Abrasive Wheels Handout

Abrasive Wheel Training

© Training & Testing Services 2008

These training notes are designed to help you improve your safety awareness in the
workplace. Whilst every care has been taken in compiling these notes, the contents should

only be used as a guide.
Machine operators should always read and follow the manufacturers’ instructions before
operating any machinery and follow any instructions or procedures that are provided by the

employer.
If you require any further information or assistance after the completion of your training

course, then please do not hesitate in contacting us.

All rights reserved.

No part of this manual may be reproduced in any form or by any means without permission
in writing from Training & Testing Services.

Training & Testing Services
Beckdale, 33 Stonebeck Avenue, Harrogate, HG1 2BN

Telephone: 01423 550751
Email: [email protected]
Web: www.trainingandtestingservices.co.uk

© Training & Testing Services 2008

Introduction

As there are no binding safety requirements across the world for abrasive products, users
are naturally worried and buying safe abrasives for the many fields of use is made that much
more difficult.
In the UK the British Abrasives Federation (BAF) provides a vehicle whereby abrasive
suppliers have the opportunity to take an active role in the generation of safety rules,
regulations and standards common to all participating countries.
In Europe, CEN (European Committee Standardisation) Safety Requirements are ultimately
adopted by all EU members and become the minimum norm to which manufacturers adhere.
ISO (International Standards Organisation) Standards developed in parallel and fully
compatible with the CEN regulations reach a global audience via the various National
Standards Associations and Institutes.
BAF Members provide specialists to help create the regulations and standards with both of
the above organisations, and work closely with BSI (British Standards Institution) and the
HSE (Health & Safety Executive) at all stages.
The BAF and its Members work in close liaison with FEPA (Federation of European
Producers of Abrasives) and the Technical Commissions within the organisation, to produce
Safety Leaflets, Safety Codes and Material Safety Data Sheets
The use of these documents plays a vital role in ensuring that up-to-date information is
available to abrasive users in domestic and export markets. The FEPA Safety Codes and
Safety Leaflets form an essential element in the development of training modules.

© Training & Testing Services 2008

1. Training & Safety

1.1 Why is Training Necessary?

Accidents involving abrasive wheel machines figure prominently in accident statistics. Many
of these accidents should never occur as they are caused directly as a result of lack of
knowledge and skill
It is a fact that most accidents are caused by the lack of or inadequate training of machine
operators and their supervisors
The risk of breakage is inherent with every abrasive wheel. If the number of breakages is to
be kept low, the initial care exercised in the design, manufacture and testing by abrasive
wheel and machine makers must be coupled with the adoption of safety measures by users.
Accident statistics indicate that nearly half of all accidents involving abrasive wheels are due
to an unsafe system of work or operator error
There is a legal requirement for all abrasive wheel machine operators to be properly trained
and certificated, and for their employer to appoint in writing and deem them competent to
operate abrasive wheel machines
The training that you will receive during this course is of a very high standard and meets all
of the relevant legal requirements
Training is also an expensive investment for your company, so for your own part it is
essential that after your course the training is practiced at all times

SAFE OPERATION IS YOUR RESPONSIBILITY

© Training & Testing Services 2008

2. The Need to Train

2.1 Course Content

The subjects that will be covered during this training course are:
• The legal duties and responsibilities of the employer and employees under
the relevant sections of Health and Safety Laws
• Different types, methods of marking and the speed of abrasive wheels
• Hazards that arise from the use of abrasive wheels
• The correct use of suitable personal protective equipment (PPE)
• Methods of storing and handling & transporting
• Methods of inspection and testing for damage of abrasive wheels
• Functions of the machine components, flanges, guards, blotters etc.
• Correct methods of dressing & balancing
• How to assemble abrasive wheels correctly to make sure they are safe to
use
• The correct adjustment of a tool rest on a bench/pedestal grinder

© Training & Testing Services 2008

3. Health and Safety Laws

3.1 The Health and Safety at Work Act 1974

Employers Responsibilities:
Section 2
Provide safe equipment and put systems in place to keep it safe
To provide adequate training and refresher training
The provision of safe systems of work
Maintain a working environment that is safe

Employee’s Responsibilities:
Section 7a:
There is a duty on employees to take reasonable care of their own health and safety and the
safety of others.
Section 7b:
Employees are required to co-operate with their employers to enable him to discharge his
responsibility under safety legislation.
Section 8:
Places a duty on all persons (not just employers) too not to intentionally or recklessly
interfere with anything provided in the interest of health and safety at work.

© Training & Testing Services 2008

3.2 The Provision and Use of Work Equipment Regulations 1998
(PUWER 98)

In relation to abrasive wheels PUWER 98 requires, among other things, that all machinery is
suitable for its intended use and is properly maintained, and that employees, including those
using, mounting and managing the operation of abrasive wheels, are fully informed and
properly trained in their safe use.

