Angle Grinders 101

Here Paul Kitchin, National Applications Manager at FEIN gives a practical guide on how angle grinders work, what are the most useful features to look out for and what separates the best machines from the rest.

Angle grinders are a staple of the UK tradesperson’s tool collection across a wide range of disciplines (not just metalworkers). Beyond occasional use, they are extremely useful to have helping users cut, polish, sand and grind a wide variety of materials. However, finding the best one for your requirements can be difficult, as there appears to be almost infinite variations available.  So here’s a handy list of features to check and compare machines and make sure you get exactly what you need.

i0000648_OFC_SCRSize and power

When it comes to angle grinders size is important. The most common sizes for electric grinders are 4.5” and 9”. Choosing which is the best for your needs depends on what types of tasks you most commonly undertake. If you’re mainly going to be carrying out heavy steel grinding, large steel cutting, cutting slabs or mortar, then a 9” grinder is best as you’ll be able cover larger surface areas more quickly. If however, you need more precision and are working with more intricate stone or metal work then a 4.5” grinder will be much more versatile and easier to handle.

Importantly, size must be matched by power and this is usually indicated by the wattage of the machine. The bigger the grinding wheel the more power it needs. For a 9” grinder I would recommend getting a machine with a 2,000 W motor as a minimum. For a 4.5” grinder I suggest a minimum motor of 750 W.


The speed of an angle grinder determines the quality of the cutting or grinding action. This is measured by no-load speeds, which means ‘how fast the disc will rotate before it makes contact with the work piece’. Angle grinders can operate at speeds between 6,000 rpm and 12,000 rpm. In my experience, how the machine then copes under load is crucial because if the grinder has a high no-load speed but its motor is underpowered or of poor quality it will not maintain a high speed throughout the task. I advise that you look for grinders with all-metal gearboxes, advanced electronics and high quality carbon brushes to ensure maximum efficiency.

IMG_0009 - For blogSafety

Accidents involving angle grinders can be nasty. The good news is that manufacturers work extremely hard to update machines with the best safety features available. Some of the most beneficial include adjustable guard wheels, soft start mechanisms and reduced kickback. The automatic kickback stop ensures it will switch the machine off in the event of a snag.

You can never be too careful when working with these machines and there are a few other safety features that often don’t get considered. Firstly, the positioning of switches is crucial – rear mounted or a good distance away from the disc is best practice. Ideally buy a model that comes with a dead-mans switch as these are the safest and will render the machine inactive as soon as the trigger is released. In addition, though it may seem a small part of a buying decision, make sure the machine has an industrially graded cable if it’s corded.

IMG_0010 - For blogComfort and ease of use

One of the final things to compare is what it feels like in the hand and what it’s like to operate day-to-day. Unfortunately you’ll never get a full picture just picking a machine up in a shop but there are a few things you can look out for that are good indicators. Firstly, do pick it up and check how comfortable the handles are, the positions of the switches (are they easily reachable) and how it feels using any auxiliary side handles. In addition, invariably users will be wearing gloves and fairly thick gloves at that, so take a pair with you and see if the switches are still easy to operate.

Secondly, do a bit of research beforehand and check things like the vibrations class and weight of the different machines you’re considering. The less vibration the better and generally the same is true of weight. However, balance plays a big part so picking it up and putting it into the common positions of use is wise.

Thirdly, changing the discs can sometimes be a real headache on poor quality machines. There is also the worry of the discs remaining tightly clamped in during use. Disc lock functionality is common but there are a number of machines available with tool-less disc changes, which are extremely useful as not only does it make the accessory change quicker, there is also less chance of loosing any additional parts or keys.

a0001291_OFC_SCRBy asking how angle grinders stack up in terms of power, size, speed, safety and comfort, tradespeople can quickly and easily sift the best from the rest.

For more information about FEIN’s range of grinders check out . Alternatively Fein is running a promotion on its compact grinders offering you a free WSG 7 grinder free (worth £71.95) when you purchase its big brother the WSG 17. The promotion runs until the 31st March with details can be found at

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