dos and dont of safe grinding on site and what things to consider

Dos and

Don’ts for

Safe

Gr inding and

WHAT

SAFETY

SHOULD BE

SAYING TO

YOU!

Grinding wheels are

safe tools when they are used in accordance with some basic rules. http://www.wsps.ca/WSPS/media/Site/Resources/Downloads/AbrasiveGrindingWheels_Final.pdf?ext=.pdf However if they are used incorrectly or not installed carefully onto the machine, there is the possibility that the grinding wheel may fracture. How should I handle and store the wheels?

■ All abrasives wheels are fragile. They should be handled with care.■ Wheel should be stored on a flat, rigid surface, avoiding damp and frost or wide variation in temperature.■ Use the oldest wheels (on “first in, first out” basis).How should I fit the wheel on the machine?

http://www.wsps.ca/WSPS/media/Site/Resources/Downloads/AbrasiveGrindingWheels_Final.pdf?ext=.pdf

http://www.wsps.ca/WSPS/media/Site/Resources/Downloads/AbrasiveGrindingWheels_Final.pdf?ext=.pdf

■ Follow carefully the instructions given in the machine handbook. ■ Never fit a wheel which is loose or too tight on the flange. ■ Align the outer flange correctly as shown in the YOUR COMPANY SHOULD AND DOES SUPPLY Safety leaflet for cutting and grinding wheels for angle grinders ■ Tighten only with the tool supplied with the machine.■ Ensure the wheel is properly gripped to prevent slippage, but do not tighten with excessive force. Never use a hammer. ■ Keep flanges and screw threads clean and free of burrs and rust.■ Replace distorted or damaged flanges before fitting the wheel.■ Run all wheels after fitting for at least 30 seconds at operating speed keeping behind the guard in case the wheel breaks.YOUR COMPANY SHOULD AND DOES recommend the use of following personal protective equipment (often written PPE) :

■ Eye protection ■ Ear protection (ear sets)■ Hand protection (gloves)■ Lung protection (dust mask, also called respirator)

■ Never remove the protective machine guard and make sure it is properly adjusted to deflect debris away from you.■ Ensure that no other person is at risk, especially near the machine while working.How should I handle the wheel after use?

■ Before storing the machine or transporting it to another location, always remove the wheel and store it as recommended. ■ Always carefully examine the wheel for damage or defects, and destroy and discard if damaged. ■ Do not fit worn out wheels on a smaller machine. Destroy them.■ If the wheel does not bear a legible expiry date, or has exceeded this date, dispose it as recommended below.■ When disposing of worn out or defective wheels, it is recommended to damage them to prevent someone from removing them from waste and re-using them.

Be sure to observe the “Dos” and “Don’ts” for safe work.The following basic rules are based on the Ordinance on Industrial Safety and Health and on Structural Standard for grinders and Related Equipment.

Dos

1Handle and store wheels in a careful manner. Observe the 3 basic rules of “no rolling, no dropping, and no contact with other objects”.Store wheels on a shelf or storage rack in a dry place.

2 If the grinding wheel is marked with a service limit, be sure to use it only within the service limit period.

3 Before mounting a wheel onto a machine, perform a visual inspection and ring test (hammering test) to check for cracks, chips, and other problems.

4 Check that the maximum operating speed, dimensions, and other specifications of the grinding wheel are correct for the machine where it will be used.

5 Check that the outer diameters and contact widths of the mounting flanges are equal and correct on the left and right sides.

6Use the blotters that are supplied with the wheels. The blotters should be larger than the flange diameter and must not be stained or torn.

7 Balance the wheel with balancing weights.

8Be sure that the work rest is properly adjusted. The wheel should be no more than 3 mm away from the work rest and 3 – 10 mm away from the adjustment piece.

9 The standard length of the wheel spindle after mounting should be 13 mm.

10

Use a grinding wheel cover which covers at least one half of the grinding wheel at all times.

11

Perform test operation for at least 1 minute before the first grinding of the day, and for at least 3 minutes before using a newly mounted wheel.For a portable grinder, be sure to perform the test operation in a safe place.

12

Wear safety goggles, dust-proof mask, and other necessary protective gear during operation.

13

In order to avoid disrupting the balance, completely shut off the coolant before stopping the wheel rotation.

14 Use shield plates or other means to protect operators from sparks.

15

In order to prevent respiratory illnesses, be sure to ensure dust control and sufficient ventilation.

Don’ts

1 Do not use a grinding wheel that was dropped or subjected to other impact, or a grinding wheel where any abnormality was found during inspection.