The regulations listed below from PUWER 98 apply to the use of abrasive wheels:

• Regulation 4: Suitability of work equipment, page 23
• Regulation 5: Maintenance, page 23
• Regulation 6: Inspection, page 26
• Regulation 7: Specific risks, page 32
• Regulation 8: Information and instructions, page 33
• Regulation 9: Training, page 35
• Regulation 10: Conformity with community requirements, page 38
• Regulation 11: Dangerous parts of machinery, page 40
• Regulation 12: Protection against specific hazards, page 42
• Regulation 13: High or very low temperatures, page 45
• Regulation 14: Controls for starting or making a significant change in operating

conditions, page 47
• Regulation 15: Stop controls, page 48
• Regulation 16: Emergency stop controls, page 49
• Regulation 17: Controls, page 50
• Regulation 18: Control systems, page 52
• Regulation 19: Isolation from sources of energy, page 53
• Regulation 20: Stability, page 55
• Regulation 21: Lighting, page 56
• Regulation 22: Maintenance operations, page 56
• Regulation 23: Markings, page 58
• Regulation 24: Warnings, page 58

Also the Health and Safety Executives publication “Safety in the Use of Abrasive Wheels”
HSG 17 should be consulted by Management or Supervisors of abrasive wheel machine
operators.

The purpose of HSG 17 is to give advice on the precautions for the prevention of accidents
in the use of abrasive wheels, in particular injury resulting from either wheel breakage or
coming into contact with a running wheel.

© Training & Testing Services 2008

4. Abrasive Wheels

An abrasive wheel is usually defined as a wheel consisting of abrasive particles bonded
together with various substances. There are two main types of bonding agent: inorganic and
organic.
Inorganic bonds are mainly vitrified, i.e. the wheel is generally fired in a furnace to give the
bond a hard, strong but brittle structure. These wheels are used for precision grinding
applications as they hold their shape, but require dressing.
Organic bonds are not fired but are cured at low temperatures and are most suited for non-
precision applications i.e. fettling and cutting off.
4.1 Inorganic Wheel

4.2 Organic Wheel

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4.3 Types of Wheel Covered These types of wheels can be put to a broad range of
uses, from glass and woodworking with traditional
1. Vitrified wheels vitrified wheels, through to grinding super tough
materials such as high alloyed steel

In addition, vitrified bonded abrasives can be shaped
into mounted wheels and points on spindles for both
industrial use and hobbyists alike.

2. Depressed centre grinding Are reinforced wheels used mainly on portable
wheels machines. Type 27 wheels are for grinding, for
example; dressing the face of a work piece, fettling
welds etc.

3. Straight sided cutting off wheels Resinoid cutting wheels can be used in several
application areas. However, because they are less
brittle than vitrified wheels, they are best suited to
heavy duty applications such as railway track cutting,
cutting needs in the automotive industry and general
cutting of steel, cast iron, bundled rods and tubes.

4. Depressed centre cutting off Are exactly the same as the straight sided cutting disc
wheels but have a depressed centre for fitment to a particular
type of machine

© Training & Testing Services 2008

5. Marking of Abrasive Wheels

When selecting a cutting disc or grinding wheel the operator tends to only check the label to
see if it is marked stone or steel to ensure that the correct wheel or disc is selected.
Use only abrasive products that conform to the highest standards of safety.
These products will bear the relevant EN standard number and or the inscription oSa

✓ EN12413 for Bonded Abrasives
✓ EN13236 for Superabrasives
✓ EN13743 for Specific Coated Abrasives
EN12413 - Bonded Abrasives - Abrasive wheels: straight, tapered, hubbed, recessed,
relieved, depressed centre, cutting-off, semi-flexible; Cup wheels, dish and saucer wheels,
disc wheels, cylinder wheels, cemented or clamped

To comply with the requirements of EN12413 the wheels or discs should be marked with the
following information:

✓ Company or Brand Name
✓ Traceability Code Number this should be on the product itself but can be

sometimes found on the packaging
✓ Dimensions in accordance with ISO 525
✓ MOS – Maximum Operating Speed
✓ Specification Mark – in accordance with ISO 525. Minimum information required:

abrasive type, grain size, grade, bond type and use of reinforcement (see paragraph
5.1)
✓ Colour Stripe (optional) Blue: 50 ms, Yellow: 63 ms, Red: 80 ms, Green: 100 ms
✓ Restrictions to use:

© Training & Testing Services 2008

RE1, Not permitted for RE 3, Not permitted for RE 6, Not permitted RE 8, To be used

hand held machines. wet grinding for face grinding with a back-up pad

Additional Pictograms: Protect Eyes: Protect Ears:
Do not use if damaged:

Protect Hands: Protect Lungs: Read the manufacturer’s
instructions

Additional information
Abrasive products for hand-held machines with type of bond B and BF: date of expiry. The
date of expiry shall at the longest be within 3 years from the date of manufacture. It is
expressed as month and year e.g. 04/2009.

