GENERAL INFORMATION___________

There are many factors involved in the selection of the right abrasive for a particular job. The comments and suggestions herein relate to average or normal conditions. However, there are endless combinations of these factors. Experience will be an important ingredient in matching the right product with a job. Following are some of the important ingredients to proper selection.

MINERALS_________________

Aluminum Oxide is an abrasive consisting of blunt shaped grain and is very tough in its lowest refined form. It is produced in a variety of refinements and by its versatility can be used from very hard to soft applications, making it the most commonly used abrasive.
Silicon Carbide is an abrasive that is hard, and sharp with exceptional strength, but due to its brittleness it breaks down faster than aluminum oxide under heavy loads.
Ceramic Grain abrasive is non-fused ceramic aluminum oxide that is extremely tough in all grades. It provides exceptional durability and cut rates. This grain is more costly, so its merits need to be evaluated against the common aluminum oxides.

MINERAL TYPES_________________

Friable abrasive grain is easily fractured by impact, therefore, constantly exposing fresh cutting crystals to the work piece making it the fastest cutting abrasive.
Semi-friable abrasive grain does not fracture as readily as friable grain, therefore, gives longer life in comparison during the grinding process, but does not cut quite as freely as the friable grain.
ABRASIVE TYPES_________________

A-Aluminum oxide is very tough and is most generally used in resin bond applications.
27A-Aluminum oxide is semi-friable and of average hardness. It is the most widely used medium density fused aluminum oxide. It is produced in a complete range of grit sizes for use in general purpose vitrified applications.
6A-Aluminum oxide is semi-friable, and of average hardness. It is the designation used for segments.
28A-Premium aluminum oxide is friable white grain which has an aggressive cool fast cutting action while holding form well. It is used in the grinding of heat sensitive alloys, taking advantage of its friability and cool cutting ability. This grain is also widely used in grinding of heat treated tool steels, high speed steels, and internal wheels.
9A-Premium aluminum oxide is friable white grain specially used in the production of our segments.
AMA-Aluminum oxide is a friable very aggressive grain for use on the smaller mounted points where a tough composition is needed.
23A-Aluminum oxide is an off white friable very aggressive grain, used in larger mounted point and wheel applications where a tougher application is indicated.
29A-Aluminum oxide is a pure fused abrasive, alloyed with chrome oxide making it pink in color. Although friable and cool cutting, it exhibits marked formholding characteristics. Applications will be found in precision, broad surface and tool room grinding on hard alloy steels.
5A-Aluminum oxide is the designation for the pink pure fused abrasive alloyed with chromium oxide, used in the manufacture of our segments. 36A-Aluminum oxide is a high chromium ruby-colored fused abrasive, free of titania. It is made by fusing high purity calcined alumina and chromium oxide. It is a friable abrasive, somewhat tougher than white, with corner-holding characteristics, which is needed for precision grinding. It is a premium priced grain as compared to 28A-white and 29A-pink, so the merits as compared to these types should be weighed.
C-Silicon carbide is a black, semi-friable medium density abrasive. It is produced in both resin and vitrified points and wheels for grinding hard or brittle materials, such as cast iron, ceramics, and glass: as well as low tensile strength, ductile non-ferrous metals. GC-Silicon carbide is a green in-color, friable, highly pure, medium density abrasive used in vitrified bonded points and wheels. It is most commonly used for grinding hard, brittle materials, such as cemented carbides, where fast cool cutting is desirable.
CG-Aluminum oxide is non-fused ceramic grain that is very tough, pure, and of uniform quality. Applications are in resin and vitrified points and wheels for high stock removal rates and long life. It performs especially well in precision grinding and fine finish applications, without excess heat generation. As it is a premium priced grain, its merits need to be weighed in comparison to the more common specifications, and is most commonly used in combination with other grains for best results. Note:11A is another designation used for CG grain.

