Power Tools

Router Incident

Routers are a common item of fixed plant used in a variety of wood machining settings and workplaces. The purpose of this alert is to advise industry of a recent incident where a worker was killed using a router to complete a job.

Background - The worker was operating an industrial router at a cabinet-making factory when the bit disintegrated and a piece of metal hit her in the chest.  The contributing factors that led to this incident included:

• use of an inappropriate bit for the tool—in this case, a bit with wings too large for the shank;
• use of a bit with a shank not long enough to be properly grasped in the collet;
• the tool not being marked with the maximum permissible speed;
• The tool not being balanced before use.

No etching of the maximum speed on the side of the bit	Router bit's wings are too large for shank

Control Measures

Manufacturers, users of router bits, and their employers should be aware of the safety   requirements involved in the use of routers.

• Ensure that the maximum permissible speed is clearly marked on the tool (preferably by etching).
• Ensure that the bit is properly balanced prior to being put on the market or into use.
• Tools should only be sharpened by a competent person or organisation and regular checks of collets should be carried out to ensure they hold router bits firmly.
• Under no circumstances should local modifications be made to bits or collets to allow the use of non-compatible components.   Staff should be trained and supervised in using these pieces of plant.

For further information on occupational health and safety, go to WorkSafe’s website: www.worksafe.vic.gov.au.

Note: This material has been prepared using the best information available to WorkSafe Victoria. Any information about legislative obligations or responsibilities included in this material is only applicable to the circumstances described 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 WorkCover Authority extends no warranties as to the suitability of the information for your specific circumstances.

Workers Hand Severed by Beam Saw - Case Study

It was reported recently that an employee from an outside industry was cutting timber with a beam saw, when his left hand became trapped in the saw during its operation, causing it to be severed at the wrist.  The safety features designed to stop the saw in an emergency could not be activated.

• The investigation revealed the following –
• Safety features of the beam saw include two safety bars and micro switches to operate the emergency stop on the control panel;
• No guarding was provided on the saw to prevent access to the blade;
• The guard at the front of the saw had three pieces of timber positioned on it, which prevented it from being activated effectively;
• The micro switches were damaged and maintenance had not been carried out on them for some time; and the micro switches required for the safety bar to operate effectively in an emergency, were not in proximity of the safety bar.

These factors contributed to this serious work injury.  The employer failed in its obligation under s.19 of the Occupational Health, Safety and Welfare Act to provide a safe system of work and to ensure that plant was maintained in a safe condition. 

The Industrial Magistrate hearing the case commented that a simple, regular test of the effectiveness of the cut-off switch would have revealed its inadequacy.

Information provided by Workplace Services

Power Saws

This is how NOT to use your power saw.  The user had removed the guards to use on another saw, but couldn’t find the other saw.  Seeing as he only needed to make two cuts, he used this piece of equipment.”

It does not matter if you have one or 1,000 cuts to make, ensure that the tools are in good working order and with all the guards attached.

This operator can consider himself very lucky that the cut was not worse.

Grinding Wheels - Guards

Information Provided by Workplace Services

• Do always handle and store wheels carefully.
• Do visually inspect all wheels before mounting for possible damage in transit.
• Do check maximum speed established for wheel against machine speed
• Do check mounting flanges for equal and correct diameter (should be at least one-third diameter of wheel and relieved around hole).
• Do use mounting blotters supplied with wheels.
• Do be sure the Work Rest is properly adjusted (centre of wheel or above; no more than 1.5mm away from wheel).
• Do always use a guard covering at least ½ of the grinding wheel.
• Do allow newly-mounted wheels to run at operating speed, with guard in place, for at least one minute before grinding.
• Do always wear safety glasses or some type of eye protection when grinding.
• Do turn off coolant before stopping wheel to avoid creating an out-of-balance condition.
• Do refer to Australian Standard AS 1788-1987, Part 2, Abrasive Wheels, if in doubt.
• Don’t use a wheel which has been dropped.
• Don’t force a wheel onto the machine, or alter the size of the mounting hole – if wheel won’t fit the machine, get one that will.
• Don’t ever exceed maximum operating speed established for the wheel.
• Don’t use mounting flanges on which the bearing surfaces are not clean and flat.
• Don’t tighten the mounting nut excessively.
• Don’t grind on the side of the wheel unless wheel is specifically designed for that purpose.
• Don’t start the machine until the wheel guard is in place.
• Don’t jam work into the wheel.
• Don’t stand directly in front of a grinding wheel whenever a grinder is started.
• Don’t grind material for which the wheel is not designed.
• Don’t operate a grinder until properly instructed.

Preventing Misuse of Angle Grinders

What is the problem? - Workers fitting saw blades to angle grinders and using them as cutting tools.