5.1 Five Main categories of the British Standards System:

1. Abrasive, means the type of abrasive material used in the wheel construction
2. Grain, means the particle size of abrasive grains. The range is expressed by a
number (very course: 4, very fine: 1200)
3. Grade, represents the tenacity with which the bonding material holds the abrasive
grain in a wheel. Wheels are graded soft – hard according to the degree of tenacity
4. Structure, means the level of porosity of the wheel, the higher the number the greater
the porosity
5. Bond, means the bonding material used in the wheel construction
Other optional categories can be used by the manufacturers if they are required

© Training & Testing Services 2008

5.2 Abrasives

The grit used is basically a self sharpening cutting tool

As the wheel/disc is used for grinding the sharp edges of the grit cut away at the material being
ground

Grit type is generally either; Aluminium Oxide (white, pink, ruby red, brown, grey, etc.) Silicon
Carbide (black or green), Ceramic (blue and pink) or any combination of these.

Aluminium oxide is by far the most popular. It is available in the following colours: White, pink,
red, ruby red, brown, and grey. Each colour has it's own grinding characteristics. Grey and
brown grit are the workhorse grits used in bench grinding and production grinding. Tough and
inexpensive they are the most 'general purpose' grit found. Can be used on low to high carbon
steels. The pink and white grits are typically used on your harder steels which need a cool,
friable cutting action to avoid burns. The ruby red grit is a special tough grit also used on tool
steels. These grits are a little bit more expensive than the grey/brown.

Silicon Carbide grits are commonly either black or green. Black silicon carbide is used to grind
non-ferrous metals such as aluminium and brass and also on plastics, rubber, and stone
products such as marble and granite. Black silicon carbide is a very sharp grit. Green silicon
carbide is an even sharper grit than black and is used primarily for carbides, titanium and
plasma sprayed materials. One interesting characteristic of silicon carbides is the effect they
have on steels. Due to the sharpness of these grits, one would think that they would be too
aggressive and not provide a good finish. In fact, on steels, silicon carbide is used as a sort of
polishing/finishing grit. It is used in tumbling processes as a surface finishing product. Also,
manufacturers will often blend a small percentage of silicon carbide in with aluminium oxide grit
in grinding wheels and honing stones to achieve a better work piece surface finish on steels.
The grit will actually dull and provide a rubbing action on steels which produces a better surface
finish.

A = Aluminium Oxide (Mainly metal)
Used for HIGH tensile strength materials such as carbon steel, alloy steel, high-speed steel,
mild steel, stainless steel (magnetic), annealed malleable iron, wrought iron, hard
bronzes, etc

Other special forms white or pink e.g.
32A for tough vanadium alloy steels,
38A for hard, heat-sensitive steels

C = Silicon Carbide (Mainly stone)
Used for LOW tensile strength such as grey iron, chilled iron, stainless steel (nonmagnetic),
brass, soft bronze, copper, aluminium, rubber, stone, marble, hard facing alloys and
cemented carbides. Chemically reacts with ferrous metals.

Other forms are available e.g.
GC, green silicon carbide used for grinding cemented carbide tools, hard and high chilled
cast irons etc

© Training & Testing Services 2008

WA = White Aluminium Oxide, This white abrasive has exceptionally fast and cool cutting
grinding characteristics, especially suitable for grinding hardened or high speed steel in
varied precision grinding operations

5.3 Grain Size

Different grain sizes are available for different types of work and they are Course, Medium,
Fine and Very Fine.

Course grain is used for rough grinding and rapid removal of materials and finer grit is used for
finishing off and delicate work.

This is denoted by a number which refers to the sieve size that the grains of abrasive grit will
pass through.

Coarse is large particles and fine is much smaller particles, the more holes to the square inch
then the finer the particles will be, the fewer holes to the square inch then the coarser the grit
particles will be.

The number 8 means that the grit is of a size which will pass through a sieve with 8 holes per
square inch and would be a coarse grain, the number 1200 means the sieve would have 1200
holes per square inch and would be a very fine grain

5.4 Grades

This indicates the strength of the bond holding the particles together, wheels are grade soft to
hard and this is denoted by the letters A-Z

A: is the softest bond

Z: is the hardest bond

This gives an indication of how quickly the grit particles will be broken away and expose
another sharp cutting edge

Generally soft wheels are more suitable for hard material and hard wheels for soft material.

Use a soft grade when:
• Machine has low horsepower.
• Good finish is important
- fine grains normally used to provide minimum burr.
• Operators cut slowly.

Use a medium grade when:
• Softer grades do not provide enough cuts
- longer wheel life is required.
• Cutting normal materials. Machine horsepower will support faster cutting rates.

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Use a hard grade when:
• Maximum wheel life is sought.
• Machine has adequate horsepower (1 hp per inch of wheel diameter is recommended).
• Burr and finish requirements are minimal. (note that fast cuts will produce a reasonably good
finish)

5.5 Structure

Indicates the porosity of the wheel and this is denoted by the numbers 0-15, 0 is the densest
structured wheel and 15 is the most porous wheel, not all wheels or discs have the structure
marked on them.