GRAIN COMBINATIONS_________________

Grain combinations used in various proportions to obtain desired results
CA
A mixture of silicon carbide and semi-friable aluminum oxide used in production of resin bonded products only.
78A
A combination of 27A and 28A aluminum oxide.
7MA
combination of 27A and AMA aluminum oxide
73A
A combination of 27A and 23A aluminum oxide
89A
A combination of 28A and 29A aluminum oxide
68A
A combination of 36A and 28A aluminum oxide
8A
A combination of 9A and 5A aluminum oxide
10A
A combination of 9A and 6A aluminum oxide
72A
A combination of 6A and 8A aluminum oxide
18A
A combination of 11A and 28A aluminum oxide
17A
A combination of 11A and 27A aluminum oxide
BG
A combination of C and GC silicon carbide

GRAIN SIZE_________________
Abrasive grain comes in a wide variety of grain sizes. For rough grinding and heavy stock removal coarse grit sizes are used, while fine grit sizes are used for work where a finer finish or a desired shape is necessary.

GRAIN SIZE SPECIFICATIONS
8 10 12 14 16Very Course-for very heavy duty grinding(snagging)
20 24 30 36 46 Coarse to heavy deburring and grinding
54 60 80 90 100 120Medium -for medium deburring, the most common for mounted point use
150 180 200Fine - for light deburring
240 320Very fine - for delicate work requiring a very fine finish
400 500 600Ulra fine - requring a super fine finish with little removal
 BOND_________________

The Bond used in producing abrasive product is what holds the abrasive grains together and has no cutting capabilities of its own. GRIER manufactures product using vitrified, resin, and latex bonds.
Vitrified bond is a glass or ceramic bond which is very hard and comparatively brittle. There are various vitrified bonds that are used to obtain certain desired results or to meet required standards. GRIER manufactures vitrified product in 11, 11B, 13, 13B, 31, 51, 22, and 41 bond.
Resin bond is a strong, tough, resilient material. It absorbs shock better than vitrified. It is used for fast stock removal and is popular with foundries with offhand operations. It works well on stainless steel, brass, bronze, and aluminum. The GRIER designation for resin bond is B.
Latex bond is the bond utilized by GRIER in its soft Griertex product.

HARDNESS_________________

The hardness designation of an abrasive is controlled by the type of bond used and the ratio of bond to grain mix.
Soft grades are generally used on very hard materials, large areas of contact or rapid stock removal.
Hard grades are generally used for soft materials, small areas and longer wheel life.

GENERAL HARDNESS RANGES FOR MOUNTED POINTS
F to I P to R T to V
Soft Medium Hard

STRUCTURE_________________

The concentration of abrasive grains for a specific area determines the structure of the product. Induced porosity is obtained by adding a material that will burn off in the firing process to produce a very open structure.

DENSITY RANGES:
1 to 3 4 to 5 6 to 9 10 to 12
Closed normal range for points and wheels open
TREATMENTS_________________

When a bonded abrasive is treated, its pores are generally filled with a substance that will assist in its working capabilities. Treatments reduce loading, aid in cutting, improve wheel life, and lubricate cutting action. Sulfur, resin and wax are the primary treatments used.
Sulfur treating is used to improve cutting action and enable a cooler operation. Sulfur treated abrasives should be used with a flood coolant.
Resin treating hardens the abrasive product and adds lubrication to assist in cutting.
Wax treating is popular when grinding brass or aluminum, for it greatly reduces loading and it lubricates the cutting action.

OTHER CONSIDERATIONS FOR GOOD WHEEL OPERATION_______

Wheel speed is very important to obtain the desired use. An operator should not exceed the speed standards given by the American National Standards Institute’s current safety requirement of maximum speeds, some of which are shown in this catalog. However, it is important to match the abrasive formula to your operational speeds. Specifications will perform differently at different speeds. You should occasionally speed test and torque test your grinder to ensure it is operating at desired levels. There are many factors that can adversely affect your grinder’s capabilities.
Run out of the grinder is a problem that must be constantly monitored. Worn chucks and lack of properly maintained grinders can result in spindle failure, wheel breakage and an unsafe condition for the operator.
Dressing your wheel or point is important to maintain the integrity of your wheel shape, cutting quality, and to minimize loading problems.