2 If the hole diameter of the grinding wheel does not match the machine, do not force the wheel onto the machine or alter its hole diameter.

3 Do not exceed the maximum operating speed that is marked on the wheel.

4Do not use mounting flanges if the surfaces which contact the grinding wheel are deformed, scratched, dirty, or corroded.Do not use flanges that do not have roll-offs. If the wheel is attached by nuts, do not use flanges (base plates) that have roll-offs.

5 When mounting onto the flanges, do not over-tighten the nuts.

6 Do not use the side of the wheel unless the wheel is specifically designed for that purpose.

7 Do not start the machine before the grinding wheel cover is installed.

8 Do not use excessive force to press the workpiece against the grinding wheel, or the grinding wheel against the workpiece.

9 Do not directly touch a rotating grinding wheel with any part of your body.

10

During test operation, do not stand in front of the grinding wheel direction of rotation.

11

When working with a portable grinder, do not place the grinder onto a table, floor, workpiece, or other surface before the grinding wheel has fully stopped.

12

Do not perform grinding in a location where there is the risk of ignition or explosion.

13 Do not enter the area where sparks are produced.

14

Do not change grinding wheels or perform test operation unless you have completed all necessary education and training.

Common gr inding faults

Problem Possible Causes Suggested Correction

Chatter vibration

Regularly spaced marks Vibration Rebalance motor and wheel.

Wide, regularly spaced marks

Vibration from belt Repalce belt.

Pulley loose or out of balance

Eliminate looseness.Balance pulley.

Long, regularly spaced marks

Wheel out of balance Wheel face out of round.

Wheel face out of round

True wheel before balancing.

Short, close, evenly spaced marks

Spindle bearings loose

Adjust spindle bearings.Warm up gringing machine to reach appropriate temperature.Check thrust bearing.

Slightly longer and more widely spaced marks

Wheel spindle run-out or outof round

Replace wheel spindle.

Long, widely spaced marks

Drive gear backlash

Replace gears.Introduce V belt drive.Check lubricated condition.

Regular or irregular marks

Faulty thrust bearing Replace thrust bearing.

Narrow, regularly spaced marks

Spindle pulley loose Tighten spindle pulley.

Longish, widely spaced discoloredmarks, distributed evenly

Glazed or loaded wheel

Use coarser grit, softer grade or more open structure wheel.

Chatter marks Incorrect wheel dressing

Redress wheel face with sharp diamond dresser.Mount diamond dresser rigidly in holder.

Irregular marks

Center holes out of round or notin lineSteady rests improperly adjusted

Check work center holes for roundness ad alignment.Check workpiece for fit to centers.Check lubricated condition between work center holes and centers.Adjust steady rests.

Marks synchronized with floorvibration

Vibration from floor

For large machines, build additional foundation separated from floor.For normal machines, try adjusting anchor bolts.Try changing machine location.Mount machine on some vibration insulating material.

Mottle marks Glazed wheelBalance and redress wheel.Remove grease or oil spots from wheel face.

Deep, narrow regular marks

Wheel too coarse Use finer grit wheel.

Problem Possible Suggested Correction

Causes

ScratchingFeed marks

Deep isolated scratches

Shedding Use harder acting wheels.Use more friable abrasive grains.

Incorrect dressing

Redress wheel face with sharp diamond dresser.After dressing, clean wheel surface with stiff-bristled brush.

Contamination by coarse grits or foreign matters

Dress or replace wheel.

Flanges looseInsert blotters between wheel surface and flanges and tightenscrews evenly.

Organic wheel deteriorated

Do not use solution-type coolant.Prevent rise in coolant temperature with cooling system during summer.Limit maximum pH (alkalinity) to 9.

Irregular scratches

Dirty coolantClean and check coolant circulating system, in particular, filter, tank, and inside guard.

Dust or othe particles

Check dust collector for proper functioning and improve workenviornment.

Draughtsboard pattern

Faulty grinding operation

Do not excessively force wheel onto workpiece.Make wheel act softer.Supply large and equal volume of coolant to grinding point.

Grain marks

Wheel too softWheel too coarse

Use finer grit or harder grade wheel.

Incorrect wheel dressing

Dress wheel with lighter cuts and slow diamond traverse rate.

Fine spirals Incorrect wheel dressing

Replace diamond dresser.Reduce traverse feed at even rate and take lighter dressing cuts.Mount diamond dresser rigidly at angle of 15 degrees againstwheel rotaion.

Make final dressing in opposite direction to initial runs.Round off wheel edges.


