https://www.worksafe.qld.gov.

au/news/safety-alerts/whsq/2015/multi-cutters-
and-other-discs-on-power-tools-and-air-tools

Purpose
To highlight hazards associated with the use of multi-cutters and grinding or cutting
discs fitted on power tools and air tools.

Background
Workplace Health and Safety Queensland have investigated a number of serious
incidents caused by using cutting and grinding discs on hand held power tools and
air tools. Common injuries are amputated fingers, severed tendons and deep cuts to
the face, upper body or legs.

Multi-cutters
Most incidents have involved multi-cutters, which are tungsten tipped saw blades
with a diameter of approximately 100mm. Photograph 1 shows a multi-cutter blade
fitted to a 100mm angle grinder.

These discs were originally designed to be used on small power saws, not angle
grinders. The injuries that can result from using multi-cutters on angle grinders are
very serious. These injuries are more serious than those associated with
conventional fibre re-enforced cutting discs, because:

 multi-cutters cut through materials at a faster rate

 multi-cutters are more prone to jamming and kickback
 the tungsten tips are sharper and generally cause a wider, deeper, and longer
wound
 the tungsten cutting tips can fly off the blade at high speed when the multi-cutter is
used as a grinding tool – due to the side loading applied to the blade
 vibration can cause the nut to loosen and allow the disc to be ejected at high speed.

Photograph 1 - multi-cutter fitted to a 100mm angle grinder

 Blades and cup stones
Serious incidents with blades and cup stones include:

 abrasive cup stones exploding causing eye and penetration injuries, similar to bullet
wounds
 concrete saw blades jamming on pipes or block work, causing kick-back that results
in the worker being hit or cut.

Recommendations
Multi-cutters

1. Angle grinders fitted with multi-cutters should not be used unless they are fitted with
full spring loaded guarding.
2. The multi-cutter blade is only used on suitable power tools in accordance with the
instructions of a competent person.
3. The centre nut securing the multi-cutter blade should be regularly checked for
tightness.
4. Multi-cutters must not be used for grinding due to the risk of tungsten cutting tips
flying off the blade.

Photograph 2 - multi-cutter fitted with full spring loaded guarding (closed)

 Photograph 3 - multi-cutter fitted with full spring loaded guarding (partially
open)

Guards
Spring loaded saw guards, such as those on circular saws, are not readily available
for angle grinders. One type of full guard currently available referred to as a hood
guard for grinders is shown in photograph 2. A competent person should determine
the suitability of the guard for their specific application.

Search the internet under 'hood guard for grinder' to locate a supplier.

General
The points below apply to the use of discs and blades on power tools and air tools.

 Discs and blades must be marked with the maximum permissible operating speed in
revolutions per minute (RPM).
 The manufacturer of the disc or blade must supply information that describes the
type of power tool or air tool that is suitable for the disc or blade to be attached to.
 The power tool is to be marked with the maximum operating speed in RPM and this
speed must not exceed the maximum allowable speed marked on the disc or blade.
 The size of the cutting or grinding disc is not to exceed that specified by the power
tool manufacturer.
 Guards should be provided on all power tools where there is a risk of the disc
ejecting, disintegrating or cutting the worker. AS 1788, Abrasive Wheels, provides
guidance on guarding abrasive wheels while AS/NZS 60745 Hand-held motor–
operated Electric Tools - Safety requirements deals with the safety of grinders,
polishers and disc-type sanders.
 Discs are installed correctly and the centre nut tightened in accordance with the
power tool manufacturer's instructions.
 Exclusion zones must be set up around workers so that other persons cannot be
injured if the worker loses control of the equipment, the disc disintegrates or is
ejected.
 Workers must hold hand power tools with both hands as specified by the
manufacturer. The worker should preferably stand with both feet on a level surface
that is not slippery and operate the tool in front of the body. Heavy and powerful
tools should not be used above chest height.
 Workers using a power or air tool must not wear loose clothing or jewellery and
must securely tie back long hair so they cannot become caught in a moving part of
the tool. Workers wearing protective clothing such as leather aprons and jackets
additional to standard personal protective equipment will be better protected from
injury when using power and air tools.
Guidance Note

