Note: Descriptions are shown in the official language in which they were submitted.
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Docket BV-2237
FRIT BONDED ABRASIVE WHEEL
John Hay
Sl Brook Street
Shrewsbury, Massachusetts 01545
Carole J. Markhoff-Matheny
Salminen Drive
Leicester, Massachusetts 01524
Brian E. Swanson
335 Church Street
Northboro, Massachusetts 01532
TECHNICAL FIELD
The invention relates to vitrified bonded
grinding wheels and more specifically to grinding wheels
bonded with a frit.
5 BACKGROUND AND INFORMATION DISCLOSURE STATEMENT
The following publications are representative of
the most relevant prior art known to the Applicants at the
time of filing of the application.
UNITED STATES PATENTS
10 1,338,598 April 27, 1920 C. W. Thomas
1.918,312 July 18, 1933 C. E. Wooddell
4,314,827 February 9, 1982 M. A. Leitheiser et al.
4,543,107 September 24, 1985 C. V. Rue
4,623,364 November 18, 1986 T. E. Cottringer et al.
15 4,741,743 May 3, 1988 K. S. Narayanan
4,744,802 May 17, 1988 M. G. Schwabel
The most significant development in the abrasive
industry in recent years is a new type of non-fused or
sintered abrasive with properties different from those of
20 other abrasives. The unique properties o this new
abrasive are primarily the result of the microstructure of
the abrasive which in turn is a result of the processing
techniques used to manufacture the material. One abrasive
of this type is disclosed in U.S. Patent No. 4,623,364.
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The product ls, basically, a sintered aluminous ahrasive
which is highly dense and has a hardness of at least 18 GPa
made up of a plurality of microcrystals o~ alpha alumina
which are generally equiaxed and have a crystal size of no
5 greater than 0.4 microns. This ultra finely crystalline
alumina is prepared by ~orming an aqueous sol from water,
finely pulverized, i.e. microcrystalline hydrated alumina,
and a mineral acid; the sol may also contain varying
amounts of zirconia or spinel forming magnesia. To the sol
10 is added an effective amount o~ submicron alpha alumina
particles which will function as seeds or a nucleating
agent when the sol is fired at elevated temperature. The
sol is cast into sheets or extruded, dried, and granulated.
The green granules are then fired at about 14pOC.
Another sintered aluminous abrasive is that
taught by U.S. Patent No. 4,314,827, the major difference
being this method does not include the addition to the sol
o~ sub micron alpha alumina seed material. Here too,
however, the composition may include other materials such
20 as zirconia, ha~nia, or mixtures of the two, or a spinel
formed from alumina and an oxide of cobalt, nickel, zinc,
or magnesium. Abrasive grain made in this manner contains
alpha alumina in the form of cells or sunburst shaped
alpha alumina crystals having a diameter of 5-15 microns,
25 is somewhat lower in density than the preceding abrasive,
and has a density of only about 15 GPa.
U.S. Patent No. 4,744,802 also describes a seeded
sol gel sintered aluminous abrasive which is seeded by
alpha ferric oxide or alpha alumina particles. The
30 product is made by preparing a sol of alpha alumina
monohydrated particles, gelling the sol, drying the gel to
for~ a solid, and sintering the calcined gel.
There are, of course, other sintered abrasives
that have been in commerce for years, such as abrasives
35 based on sintered bauxite and sintered alumina-zirconia.
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While sintered aluminous abrasives have
properties that should make them outstanding abrasives,
they do not ~ive up to expectations in two significant
areas. One area is dry grinding with wheels wherein the
5 abrasive is bonded with the more commonly used vitrified
bonds, i.e. those that are fired and matured at
temperatures of about 1220C or above. As stated in U.S.