5.6 Bond types

This indicates the substance or method to bond the grit particles together
B = Resinoid, BF= Resinoid Reinforced: Most cutting disc are of this type, where grit
is held by some form of synthetic resin. Usually reinforced synthetic resin is used,
showing that the cutting off disc is reinforced. This is normally by means of nylon mesh
which can be seen on the surface or cutting edge of the disc.
V = Vitrified: Abrasive materials mixed with clay and baked to give a solid wheel. Many
bench mounted machines are vitrified wheels.
S = Silicate: Similar to vitrified with silicate of soda added, generally softer, milder
grinding action than vitrified wheels. Used for grinding tools.
R = Rubber: Rubber wheels are used for precision burr free cutting operations and are
generally always used with coolants
RF = Reinforced Rubber: As above but can be used on a portable machine
E = Shellac: It's an organic bond used for grinding wheels that produce very smooth
finishes on parts such as rolls, cutlery, camshafts and crankpins and used for cool
cutting of hardened steels.
Mg = Magnesite is used in manufacturing soft grinding wheels and spring grinding

© Training & Testing Services 2008

5.7 Marking of Abrasive Wheels

EN13236 - Superabrasives -
To comply with the requirements of EN13236 the wheels or discs should be marked with the
following information:

✓ Company or Brand Name

✓ Traceability Code Number this should be on the product itself but can be
sometimes found on the packaging

✓ Dimensions
✓ MOS – Maximum Operating Speed
✓ Colour Stripe (optional) Blue: 50 ms, Yellow: 63 ms, Red: 80 ms, Green: 100 ms
✓ Direction of run, Wheels should be marked with a direction of run arrow
✓ Restrictions to use
EN13743 - Coated Abrasives - flap wheels, flap discs, vulcanised fibre discs and spindle
mounted flap wheels
To comply with the requirements of EN13743 the wheels or discs should be marked with the
following information:

✓ Company or Brand Name

✓ Traceability Code Number this should be on the product itself but can be
sometimes found on the packaging

✓ Dimensions
✓ MOS – Maximum Operating Speed
✓ Restrictions to use

© Training & Testing Services 2008

6. Speed

The maximum operating speed is marked on every wheel in two ways:
1. The peripheral surface speed which is given in metres per second (m/s)
2. The rotational speed which is given in revolutions per minute (rpm)
As a disc/wheel is worn down the speed of the cutting edge at its periphery becomes less
due to the reduced diameter if the rotational speed remains constant.
Some abrasive wheel machines are designed so that the spindle speed can be increased to
compensate for this as the wheel diameter reduces. When using this type of machine always
ensure that the spindle speed is reduced to its original value before fitting a new wheel.
This can lead to accidents as the cutting efficiency of the disc/wheel is reduced, the operator
may apply more pressure to the work and this can cause failure of the disc/wheel.
The speed of the spindle is marked on the machine in revolutions per minute (RPM)
The speed at the outer edge or cutting face of the disc/wheel is measured in meters per
second (M/S)
When selecting a wheel or disc the operator must check that the speed marked on the wheel
is greater than the speed that is marked on the machine.
Never operate abrasive wheels at speeds (rpm) in excess of that marked on the wheel.
Over speeding is one of the main causes of wheels bursting.
Just to illustrate the point, a fragment from a burst wheel operating at 35 m/s (typical vitrified
grinding wheel on a bench grinder) will be travelling at approx 80 mph and for 80 m/s (typical
resin bonded wheel on an angle grinder) 210mph
Remember that centrifugal force (the ultimate cause of wheel bursts) increases not directly
with speed, but as the square of the speed. The speed at which the wheel rotates is
therefore extremely important. It can not be too strongly emphasised that doubling the speed
in the wheel increases fourfold the stresses in the wheel
Wheels/disc are tested to one and a half their rated speed

Remember the speed on the machine must never exceed the speed
marked on the wheel or disc.

© Training & Testing Services 2008

7. Hazards and Precautions

7.1 Wheels Breaking

The risk of breakage is inherent with every abrasive wheel. If the number of breakages is
to be kept low, the initial care exercised in the design, manufacture and testing by
abrasive wheel and machine makers must be coupled with the adoption of safety
measures by users. The following are the main causes of abrasive wheels breaking

• Speed of machine too fast for disc: Always ensure that the speed of the wheel is
greater than the speed marked on the machine

• Incorrectly mounted, Abrasive wheels should only ever be mounted by trained and
authorised operators

• Damaged wheel, It is the operators responsibility to inspect and if relevant test the
wheel for damage prior to mounting

• Wrong wheel for job, Operators should check and read the label carefully to ensure
that the correct wheel has been selected

• Incorrect use of disc/wheel i.e. abuse, side grinding, applying pressure,
bumping etc. Remember a cutting wheel is designed for cutting only, not grinding,
do not exert excessive pressure onto the wheel. If cutting efficiency has been lost
due to reduced diameter then change the wheel

• Cutting too Deep, Material bending, Pipe work, steel reinforcing bar etc. will bend
whilst been cut, this can cause the wheel to be grabbed and then break

• Unbalanced wheel (contaminated by liquid), etc. Do not use any wheel if there
are any signs of contamination by fuels, oils, solvents etc.