Safe use of angle grinders

Practical advice for employers on controlling hazards when
using angle grinders.
March 2011

Background How to use the table

Angle grinders are versatile hand-held tools commonly The table over the page lists and shows examples of the
used in the manufacturing industry, in particular the metal main hazards when using angle grinders. It also includes
fabrication sector. Their ability to perform a variety of tasks the possible consequence of the hazard and provides a list
is due to the different accessories that can be attached of recommended controls. The zone numbers in the table
to them. refer to what is shown in the picture below.
The type of attachment placed on an angle grinder depends
on the task being performed and the materials being used.
The most common uses for angle grinders include grinding
(with abrasive discs) and cutting (with cut-off discs) –
however attachments will vary depending on whether the 3
operator is working with metal, stone, tiles or other materials.

Main hazards 2
The most common causes of injury to operators
and nearby workers from angle grinders are lacerations
from attachments that break and become projectiles, 1
and lacerations from angle grinder kickbacks. 4

Kickback happens when the angle grinder suddenly

thrusts back towards the operator as a result of it
grabbing or jamming on the materials being worked on.

Employers must provide a safe work environment

for workers by implementing adequate controls to all
identified hazards. The zones of an angle grinder are:

Before implementing controls, employers should consider: 1. angle grinder attachments

2. angle grinder
• if it is necessary to perform the task (eg if the weld 3. angle grinder operators
4. angle grinding workspace.
will be hidden from sight and profiling is not needed
for stress distribution, does it have to be ground?)
• safer ways to achieve the end outcome
(eg using a bench-mounted saw for cutting).

When purchasing an angle grinder, the following safety

features should be considered:
• anti-kickback safety clutch
• soft-start vibration reducing handle
• restart protection
• grinder fitted with braking system to rapidly stop the wheel
• noise-reduction grinding disk.

GUI0142/01/03.11 1
 Guidance Note Safe use of angle grinders

Hazard Possible consequence Recommended controls

Zone 1: Angle grinder attachments

Attachments are inappropriate Kickback can occur or • Ensure the attachment selected is designed for
for the task (eg using an attachment can break, becoming the purpose it will be used (eg only use abrasive
abrasive disc for cutting) a projectile and striking workers. discs for grinding and cut-off discs for cutting).

Attachments that are not Kickback can occur or blade • Only use attachments designed for use on angle
designed for angle grinders teeth can detach at high speed, grinders.
are used (eg using circular saw becoming projectiles and striking • Do not use circular saw blades on angle grinders
blades for cutting) workers. (see picture).

Attachment is not appropriate Attachment can break, becoming • Clearly identify the material being prepared
for the material being worked on a projectile and striking workers. and ensure the attachment is appropriate.
(eg using a masonry cut-off disc • Identify any surface coatings that may be
on metal) dangerous when worked on (eg lead).

Attachment is too large or small Attachment can break or detach • Only use attachments designed for the size
for the angle grinder from the angle grinder and strike of the angle grinder used.
the operator and nearby workers. • Ensure the attachment centre hole matches
the size of the angle grinder spindle.

The speed rating – revolutions Attachment can break, becoming • Ensure the maximum speed (RPM) marked on
per minute (RPM) – of the a projectile and striking workers. the attachment is higher than the maximum speed
attachment is lower than the of the angle grinder (see picture).
maximum speed of the angle
grinder

4.5”
Max RPM: 13,300

• Do not use attachments that have decreased

in size (through use) on small angle grinders.

2
 Guidance Note Safe use of angle grinders

Hazard Possible consequence Recommended controls

Attachments used are Warped or damaged attachments • Before use, inspect attachments for excessive
excessively worn or damaged can cause excessive vibration, wear or damage.
resulting in sprains and strains. • Discard worn or damaged attachments.
Attachments can also break,
becoming projectiles and striking
workers.

Guard has been removed Debris or hot sparks fly back • Never remove guards.
or incorrectly positioned at the operator, causing burns • Ensure guards are fitted securely in the correct
(eg removing the guard to use or lacerations. position before use and are resistant to bending
a larger attachment) and twisting.
Operator’s hand makes contact
with moving parts, resulting in • Ensure the thickness and diameter of attachments
amputations or lacerations. is within the angle grinder ratings.