Patent No. 4,543,107, attempts to use sintered aluminous
abrasive bonded with such vitrified bonds in dry grinding
10 were not completely successful. This is completely
contrary to what happens with abrasive products bonded with
so-called resinoid or organic polymer bonds; these bonds
mature at temperatures i.n the range of 160~C to 225C. The
same is true when the sintered aluminous abrasives are used
15 in coated abrasive products. Organic bonded grind.ing
wheels are exemplified in U.S. Patent No. 4,741,743. A
seeded sol gel type abrasive Patent No. 4,623l364 is ~onded
with a phenol-formaldehyde type bond, in combination with a
co-fused alumina-zirconia abrasive. The unique properties
20 of the seeded sol gel sintered aluminous abrasive in
combination with the cofused alumina-zirconia produce a
synergistic effect and result in cut-off wheels with
grinding qualities or G-ratios significantly superior to
wheels containing the seeded sol gel sintered aluminous
25 abrasive alone or the cofused alumina-zirconia alone.
Under two sets of grinding conditions, the wheels
containing sintered aluminous abrasive alone were superior
to wheels containing the heretofore superior cofused
alumina-zixconia abrasive; in one case the former was 100%
30 better in G-Ratios than the latter.
The problem of extremely poor performance in dry
grinding with sintered aluminous abrasive in the more
commonly used vitrified bonds is addressed by U.S. Patent
No~ 4,543,107. The inventor discovered that i~ the
35 viscosity and/or maturing temperature of the bond is
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properly controlled, then the superior properties of
sintered aluminous abrasive are brought out. This was
accomplished by reducing the firing temperature (maturing
temperature of the bond) to 1100 or less for conventional
5 bonds or 1220C or less for the higher viscosity bonds.
While U.S. Patent No. 4,543,107 has solved the
problem of poor dry grinding properties associated with
sintered aluminous abrasive bonded with the commonly used
vitrified bonds, it has done nothing for the other
10 significant area where the inherent goodness of sintered
aluminous abrasives is not observed and that is in the very
important grinding operation called wet grinding. In this
type of operation, the workpiece and the grinding wheel are
flooded with a coolant which can be essentiaI;ly all water
15 but may contain minor quantities of bactericide,
antifoaming agents and the like, or, water containing 5~10%
of a water soluble oil, or an all oil coolant; the instant
invention and this discussion is concerned only with the
water based coolants. It is well known that some decrease
20 in grindiny quality or G-Ratio is experienced in certain
types o~ grinding, when a given vitrified bonded wheel goes
from dry grinding to grinding with water. The drop is
much more serious, however, in certain situations being as
large as 90% -for vitrified bonded sintered aluminous
25 abrasive wheels. Particularly in the case of wheels made
with abrasive made according to the seeded sol gel
technique referred to above, the reduction in G-ratio
amounts to a loss of essentially all of the inherent
sl~periority of that abrasive as compared to the
30 conventional fused alumina which shows a drop of about 30%
if the G-ratio for all infeeds are averaged.
As is also well known in the art, the use of a
given vitrified bonded grinding wheel wet grindiny does not
always produce results where there is a drop in grinding
35 quality and other aspects of the grinding operation such as
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power consumption; the coolant in some wet grindingoperations can actually cause the grinding quality to
increase over that which results when dry grinding. In the
case of sintered aluminous abrasives bonded with a
5 conventional vitrified bond, the increase in grinding
performance as a result of the coolant doesn't occur or is
minimized. In other words, the exposure of the
combination of commonly used vitrified bonds and sintered
aluminous abrasives to water destroys a major part of the
10 superior properties of that particular abrasive type. It
is this very phenomenon with which the present invention is
concerned.
Of relevance to the present invention are U.S.
