Grinders

Air-powered grinders are more suited to continuous use in comparison to cordless or electric grinders for several reasons -

• They have fewer internal components, which means they are lighter in weight, which enhances operator comfort and reduces fatigue.
• They are less prone to overheating because they are air-powered and don't rely on an electric motor, which is more prone to heat build-up during extended use. As long as the air compressor can supply a consistent flow and pressure (measured in CFM and PSI), the grinder can operate continuously with stable performance.

The limitation of a pneumatic grinder is that it requires an air compressor to function, which needs to be able to keep up with the grinder's demands, and they are also louder than cordless and battery-powered grinders.

The grinder should be cleaned after each use by removing dust, metal particles and any other debris that may have built up in the vents and moving parts, because this build-up can cause overheating and also reduce efficiency.

If the operator is using a pneumatic grinder, then it is key to ensure that the air inlet is clean and free from contaminants. It should be lubricated to the manufacturer's specifications, by adding a few drops of air tool oil into the air inlet to reduce internal wear and prevent corrosion.

Always store the grinder in a dry and clean environment, away from extreme temperatures, to avoid corrosion.

Finally, ensure that the grinding discs show no cracks or wear, otherwise they will put strain on the grinder by forcing it to work harder, and damaged discs create a potential safety hazard.

Choosing a grinder for metalworking depends on the type of work, material and level of precision needed.

If the work is for heavy material removal or cutting, then an angle grinder would be most suited, however if the work needs to be more precise, such as for deburring or polishing, then a die grinder is more suitable.

Sometimes grinding work is continuous or carried out for prolonged periods, and if so, then we would recommend using a pneumatically powered grinder, because they are less prone to overheating through heavy use and are lighter to handle, which will reduce operator fatigue. If the grinding work is likely to be carried out remotely, or away from a power source, then a battery-powered grinder will be more useful, but ensure there is a spare battery available to reduce downtime when a battery runs out of power.

Finally, ensure the grinder has sufficient power (if electric or cordless), or the air flow and pressure (if air-powered), are adequate to ensure the grinder won’t get bogged down under load.

When using a grinder it is important to wear personal protective equipment (PPE), because these tools produce sparks, debris, noise and vibration.

Always wear goggles or a full-face shield to protect against flying metal fragments or sparks. Wearing standard glasses will not protect the operator sufficiently against any debris flying from a grinder.

Wear durable, well-fitted work gloves to improve grip and protect the hands against sharp edges, heat generated from grinding, as well as vibration.

A dust mask or respirator is always advised to be used to prevent the inhalation of harmful particles, particularly when grinding materials that produce fine dust, such as metal, paint or wood.

Clothing should be made from non-flammable material, not be loose (to minimise the risk of getting caught in the grinder) and involve long sleeves to protect the skin from anything that could be ejected from the grinder when it is in use. Steel-toe boots should also be worn to protect the feet from anything heavy that could be dislodged during grinding and fall. 

For cutting, we recommend using a cutting disc up to 3mm thick. The thinner the blade is, the easier it will cut through materials like metal, steel and stone. The thinner profile reduces resistance, which enables the operator to carry out fast and clean cuts.

When grinding, use discs that are usually 6mm or thicker and can handle pressure from multiple angles, due to them being reinforced. Examples of what a grinding disc would be used for include, smoothing welds, removing excess material or shaping metal surfaces.

Bench grinders are most commonly used to sharpen tools, such as chisels, drill bits, lawnmower blades and axes. Bench grinders can resharpen metal-edged tools quite quickly, however the operator needs to be careful as they can remove material fast, so there’s a risk of overheating or over-grinding the tool.

Cordless grinders, especially higher voltage models (18V or higher), provide very similar performance to corded and air grinders, due to modern advancements in battery technology, allowing them to produce high torque and maintain consistent speed under load.

However, they do have limitations in comparison to corded and air grinders, with battery life being the main one. We recommend always carrying a spare battery to reduce any downtime when one battery runs out of power. The other limitation is overheating. An air grinder can grind continuously because it is less likely to overheat, as it has fewer internal components than other grinders, however a cordless grinder may overheat when under continuous and heavy load, such as during deep grinding on thick steel.

We always recommend using an air grinder for non-stop industrial use, however, if the grinding work is in a remote location or where power access is limited, then a cordless grinder will still get the job done.

Runout on a grinder refers to how much a grinder’s spindle or mounted disc deviates from a perfectly true rotation, with just a little bit of runout affecting grinder performance and accuracy, because it means the disc is wobbling and having an inconsistent contact with the work surface.

Runout increases vibration on the grinder, which leads to increased wear on the disc and also the tool, particularly on the bearings. In addition, the increased vibration makes the grinder harder to control and operate, which increases operator fatigue.

To avoid or minimise runout, always ensure that discs are mounted correctly onto the tool and then secured, and also regularly inspect the grinder for any wear before use.

Standard grinders are not normally suitable for use in hazardous or explosive environments because they can produce sparks and have components that may ignite flammable gases or vapours.

An ATEX approved grinder would need to be used, which is designed to not create sparks, has reduced vibration and operates at a lower temperature.

The main advantage that variable speed grinders provide is control for the operator. High speeds are ideal for cutting through materials like steel or grinding aggressively, whilst lower speeds are better for polishing or working on softer materials, such as wood.

By being able to control the RPM it means that the operator is able to control the heat generated from grinding and cutting, which is important when working on thin metals or when trying to avoid burning or discolouration. A slower speed will generate less heat than a faster speed.

Ultimately, a variable speed grinder improves versatility for the operator because it means that one tool can cut, grind and polish many materials.