What are the risks?

• The blade saw can jam or kickback (the disk thrusts back towards the user) and the exposed blade can strike the operator.
• The blade’s teeth or hardened tips can also become projectiles if they detach at high speed.
• A worker was seriously injured while using an angle grinder fitted with a tungsten-tipped saw blade.  The angle grinder was being used to cut a hole in the top of an aluminium fuel tank when the saw blade jammed, causing the angle grinder to kickback onto the worker.

Angle grinders are not designed to operate as power saws, as they:

• are not fitted with sufficient guarding to protect the operator if the blade jams, disintegrates or kicks back.
• are not fitted with retractable guards that provide the same safety a power saw provides
• rotate at faster speeds and generate greater torque than power saws.

What is a solution to the problem?

Put in place risk control measures to eliminate or minimize risks by:

• using the right tool for the job.  Circular saw blades should never be fitted to an angle grinder
• only using blades specified by the manufacturer of the angle grinder (if in doubt, check with the manufacturer before fitting and using.)
• Using a safer alternative method of cutting for the task (such as a power drill, reciprocating saw, jigsaw with an aluminium blade or a purpose built cold metal cutting power saw).
• Wearing adequate eye and face protection when using an angle grinder. Hearing protection and flame-resistant clothing should also be worn.
• Be adequately trained in the safe use of angle grinders.

WorkSafe Advisory Service - Toll-free 1800 136 089

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

Preventing Electrical Shock From Power Tools and Electrical Leads

(Article from WorkSafe Victoria)

Workers using portable power tools and electrical leads that are electrically faulty or damaged, may suffer electrical shock, which could result in death, heart problems, internal organ damage or burns.

When using electrical leads and power tools:

• visually inspect prior to use – don’t use equipment if it has been modified or damaged
• plug tools into socket outlets that are protected by a residual current device (RCD) or use a portable RCD (RCDs are also known as safety switches).
• plugtop type RCDs should not be fitted to power tools or equipment, as the RCD cannot be readily tested.
• ensure power circuits are protected by the appropriate rated fuse or circuit breaker to prevent overloading
• if the circuit keeps overloading, don’t increase the fuse rating as this creates a fire risk due to overheating
• arrange electrical leads so they will not be damaged.  Avoid running across the floor or ground, through doorways and over sharp edges.  Use lead stands or insulated cable hangers to keep leads off the ground
• don’t use leads and tools in damp or wet conditions, unless they are specially designed for those conditions.
• to ensure RCDs continue to provide shock prevention, implement an electrical testing regime.

A Personal Experience –

This person had a very narrow escape a while back, when he picked up a power cord that had been left by a previous user in his workplace, plugged it in, then walked with the cable in his hand, unraveling it as he went along.  He reached the end of the cord, completely unaware that someone had cut the end off!  He received a severe electrical shock, but had the presence of mind to fling the cord around a nearby verandah post, which wrenched the live cord out of his hand, possibly saving his life.  He was left lying on the ground suffering from shock, but thankfully, survived his ordeal.  He now checks that the cord he is using is safe – damaged electrical cords need to be safely disposed of or repaired immediately.

Don’t get electrocuted by your welding machine

(article supplied by Work Cover Corporation)

They say “it’s the volts that jolts”.  But experiments prove that an electric current of only about 50 milliamps lasting for only one second can have a severe, possibly fatal, effect on the human body.  The resistance of the human body measured from hand to hand, or hand to foot is about 1,000 ohms, which means that it only takes about 50 volts differential to send 50 milliamp current across this resistance.  That is why 32 volts or less is classified as ‘extra low voltage’ in AS 3000, and a voltage between 32 and 250 volts is classified as ‘low voltage’.

But don’t be misled into thinking that because it is called low voltage that it is relatively safe.  Voltages even as low as 50 volts for very short periods can be fatal.  And these experimental calculations assume hand to hand or hand to foot resistance.

What if the actual environmental conditions when working with electrical equipment, are much worse than those assumed in the above experiments.  Take, for example, electric arc welding.  You can often be working in a confined space and often in a cramped position.  The workspace might be hot and poorly ventilated.  You are uncomfortable and sweaty.  If you lean directly against the body of the workpiece, say, with your damp clothed shoulder, or even upper arm and your opposite hand comes into contact with the live welding electrode, you could have 80 volts from the secondary side of the welding transformer passing through your body, not dry hand to dry hand or foot, but through a shorter resistance from hand to opposite shoulder and with better contacts caused by the sweat and damp clothing.  And your heart is directly in the path.