Patent Numbers 1,338,598 and 1,918,312. ~hey are relevant
15 for their teaching of bonding abrasive grain with a frit to
form a grinding wheel. The abrasive grain in both patents
is the fused alumina type. Frits are well known materials
and have been used for many years as enamels for coating,
for example, metals and jewelry and for bonding abrasives
20 as evidenced by the foregoing patents. Frit is a generic
term for a material that is formed by thoroughly blending
several minerals, oxides, and other inorganic compounds,
followed by heating the mixture to a temperature at least
high enough to melt it, the glass is then cooled and
25 pulverized. There are almost an infinite number of
possible frits in view of the numerous combinations of
materials and amounts thereof. Some of the more common
materials that are used to form frits are: feldspar,
borax, quartz, soda ash, red lead, zinc oxide, whiting,
30 antimony trioxide, titanium dioxide, sodium silicofluoride,
flint, cryolite, and boric acid. Several of these
materials are blended together as powders, fired to use
the mixture, and the fused mixture is then cooled. The
cooled glass is comminuted to a very fine state. It is
35 this final powder that is used to bond abrasi~e grain to
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form a grinding wheel.
DISCLOSURE OF THE INVENTION
The present invention resides in the discovery
that the known drastic drop in grinding quality which
5 results when vitrified bonded sintered aluminous abrasive
wheels are utilized with a water based coolant, can
essentially be eliminated or drastically reduced by using a
frit for the bonding medium, i.e. a vitreous bond
composition that has been prefired prior to its e~ployment
lo as the bond.
The term frit as used herein ~eans the product
which results when the usual vitrified bond materials are
prefired at temperatures of from 1100C to 1800~C for as
long as required to form a homogeneous glass. The
15 temperature and time required to form the frit depends on
its composition.
Some frits are relatively low melting so that
when such a frit is used as a grinding wheel bond the green
wheel is fired a~ a relatively low temperature, e.g. around
20 900C, as compared to more conventional vitrified bonds
which need to be fired at 1220C or higher. It has been
found khat high firing temperatures are seriously
deleterious to the dry grinding properties of the vitrified
bonded wheel. This particular problem has been solved by
25 using low fired vitrified bonds but this solution has no
effect on the grinding quality of such wheels when used
with a water based coolant (see U.S. Patent No. 4,543,107).
The present invention is a major advancement over the prior
art because the relatively low firing temperature of the
30 fritted bond preserves the superior dry grinding
characteristics of sintered aluminous abrasives, and
additionally extends those superior properties into wet
grinding with a water based coolant. The importance of
this development is readily appreciated when one realizes
35 that a very substantial amount of grinding done with
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vitrified wheels is done with a water based coolant.
There are several so-called sintered aluminous
abrasives currently known such as sintered bauxite, the
seeded sol gel abrasive taught by U.S. Patent 4,623,364
5 and sol gel abrasive such as described in U.S. Patent No.
4,314,827. The seeded sol-gel process produces sintered
aluminous abrasives of extremely fine crystallinity. That
is particularly true of the seeded sol gel process of the
i former patent. The exact reason why the present invention
10 results in grinding wheels with improved performance in
wet grinding with sintered aluminous abrasives is not
completely understood. However, it may be related to the
absence in the frit bond of materials which give off
chemically combined water or which melt at temperatures
15 below the firing temperature of the abrasive and thus reac~
with said abrasive. It is theori~ed that the increased
surface reactivity of the sintered aluminous abrasives make
them more susceptible to attack by (lj chemically combined
water released from clays normally found in vitrified bonds
20 when fired at 600C or higher, or, (2) chemically combined
water from hydrated boron compounds, or, (3) molten B203 ak --
580C and higher.
~ While the invention has a most pronounced effect
;~ on vitrified bonded wheels wherein all the abrasive is the
~ 25 sintered aluminous type, it is also effective when the
¦ grinding wheel contains as little as 10% by weight of
sintered aluminous abrasive and up to 90~ by weight of a
secondary abrasive of a different type. In other words,
the present invention includes mixturPs of 10% to 100~ by
30 weight of sintered aluminous abrasive and 0% to 90% of a
i secondary abrasive. In some grinding applications the
addition of a secondary abrasi~e is for the purpose of
reducing the cost of the grinding wheel by reducing the
amount of premium priced sintered aluminous abrasive.
~l 35 In other applications a mixture of sintered aluminous
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abrasive and a secondary abrasive has a synergistic effect.