Prevent wheel edge from digging in workpiece.Grind workpiece under light load which provides low grinding force, and use additional steady rests so that it cannot be inclined bygrinding force.Reduce table speed or change some speed per pass.

Spiral feed marks

Contact with wheel edge Round off wheel edges.

Wrong grit size

Use finer grit for rough finishing and relatively-coarse grit for finishing.Reduce wheel infeed rate and traverse rate gradually to allow wheelto completely spark out.


Take lighter dressing cuts and reduce diamond traverse rate.

Head and tailstock out of alignment

Check head and tailstock, and tableways.


LoadingGlazingShedding Large wheel wear

Grinding marks on workpieceWorkpiece taperedShedding

Wheel too soft

Reduce wrok speed, wheel traverse rate and wheel infeed rate.Increase wheel speed, wheel diameter, and wheel thickness.Take lighter dressing cuts and reduce diamond traverse rate.

Poor cutting abilityWheel glazingWheel loadingBurned workChatter marks

Wheel too hard Increase work speed, wheel traverse rate and wheel infeed rate.Reduce wheel speed, wheel diameter, and wheel thickness.Redress wheel face frequently with sharp diamond dresser.

Use coarse grit, or softer grade wheel.

Loading

Wheel specification unsitable

Use coarser grit, softer grade, or more open structure wheel.


Use sharp diamond dresser.Increase diamond traverse rate and then clean wheel surface.

Poor coolant quality

Change coolant or use high detergent type.


Grind under conditions which provide softer wheel acts.

Glazing

Wheel specification unsuitable

Use coarser grit, softer grade, or more open structure wheel.Use more friable abrasive grains.


Use sharp diamond dresser.Increase diamond traverse rate.Take heavier dressing cuts.

Poor quality/quantity coolant

Increase lubricity of coolant.In addition to improving coolant supply method, supplylarge and equal volume of coolant to grinding point.


Grind under conditions which provide softer wheel acts.


Burn, crack, and workpieceinaccuracy

Burnt and cracked work

Wheel specificationunsitable

Use softer grade, or more open structure wheel.Dress more frequently.

Poor coolant quality,quantity and distribution

Increase lubricity of coolant.(Oil or water-soluble coolant is better for use.)Supply large and equal volume of coolant to grinding point.Improve coolant supply method and direct coolant effectivelyat grinding points. (Ex. Installtion of high-pressure coolant system.)


Reduce wheel infeed rate and increase wheel traverse rate.

Inadequate heat treatmentof workpiece

Increase tempering temperature and remove anyremaining unstable structure from workpiece.

Out-of-round work

Incorrect work centersWork not high eoungh abovecenter(centerless grinding)

Drill work center holes correctly.Regrind and lap work center holes.Lubricate centers and work center holes sufficiently.Readjust work blade. (Centerless grinding)

Poor wheel dressing

Adjust dressing tool so that the circumference ofthe wheel touches the circumference of the work

Work out of balance Rebalance workpiece.


Do not allow wheel to separate from work edge.Reduce wheel infeed rate.Reduce wheel speed and wheel diameter.


Use softer grade wheel.

Out of cylindricity Wheel specification unsuitable

For plunge grinding, ensure that wheel width is larger than work width.Use harder grade wheel.


Adjust dressing tool so that the circumference ofthe wheel touches the circumference of the work


Check steady rest position.Feed table more smoothly.Do not allow wheel to separate from work on both edges.

Work thermally-expanded

Supply plant of coolant.Re-examine coolant supply method.(Ex. Installation of high-pressure coolant system.)Reduce wheel infeed rate and increase wheel traverse rate.

Workpiece not flat orparallel (thin workpiece)


Insert suitably-thick metal lat between magneticchucks and workpiece to reduce magnetic force of chuck.


Use softer grade, or coarser grit wheel.Dress more frequently.

Poor coolant quality,quantity, and distribution

Increase lubricity of coolant.(Oil or water-soluble coolant is better for use.)Supply large and equal volume of coolant to grinding point.Improve coolant supply method and direct coolant effectively at grinding points. (Ex. Installation of high-pressure coolant system.)

L isted by Gr inding Operat ionCylindrical grinding

Problem Possible Cause Suggested Correction

Chatter vibration Chatter marks Incorrect wheel

dressing

Redress wheel face with sharp diamond dresser.Mount diamond dresser rigidly in holder.

Short, close,evenly spaced marks

Spindle bearings loose

Reduce wheel speed.Re-adjust and tight spindle bearings.Give sufficient time for spindle bearings to warm up.(Warm up grinding machine to stablize bearing temperature.)Tighten thrust bearing.

