- Types and General Characteristics of Angle Grinders
- Types of Angle Grinder Discs
- Safety First
- Which angle grinder should I buy?
- Popular 4.5 inch Angle Grinders in the UK
- So what is the best 4.5 inch angle grinder in the UK?
One the most versatile tools to have in the home workshop is the angle grinder. Angle grinders are used to cut, grind and polish metal, as well as to cut and grind masonry. Although one does not immediately associate angle grinders with woodworking, they can also be used very effectively to sand down and shape wood.
Of course as with any popular power tool, there are a number of makes and models available on the market each with its own features and unique characteristics, often making it a challenge for the average DIY-er to choose the best angle grinder for their workshop and one that perfectly suits their needs. So here at DIY-high, we are going to examine the humble angle grinder in all of its glory, looking at the different types available and the different features that various brands and models offer, in an effort to make your angle grinder buying decision an easier process.
Types and General Characteristics of Angle Grinders
Angle grinders are usually referred to by the size of the cutting or grinding wheel that they accept. They come in a range of sizes to accommodate the variety of metal-working and stone-shaping jobs one finds in a typical workshop or job site. The most common angle grinder sizes range from 4.5 inch machines up to 9 inch behemoths, and although there are both smaller and bigger angle grinder-esque machines available, they are less commonly classed within the angle grinding category. Angle grinder sizes may be represented either in imperial or in metric units. The common sizes include:
- 4.5 inch angle grinders (115 mm)
- 5 inch angle grinders (125 mm)
- 6 inch angle grinders (150 mm)
- 7 inch angle grinders (180 mm)
- 9 inch angle grinders (230 mm)
4.5 inch angle grinder: The most popular angle grinder in workshops of today is the 4.5 inch machine which has the characteristics to satisfy the requirements of most DIY-ers and work professionals while not being overly expensive.
Spindle size: The commonly used angle grinders, from the 4.5 inch angle grinder up to the 9 inch angle grinder all possess the same size spindle namely, 22.2 mm in diameter or an M14 thread. This near universal spindle size makes life easier when buying cutting and grinding wheels, however, extreme care should be taken not to use wheels that are designed for one size of angle grinder in another size machine due to the different rotational speed specifications.
Mains vs battery-powered: Angle grinders also come in both mains electricity-operated as well as battery-operated formats. Although battery-operated power tools have their obvious advantages, due to the rotational speeds and power required for most jobs with angle grinders, corded mains-operated angle grinders tend to be the favoured type in the workshop, while battery-operated angle grinders are more useful for smaller less demanding cutting and grinding jobs. In this article, we are going to focus primarily on the corded variety.
Types of Angle Grinder Discs
As angle grinders can be used in a variety of different cutting and grinding jobs, there is naturally a wide range of different cutting and grinding wheels available each ideally suited to cutting, grinding or polishing a specific material. Discs and wheels for angle grinders are usually labelled with the material they should be used on, which includes:
- Steel cutting (usually made from aluminium oxide)
- Stainless steel cutting (usually labelled “INOX”)
- Metal grinding
- Masonry cutting (usually made from silicon carbide)
- Masonry grinding
- Wood sanding and shaping
- Paint removal
Disc thickness: In general, discs made for grinding and polishing will be relatively thick in order to withstand the pressures experienced on the flat surface of the disc, while cutting discs will be comparatively thinner and should never be used for grinding or polishing due to their greater fragility.
Direction of rotation: Some angle grinder wheels, particularly cutting discs, have a specific direction in which they should turn during operation, therefore they should only be installed on the angle grinder in a single orientation to ensure that they turn the correct way. These unidirectional discs will have their direction of rotation clearly marked on them, while those wheels that have no directional markings may be installed on the angle grinder either way round.
Threaded discs: Some angle grinder discs have a threaded spindle hole that allows them to be quickly installed on to an angle grinder by simply winding it on to the M14 thread that is typical of most angle grinder spindles. In such cases, using the wheel locking flange nut to secure the disc to the angle grinder is not always necessary as the disc will only wind on even more tightly as it spins in the angle grinder.
When it comes to angle grinders, safety is the number one priority above all else as this category of power tool can be more dangerous than most if used improperly or if the right safety precautions are not taken. Consequently we’re going to dedicate a whole section here to looking at the safety aspects of using angle grinders.