However, in any case, if a significant amount of sintered
aluminous abrasive is utilized in a vitrified wheel for wet
grinding, the abrasive should be bonded with a frit in
5 accordance with the present invention. Examples of such
secondary abrasives include fused alumina, cofused alumina-
zirconia, silicon carbide, boron carbide, garnet, emery,
flint, cubic boron nitride, diamond, or mixtures thereof.
In the simplest and preferred embodiment, the
10 invention is the combination of sintPred aluminous
abrasive, alone or admixed with a different abrasivP,
bonded entirely with a frit. However, relative to some
grinding operation wheels with advantageous properties can
result when the bond also contains other than only frit.
15 The bond may be made up of a combination of at least 40%
frit with the remainder being unfired clay or any
combination of unfired vitrified bond ingredients. While
fillers and grinding aids are more widely used in resinoid
bonded grinding wheels, these materials can be incorporated
20 in vitrified bonded wheels to advantage in some grinding
applications. From 1% to 40% by weight of a filler or
grinding aid such as mullite, kyanite, cryolite, nepheline
syenite and like minerals, or mixtures when made part of
the bond ~ormulation may produce improved results.
The preferred sintered abrasives for use in the
invention are the dense, finely microcrystalline alpha
alumina abrasives produced by the seeded sol gel technique
of U.S. Patent 4,623,364 and the non-seeded 501 gel
technique of U.S. Patent 4,314,827, the most preferred
30 being the dense finely crystalline alpha alumina seed gel
abrasive of the former patent. In addition to alumina, the
abrasive of the former patent may optionally also include
an effective amount of a grain growth inhibitor such as
silica, chromia, magnesia, zirconia, hafnia, or mixtures
35 thereof, although addition of such materials is not
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required; the abrasive of the latter patent in addition to
alumina, must include (1~ at least 10~ of zirconia,
ha~niat or a comhination of zirconia and haf~ia, or (2) at
least 1% of a spinel derived from alumina and at least one
5 oxide of a metal selected from cobalt, nickel, zinc, or
magnesium, or (3) 1-45% o~ zirconia, hafnia, or the
combination of zirconia and hafnia and at least 1% of
spinel. In addition the present invention is applicable to
a broad range of grinding grades, i.e. volume percentages
10 of abrasive grain, bond, and pores. The wheels may be made
up of 32% to 54% abrasive grain, 2% to 20% bond, and 15%
to 55~ pores.
EXAMPLES OF THE PREFERRED EMBODIMENTS
Exam~le I
A series of vitrified bonded wheels measuring 5
inches in diameter, 0.5 inch thick, and having a 1.25 inch
hole were made by conventional mixing, cold molding and
firing methods. Wheel A contained a commercial fused
alumina abrasive bonded with a commercially available non-
20 fritted vitrified bond. This wheel is commercially sold by
Norton Company of Worcester, Massachusetts and designated
as 32A54-J8VEE. The product was fired in a commercial
firing cycle. Wheel B was another product available from
Norton Company but this wheel contained a seeded sol gel
25 sintered aluminous abrasive of the type disclosed in U.S.
Patent No. 4,623,364. The abrasive was bonded with a non-
fritted vitrified bond and fired in another commercial
firing cycle and designated as SG54-JVS. Wheel C was the
invention wheel containing the same sintered aluminous
30 abrasive as did wheel B but the bond was a fully or
completely fritted vitrified bond composition purchased
from the O. Hommel Company of Pittsburgh, Pennsylvania.
The powdered frit had a particle size of -325 mesh U.S.
Standard Sieve Series, and O. Hommel's designation for
35 this frit was 3GF259A. On a weight percent basis, the frit
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was made up of 63% silica, 12~ alumina, 1.2% calcium oxide,
6.3% sodium oxide, 7.5~ potassium oxide and 10% boron
oxide. The green wheel was ~ired at soooc~ to mature the
bond, the firing cycle being a 2SC/hr. rise from room
5 temperature to ~00C, a soak at 900C of 8 hours, and a
free rate of cooling down to room temperature.
