GRINDING WHEELBASIC TRAINING

n Pacific Grinding WheelCompany

GRINDING WHEEL FUNCTION

n To remove material from a work piece in anabrasive action

n Each grain acts as a cutting tooln It is a chip formation processn The only self sharpening cutting tooln Consider as abrasive machining

GRINDING WHEELCOMPONENTS

n Abrasive Type A60-M5-V

n Abrasive size A60-M5-V

n Grade/Hardness A60-M5-V

n Structure A60-M5-V

n Bond A60-M5-V

STANDARD MARKING SYSTEM

n Industry StandardPrefix Abrasive Grain Size Grade Structure Bond Type Suffix

W A 46 K 5 V 17

ABCDEFGHIJKLMNOPQRSTUVWXYZ

V-Vitrified

B - Resin

R - Rubber

E – Shellac

P - Epoxy

4 105 116 127 138 149 15A - Aluminum Oxide

C - Silicon Carbide

Z - Zirconia

Manufacturesabrasive code

Coarse8101214162024

Medium30364660

Fine80100120150180

VeryFine220240280320400500600

Manufacturesbond code

ABRASIVE GRAIN TYPES

n Abrasive Typesn Aluminum Oxiden Silicon Carbiden Cubic Boron Nitride (CBN)n Synthetic Diamond

ABRASIVE GRAIN PROPERTIES

n Friability - Ability to fracture under pressureso that as the cutting edges become dull, thegrain breaks off and exposes sharp newcutting edges.

ABRASIVE GRAIN PROPERTIES

n Hardness - Ability to scratch or penetrate thework piece.

n Size - Sizing is accomplished by the size of thescreen through which the grain will pass.

ABRASIVE MANUFACTURING

n Manufacture Processn Bauxite + Coke + Iron Boringsn Cylindrical furnace 7’ dia x 6’ highn Heated by electrodes to 3,700degress for 16 to

36 hoursn Poured into moldsn Cooled, broken, crushed to size

ABRASIVE GRAIN TYPESAluminum Oxide - Types

n Regularn Brown in colorn Strongest and toughestn Used in severe operations and on soft steels

n Semifraiblen Light brown or blue/gray in colorn Cooler cutting than regular brown aluminum

oxiden Used on harder material

n Friablen White (pink,ruby & gray) in colorn Fractures very easilyn Used on hard steels and alloy steels

ABRASIVE GRAIN TYPESSilicon Carbide - Types

n Regularn Black colorn Used on iron base materials, marble, ceramics,

aluminum, brass and copper.

n Greenn More friable than blackn Suited for carbide and other very hard materials

n Review Pacific Specifics Handbookn Abrasive and Bond designations

ABRASIVE GRAIN TYPESZirconia and Ceramic - Types

n Friablen Faster removaln Free cutting actionn Less pressure needed

n Toughn Longer lifen Form Holdingn More pressure needed

n Ceramic Abrasive (3M Cubitron)n Longer Lifen Aggressive removal ratesn Cooler cuttingn Good form holdingn Best on hard materials over 50 RC

BONDS

n Definitionn Material used as the “GLUE” to hold the

abrasive grains together. Bond has no cuttingaction.

GRADE/HARDNESS

n Definitionn The strength with which the bond holds the

abrasive grain together

n Indicated by a lettern A (Softest) -------------------------- Z (Hardest)

ABCDEFGHIJKLMNOPQRSTUVWXYZ

Grade/Hardness

n Softer Grade Wheeln Faster cuttingn Less chattern Lower amps/powern Lower wheel lifen Worse finishn Less form holding

n Harder Grade Wheeln Slower cuttingn More chattern Higher amps/powern Longer wheel lifen Better finishn Greater form holding

STRUCTURE

n Definitionn Indicates the density of the wheel (or) the

spacing of grain and bond

n Indicated by a numbern 4-6 (Dense)n 7-9 (Open)n 10 + (Induced Porosity)

BONDSTypes

n Vitrifiedn Designated by the letter “V”n Glass or Porcelainn Normal operating speed is 6,500 sfpmn Breaks down due to pressuren Very rigid, stiff

n Resinn Designated by the letter “B”n Can operate at higher speeds (9,500-16,000

sfpm)n Suited for cut-off wheels, foundry wheels and

roll grindingn Breaks down due to heat and pressuren Resilient, Forgiving

n Shellacn Designated by the letter “E”n Very cool cuttingn Used for roll grindingn Resilient, very forgiving