The flange and centre hole in Attachment can detach from the • Ensure the flange and hole in the attachment
the attachment are different sizes angle grinder’s body and lacerate centre are the same size (eg buy inserts that
the operator and nearby workers. provide the correct spindle hole).
The angle grinder can also
vibrate excessively, resulting in
sprains and strains.

Flanges and nuts are worn Attachments can become • Ensure flanges and nuts are free from wear
or damaged projectiles if they detach from tor damage before use.
the angle grinder. • Discard worn or damaged flanges or nuts.

Zone 2: Angle grinder

No auxiliary handle on angle Operators have reduced control • Before use, ensure the auxiliary handle is attached.
grinder of the angle grinder, which can • Ensure operators grip both handles during use.
cause lacerations as operators
• Ensure the handle is adjustable if there are multiple
may be unable to stop the angle
users (see picture).
grinder making contact with
them during kickback.

Outer body of angle grinder Operators can sustain • Before use, inspect angle grinder body and leads
or electrical cord is damaged an electric shock. for damage.
or has exposed wires • Repair or discard damaged angle grinders.
• Use a safety switch or residual current device.

3
 Guidance Note Safe use of angle grinders

Hazard Possible consequence Recommended controls

No cut-off switch Operators are unable to stop the • Ensure angle grinders have a cut-off switch.
angle grinder in an emergency.

Air vents are not regularly Build up of dust and debris can • Regularly clean air vents and maintain angle
cleaned cause the motor to short-circuit, grinders in good working condition.
resulting in an electric shock.

Zone 3: Angle grinder operators

Operators are inexperienced Incorrect angle grinder or • Ensure operators are provided with training
(eg apprentices, trainees, young attachment may be selected and supervision on the safe and correct use
workers or experienced workers (see consequences under of angle grinders.
new to the task) or not trained Zone 1). • Ensure operators demonstrate competency
in the safe use of angle grinders in performing the task safely.
Unsafe use of angle grinder
can result in serious injuries to
operators and nearby workers.

Angle grinder is the incorrect Operators can have difficulty • Only use angle grinders that are an appropriate
size for the task controlling the angle grinder size for the task.
and may become injured if it
moves suddenly (eg kickback).

Pressure is applied during Attachments can break under • Ensure operators do not apply pressure
operation pressure and strike workers. to the angle grinder during use.
Excessive pressure can
also increase the likelihood
of kickback.

Angle grinder is used in a wet Operators can sustain an electric • Ensure operators do not use liquids when working
environment shock. with angle grinders.
• Ensure angle grinders are used in a dry
environment.

Angle grinder is used before Kickback can happen or • Before use, ensure operators allow the angle
it reaches speed attachments can shatter, grinder to run to speed.
resulting in lacerations.

Angle grinders are placed on Angle grinders can move along • Ensure angle grinders stop turning before being
the ground or benches while still a surface while running. put down.
running The rotating parts can result
in amputations or lacerations
to nearby workers.

Running angle grinders are Moving parts can make contact • Ensure angle grinders have stopped turning
carried around the workplace with the operator or other (eg parts are stationary) before they are moved
workers, resulting in amputations around the workplace.
or lacerations.

4
 Guidance Note Safe use of angle grinders

Hazard Possible consequence Recommended controls

Operator is positioned Operator’s ability to move out • Ensure operators do not position their bodies
directly behind the angle of the angle grinder’s path during directly behind the angle grinder when working.
grinder during use kickback is reduced.

Workers are exposed to Workers can sustain hearing loss. • Ensure workers wear hearing protection.
extended periods of noise • Ensure workers have audiometric testing
from angle grinders when assessed as necessary.

No or inappropriate personal Workers can sustain breathing • Ensure operators and nearby workers wear
protective equipment (PPE) worn difficulties from dusts or vapours. appropriate PPE (eg hearing protection, safety
goggles, face shield and fire-retardant clothing).
Workers can be struck by flying
debris or hot sparks.

Zone 4: Angle grinding workspace

Workpiece is not supported Kickback can happen and • Ensure the workpiece is appropriately supported,
the angle grinder can strike considering its size, shape and the location of the
the operator. angle grinder.