All three wheels contained 48% by volume of
abrasive but whereas wheels A and B contained 7.2% by
volume of non-fritted vitrified bond, the amount of bond in
10 wheel C was increased to 9.1% by volume~ which in turn
resulted in a corresponding reduction in porosity. The
reason for increasing the amount of bond in the invention
wheel C was to make the hardness of wheel c about equal to
the hardness of the wheels A and B. Fritted bonds tend to
15 be softer acting, i.e~ weaker, than conventional non-
~ritted bonds so that an equal amGunt of bond would have
prejudiced the grinding results.
The mix for wheel C was prepared by adding to a
Hobart mixer the following materials in the order and
20 amounts indicated and thoroughly mixing.
' Material Amount
Sintered aluminous abrasive 500 g 46 grit and
according to U.S. ~,623,364 500 g 60 grit
Dextrin 12 g
~ Glycerine 1 g
3 Water 28 g
0. Hommel frit 119.7 g (-325 mesh)
Dextrin 20 g
~-, 30
A 373.4g portion of the thusly prepared mix was placed in a
cylindrical steel mold, including top and bottom plates and
i an arb~r which when assembled formed a cavity 5.5 inches in
; diameter, 0.5 inch thick with a 1.25 inch hole. The wheel
35 was pressed to size at room temperature and fired according
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to the firing cycle described above. After firing, all the
wheels were sided down to 0.25 inch thickness and were
tested plunge grinding on a 4340 steel block 16 inches long
using a water based coolant composed of 2.5% Whike and
5 Bagley E55 coolant with the remainder being water. Rlunges
were 0.5 and l mil downfeed for a total of 100 mils. Both
wheelwear and material removed were used to calculate the
grinding ratio, by dividing the tutal material removed by
the total wheel wear; the power consumed was also
10 deter~ined in terms of horse power consumed per cubic inch
of metal removed. The grinding results are contained in
Table I.
Table I
Wheel Abrasive Down FeedG-Ratio HP/in3
A Fused 0.5 36.8 4.37
Alumina 1.0 36.6 5.87
B Sintered 0.5 117.2 4.36
Aluminous 1.0 57.2 5.94
C Sintered 0.5 347.8 3.21
Aluminous 1.0 106.3 4.97
The effect on the grinding quality, i.e. G-Ratio,
wet grinding with wheels containing the sintered aluminous
abrasive shows the direct influence of substituting the
frit of wheel C for the more conventional non-fritted bond
25 of wheel B. The invention wheel C had a G-Ratio at 0.5 mil
infeed about 300% greater than that of B, and at 1.0 mil
infeed C was 186% better than B. When the invention wheel
C was compared to wheel A which contained a standard fused
alumina bonded with a non-fritted vitrified bond it can be
30 readily seen how the frit of wheel C brought out the full
superiority of the seeded sol gel sintered aluminous
abrasive with the latter exhibiting grinding ratios 945%
and 290% higher than wheel A at 0.5 and 1.0 mil downfeeds
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respectively. It should be noted that the inventlon wheel
consumed 15-25% less power to remove a cubic inch metal as
compared to wheel A.
Example II
~ sintered aluminous abrasive of the type
disclosed in U.S. Patent No. 4,314,327 was bonded with a
frit and tested plunge grinding 52100 steel. Wheels
containing this abrasive were designated as D. A wheel
designated as E of the same grade but containing the
10 sintered aluminous abrasive of Example I was tested along
side of wheel D. The wheels were made in the same manner
as described in Example I except that wheels D and E were
made from abrasive~bond mixes of the following composition,
with the various materials being added to the,mixer in the
15 order indicated.