PACIFIC BONDSMOST POPULAR BOND SYSTEMS

n Vitrifiedn VB

n General purpose

n VR / VR1n General purposen Use with ceramic mixtures

n VAn Salmon colored

n VS6n Softest acting

n VSn General purpose / Silicon Carbide

n VCCFn Creep Feed / open structure

n VCPn Tamped / controlled porosity

PACIFIC BONDSMOST POPULAR BOND SYSTEMS

n Resinn BB2

n General purpose

n BGn Cut off / surface grinding

n BH4n High strength

n BRGn Resin / Rubber modified

n D29 / BVN4n Foundry products

n Epoxyn PAC

n Poured epoxy

SPECIFICATION SELECTION

n Factors When Selecting A Grinding Wheeln Material to be ground - type and hardnessn Stock to be removedn Workpiece geometry and surface finish requiredn Grinding machine - type, horsepower and

conditionn Wheel speeds and feedsn Grinding contact arean Grinding fluid - wet or dryn Severity of operationn Dressing method

n Grinding Engineering Form – Fax to PGWn Get the details. You can not improve grinding

performance with out understanding all theparameters.

SPECIFICATION SELECTION -FACTORS

n Type of Materialn Steels (Aluminum Oxide)n Low tensile strength materials and non metallic

materials (Silicon Carbide)

n Hardness of Material

n Hard materialsn Finer grit sizesn Friable abrasivesn Softer grade wheelsn Sharper Abrasives

n Soft materialsn Coarse grit sizesn General purpose abrasivesn Harder grade wheels

SPECIFICATION SELECTION -FACTORS

n Stock to be removed

n Light stock removaln Friable grainsn Finer grit sizesn Softer grade wheels

n Heavy stock removaln Tougher grainsn Coarser grit sizesn Harder grade wheels

n Workpiece geometry

n Flat/Uninterrupted surface (no form)n Finer grit sizesn Softer grade wheelsn Open Structures

n Form/Interrupted surfacen Coarser grit sizesn Harder grade wheelsn Tighter structures

SPECIFICATION SELECTION -FACTORS

n Surface Finish

n Better finishn Finer grit sizesn Harder grade wheelsn Less friable abrasives

n Worse finishn Coarser grit sizesn Softer grade wheelsn More friable abrasives

n Machine Horsepower

n Higher horsepowern Harder grade wheelsn Tougher abrasives

n Lower horsepowern Softer grade wheelsn Friable abrasives

SPECIFICATION SELECTION -FACTORS

n Wheel Speed

n Faster wheel surface feet per minuten Softer grade wheels

n Slower wheel surface feet per minuten Harder grade wheels

n Grinding Contact Area

n Large contact arean Softer grade wheelsn Coarser grit sizen Friable abrasives

n Small contact arean Harder grade wheelsn Finer grit sizen Tougher abrasives

SPECIFICATION SELECTION -FACTORS

n Wet or Dry Applications

n Wetn Harder grade wheelsn Tougher abrasivesn Open structures

n Dryn Softer grade wheelsn Friable abrasivesn Tighter structures

SPECIFICATION SELECTION

n Abrasive Grain Selectionn 50A

n Light feed rights (.001” or less)n Used on heat sensitive materialsn Most friable abrasiven Coolest cuttingn White in color

n 53An Heavy feed rates (.005” or more)n Better for form holdingn Good for rough grindingn Ruby color

n 54An Mixture of 53A (ruby) and 50A (white)n Medium feed rates (.002 “ - .003”)n Good multi-purpose abrasiven Most versatile

SPECIFICATION SELECTION

n Abrasive Grain Selectionn 49A

n Light to medium feed rates (.001’ - .003”)n Good general purpose abrasiven Cool cuttingn Similar to 54A in applicationn Pink in color

n 56A 81An medium to heavy feed rates (.001” - .006”)n Good multi-purpose abrasiven Very versatilen Light pink and cream in colorn Replaces 32A

n 42An Mixture of 50A and An General purpose grain mixturen For both soft and medium hard steelsn Brown/white or blue/white in color

SPECIFICATION SELECTION

n Abrasive Grain Selectionn 75C / C

n Used on non-metallic materialsn Iron, plastic, glass etc…n Used in fine grit sizes for finish grindingn Black in color

n 80Cn For sharpening carbide toolsn Used on some difficult to grind alloysn Used in very fine grit sizes for finish

grindingn Green in color

n Silicon Carbide abrasives are goodthermal conductors of heat.

