Safe use of abrasive wheels - fact sheet
Information about the safe use of abrasive wheels and tools in the workplace.
Abrasive wheels are typically used within industry for grinding, shaping or cutting metallic objects. They may be fitted to either portable / hand-held (angle grinders) or fixed grinding machines (mounted to a bench or pedestal).
There are various types of abrasive wheels to suit different applications. This guidance primarily focuses on fixed grinding machines fitted with wheels formed by abrasive particles being bonded together, i.e. bonded abrasives.
When using abrasive wheels, injury may occur from contact with the rotating wheel or wheel breakage.
Bonded abrasive wheels are inherently fragile and can be easily damaged. Abrasive wheels which contain damage or flaws have the potential to fracture and break apart during operation. This may result in serious or fatal injuries due to the high velocity of the ejected parts.
Figure 1 shows an example of a bonded abrasive wheel (300mm diameter) which broke apart during operation, resulting in fatal injuries to the operator.
Practices likely to affect the integrity of a grinding wheel include:
- incorrect application
- improper mounting
- malpractices during grinding operations
- grinding machine defects and
- poor storage and handling.
Abrasive wheel selection
Not all abrasive wheels are the same. When selecting an abrasive wheel, you must ensure it is compatible with the grinder and is suited to the intended application. The use of incompatible abrasive wheels may cause the wheel to fracture. You should consider:
- compatibility with the material and task.
Abrasive wheels are manufactured from various abrasives, grit sizes and bonding materials to suit a range of applications. Where doubt exists contact the manufacturer to determine suitability
- compatibility with the grinding machine.
- The maximum operating speed marked on the wheel must be greater than the spindle speed of the grinder
- The physical characteristics of the wheel such as: outer diameter, width, bore diameter and shape (straight sided, tapered, cupped, etc)
Mounting / installation
Abrasive wheels must be installed by an appropriately trained person. When preparing to install an abrasive wheel, the wheel should be closely inspected for any signs of damage. Damaged wheels must not be used. The installer must confirm compatibility (with material, task and machine) prior to installation.
Doing a ring test
Cracks in abrasive wheels may not always be visually evident, but many wheels can be checked for cracks by carrying out a ring test. This is achieved by suspending the wheel from the bore (either on your finger or small pin) and tapping it with a light, non-metallic implement (heavy wheels should be supported on a clean, hard surface). The wheel should produce a clear metallic ring. If the wheel sounds dull or dead, it may be cracked and should not be used.
Read the manufacturer's instructions
As some variation exists between different grinding machines and abrasive wheels, the installer should refer to the machine manufacturer’s instructions for the relevant installation and retention requirements. Typical installation requirements include:
- the machine spindle should be free of burrs or damage (Figure 2). The wheel should fit freely but not loosely on the spindle
- the abrasive wheel should be mounted between recessed flanges of equal diameter which are usually at least one third of the diameter of the wheel. The contact faces of the flanges must be free of burrs or rough edges which may otherwise damage the wheel
- a bush (where used) should not project beyond the sides of the wheel
- the clamping nut should be tightened only sufficiently to hold the wheel firmly
- the guard and work rest should be reinstalled, and clearances adjusted. Before turning the power on, turn the wheel by a hand a few revolutions to confirm it clears both the work rest and guard
Safe work practices
Workers must receive relevant training on how to safely operate a grinder. The training must be specific to the type of grinder and the tasks being undertaken. Examples of safe work practices include:
PPE and appropriate clothing
- appropriate personal protective equipment must be used
- loose clothing may be drawn in between the wheel and workpiece and should not be worn. Similarly, long hair should be tied back
- ensure grinding is carried out in an area away from other workers and the working area around the grinding operations are kept clear
Correct operation of grinder
- new or re-fitted wheels should be trial run at full operating speed for at least one minute before the workpiece is applied. During the trial run everyone should stand clear
- excessive vibration usually indicates that the wheel is out of round. Such wheels should not be used until they have been balanced by dressing. Wheels which cannot be balanced by dressing shall be removed
- never force the wheel by exerting excessive pressure on it. The wheel characteristics (abrasive, grit size, grade and porosity) govern its cutting power
- never grind on the side of the wheel unless permitted by the wheel manufacturer. Most wheels are designed for grinding on the outer (peripheral) surface only
- ensure the work rest (where fitted) is adjusted as close to the wheel as practicable and securely fixed in position. The gap between the wheel and work rest should be maintained at less than 2mm as the wheel wears down
- never impact the wheel with tools or the workpiece. Contact with the wheel shall be made by exerting gradual, even pressure.