TROUBLE SHOOTING_________________

TYPICAL PROBLEMS
PROBLEM
Wheels that load
POSSIBLE CAUSE
Hard wheel or too fine grit
Insufficient pressure (be careful of too much pressure)
Excessive RPM

PROBLEM
Burning workpieces
POSSIBLE CAUSE
Wheel too hard or fine grit
Insufficient grinding pressure
Improper bond

PROBLEM
Chatter Marks
POSSIBLE CAUSE
Hard Wheel
Overhang too much
Wheel needs truing or dressing
Collet on grinder is worn

PROBLEM
Scratch marks on workpiece
POSSIBLE CAUSE
Need finer grit

PROBLEM
Insufficient stock removal
POSSIBLE CAUSE
Wheel too soft
Improper grain type
Short wheel life
Wrong specification (many factors involved)
Out of balance situtation with grinder

CONVERSION TABLE -WHEEL SPEEDS_________________

REVOLUTIONS PER MINUTE FOR VARIOUS DIAMETER OF GRINDING WHEELS TO GIVE PERIPHERAL SPEED IN FEET PER MINUTE AS INDICATED
SURFACE SPEED IN FEET PER MINUTE
Diameter of Wheel in Inches   Diameter of Wheel in Inches
4,0004,5005,0005,5006,0006,5007,0007,5008,0008,5009,0009,50010,000”12,00012,50014,20016,00016,50017,000
REVOLUTIONS PER MINUTE REVOLUTIONS PER MINUTE REVOLUTIONS PER MINUTE REVOLUTIONS PER MINUTE
115,27917,18919,09921,00822,91824,82826,73728,64730,55832,46734,37736,28738,19745,83747,74654,24061,11563,02564,9351
1-1/210,18611,45912,73214,00615,27916,55217,82519,09920,37221,64522,91824,19225,46530,55831,83136,16040,74442,01743,2901-1/2
27,6398,5949,54910,50411,45912,41413,36914,32415,27916,23417,18918,14419,09922,91823,87327,12030,55831,51332,4682
2-1/26,1126,8757,6398,4039,1679,93110,69511,45912,22312,98713,75114,51515,27918,33519,09921,69624,44625,21025,9742-1/2
35,0935,7306,3667,0037,6398,2768,9139,54910,18610,82311,45912,09612,73215,27915,91518,08020,37221,00821,6453
3-1/24,3654,9115,4576,0026,5487,0947,6398,1858,7319,2769,82210,36810,91313,09613,64215,49717,46218,00718,5533-1/2
43,8204,2974,7755,2525,7306,2076,6857,1627,6408,1178,5949,0729,54911,45911,97313,56015,27915,75616,2344
53,0563,4383,8204,2024,5844,9665,3485,7306,1126,4946,8757,2577,6399,1679,54910,84812,22312,60512,9875
62,5462,8653,1833,5013,8204,1384,4654,7755,0935,4115,7306,0486,3667,6397,9589,04010,18610,50410,8236
72,1832,4562,7283,0013,2743,5473,8204,0934,3654,6384,9115,1845,4576,5486,8217,7498,7319,0049,2767
81,9102,1492,3872,6262,8653,1043,3423,5813,8204,0584,2974,5364,7755,7305,9686,7807,6397,8788,1178
91,6991,9102,1222,3342,5462,7592,9713,1833,3953,6083,8204,0324,2445,0935,3056,0276,7917,0037,2159
101,5281,7191,9102,1012,2922,4832,6742,8653,0563,2473,4383,6293,8204,5844,7755,4246,1126,3036,49410
121,2731,4321.5921,7511,9102,0692,2282,3872,5462,7062,8653,0243,1803,8203,9794,5205,0935,2525,41112

 STANDARD MARKING CHART_________________

Sequence 1 2 3 4 5 6 7
Mfg Prefix Abrasive Type Grit Size Grade Structure Bond Type Mfgrs Records
27 A 60 M 8 V 11
Abrasive
Grain		 a=A/O
C=S/C		 GRIT HARDNESS DENSITY V=Vitrified
B=Resinoid		 Specific
Bond
RETURN

rev. 12/12/03
© 2003