© Training & Testing Services 2008

7.2 Accidents that may occur with Abrasive Wheel Machines

Accidents involving abrasive wheel machines often result in serious personal injury to the
operator and in some cases even fatality. The following are some of the common causes of
these accidents:

• Contact with wheel, Remember the wheels are designed for cutting through stone
and steel, therefore skin and bone isn’t a problem.

• Guard removal, It is a legal requirement that all abrasive wheel machines are
guarded, the guard is there to protect you if anything should go wrong.

• Guard not adjusted correctly, If the guard is not adjusted to the correct position,
then it cannot give you the protection that you require

• Controls of tool damaged (unable to switch off), The on/off switch must function
correctly so if an accident should occur the machine can be switched off immediately

• Tool not disconnected when changing wheels, The machine must be isolated
when changing the wheels and steps taken to ensure the power supply cannot be re-
connected accidentally while changing the wheel.

• Ties, scarves, loose clothing etc. Make sure that all clothing, jewellery, long hair
etc. is kept well out of the way and it is recommended that abrasive wheel machine
operators should wear flame proof overalls.

• Untidy working area causing tripping, slipping, whilst the tool is working, Good
housekeeping will reduce the likelihood of an operator slipping or falling while
operating an abrasive wheel machine

• Eye protection, Must be provided and worn in accordance with the Personal
Protective Equipment Regulations 1992, see section 8 for further details

• Work rest not secure or adjusted correctly, The work rest should be securely
clamped to the machine and readily adjustable to follow wheel wear. The work rests
should be kept adjusted as close as is practicable to the periphery of the wheel to
prevent anything from getting between the wheel and the rest

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7.3 Hazards to others on site

• Clear area, Remember you are not just responsible for your own safety, you are also
responsible for others around you, if they are not there you can not hurt them

• Barriers, Should be used if required to keep people away from your work area
• Noise, Operators should wear hearing protection as provided under the Personal

Protective Equipment Regulations 1992
• Flammable Substances/Atmosphere Fires and explosions have been caused in

the past by careless use of abrasive wheel tools, all site rules and the terms of any
hot work permits should be strictly adhered to
• Sparks given off, Operators should be aware of the spark area and take suitable
steps to prevent the risk of fire or to other people as appropriate

7.4 Others Hazards

Electric Grinding Machines

These are the most common types of machines on which abrasive wheels are used.
Electrical safety must also be considered when using this type of machine.
All hand held electrical machines supplied after 01/01/97 should carry the relevant CE
marking.

• Inspection and Maintenance, Routine checks, regular inspection and
preventative maintenance are essential if accidents are to be avoided

• Cables, Should be free from damage and steps should be taken to prevent trips
and falls from cabling

• Use in damp/wet conditions, 110v or 240v tools are not designed to be used in
damp or wet conditions

• Should be 110 voltage system on site, The preferred voltage for these
machines on a construction site is 110v. However, if a 240v supply has to be
used then the supply to the portable machine should be protected by an RCD

© Training & Testing Services 2008

Petrol Engine Machines

These machines are normally used for cutting operations using reinforced resin bonded
wheels or diamond wheels. One particular safety problem with this type of machine is
overspeeding. This may be due to a number of causes including; the mixture setting
(petrol/air ratio) together with the ignition timing. The speed governing device should be
given close attention and the accumulation of dust is a common cause of failure

• Leaks check fuel cap for rubber sealing ring, Many of these caps have a rubber
sealing ring fitted, check that the ring is in place and un damaged to prevent fuel
leaks

• Proper petrol storage can, Petrol should be stored in a proper petrol storage can
and away from sources of heat or ignition

• Filling (use funnel), Always fill up well away from where you intend to start cutting
• Fumes inside buildings, confined spaces etc…. Remember it is a petrol engine

machine and therefore will exhaust poisonous fumes just as a car does

Pneumatic Grinding Machines

Although there should be no electrical risk with this type of machine it is vital that the air
supply is clean and water free. Particular attention should be paid to the maintenance of two
devices.

• The maximum speed governor, ingress of dust into this device is a
common cause of failure

• Any form of pressure reduction valve that will prevent over pressurization

© Training & Testing Services 2008

8. Personal Protective Equipment

Personal protective equipment should be supplied and worn in accordance with the
requirements of the Personal Protective Equipment Regulations 1992 and the Noise at Work
Regulations 1989.