Although manual metal arc welding (MMAW) can be performed perfectly safely, there are circumstances when there is substantial risk of electric shock.  It is obvious that poorly maintained or badly connected equipment may be extremely hazardous.  What is not so well known is that an electric shock from a welding machine can have such serious consequences.  MMAW is risky because the electrode is changed frequently while the electrode holder is electrically live.

Many welders admit to suffering a shock if they simultaneously touch live parts of the electrode holder and the workpiece.  In most cases the consequence is only an unpleasant tingle, but sometimes the shock can lead to muscular spasms causing a fall from a height or the injury by victim striking against something.  Death by electric shock is rare, but is a real possibility.  Fuses and earth leakage devices will have no effect on reducing this hazard.

Factors which affect the severity of the shock are:

• The open circuit voltage of the welding machine, and whether the machine supplies alternating or direct current (AC is 2 to 3 times more dangerous than DC, because AC causes muscles to grip tightly).
• The pressure the victim exerts on the electrode and workpiece, because increased pressure means better contact.
• The effectiveness of insulation (gloves etc.) at the contact points, the presence of moisture from rain, perspiration or other source.
• Which parts of the body are in contact with the work and electrode, (the worst current flow path is between the left hand and torso.
• The susceptibility of the victim to shock, which is dependent on health and other factors.
• Precautions against this risk include use of properly maintained equipment, correct protective equipment and sound work practices.

To avoid electric shock –

• avoid bare skin contact with the electrode, and either
• prevent contact with the workpiece, or
• select a low voltage welding machine.

Avoiding Contact with the Electrode

 Handle the electrode holder carefully. 

Use dry welding gloves on both hands when handling the electrode holder or gun, particularly when changing electrodes.  Do not hold electrodes under the arm pit while changing them.  Do not wrap the electrode lead around yourself.  Remove stub ends and part used electrodes from the holder immediately welding is finished.

Ensure the electrode lead is live only while you are welding.  Do not drag live cables to the work position.  Turn off the power when welding is finished or during breaks.

Avoiding Contact with the Workpiece

Avoiding contact with the electrode is not sufficient, because an accidental brush with the electrode tip may also cause a shock.  Where possible, avoid contact with the workpiece.  Where possible, cover exposed parts of the workpiece, workbench and concrete or metallic flooring with insulation such as heat resisting blankets, rubber matting or wooden duckboards.

Wear appropriate safety clothing.  As a minimum, this should comprise heavy non-synthetic shirt and trousers or overall, rubber soled safety shoes and welding gloves.  Additional protection such as leather jacket, apron, knee pads and cap provide useful extra protection, although their brass fasteners tends to negate their electrical insulation properties.

Keep the work area, insulation and clothing dry.  In hot conditions, the risk of electrocution is increased because of clothing and equipment being soaked in perspiration.  The risk is far worse in closed environments, such as tanks or vessels, particularly when these are exposed to the sun’s heat.  Take frequent rest periods, during which time dry off equipment and clothing.  Frequently change or alternate gloves and protective clothing to avoid perspiration accumulating.  Ventilate or if possible, air condition the work area.  Ventilation will help dry perspiration and cool the body.  Cool the face with an air fed mask.  If clothing becomes saturated with perspiration, it must be changed.

Welding Machines for Electrically Hazardous Environments

If insulation of the welder from the work-piece cannot be guaranteed, the environment must be considered as electrically hazardous.  Such environments are whenever the welder has to work on or in the work-piece.  Freedom of movement is often restricted, so that the welder is forced to perform work in a cramped (kneeling, sitting or lying) position.  The hazard is compounded in wet, damp or hot locations, where humidity or perspiration considerably reduces the electrical resistance of the human body and the insulating properties of accessories.  Examples include shipbuilding work, inside vessels or pipes, in damp trenches, large steel structures and underground mines.  The hazardous environment does not need to be a confined space.

If the environment is considered electrically hazardous, then the welding equipment should have a safe voltage.  AS/NZS 3195 covers portable welding machines for both hazardous and non-hazardous environments.  The maximum OCV of direct current welding machines for both hazardous and non-hazardous environments is 113 volts.  Alternating current machines for hazardous environments should have a maximum OCV of 48volts rms instead of the normal requirement of 80 volts.  Portable welding machines for hazardous environments carry a label indicating this.

In line with international standards, there are moves to adopt similar requirements for non-portable welding machines currently covered by AS 1966.  Until such measures are adopted it is wise to measure the OCV of AC machines to determine their suitability for use in hazardous environments.  Voltage limiting safety devices are available which may be fitted to any welding machine.  Such a device automatically limits the voltage to less than 25 volts and only applies the full OCV when the electrode is struck.

This information is provided to offer guidance on a particular aspect of legislation.  It is not to be taken as a statement of law and must not be construed to waive or modify any legal obligation.