Workpiece is not secured Workpiece can become • Ensure the workpiece is secured, considering
and moves around a projectile, striking the operator the type of material, its shape and size (eg clamps).
and nearby workers.

Task is performed on the ground Operators can sustain muscular • Ensure workers only use angle grinders when
or requires awkward positions sprains and strains to the back, required (eg if a welded join will not be seen on
neck, shoulders, arms and hands. the final product and profiling is not required for
stress distribution, using an angle grinder may not
be necessary).
• Ensure, where possible, work is positioned in the
operator’s best working zone – between shoulders
and knees (see picture).

Low risk

Medium risk

High risk

• Consider using mechanical aids to assist

in performing tasks (eg jigs or robotics).

5
 Guidance Note Safe use of angle grinders

Hazard Possible consequence Recommended controls

Dusts or vapours remain in Workers can experience • Ensure the work area is adequately ventilated
the work area when using angle breathing difficulties as the (this may require natural airflow or extraction units).
grinders grinding of some materials, • Ensure the work area is regularly cleaned and
including those that have been dusted.
coated in other substances,
can create dangerous fumes.

Flammable substances near Substances can be ignited • Ensure flammable substances are not placed
angle grinders by angle grinder sparks, resulting or stored in areas where angle grinders are used.
in fires and burns to workers.

Untidy and unorganised work Workers can slip or trip over • Ensure the work area is regularly inspected
environment workpieces, materials, leads and dust and cuttings are cleared away.
and angle grinders. • Ensure materials and workpieces not being used
are stored until required.
• Ensure angle grinders are not stored on the ground.
• Ensure angle grinder leads are not too long.

Note: This guidance material has been prepared using the best information
Further information available to the Victorian WorkCover Authority and should be used for general
use only. Any information about legislative obligations or responsibilities
Contact the WorkSafe Victoria Advisory Service included in this material is only applicable to the circumstances described
on 1800 136 089 or go to worksafe.vic.gov.au in the material. You should always check the legislation referred to in this
material and make your own judgement about what action you may need
to take to ensure you have complied with the law. Accordingly, the Victorian
Related WorkSafe publications WorkCover Authority cannot be held responsible and extends no warranties
as to the suitability of the information for your specific circumstances;
A guide to safety in the metal fabrication industry or actions taken by third parties as a result of information contained
in the guidance material.
Metal Fabrication – Improving health and safety
through layout and design

6
A Health and Safety Solution

Preventing misuse of angle grinders

as saws
What is the problem? What is a solution to the problem?
Workers fitting saw blades to angle grinders and Put in place risk control measures to eliminate
using them as cutting tools. or minimise risks by:
• using the right tool for the job. Circular saw blades
What are the risks? should never be fitted to an angle grinder
The blade saw can jam or kickback (the disk thrusts • only using blades specified by the manufacturer
back towards the user) and the exposed blade can of the angle grinder (if in doubt, check with the
strike the operator. manufacturer before fitting and using)
The blade’s teeth or hardened tips can also become • using a safer alternative method of cutting for
projectiles if they detach at high speed. the task (such as a power drill, reciprocating saw,
jigsaw with an aluminium blade or a purpose built
A worker was seriously injured while using an angle cold metal cutting power saw)
grinder fitted with a tungsten-tipped saw blade.
• wearing appropriate hearing protection, safety
The angle grinder was being used to cut a hole in the glasses or a face shield when cutting or grinding.
top of an aluminium fuel tank when the saw blade
Flame-resistant clothing should be worn for hot work.
jammed, causing the angle grinder to kickback
onto the worker. • ensuring workers are adequately trained in
the safe use of angle grinders.
Angle grinders are not designed to operate as
power saws, as they: Further Information
• are not fitted with sufficient guarding to protect
the operator if the blade jams, disintegrates or WorkSafe Advisory Service
kicks back Toll-free: 1800 136 089
• are not fitted with retractable guards that provide Email: info@worksafe.vic.gov.au
the same safety a power saw provides worksafe.vic.gov.au
• rotate at faster speeds and generate greater
torque than power saws.

The problem A solution

Circular saw blades should not be fitted to an angle grinder. Only use angle grinders for the specific material and purpose for
which they are designed.

HSS0066/03/02.10