Operators of abrasive wheel machines are exposed to a number of risks including:

• Injury to the eyes from flying abrasive and metallic particles

• Inhalation of dust (see HSE notice SR21)

• Physical injury due to flying wheel fragments or work pieces

• Noise and vibration

• On some sites they will also be an additional requirement for head, feet and
hand protection

8.1 Eye Protection

Eye protection must be provided and worn in accordance with the Personal Protective
Equipment Regulations 1992

Frames and goggles must be marked BS or CE EN 166, in addition grade B impact with
large dust particle protection (4) and molten metals and hot solids protection (9) are required

8.2 Vibration

Processes where the machine or work piece is hand held can cause vibration injury, action
will need to be taken if the operator suffers from pain, numbness, pins and needles after 10
minutes continuous use of the machine. The effects of vibration will increase in cold weather,
so try and keep your hands warm and use modern machinery with lower vibration values.

Maintain all machinery in good condition and stop and have it checked if excessive vibration
occurs. Use good quality abrasive products and keep them in good condition, do not grip the
machine or work piece too tightly and don’t use excessive pressure.

Avoid continuous work with the machine; ensure that you use the correct wheel for the
material that you are working with.

8.3 Dust Protection

Depending on the type of material that is been cut or ground will depend on the amount and
type of dust that is given off, if dust masks or respirator kits have been provided by the
employer then they should be worn accordingly. Magnesium alloys contain a large
proportion of magnesium, the dust produced by grinding and cutting will burn freely and
when mixed with air and is capable of forming an explosive mixture. Dust extraction systems
should be kept clean and free from deposits of sludge

© Training & Testing Services 2008

9. Storage, Handling & Inspection of Abrasive
Wheels

Wheels should be carefully unpacked, cleaned with a brush and checked for any signs of
possible damage.

9.1 Storage of Cutting Discs

• Store on a flat shelf
• Keep out of extremes of heat and cold
• Keep away from fuels, solvents, paints etc.
• Protect from possible damage by other tools
• Keep dry
• Resin bonded wheels can be affected by surface oxidisation if stored for long

periods in damp conditions

9.2 Storage of Vitrified Wheels

• Stored on edge in cradles or other arrangements to prevent rolling or falling

9.3 Handling of Abrasive Wheels

All abrasive wheels are relatively fragile; it should not be assumed that organic bonded
wheels (resin, rubber etc.) will stand rough handling. The following rules should be observed
to avoid cracking and breakage

• Always handle with care
• Do not throw into stores or back of vans with other tools
• Care is required when opening packs of discs
• Do not drop
• Vitrified wheels particularly susceptible to cracking if dropped

© Training & Testing Services 2008

9.4 Inspection & Testing of Abrasive Wheels

Vitrified wheels are tested by means of the “Ring” Test. Suspend the wheel by the hole using
a finger or screwdriver, tap the side of the wheel with a piece of plastic or wood. It should
Ring. If it sounds dull there is likely to be damage.
Cutting off discs cannot be tested by the ringing method. These discs are reinforced,
therefore extra care is required with inspections
Inspect Wheels and Discs for:

• Damage
• Flaws
• Contamination
• Central bush or insert damage
• Blotters missing or crumpled
• Dirt, grit on sections of the wheel or discs where flanges will bear
• Speed
• Suitability for work
• Suitability for fitting to machine

DO NOT USE IF IN DOUBT

© Training & Testing Services 2008

10. Abrasive Wheel Machine Components

10.1 Flanges

The major stresses produced in an abrasive wheel tend to become greater nearer the hole.
It is therefore important that stresses due to the mounting and driving are as far from the
hole as possible. This is achieved by recessing the side of the flange next to the wheel. With
certain exceptions every abrasive wheel should be mounted with flanges which are at least
one third the size of the wheel

• Must be purpose made (not washers, pieces of scrap metal etc…)
• Must be the same size on both sides of the wheel
• Must be undercut so that it does not bear on the centre of the wheel (stresses

concentrate at this point)
• Check that the flanges are undamaged, or distorted
• Must not have pieces of old blotter, dirt etc… on them
• Inner flange is keyed to spindle, not less than one third of the diameter of the

abrasive wheel or disc. However smaller flanges are permitted with a cutting
disc less than 230mm (9inch) in diameter
• Only the correct spanner to be used to tighten flanges
• Tighten hand tight only
• Check nuts, holes in flanges etc. For signs of abuse and incorrect tools used
• If damaged this can affect the tightening, leading to over tightening and
possible crushing of wheel surface

© Training & Testing Services 2008

10.2 Spindles

The abrasive wheel should fit freely but not loosely on the spindle. If it grips the spindle or
flange, heat generated could cause the spindle to expand and possibly crack the wheel
surface.

