cutting
points) drives the formation of scattering marks on the work-piece surface
upon machining which later affects the surface quality of the workpiece.
▪ However, this damage can be reduced by the application of a coolant to aid in
removing the heat created by the work piece-tool interaction.
▪ The primary objective of lubricators is to decrease the amount of friction
between two sliding surfaces and to maintain the work piece surface property
without any alteration or damages

87. ▪ Synthetic, semi-synthetic, soluble and straight oil coolants are commonly
used in grinding applications.
▪ The petroleum-based soluble oil based coolants provide more lubricity than
synthetics, but soluble oil has poorer cooling and cleaning characteristics.

88. ▪ The coolants also used to protect the machined surface from corrosion.
▪ Usually, coolant is applied directly to the grinding zone to limit the heat
generation. The fluid accomplishes this by reducing the amount of friction in
the grinding zone through its lubrication properties which minimize the
cutting forces thereby saving the energy.
▪ These results in an increased of cutting tool life (grinding wheel) and capacity
utilization. Thus the production is kept consistently at a high level in terms of
quality and efficiency.
▪ Thus, a proper selection of coolant is crucial to eliminate the heat effectively
and efficiently.
▪ In addition, the cutting fluid also helps to flush the produced chips from the
grinding process. Whereby improper chip removal could clog and damage the
wheel.
▪ Also, the forces and energy input would substantially increase due to clogging
and would result in heat input to the work-piece

89. ▪ In grinding process, coolants are used to improve the surface finish, wheel
wear, flush the chips and to reduce the work-piece thermal deformation.
▪ Lubrication in the form of oil — either organic or synthetic — is applied to the
grinding wheel to control chip formation.
▪ Without lubrication, excess material will accumulate in the form of chips,
which can affect the grinding wheel’s performance and, therefore, the finished
product.
▪ Of course, lubrication works to lubricate the grinding wheel by reducing
friction, but it’s also used to hold the chips in place so that the excess
material can be removed with greater ease.

90. ▪ The conventional cooling technique, i.e., flood cooling delivers a large amount
of fluid and mist which hazardous to the environment and humans.
▪ Industries are actively looking for possible ways to reduce the volume of
coolants used in metal removing operations due to the economical and
ecological impacts.
▪ Thus as an alternative, an advanced cooling technique known as Minimum
Quantity Lubrication (MQL) has been introduced to the enhance the surface
finish, minimize the cost, to reduce the environmental impacts and to reduce
the metal cutting fluid consumptions.
▪ Nanofluid is a new-fangled class of fluids engineered by dispersing
nanometre-size solid particles into base fluids such as water, lubrication oils
to further improve the properties of the lubricant or coolant.

93. ▪Surface grinding
▪Cylindrical grinding
▪Internal grinding
▪Centerless grinding
▪Creep-feed grinding
▪Heavy stock removal by grinding

113. Tool post grinder
Bench and pedestal grinder

117. The effect of vibration on the work piece
▪The major effect is poor surface finish.
▪It is very important for grinding machine.
▪Dimensional accuracy of job is also effected.
▪This is mostly due to chatter vibration.
▪Chatter marks are proof for the effect of vibration on
the work piece

121. GRINDING ISSUE CAUSES CORRECTION
CHATTER Faulty coolant Clean coolant tank and lines. Replace dirty or heavy
coolant with correct mixture
Out-of-Balance Rebalance on mounting before and after dressing.
Run wheel without coolant to remove excess water.
Store a removed wheel on its side to keep retained
water from causing a heavy side.
Tighten wheel mounting flanges
Make sure wheel center fits the spindle
Wheel out of
round
True before and after balancing.
True sides and faces
Wheel too hard Use coarser grit, softer grade, more open bond
Improper
dressing
Use sharp diamond and hold rigidly close to the wheel.
It must not overhang too far
Check diamond in mounting for rigidity