The most important precaution to take when operating an angle grinder is to ensure that all the correct safety equipment is used to protect oneself in the event of an angle grinder wheel failure or other mishap. The following safety kit is essential and should be worn at all times whenever an angle grinder is in use:
- Impact-resistant safety glasses
- Face shield
- Dusk mask
- Thick pair of gloves (preferably that extend over the wrists)
- Thick clothing or overalls (ensuring all areas of exposed flesh are covered)
Angle grinder wheel rotation speeds
In general, the smaller the angle grinder, the greater the speed at which its cutting or grinding wheel will spin. As the wheels themselves usually have a maximum rated speed at which they can be spun, a cutting or grinding wheel should never be used on a smaller angle grinder than it was designed for, otherwise one risks having the disc fail and disintegrate at the higher speeds of the smaller angle grinder causing a significant safety risk to the operator. Furthermore, some types of angle grinder wheels, namely metal cutting discs, tend to get smaller as they are used, and a common misconception is to use the worn-down discs in a smaller angle grinder once they get to a size that fits the smaller machine – this should never be done since the wheel is unlikely to have been rated for the higher speeds of the smaller grinder! Maximum rotational speeds are usually indicated on the angle grinder wheels themselves and these should be strictly adhered to at all times.
Safety guard removal
All angle grinders come fitted with an adjustable wheel guard that protects the operator’s hands from accidentally touching the cutting or grinding wheel when in operation. The guard is also there to help prevent debris and sparks from coming towards the operator while the angle grinder is in use, and it also acts as a barrier in the event of the angle grinder disc breaking up. Consequently, removal of the protective guard from angle grinders should rarely, if ever, be done. There are some occasions when the guard has to be removed in order to perform the task at hand, such as when grinding on a flat surface using a flat wheel, however, on these occasions the type of angle grinding wheels used are inherently at a lower risk of breakage and therefore less of a safety hazard.
Cutting and grinding technique
A little bit of skill is required when using an angle grinder and there are a few things to remember when operating the tool:
- When switching on the angle grinder, always wait for it to reach full speed before touching it to the workpiece.
- Always make contact with the workpiece gently and avoid any heavy-handed actions with the angle grinder when in operation.
- Keep the wheel moving back and forth over the workpiece, particularly when cutting. This ensures that heat does not build up in any one spot on the workpiece.
- When metal cutting, never apply sideways pressure or attempt to change the direction of the cut, as this puts undue pressure on the cutting wheel and puts it at a greater risk of breakage.
- When cutting with an angle grinder, always start from the back (ie. closest to the operator) of the workpiece and work forward. This allows the operator to easily see where the cutting line is on the workpiece during the whole cutting process.
Angle grinding wheel care
Care should be taken when handling and storing angle grinder discs to ensure that they do not become damaged, cracked or weakened and that they don’t become a safety hazard when used on the angle grinder. Handling tips include:
- Never expose angle grinder wheels to water or any other solvent as the bond that holds the material of the wheel together may be adversely affected.
- Never throw or drop angle grinder wheels. Any cracked or partially damaged discs should be discarded and never used.
- Many angle grinder wheels have an expiry date, and should never be used beyond this date as many disc types can slowly deteriorate over time even when stored properly.
Steel & stainless steel: When cutting and grinding metal, it is important to know which type of metal you are dealing with. Most angle grinder metal-specific discs are designed for the cutting and grinding of steel or, if they are labelled with ‘INOX’, stainless steel.
Aluminium: Since the wheels for cutting and grinding metal are usually made from aluminium oxide, they can not be used successfully to cut and grind aluminium. Instead, to cut and grind aluminium-based materials, masonry-specific cutting and grinding discs can be used, but in such cases, care has to be taken since the dust produced will be flammable and poses an explosive risk.
Copper & magnesium alloys: Cutting and grinding of some copper alloys can be detrimental to health as they can release toxic substances during the process, while the dust produced from machining magnesium-based alloys can pose a significant fire hazard.
Other safety tips
- When cutting and grinding any metal, a lot of hot sparks are generated which represent a fire hazard. Consequently, all flammables should be removed from the area beforehand.
- Always buy good quality cutting and grinding wheels as they are more likely to have been thoroughly tested and are less likely to break.
- Never use an angle grinder wheel designed for cutting in a grinding job as cutting wheels are thinner and more susceptible to breakage from perpendicular forces.
- Always use the broad flat surface of a grinding wheel for grinding and not its perpendicular edge.
- Never use an angle grinder to cut wood or any other material for which the angle grinder blade has not been designed to work with.
Which angle grinder should I buy?