• Must be correct size for the hole in the wheel/disc
• The fit on the spindle must not be to tight or to loose
• Nylon or similar material bushes may be fitted

10.3 Wheel Bushes

Wheel bushes are inserts made of plastic or metal and are used to reduce the hole size in
an abrasive wheel so that it can be mounted correctly on a smaller spindle. Bushes are not
recommended for use with wheels that are fitted to portable grinding machines

10.4 Blotters

Blotters are usually made from compressed board as supplied by the manufacturers should
be used between the wheels and their flanges. The main purpose of blotters is to distribute
the clamping force of the flanges evenly on the wheel surface, but they also prevent slipping
at lower clamping forces and reduce wear on the flanges. A blotter can serve as a label;
however a label cannot serve as a blotter

• Must be smooth, free from bumps, wrinkles, dirt, etc….
• Must be on both sides of the wheel
• The purpose of a blotter is to spread the load, improve the friction grip of the

flanges, reduce the effect of small surface imperfections
• Must be provided for all vitrified abrasive wheels
• Must be provided for all cutting off disc over 400mm in diameter
• Blotters are sometimes supplied loose
• Not required on cutting off discs of 400mm in diameter or less, or on

depressed centre discs

© Training & Testing Services 2008

10.5 Guards

In spite of the care taken by abrasive wheel manufacturers in the design, manufacture and
testing of abrasive wheels, the risk of breakage is inherent in all types of wheel and a guard
of adequate strength must be provided to prevent injury from flying particles of abrasive
wheels.

A guard has 2 major functions; firstly to contain pieces of the wheel if the wheel breaks; and
secondly to prevent, as far is reasonably practicable the operator from coming into direct
contact with the wheel.
The guard will also give the wheel some protection from inadvertent damage and prevent
oversized wheels from being fitted to the machine.

• Must be fitted
• Must be strong enough to contain pieces of wheel if it burst
• Cutting off wheel, depressed centre disc, fitted to portable machine guards

must cover at least 175 degrees of the edge of the disc
• Must be securely fitted to machine. The guard must be removable by 2 dis-

similar actions to prevent accidental release
• Guards must be adjusted to carry out work before the machine is switched on

10.6 Stopping & Starting

The means for stopping and starting grinding machines should be clearly marked, placed in
a safe position and within easy reach of the machine operator. On portable machines the
controls should be located so there is no risk of accidental starting when placed on a flat
surface.

• Controls must be in good working order
• The on/off switch must be in a position or be protected so that it cannot be

accidentally knocked on or off

© Training & Testing Services 2008

11. Truing & Dressing

Truing is the process of restoring the shape to a grinding wheel, regular truing of a grinding
wheel will ensure the wheel remains concentric on its spindle. A wheel that is out of shape
will cause excessive vibration and periodic knocking of the work against the wheels surface
and this will lead to damage to the wheel surface such as glazing which will impair the
wheels ability to grind effectively and may cause the operator to apply more pressure to the
work and cause failure of the wheel.
Regular dressing of the wheel is essential for efficient grinding and frequent light dressing of
the wheel is preferable to occasional severe dressing. When dressing or truing the following
precautions should be taken:

• Hand dressers should be properly supported
• When using a “star” type dresser, the lugs should be anchored over the work

rest
• Care should be taken to prevent the dresser from becoming jammed between

the work rest and the wheel surface
• It is important that the work rest on which the dresser is used is undamaged or

distorted before dressing the wheel, if the work rest is damaged it is
recommended that a new one should be used for the purposes of dressing
There are many different types of dressers available on the market and if you are unsure of
which one should be used then the wheel or machine manufacturers should be consulted

© Training & Testing Services 2008

12. Wheel Balancing

There are two primary causes of unbalance in a grinding wheel. One source, density
variation, originates in the wheel-moulding process. The other source is wheel geometry.
Factors such as variations in thickness, the perpendicularity of the arbor hole to each side,
and concentricity all influence balance.

After grinding wheels are moulded and finished to final tolerances, they are balance-checked
as a final inspection step. At this point, the manufacturer may perform a correction procedure
to improve a wheel’s balance condition.

Other factors, such as incorrect installation, can also throw wheels out of balance. To
consider just one source of imbalance, remember that the user must properly mount the
wheel on the machine tool. It’s critical to follow the manufacturer’s directions. For example,
the “mount-up” arrow on wheels indicates the location of the light point. Mounting the wheel
with the mount-up arrow pointing up means that the wheel will have the least amount of
unbalance after wheel dressing.

• Lock the wheel to be balanced on to its flange and fix the balance weights at
1800 i.e. opposite each other.

• Put on to the machine and lightly dress the wheel until it is dressed on all its
peripheral surface.

• Remove from the machine and mount it on the balancing mandrel.

• Ensure the balancing equipment is set with the knife-edges truly horizontal.

• Place the mandrel on the knife-edges with the wheel positioned central to the
cradle and parallel to either side.

• Let the wheel gently rotate on the knife-edges until it comes to rest – mark the
top of the wheel with chalk or ink marker.