122. GRINDING ISSUE CAUSES CORRECTION
CHATTER Faulty work
support or
rotation
Use sufficient number of work rests, one every 9 inches
of work length, and adjust them more carefully.
Use proper angles in work centers
Clean dirt from footstock spindle and be sure spindle
is tight
Make certain that work centers fit properly in spindles
Improper
operation
Reduce rate of wheel feed
Work vibration Reduce work speed
Check workpiece for balance
Outside
vibration
transmitted to
machine
Check and make sure that the machine is level and
sitting solidly on foundation
Isolate machine and foundation
Interference Check all guards for proper clearance

123. GRINDING ISSUE CAUSES CORRECTION
CHATTER Wheelhead Check spindle-bearing clearance
Use belts of equal lengths or uniform cross section on
motor drive
Check drive motor for unbalance
Check balance and fit of pulleys
Check wheel-feed mechanisms to see that all parts are
tight
Headstock Incorrect work speeds
Check drive motor for unbalance
Make certain that headstock spindle is not loose
Check work-center fit in spindle
Check wear of faceplate and jackshaft bearings

124. GRINDING ISSUE CAUSES CORRECTION
Spirals (traverse
lines) on workpiece
with same lead as
the rate of traverse
Machine parts
out of line
Check wheelhead, headstock, and footstock for proper
alignment
Truing Point truing tool down 3 degrees at the work-wheel
contact edges
Make edges of face round

125. GRINDING ISSUE CAUSES CORRECTION
Check marks of
workpiece
Improper
operation
Do not force wheel into work
Use greater volume of coolant and more even flow
Affirm the correct positioning of coolant nozzles to
direct a copious flow of coolant to the wheel-work
interface
Improper wheel Make the wheel act softer. Use a softer grade wheel
Review the grain size and type of abrasive. A finer grit
or more friable abrasive, or both, may be called for.
Improper
dressing
Make sure you have a sharp, good quality diamond
that is well set
Increase speed of the dressing cycles
Make sure the diamond is not cracked

126. GRINDING ISSUE CAUSES CORRECTION
Burns or
discoloration of
work
Improper
operation
Decrease rate of infeed
Do not stop work while in contact with wheel
Improper wheel Use softer wheel or obtain soft effect
Use greater volume of coolant
Improper
dressing
Check dressing tool for sharpness
Increase speed of dressing cycle
Isolated deep
scratches on work
Improper wheel Use finer wheel and consider a change in abrasive type
Improper
coolant and/or
coolant filter
Use coolant that settles chips
Check coolant filter

127. GRINDING ISSUE CAUSES CORRECTION
Fine spiral or
thread scratches
on work
Improper
operation
Reduce wheel pressure
Use more work rests
Reduce traverse with respect to work rotation
Use different traverse rates to break up pattern when
making numerous passes
Keep edge of wheel from penetration by dressing wheel
face parallel to work
Faulty wheel
dressing
Use slower or more even dressing traverse
Set dressing tool at least 3 degrees down and 30
degrees to the side from time to time
Tighten holder
Do not take too deep a cut
Round off wheel edges
Starting dressing cut from wheel edge may help
Narrow and deep
regular marks
Wheel too
coarse
Use finer grain size

128. GRINDING ISSUE CAUSES CORRECTION
Wide irregular
marks of varying
depth
Wheel too soft Use harder grade of wheel
Widely spaced
spots on work
Oil spots or
glazed areas on
wheel face
Balance and true wheel
Keep oil from wheel face
Irregular “fishtail”
marks of varying
lengths and widths
Dirty coolant Clean tank frequently
Use filter for fine-finish grinding
Flush wheel guards after dressing or when changing to
a finer wheel

130. ▪ Glazed wheel will affect finish, accuracy, and metal-removal
rate.
▪ Main causes of wheel glazing are:
• Wheel speed too fast
• Work speed too slow
• Wheel too hard
• Grain too small
• Structure too dense