A guard of adequate strength should be provided, where practicable, to achieve the following:
- contain wheel fragments in the event of fracture
- reduce the likelihood of the operator coming into contact with the wheel
- protect the wheel against inadvertent damage
- prevent an oversize wheel from being fitted.
The guard must be fabricated from a material of adequate strength to withstand the impact force of any ejected wheel fragments.
The guard should enclose the wheel to the greatest possible extent, keeping the opening as small as possible. Adjustable hoods or tongues may also be incorporated into the guard to compensate for the increased exposure as the wheel wears down.
When a guard is constructed from several component parts, the fasteners shall be of adequate strength to prevent separation of the guard in the event of wheel failure. This also applies to any fasteners used to anchor the guard to the machine frame.
Personal protective equipment
Suitable eye protection shall be provided and used by operators for all grinding operations.
Protective visors or shields may be installed on some fixed grinders to protect the operator from flying particles. However, these devices shall not exclude the use of eye protection.
Other personal protective equipment may be required depending on the nature of the grinding operation. This may include aprons, gloves, safety shoes, hair nets, hearing and respiratory protection.
The grinder must be inspected prior to each use and maintained in accordance with the manufacturer’s requirements. Inspection and maintenance may include ensuring the:
- machine is kept clean and free of grinding dust or other contamination
- wheel is in serviceable condition, i.e. undamaged, balanced, no evidence of loading (clogged with material) and dimensionally acceptable
- work rest is undamaged, adjusted as close to the wheel as practicable and securely fixed in position
- protective guard and visor (where fitted) are secure and undamaged. Inspect guards for cracks and retention of all fasteners
- machine spindle is undamaged and there is no excessive play
- exhaust system (where fitted) is functioning correctly
- electrical safety of the machine, including switches, supply lead and Residual Current Device (RCD) where fitted.
Dressing is a process where material is removed from the working surface of the abrasive wheel. Dressing is necessary for efficient production and maintaining the integrity of the abrasive wheel. Frequent light dressings are generally preferable to occasional severe dressings.
A revolving cutter type dressing tool (Figure 3) is most commonly used for dressing. When using this type of dressing tool, it should be supported on the work rest, with the work rest adjusted away from the wheel to allow the heel of the dresser to hook over the work rest.
There are many types of abrasive wheel dressers, with different methods of use. Where necessary, the wheel and machine manufacturers should be consulted to confirm the most appropriate method.
Handling and storage
Care shall be exercised when handling and storing abrasive wheels to prevent damage. All abrasive wheels are fragile, though some are more susceptible to damage than others. Appropriate precautions include:
- handle wheels carefully to prevent dropping or bumping them together
- do not roll wheels
- use suitable plant which provides adequate support to transport large wheels.
Abrasive wheels should be stored in an area that is dry and not subject to large changes in temperature. Some bonded abrasives may be affected by excess humidity, dampness and extreme temperatures.
The wheels should be stored in suitable racks and located as near as practicable to the grinding location but remain protected from traffic or excessive vibration.
Wheels may be stored horizontally on a flat surface or suspended vertically from pegs through the centre hole of the wheel. Guidance should be obtained from the manufacturer to determine the most appropriate method of storage, especially for thin wheels.
- Australian Standard AS1788.1-1987 Abrasive Wheels, Part 1: Design, construction and safeguarding
- Australian Standard AS1788.2-1987 Abrasive Wheels, Part 2: Selection, care and use
- Health and Safety Executive (HSE), UK, guide: Safety in the use of abrasive wheels