• Move the balance weights 900 from the mark to be diametrically opposite each
other.

• Move each weight equally towards the mark, in small increments until the
wheel remains static in any position on the knife-edges. It will then be in static
balance.

• Refit the wheel to the machine and lightly redress again.

• It will then be in balance, dynamically, on the wheel spindle and ready for use.

© Training & Testing Services 2008

13. Summary of Mounting Procedures

Before mounting an abrasive wheel on a machine it is important that the wheel is of sound
manufacture and is only mounted on a well designed machine that is regularly maintained.
The mounting of wheels should only ever be carried out by personnel who have been trained
in the safe use of abrasive wheel machines.

✓ Switch off power at the mains, pull out plug, stop engine, turn off the air at the
compressor etc. Before doing anything

✓ Remove flanges using the correct spanner and remove the old disc/wheel

✓ Check and clean the flanges carefully

✓ Is the wheel/disc correct for the job? Check the label

✓ Is the wheel/disc suitable for the machine? Check the spindle size and the
correct fitting

✓ Is the disc reinforced for portable machines

✓ Assemble wheel/disc and flanges carefully making sure the wheel/disc is
centralised. Check that the undercut side of the flanges are next to the
disc/wheel surface. Fit loose blotters either side of the wheel/disc if required. If
blotters are already fitted to the wheel/disc check for wrinkles

✓ Tighten nut or outer flange carefully to hand tightness, only using correct
spanner. (Note: the nut should tighten in the opposite direction to the rotation
of the wheel).

✓ Turn the wheel/disc by hand slowly and check that the flanges are bearing
evenly on both sides and that the wheel/disc appears to be centralised.

✓ Adjust the guard, reset if applicable to correct position for work

If satisfied that everything is in order:

✓ Check the area is clear of other persons

✓ Check you have no loose clothing. Ties etc…

✓ Reconnect the power supply to the machine

✓ Wear eye protection

✓ Final check that all other persons are clear

✓ Switch the machine on, if possible stand clear and allow to build up to full
running speed for a short period of time, at least 1 minute if fitting a new wheel

If no problems then machine is ready for use

© Training & Testing Services 2008

14. Summary of Operating Precautions

Machine operators should always read and follow the manufacturers’ instructions before
operating any machinery and follow any instructions or procedures that are provided by the
employer.

✓ Check to see that the wheel/disc has been mounted correctly, mounting of
abrasive wheels should only be conducted by trained and authorised personnel

✓ Check the floor area before starting work, should be maintained in good condition
and free from obstructions

✓ Make sure the material to be cut/ground, is secure, the work piece should be
securely clamped before starting work

✓ Only cut or grind material that the wheel is designed for, using the wrong type of
wheel for certain materials is dangerous and can cause the wheel to burst

✓ Check that the controls operate freely, the on/off switch must operate correctly

✓ Check that the guards and rest if applicable are secure and in the correct
position, the guards must be fitted and in the correct position before the machine is
switched on

✓ Wear the correct eye protection, adjust the screen on the bench grinders, eye
protection must be provided and worn in accordance with the requirements of the
PPE Regulations

✓ Always turn off the coolant before stopping a grinding wheel, leaving the coolant
running while a grinding wheel is stopping can cause the wheel to become
unbalanced

✓ Check for loose clothing, so nothing can be caught in the machine mechanism

✓ Do not bump or exert pressure on to the wheel, excessive pressure can lead to
the failure of the disc or wheel

✓ Do not try to make cuts wider by moving the disc from side to side, or attempt
to fit multiple wheels to portable machines

✓ When cutting and grinding ensure that there is sufficient lighting, working in
poor lighting conditions is dangerous and can lead to accidents

✓ Do not grind on the side of the wheel, grinding on the side of a straight sided
wheel is dangerous and can lead to failure of the wheel

✓ As the diameter of the wheel decreases, the peripheral speed decreases, loss
of efficiency, change wheel or disc, otherwise the operator may apply too much
pressure to the wheel and cause the wheel to break

© Training & Testing Services 2008

✓ Allow the disc/wheel to run down to stop, do not press an object against the
wheel/disc to stop it and never leave a machine unattended until the wheel has
come to a complete stop, wheels should never be brought to a stop by applying
pressure to the periphery of the wheel

✓ Make sure no one else is affected by your work, you are responsible not only for
yourself but for everyone else who may be affected by your work activities

✓ Report all accidents, near misses and wheel breakages to your supervisor, no
matter how minor the accident or near miss report it straight away

✓ Used or defective abrasives should be disposed in accordance with local or
national regulations, be aware that used abrasive products could be contaminated,
disposed abrasive wheels should be damaged to prevent them from being taken and
re-used

✓ Check for flammable liquids, gases or sparks, Fires and explosions have been
caused in the past by careless use of abrasive wheel tools, all site rules and the
terms of any hot work permits should be strictly adhered to

© Training & Testing Services 2008

© Training & Testing Services 2008