WHEEL D
Material Amount
Sintered aluminous abrasive 2,000 g 60 grit
according to U.S. 4,314,827
Dextrin 24 g
Glycerine 2 g
Water 72 g
o. Hommel frit 314.4 g
Dextrin 40 g
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WHEEL E
Material Amount
Sintered aluminous abrasive 2,000 g 60 grit
according to U.S. 4,623,364
Dextrin 24 g
Glycerine 2 g
Water 62 g
O. Hommel frit 303 g
Dextrin 30 g
10 The thusly prepared mixes were molded into wheels
measuring 5 inches in diameter, 0.625 inches in thickness,
with a 0.875 inch hole. The wheels were fired in the same
firing cycle as set out in Example I for Wheel C. The
finished wheels had volume percent make-ups of 40%
15 abrasive, 11.5% bond, and 48.5% pores. After finishing,
the wheels were tested in cylindrical plunge O.D. grinding
using several different constant forces with each wheel.
The results are contained in Table II showing the G-Ratio
and power of each force level and the average. The test
20 was done in a water soluble oil coolant made up of 95%
water and 5% Cincinnati Milacron Cimperial 20 oil, a wheel
speed of 8650 surface feet per minute, a work speed of 150
feet per minute, and the wheels were trued with a single
point diamond using a 0.001 inch diametral dress depth and
25 a 0.005 inch/revolution lead.
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TABLE II
Forcs Power
Wheel lbs~in. ~ h~in.
D 111 85.6 8.9
171 103.3 14.1
217 82.2 17.9
166 ave. 90.2 ave.13.6 ave.
E 97 92~4 ~.3
15~ 81.7 12.4
67 108.8 5.8
96 70.3 15.6
128 ave. 38.3 ave.10.5 ave.
Example I shows the drastic improvement in
grinding properties affected by bonding that particular
15 sintered aluminous abrasive with a frit. The data in Table
II shows the same effect on a second type of sintered
aluminous abrasive when bonded with a frit, the data
comparing wheel D with frit bonded sintered aluminous
abrasive according to U.S. Patent 4,314,327, as well as
20 wheel E with frit bonded sintered aluminous abrasive of
U.S. Patent No. 4,623,364.
EXAMPLE III
The bond of the present invention does not need
to be composed entirely of frit. In some cases it may be
25 advantageous to reduce the amount of frit and add a
quantity of unfritted bonding material. This ap~ears to be
the case plunge grinding 52100 steel according to the data
in Table III below. Three wheels were made utilizing the
sintered aluminous abrasive of U.S. Patent 4,623,364. A11
30 of the wheels contained 48% by volume of abrasive. The
wheel designated as F was bonded with a conventional
commercial vitrified bond designated as bond VS used by
Norton Company of Worcester r Massachusetts. In wheel G the
abrasive was bonded with the same frit that was used in
35 wheel C of Example I and wheels D and E of Example I~; the
entire bond was frit. The bond in whsel H, on the other
hand, was made up of 71% by weight of frit and 29% by
14
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weight of Kentucky ball clay. The frit was a frit prepared
by the Ferro Corporation of Cleveland, Ohio. Because
fritted bonds are inherently softer acting in grinding than
non-fritted bonds, as pointed out above, the fired volume
5 percent content of wheel F was adjusted downward by
reformulating the bond composition prior to firing. Thus
on a fired volume percent basis, wheel F was 48% abrasive,
9.1% bond, and 42.9% pores; wheels G and H were 48%
abrasive, 11.5% bond, and 40.5% pores. This produced
10 wheels of the same hardness.
Wheels of the same size as in Example II were
made in the same manner as in Example I from mixes having
the following compositions, with the various materials
being added to the mixer in the order they are listed.
WHEEL G
Materlal Amount
Sintered aluminous abrasive
according to U.S. 4,623,364 2000 g 80 grit
Dextrin 24 g
Glycerin 2 g
Water 60 g
O. Hommel frit303 g
Dextrin 30 g
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WHEEL H
Material Amount
Sintered aluminous abrasive
accoxding to U.S. 4,623,3642000 g 80 grit
5Dextrin 24 g
Glycerin 2 g
Water 40 g
209.2 g Ferro ~rit and
85.2 g clay prebatched 294.4 g
10Dextrin 16 g
The green wheels G and H were fired at 900C to
mature the bond; the green wheel F because it contained the
prior art commercial bond, was fired in a commercial firing
cycle. The finished wheels were then subjected to a
15 grinding test identical to that described in Example II
with the following results.
