What is an Abrasive Wheel?

If you’ve ever worked with or seen someone use an abrasive wheel, you won’t be surprised to hear that they cause accidents – and even fatalities. Anyone required to use an abrasive wheel in the workplace needs to take this responsibility seriously and never get complacent.

According to the Health and Safety Executive, almost half of accidents that involve an abrasive wheel are attributed to operator error or an unsafe work system. There are around 5,000 injuries recorded each year by angle grinders alone, which makes them the third most dangerous tool, and around 11% of acute forearm and hand injuries are caused by this tool.

However, abrasive wheels aren’t just found in angle grinders, they’re in all sorts of tools, which means the injury statistics for abrasive wheels will be much higher. In this article, we’ll cover everything you need to know about abrasive wheels, including abrasive wheel regulations and the legal requirements for abrasive wheel training.

What is an abrasive wheel?

Abrasive wheels are wheels, cones or cups that have abrasive particles like grit that are bonded with either inorganic or organic substances like resin.

These bonds are cured at low temperatures. They’re shock-resistant, self-dressing, and tough. These materials are more suited to applications that don’t need a lot of precision such as cutting off or fettling.

Organic bonding substances are used for handheld and portable tools and machines. Inorganic bonding substances are usually used for grinding applications that require precision. These have a strong, hard, yet brittle structure and hold their shape. Inorganic bonds require a lot of heat for curing and are furnace-fired.

Because there are so many different abrasive wheels, they’re defined by their characteristics, including:

• Grit size.
• The coating or bonding substance.
• The type of abrasive material used.
• The grade of the wheel.
• The structure of the wheel.

Uses of abrasive wheels

Abrasive wheels are used to modify or prepare surfaces (either internal or external). They use abrasive cut-off, face grinding or periphery grinding. They can also be used for cutting, polishing, sanding, deburring and finishing.

The relative resistance, toughness, friability (how self-sharpening they are) and hardness are decided by the type of abrasive material the wheel contains. Some abrasive particles include aluminium, boron and silicon.

The coating or bonding material (organic/inorganic) determines the shape and structure of the abrasive wheel. The bonding material needs to withstand the forces the wheel is subjected to, including centripetal force, shock, friction and high temperatures.

The structure of the abrasive wheel determines the grade and grain spacing as well as the volume. Hard abrasive wheels are usually used on softer materials, while softer abrasive wheels are typically used on harder materials.

Users select the abrasive wheels according to certain criteria. This includes:

• The machine spindle speed.
• The surface type (e.g., wood, metal, stone, etc.).
• The size of the contact area (between the material and the wheel).
• The machine type.
• The wheel state.

What are the dangers of abrasive wheels?

As we’ve already mentioned, abrasive wheels can cause devasting injuries and even death. Anyone who uses an abrasive wheel, whether at home or in the workplace, is exposed to a number of risks and dangers.

These include:

• Injuries to the eyes caused by flying metallic and abrasive particles.
• Dust and fume inhalation from dry grinding (in the long term, this can cause lung damage).
• Injuries due to ejected workpieces or flying fragments.
• Vibration (over time, this can lead to hand-arm vibration syndrome, which can cause pain or loss of digits due to restricted blood flow).
• Noise (over time, this can cause hearing loss).
• Injury due to loose clothing like sleeves or ties.

Due to the dangers present, abrasive wheels need to be inspected.

Causes of injuries

There are many reasons why abrasive wheels cause injuries. Here, we’ll explore the most commonly occurring problems.

Wheel contact

Abrasive wheels rotate at speed, and as a result they will cause a severe injury if they are in contact with flesh. This is more likely for handheld tools like angle grinders as their abrasive wheels rotate at exceptionally high speeds.

Wheels breaking

If an abrasive wheel breaks while in use, this can cause horrific injuries and even death. This is because the wheel is turning at a high speed, which means if it were to break, fragments of it would be ejected at that speed. Ejection speeds can be as high as 100 miles per hour.

Workpiece or particle ejection

Abrasive wheels wear down and shed particles as they do so. Usually, you’ll see this as sparks. Sparks can cause skin damage. They’re also really dangerous if they get into the eyes and can cause blindness. It’s also possible for a workpiece to be ejected at high speed.