20 30 40 50 60 70

SPECIFICATION SELECTIONSPECIFICATION SELECTION

n Abrasive selection depends on workpiece andhardness

n Above 40 Rc, there are several candidate abrasives.Mixed regular and friable aluminum oxide andfriable aluminum oxide are popular up to 58 Rc.Above 58 Rc, friable aluminum oxides are popular.

Rockwell Hardness

Regular Aluminum Oxide

Mixture of Regular Aluminum Oxideand Friable Aluminum Oxide

Dominant - Regular

Friable Aluminum OxideWhite - Pink - Ruby

Ceramic and Aluminum Oxidemixtures

12 14 16 20 24 30 36 46 54 60 70 80 90 100 120 150

Coarse Medium Fine

FoundrySnagging

Vertical SpindleSurface Grinding

Horizontal SpindleSurface Grinder

Form Grinding

Portable Grinding Tool & Cutter Grinding

Dry Cutoff Thread Grinding

Centerless & Cylindrical

Wet Cutoff

Bench Grinding

Hot Mill Roll Grinding Cold Mill Roll Grinding

SPECIFICATION SELECTION

n Grit Size Selection

SPECIFICATION SELECTION

n Grit Size Selectionn Use Coarse Grit

n Rapid stock removaln Large areas of contactn When finish is not importantn Soft, ductile materials

n Use Fine Gritn When form holding is neededn Small areas of contactn Fine finishesn Hard, brittle materialsn Hold radius

Grit Size 46 54 60 80 100 120 150 220

Finish (RMS) Over 32 20 - 32 15 - 20 12 - 18 10 - 15 8 - 12 6 - 10 5 - 6

Radius Over .020 .017 - .020 .016 - .020 .010 - .020 .008 - .010 .005 - .008 .004 - .006 .003 - .005

SPECIFICATION SELECTION

n Wheel Grade Selection - Hardness

D E F G H I J K L M N O P Q R S T U V W X Y Z

Segments Cylindrical

Honing Sticks

Dressing Sticks

Surface Grinding

Bench Grinding

Cutter Grinding Thread Grinding

Crank and Cam Grinding

Internal Grinding

FoundrySnagging

Saw Gumming

Centerless Grinding

SPECIFICATION SELECTION

n Structure Selection - Vitrified Bonds

n Closed structuren Form holdingn Tool and Cutter sharpeningn Numbers form 4 - 6

n Open Structuren Surface grindingn Cylindrical grindingn Most popularn Numbers from 7 - 9

n Induced Porosityn Surface grindingn Blanchard grinding (Segments/Cylinders)n Heat sensitive partsn Numbers from 10 and up

STANDARD WHEEL SHAPES

STANDARD WHEEL SHAPES

SPECIAL WHEEL FACES

WHEEL CARE & SAFETY

n Grinding Wheel Caren Inspection

n Visually inspect for chips, cracks or damage to wheeln Vitrified Only

n Ring test with wooden or plastic handle

n Wheel Handling Rulesn Handle wheels carefully to prevent dropping or bumpingn Do not roll wheel on its edgen Use trucks or suitable conveyors which support heavy

wheelsn Stack wheels carefully on trucks to prevent damage in

transitn Do not pile any materials or tools on top of a grinding

wheel

WHEEL CARE & SAFETY

n Grinding Wheel Caren Wheel Storage

n Do not subject wheels to :n Humidity , water or other liquidsn Freezing temperaturesn Sudden temperature change

n Wheels should be stored in proper racks, bins or drawers

WHEEL CARE & SAFETY

n Grinding Wheel Safetyn Check MOS against machine speedn Never force a grinding wheel onto a machine spindlen Do not use flanges that are not flat and cleann Wear safety glassesn Always use a wheel guard that cover at least 1/2 of

wheeln Always stand to one side when starting the wheeln Allow a newly mounted wheel to run one minute

before usingn Never grind on the side of the wheeln Always shut off the coolant before stopping the

grindern Never force the wheel by suddenly jamming work into

itn Grind only materials for which the wheel is designed