So now we know the different types of angle grinder out there and the different types of jobs we can use an angle grinder for, how do we go about picking the right one for our workshop given all the different makes and models? One of the ways to make your angle grinder decision is to look at the different features and characteristics that each one offers. Below we go through each of the components that we find on today’s modern angle grinders and their usefulness in the workshop.
One of the key components of angle grinders is the wheel guard which protects the user from accidentally touching the spinning wheel and from any debris ejected off the workpiece towards him. This wheel guard, which only shields part of the angle grinder wheel, has to be regularly adjusted so that it is optimally positioned as the angle grinder is operated in different orientations. Consequently, the mechanism for adjusting the wheel guard is an important feature to take into account when choosing an angle grinder. Most budget angle grinders facilitate wheel guard adjustment via a screw that needs to be loosened and tightened using a screwdriver. This can make regularly adjusting the wheel guard a tedious task. As a consequence, those that plan to use an angle grinder more intensively, should opt for an angle grinder where the wheel guard can be instead adjusted through the use of a finger latch making it a much quicker and easier process.
Another important feature of angle grinders is the side handle which should always be made use of to ensure full control of the angle grinder during use. Almost all angle grinders have the facility to attach the side handle to either side of the angle grinder in order to accommodate both left-handed and right-handed users. Some angle grinders even have the ability to attach the handle in other positions (such as to the back of the machine) which can make the angle grinder even more comfortable to work with in certain situations.
In general, angle grinders favour one of two types of handle orientation. Some brands of angle grinders, such as DeWalt angle grinders, favour a side handle that is oriented exactly perpendicular to the body of the machine, whereas other brands such as Bosch or Makita angle grinders have handles that are tilted forward at an angle greater than 90° to the body of the tool. Which is better comes down mostly to personal preference, although some more experienced angle grinder users have sometimes suggested that having a side handle at 90° is more comfortable and less obstructive specifically when using the angle grinder for cutting.
Dead man’s power switch
Most budget 4.5 inch angle grinders have a sliding power switch which can represent a safety hazard if the power switch is inadvertently locked in the ‘on’ position when the angle grinder is being plugged in. In such cases, the power tool will turn on unexpectedly presenting a significant safety risk to the operator and those around him. To counter this safety risk, some more expensive angle grinders will feature a dead man’s switch that ensures that the power switch cannot physically be left in the ‘on’ position when there is no electrical power to the angle grinder.
Restart (No-Volt) protection
Another risk arises, especially on older angle grinders, if power is suddenly lost to the machine while it is in operation. If power is then restored to the angle grinder, the tool will reactivate unexpectedly raising the safety risk to the operator. As a result of this safety hazard, more recent 4.5 inch angle grinders will have a restart protection feature, which prevents tool re-activation after a power failure without power switch cycling.
Some angle grinders have a feature known as ‘soft start’ which means that the angle grinder does not immediately reach full rotational speed when switched on but instead more slowly revs up to its maximum speed. This has the advantage of reducing the kickback that an operator experiences when first starting the power tool making it a little safer to use.
Angle grinder girth
The body thickness or girth of the angle grinder can also be an important factor to take into consideration when purchasing the power tool, as angle grinders with a larger girth can make holding onto them more challenging particularly if the operator has smaller hands. So as a general rule, the smaller the girth of the angle grinder, the less tiring it will be for the hands. This, in turn, will allow for longer operating times, an important consideration since most angle grinder cutting and grinding tasks require significant amounts of time to complete.
Popular 4.5 inch Angle Grinders in the UK-- Information not available
So what is the best 4.5 inch angle grinder in the UK?
The DeWalt DWE4206K is our current favourite in the 4.5 inch angle grinder category, exhibiting a range of features as well as robustness, and all for a non-bank breaking price. The DWE4206K angle grinder incorporates a very powerful 1010W electric motor capable of taking on almost any cutting or grinding job. It also features tool-free wheel guard adjustment using a finger latch system, and a unique DeWalt-designed dust ejection system that minimises dust and debris ingress into the body of the tool that houses the motor (see video below). The DeWalt machine’s body also sports a small girth or thickness, making holding and handling the angle grinder a comfortable experience. In terms of safety, the DWE4206K has most of the essential safety features you would want in an angle grinder. These include a safety switch and restart protection to ensure that the power tool cannot be inadvertently activated even after a temporary power failure. It also incorporates the soft start feature which reduces the kickback from the power tool on startup. All in all, the DeWalt DWE4206K angle grinder is worth getting if you’re planning to do a serious bit of metal or stone cutting or grinding, or you are planning to use an angle grinder on a frequent basis, as you will be thanking yourself for that extra bit of quality in getting the job done.