Drawing in

Anything that comes into contact with the abrasive wheel can get caught in it and drawn in. If this is the operator’s clothing like a sleeve or a tie, they can be drawn into the machine and injured.

Unfortunately, lots of accidents happen with abrasive wheels and most of them are due to wheel contact or wheel breakage. The breakage risk is there in every abrasive wheel but there are regulations for design, manufacturing and testing to keep this likelihood down. It’s also important for users to inspect abrasive wheels before using them and whilst using them.

What machines are associated with abrasive wheels?

Lots of machines use abrasive wheels.

These include:

Angle grinders

Angle grinders might also be called disc grinders or side grinders. They’re a type of handheld power tool that’s used for abrasive cutting and polishing. Originally, they were only used with rigid abrasive discs but now there are all sorts of attachments and cutters available.

These tools are either powered by compressed air or an electric motor. They’re used for removing excess material and are used widely in construction, metalwork, emergency rescues, and even bicycle theft.

Chop saws

Chops saws are power tools that are used to make a straight cut in wood. Some chop saws have features that mean you can measure and cut angles in the wood – this would then be called a mitre saw. A chop saw looks like a circular saw, but these are faster and more precise.

Bench grinders

Bench grinders are a permanently installed type of grinder. They’re used in workshops to perform rough grinding.

Petrol cut-off saws

Petrol cut-off saws are also known as steel chop saws. They’re hand-operated machines that are used to cut small areas of steel, stone, asphalt and concrete. They’re often the go-to cutting machine in the construction industry.

Table saws

Table saws are also known as bench saws. They’re a tool used with woodwork. The abrasive wheel protrudes through the bench. The bench supports the material as it’s being cut.

What are the different types of wheels?

Since abrasive wheels are very dangerous, it’s important that the right one is used. There are different types of wheels designed for different machines and purposes.

Here are some abrasive wheel types.

Straight grinding wheels

These are the most common abrasive wheels, and you’ll find them on bench grinders.

Cylinder / wheel ring wheels

These have a wide and long surface but don’t have mounting supports in the centre. They’re used in vertical or horizontal spindle grinders to make a flat surface.

Tapered abrasive wheels

Tapered wheels are the same as a straight grinding wheel, but they taper outwards and are wider in the centre than they are at the edges. They’re used for gear teeth or thread.

Straight cup wheels

Straight cup wheels are used to make flat surfaces and for sharpening tools in cutter grinders. They’re shaped like a cup, as you might expect from the name.

Dish cup wheels

A dish cup wheel is used to cut slots and crevices and is very thin. It’s shaped like a dish cup and has a flat centre that points outwards towards the edge.

Saucer grinding wheels

Saucer grinding wheels are used for milling cutters and twist drills. These are flatter than dish wheels.

What are the different types of abrasive wheels?

You might see the abrasive wheel types listed with numbers:

• Type 1 – Straight Wheel.
• Type 2 – Cylinder Wheel.
• Type 4 – Tapered Wheel.
• Type 6 – Straight Cup Wheel.
• Type 12 – Dish Cup Wheel.
• Type 13 – Saucer Wheel.

You can find images of these abrasive wheels on the Health and Safety Executive website.

What are the different wheel markings?

Abrasive wheels regulations require them to have markings as per Annex A of British Standard EN 12413 and British Standard ISO 5255.

Wheel markings are important as they show you which wheel you should use for the type of machinery and task. If the wrong wheel is used, it could cause injury or death.

When workers are required to replace abrasive wheels, they need the right knowledge, which is why employers need to follow abrasive wheel training legal requirements.

Abrasive wheel markings

All abrasive wheels must have the following markings:

• Trademark and test records.
• Restrictions.
• Speed strip.
• Expiry date.
• Dimensions (in mm).
• Specification mark.
• Code number.
• The speed marked clearly (in RPM).
• The maximum operating speed and ISO Type number (shape).

The expiry date

All abrasive wheels with organic bonding to be used with a handheld tool have an expiry date that’s three years after manufacture.

