Important safety factors to consider when choosing products for cutting and grinding with angle grinders

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A right-angle grinder, commonly known as an angle grinder is a very powerful and useful tool but can also be a very dangerous tool if not used correctly.

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Selecting the correct size machine is essential to ensure a safe operation – for instance using a 230mm diameter machine to grind down welds on palisade fencing will prove to be very unmanageable and quite possibly very dangerous.

Conventional angle grinders come in various sizes ranging from 100mm up to 230mm diameter, with the 115mm and 230mm diameter as the most popular in South Africa.

When selecting the correct angle grinder, the size of the disc that will be used should be considered. A disc too large for the given machine (i.e. using a 125mm diameter disc on a 115mm diameter machine) will run at a higher speed than it is rated for, resulting in a very dangerous operation. Disc size diameters are clearly displayed on the labels for easy reference.
Further to selecting the correct sized disc, power and speed of the angle grinder also plays a significant role. POWER refers to the measurement of input or output wattage that the machine uses (depending on the manufacturer). Generally, the rule of thumb is that a higher power rating ensures a better performance of the abrasive product. When an abrasive disc is cutting or grinding, it is putting additional load on the machine. If the machine is under-powered, the extra strain may cause a reduction in motor speed, causing potential damage to the machine and underperformance of the disc. More often than not, an underperforming disc then results in more pressure being applied by the operator which then makes the disc perform even worse and also potentially causes disc breakages.

SPEED on the other hand, is clarified as the rate at which the disc will turn (measured in Metres per Second and stated as the RPM). The maximum operating speed of a standard cutting or grinding disc is 80 metres per second (peripheral speed). Depending on the size of the disc, this will then relate back to a higher or lower RPM rating; 80m/s on a 115mm disc equates to 13 300 RPM, while 80m/s on a 230mm disc equates to 6650 RPM. For this reason, it is imperative that an angle grinder must only be used with a disc size particularly made for that machine.
Another very important factor to consider would be the standard accessories. All angle grinders should have a safety guard that must be fitted to the machine at all times , a handle and a retainer nut for securing the disc. Retainer nuts are available in various types and they are for fitting the disc to the machine, including are some that don’t require a spanner to fasten and loosen. Regardless of which type, make sure that you are not over tightening it as these machines are designed to self-tighten on start-up, therefore requiring only tightening by hand.
Remember to inspect discs for potential damage prior to use. The periphery of the disc should be intact, not chipped or frayed and it should be flat, not warped. Never attempt to bend or twist the disc as the fibre reinforcing will be damaged and potentially form a dangerous crack.

Safe usage and operation pictograms are displayed on each disc label that should present the following markings:

    OSA – Organisation for Safety of Abrasives: These manufacturers commit to certified quality management with documented processes and internal testing facilities of the highest competence ensuring product safety for the end user

    EN Standard – European safety requirement for bonded abrasive products (such as cutting and grinding discs – EN 12413)

    Safety pictograms – these pictograms show the required PPE to ensure safety for the operator and includes gloves, ear protection, eye protection etc.

    Material Applications – the disc will identify which type of materials it may be used on. Note that this will quite possibly only be a general identifier (such as “Metal”). Contact the manufacturer should you require more detail on specific applications.

    Wheel type – this will tell you whether the disc is manufactured for free hand cutting, stationary machine cutting or grinding applications.

    A cutting disc should never be used to grind with or cut anything but in a straight line. Bending the disc to cut a curve or radius will result in the fibre reinforcing becoming damaged and may cause wheel failure.

    For grinding applications, a minimum grinding angle of 30 degrees is essential. This is what is termed the angle of attack. The optimal range is between 30 and 40 degrees to the surface. Should you increase the angle of attack, the disc will be dressed more and the effectiveness of the grind will be reduced. This could also lead to chatter marks and large, deep scratches in the workpiece. Should you reduce the angle of attack, you run the risk of overheating the face of the disc which will cause the disc to start fragmenting and may become a major safety hazard.

    Taking the time to choose the correct tool and using this in conjunction with the highest quality, value for money abrasive products will ensure that you complete your task safely and with minimal effort.

For more information, please contact: 011 271 6400 | info@grindtech.com | www.grindtech.com.

Grinding Techniques Your Partner in Ship Building and Repairs

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A wide variety of abrasives coated and bonded are used when building and repairing marine vessels. Grinding Techniques, a local manufacturer of bonded, and converter of coated abrasives is your perfect partner with quality abrasive products suited to various applications for the ship building and repair industry. The first thing that comes to mind when one thinks of large marine vessels being built and repaired would be enormous structures fabricated from very large pieces of metal.

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There are however thousands of parts inside a ship that also need to be fabricated and maintained by using a wide variety of bonded and coated abrasives. Cutting and grinding discs form a big part of the selected abrasive product range whilst fabricating these smaller parts which will include the vessels tubes, pipes, stairs and even the balustrades to mention a few.

Grinding Techniques locally manufactures a comprehensive range of Superflex cutting and grinding discs for all applications and materials to be cut or ground. Further to this, we also carry a full range of coated abrasive products for the finishing and polishing requirements of these manufactured parts.

When it comes to cutting and grinding applications on a vessel there would be a variety of scenarios to be considered, for example the accessibility of the area where the work needs to be performed and what material type is to be cut or ground. Understanding the final required finish of the material to be worked on is also of utmost importance when selecting the best suited abrasive product for the job at hand. Angle grinders would be the most preferred power tool to use in confined spaces of a vessel due to their size and the comfort of use they offer to the operator. Carbon steel, aluminum and stainless steel would be the most common material used for components in ship building. Special care needs to be taken when selecting the ideal cutting or grinding disc for each material type and application. Always ensure that the correct specification cutting or grinding disc is used for the type of material to be worked on. One of the common challenges in shipbuilding with various materials involved is the cross-contamination of cutting and grinding discs and material ground. Products specifically designed to cut aluminum for example should not be used to cut steel and stainless steel. When cutting stainless steel for example always use the disc on stainless steel only for its entire life cycle to preserve optimal product performance and avoid cross-contamination of materials. At Grinding Techniques, we have a full range of application specific “Superflex” cutting and grinding discs for every material to be cut or ground. Contact one of our product specialists for a safe and task specific abrasive solution for your applications.

Our full range of coated abrasive products include flap discs, resin bonded fiber discs and Velcro backed sanding discs to name a few – all manufactured with the highest materials to meet any surface finish requirement. In addition to this, we also offer a full range of wire brushes used in the ship building and repair industry.

At Grinding Techniques, the safety of our customers is a top priority. Operator training is offered to reduce the labor time spent while cutting and grinding as products perform at their best when used at the correct angle, pressure and speeds on the correct materials.