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Multi-cutters and other discs on power tools and air tools

Published: November 2008

Purpose
Background
Multi-cutters
Blades and cup stones
Recommendations
Legislative requirements

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 (WHSQ) has recently 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.

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, and
• 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.

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. Spring loaded saw guards, such as those on circular saws, are not readily available for angle grinders. One type of full guard currently available is shown in photograph 2.
2. 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)

Guard availability

WHSQ has set up a register to record manufacturers and retailers of the guard shown in photos 1 and 2. For information on this register contact the Workplace Health and Safety Infoline 1300 369 915. Manufacturers and retailers can have their contact details added to the register by also contacting the WHS Infoline.

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.
• 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 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.
• Exclusion zones must be set up around workers so that other persons cannot be injured if the worker looses control of the equipment or the disc disintegrates.
• 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.

Legislative requirements

Section 28 of the Workplace Health and Safety Act 1995 (PDF, 766 KB) lists obligations of persons conducting a business or undertaking. Section 32 lists obligations of designers, manufacturers, importers and suppliers of plant (tools and machinery) and Section 36 lists obligations of workers and other persons.

Information contained in this alert may help people meet their obligations by managing the risks associated with the use of multi-cutters and discs.