The code number

This is a traceable number that indicates the wheel’s manufacturing details.

The maximum operating speed

When an abrasive wheel has a diameter greater than 80 mm, the maximum operating speed needs to be marked on the wheel. The speed should be written in RPM (revolutions per minute) as well as m/s (metres per second).

When wheels are under 80 mm, it’s not practical for them to be marked because of their small size. However, the maximum speed for these should be written somewhere on a workshop notice where it is clearly visible.

When speeds are 50 m/s or more, there will be a colour-coded stripe on the wheel.

Here is an example image taken from the HSE website.

What the code number means

Typically, the first letter means the type of abrasive, then there’ll be a number that denotes the size of the grain. After, you’ll have a letter that details the bond hardness and then some letters for the type of bond. It isn’t a standardised procedure though, as all manufacturers have their own way of doing things.

Abrasive wheels regulations

It is the Provision and Use of Work Equipment Regulations Act 1998 (PUWER) that determines abrasive wheels regulations.

The regulations were put in place with an aim to keep workers safe while using equipment and machinery.

PUWER is there to ensure all equipment and machinery in a workplace:

• Is suitable for its intended use.
• Undergoes regular safety maintenance.
• Is used only by trained and competent people.
• Undergoes regular inspections by a trained and competent person.

PUWER abrasive wheels regulations apply to all UK businesses, including employers, self-employed people and supervisors.

PUWER also includes abrasive wheel training legal requirements. The Act says:

“Anyone whose job requires them to use the equipment OR carry out repairs or modifications to equipment, OR to perform maintenance work or servicing operations must be properly trained to do so.”

The regulations also state that anyone using abrasive wheels must:

• Have a training certificate.
• Be deemed competent.
• Follow COSHH (Control of Substances Hazardous to Health) regulations and the Control of Noise at Work Regulations 2005 and wear appropriate protective equipment.

Protective equipment

When working with abrasive wheels on a construction site, there needs to be head protection in addition to feet and hand protection.

When using abrasive wheels, eye protection should be used, and it should conform to personal eye protection specifications and standards (BS EN 166/167/168).

For dust protection, face masks should be worn, and they should comply with BS EN 149.

Abrasive wheel training

Abrasive wheel training legal requirements mean that you can’t operate a machine with an abrasive wheel without being trained.

Abrasive wheels are extremely dangerous. The only way risk can be reduced is through comprehensive training.

There are different training options depending on the worker’s needs. This depends on their job role and the equipment they use or supervise others using.

Training should cover the following:

• Risks and hazards that arise from using abrasive wheels and the precautions that need to be taken.
• How abrasive wheels are marked with their size, type and maximum speed.
• How abrasive wheels should be stored, handled and transported.
• How abrasive wheels should be inspected and tested for damage.
• How the components used alongside abrasive wheels function (i.e., blotters, nuts, flanges, bushes, etc.).
• How abrasive wheels are assembled so that they are properly balanced and adequate for use.
• How to dress an abrasive wheel (this means removing material from the cutting surface to sharpen it).
• How to adjust the bench or pedestal on a grinding machine.
• How to use PPE (personal protective equipment) like eye protection.

Training records should be kept that show the person’s name and the date they did the training.

COSHH Regulations and training

As well as training in how to use abrasive wheels, both employers and workers should be trained in Control of Substances Hazardous to Health (COSHH) Regulations 2002. These regulations cover dust and fumes and how they can be hazardous to health. When using abrasive wheels, dust and fumes are commonplace.

When cutting concrete and stone, RCS (respirable crystalline silica) is a known problem.

How long abrasive wheel training lasts

There is no formal period of validity for abrasive wheel training.

The Health and Safety Executive (HSE) website states how refresher training must be carried out whenever it feels necessary. For example, if there is a change in equipment, working practices or working conditions – or whenever else it is deemed necessary.

Summary

Abrasive wheels are used in grinding machines. These machines can be extremely dangerous when not used properly, which is why employers and workers need to take extra care when using them. It’s important for all involved to have adequate training so that no problems or injuries occur. If in doubt, consult the HSE website’s safety in the use of abrasive wheels page.