Slightly longer and morewidely spaced marks

Wheel spindle run-out or out ofround

Replace spindle if it is twisted or warped, or out of round.

Regularly spaced marks

Vibration Rebalance wheel.Rebalance motor and wheel spindle.

Check fit between flanges and wheel spindle.

Short, regularly spacedmarks

Spindle pulley loose Tighten spindle pulley.

Wide, regularly spacedmarks

Vibration from flat beltFlat belts to have a uniform thickness and width.All sections to have same pliability.

Pulley loose or out of balance

Rebush or lap to suite spindle.Balance carefully.

Regular, widely spaceddisclosed chatter marks


Use coarser grit, softer grade, or more open structure wheel.(More likely to be caused by glazed or loaded wheel.)

Long, regularly spacedmarks

Wheel out of balanceTrue wheel before rebalancing.Rotate wheel to spin out excess coolant.

Wheel face out of round

True wheel before and after balancing.True wheel perimeter and sides.

Long, widely spacedchatter marks

Drive gear backlashReplace old and worn-out gear.Introduce V-belt drive.Check lubricated condition.

Regular or irregularmarks

Faulty thrust bearing Replace thrust bearing.

Even and regularly oriregularly space marks

Belt joint (belt lacing) Use endless belt.

Irregular chatter marks Center holes out of

round or notin line

Check workpiece for fit to centers.Lubricated centers and work center holes.

Rests improperly Adjust rests to fit to

adjusted workpiece.


Scratching Deep, narrow, regularscratches

Wheel specification unsuitable Use finer grit wheel.

Wide, irregular scratches

Wheel specification unsuitable Use harder grade wheel.

Mottle marks Faulty wheel face Balance and redress wheel. (Wheel glazing)

Irregular marks

Belt fluttering Replace belt.

Dust settling on machine

Keep air and shop clean.

Install dust collectors.

Deep isolated scratches


Dress wheel face with sharp diamond dresser.

After dressing, flush wheel face with coolant to clean.

Chemical action of cutting fluid

If too strong alkaline coolant was used for organic bond, reduce soda content,or change coolant.

Deep irregular scratches Flanges loose Re-tighten flanges.

Irregular marks of variouslengths

Dirty coolantProvide efficient filter.

Clean out tank more frequently.

Grain marks Wheel specification unsuitable

Use finer grit or harder grade wheel.


Dress wheel with ligher cuts and slow diamond traverse rate.

Incorrect grinding conditions

Commence grinding using high work speed and wheel traverse rate to removeprevious wheel maks, finish with high work speed and slow traverse, and allow

wheel to completely spark out.

Spirals

Fine spirals


Replace diamond dresser.

Dress wheel with lighter cuts and slow diamond traverse rate.

Mount diamond dresser rigidly in holder.

Make final dressing in opposite direction of initial runs.

Set diamond dresser downwards at angle of 15 degrees against wheel rotation.

Round off both wheel edges.


Avoid having only one of wheel edges in contact.

Reduce wheel infeed rate.

Reduce wheel traverse rate per revolution of workpiece.

Arrange additional steady rests.

Uneven traverse lines

Table traverse mechanism worn

Eliminate looseness.

Replace all worn parts.

Spiral pattern onworkpiece whose leadcorresponds to traverse

Run-out Check centers for run-out.


Mount diamond dresser tool to ensure that the point of diamond contact is that ofwheel contact on the workpiece.

Set diamond dersser download at angle of 15 degrees against wheel rotaion.

Round off both edges of

wheel.


Improper wheel grade

Poor cutting ability Wheel glazingWheel loadingBurned workChattering marks

Grade too hard

Increase work speed and wheel traverse rate.

Increase wheel infeed rate.

Reduce wheel speed, outside diameter, and thickness.

Redress wheel face with sharp diamond dresser.

Use softer grade and / or coarser grit wheel.

Grindig marks on workpieceLarge wheel wearWorkpiece tapered

Grade too soft

Reduce work speed and wheel traverse rate.

Reduce wheel infeed rate.

Increase wheel speed, outside diameter, and thickness.

Take lighter dressing cuts and reduce diamond traverse rate.

Do not allow wheel to separate from workpiece when table reciprocates.

Wheel loading

Metal rigidly fixed on theabrasive particles or lodgedin wheel pores


Use coarser grit and/or more open structure wheel.

Use more friable abrasives.



Increase diamond traverse rate.

After dressing, flush wheel face with coolant to clean.

Poor coolant quality/quantity

Supply plenty of cleaner coolant.