TABLE III
Force Power
Wheel lb/in G-Ratio hP/in
F 80 116.1 7
171 75.9 15.3
196 53.8 17
149 ave. 81.9 ave.13.1 aYe.
I 25 G 79 191.9 7.3
166 132.8 15.5
18~ 31.6 16
158 70.6 15.8
146 132.7 13.5
147 ave. 111.8 ave.13.6 ave.
H 96 162.3 9.2
150 171.6 14.1
187.5 6.1
97 109.6 17,5
127 ave. 157.8 ave,11.7 ave.
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Wheel H which contained only 71% frit had even a
higher grinding quality i.e. G-Ratio, in this particular
grinding operation, than did wheel G, the all frit bonded
wheel. Both wheels were superior to wheel F which was
5 bonded with a standard non-fritted bond.
EXAMPLE IV
The vast improvement in wet grinding with frit
bonded sintered aluminous grinding wheels as compared to
wheels bonded with the more conventional vitrified bonds
10 continues to manifest itself even when the sintered
aluminous abrasive is mixed with a second abrasive which is
not a sintered aluminous abrasive.
Vitrified bonded wheels measuring 5 inches in
diamet~r and 0.625 inches thick with a 0.875 inch hole were
15 ma~ufactured in the conventional manner. One set of
wheels, designated as I was bonded with O. Hommel frit
3GF25gA and fired at 900C to mature the bond; the other
set of wheels identified as J was bonded with a commercial
bond used by Norton Company of Worcester, Massachusetts
20 designated as H~4 and these wheels were also fired at
900C. The wheels were straight rim type wheels widely
used for many grinding operations where the abrasive is
diamond or cubic boron nitride CBN. The rim or grinding
section of the wheels were made from the following mix
25 composition and resulted in the indicated finished volume
percent composition.
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Wheel I Wheel J
Material Vol. % Formula Vol % _ Formula
N 98 2 g 98.19
CB ~140jl70 (140/170
grit) grit)
Sintered aluminous 39.6 g
Abr.(US 4,623,364) 39 (150 grit) 39 39.96 g
O. Hommel frit 2716.9 g
HA4 bond 14.6110.56 g
DWC 5.5 g
Dextrin 0.21 g
Aeromer 30 2.08 g
Pores 25 37.39
15 The core of the wheels had the following mix
composition and finished volume percent composition.
Wheel I _ Wheel J
Finished Mix Finished Mlx
Material Vol. %Formula Vol. % _ Formula
38A150 * 44.8342.78g 39298.97 g
37C150 ** g56.32 g
O.Hommel frit 25.2118.05 g
HA4 bond 14.6179.00 g
DWC *** 32.26 g
25 Dextrin 1.56 g
Aeromer 30 15.31 g
Pores 30 37.39
* 150 yrit 38 ALUNDUM sold by Norton Co., Worcester, MA.
'. ** 150 grit silicon carbide sold by Norton Co.,
i 30 Worcester, MA.
*** 2.28% methyl cellulose, 9.78% glycerine, and 87.94%
water by weight.
The finished wheels were tested grinding 52100
steel using a coolant made up of water and a water soluble
oil at 10:1 water to oil. The results were as follows:
~ Trade mark
, .
18
. . : . -
.~ , , .
....
~32',~9~8
TABLE IV
Force Power
Wheel lb/in. G-Ratio hp/in.
I 99.5 644.1 9.9
159 412.2 15.7
J 106 350.7 10.6
176 211~0 16.0
Even when about 20% of the sintered aluminous
abrasive ls removed from the wheel and CBN put in its
place, the effect of the frit bond is dramatic. At a force
of about 100 lb/in. the fritted bond wheel I had a G-Ratio
84% higher than that of wheel J containing the commercial
bond ~A4, and at 159 and 176 lb/in. the G-Ratio of wheel I
was 95% higher than that of wheel J.
19
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