Reduce work speed and wheel traverse rate.

Increase wheel speed, outsdie diameter, and thickness.

Supply plenty of coolant.

Wheel glazing Shiny appearance


Use softer grade and/or coarser grit wheel. Use more friable abrasives.



Increase diamond traverse rate.

Take heavier dressing cuts.

Incorrect quality coolant

Reduce oil level - increase amount of coolant.


Increase work speed and wheel traverse rate.

Reduce wheel speed, outside diameter, and thickness.

Increase wheel infeed rate.

Workpieceinaccuracy

Out-of-round work

Uneven pressure on driving dog

Provide cushion between drive pin and driving dog.

See Causes and Suggested Correction for out-of-round work listed in Common Grinding Faults.

Out of cylindricity

Faulty machine or setting

Repair or replace worn parts.

Adjust both head and tailstock.

See Causes and Suggested Correction for out of cylindricity listed in Common Grinding Faults.

Burn Discolored workpiece


Adjust drive to avoid belt slippage.

See Causes and Suggested Correction for burnt and cracked work listed in Common Grinding Faults.

Centerless grinding


Chatter vibration Chatter marks


Use coarser grit or softer grade wheel.

Balance wheel.


Reduce wheel infeed rate or workpiece through feed.

Incorrect wheel dressing Increase diamond traverse rate.


Adjust spindle bearings, drives and other parts to eliminate looseness.

Lower wrok blade in relation to centerlines of two wheels.

Reduce blade grade. (An angle of approximately 30 degrees is good for general runof work.)

Scratching Feed marks

General lines/scratches


Grind work blade to eliminate dirt (chips and abrasives) and wear from it.

Wheel specification unsuitable Use harder grade wheel.

Dirty coolant Use clean coolant with greater lubricity.

Spirals with irregularbrightness


Remove dirt or oil from work blade.

Incorrect wheel dressing Dress regulating wheel at the same angle as dressing grinding wheel(in order to prevent bent caused by uneven grinding

force).

Dress wheel to ensure that it has slight gradient upward to exit side.

Spirals


Dress wheel so it stops grinding 1/2 from exit edge.

Round off both edges of wheel.

Guides improperly adjusted

Set guides parallel to wheel face by using lining bar of approximately equal diameterto workpiece.

Workpieceinaccuracy

Out-of-round work


Use softer grade wheel.

Balance and rederss wheel.

Redress regulating wheel as well.


Make first cut light at high traverse rate to attain maximum straight effect.Then use heavier cuts and finish with a light cut.

Poor quality/quantity coolant

Supply plenty of clean coolant.

Incorrect workpiece center height

Isodiametric shape (triangular or pentagon): Raise work center in relation towheel centerlines.Polygonal (flower-petal) shape: Lower work center in relation to wheel centerlines.

Out of cylindricity

Improper regulating wheel

Concave workpiece: Increase angle of regulating wheel housing.

Barrel-shape workpiece: Decrease angle of regulating wheel housing.

Guides improperly Set entrance and exit guides

adjusted parallel to wheel face.

Internal grinding


Workpieceinaccuracy

Out-of-round work

Faulty grinding operation Adjust work chuck



Out of cylindricity


Increase quill rigidity (by changing quill material for example.)If it is caused by shedding, use harder grade wheel. If wheel acts too hard, use softer gradewheel.


Increase wheel width to size larger than workpiece width so that wheel edges on both sideswill not affect grinding.Adjust wheel head angle and infeed rate.



Burn, cracks

Faulty grinding operation Increase work speed.

See Causes and Suggested Correction for burnt and cracked work listed in Common Grinding Faults.

Wheel breakageProblem Possible Causes Suggested Correction

General breakage Incorrect wheel mounting on flanges

Wheels to be good sliding fit on wheel spindle when mounted onto flanges.(If too tight to slide on, wheel will be broken within 3 minutes of starting operation.)

Radial break in 3 or more pieces

Incorrect grinding workFaulty grinding operation

Do not use wheel at speeds exceeding maximum operatingspeed marked on wheel or inspection sheet.Prevent overheating caused by excessive infeed.

Prevent overheating caused by insufficient coolant.Perform ring test on wheel before mounting wheel onto flanges.

Incorrect wheel mounting on flanges

Do not tighten wheel with uneven pressure.Flanges and wheel to be free from foreign particles in between.Be sure to use blotters.

Radial break in 2 or more pieces Faulty grinding operation

Avoid excessive force on wheel sides if wheel is allowed to grind on sides.

dos and dont of safe grinding on site and what things to consider

Leadership & Management