Ask any workshop guy about grinders, and what usually comes to their mind is the handheld angle grinder – a versatile tool that’s easy to use for a wide variety of cutting, sanding and shaping applications.
If you’re working with wood, metal or stone, there’s an angle grinder wheel that will make your life much easier and are considered "an essential tool" in a metalworker’s tool bag.
Safety Is Crucial With Angle Grinders: Angle grinders are powerful tools for their size, though, with discs that spin as quickly as 8,000 RPM. Always make sure you have eye protection when using one, since using one will always send debris, sparks, and fragments flying out at a high speed.
Angle grinders have guards for a reason, and working without it is generally not recommended. Safety is a priority when using an angle grinder – make sure to invest in hearing and eye protection.
Angle Grinders vs. Straight Or Die Grinders
There are a couple of different grinders out there and comparing the three main types will help give you a better overall idea of what angle grinders are and why they are usually preferred over the other two types.
Angle Grinders: Are so called for the 90-degree angle that the gear head and the attached disc makes when held in your hand. Most likely, this term has come up to distinguish them from the straight grinder, which takes discs and wheels right on the end of the tool.
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Straight Grinders: Straight grinders have the wheel in a 90 degree angle (compared to an angle grinder) which makes it useful for grinding the outer edges of pieces and inner parts of pieces when a different grinding stone is attached. The angle makes it useful for different projects where an angle grinder may be a little tough to use.
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Die Grinders: Die grinders work much the same way that a straight grinder does, but instead of abrasive discs, they take dies that work much like a drill bit in action. Usually the abrasives used are smaller in size to get into tighter areas and are great for deburring rough metal edges.
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What Can I Use An Angle Grinder For?
Angle grinders were originally designed for abrasive discs, but their versatility and popularity have encouraged manufacturers to adapt them for a wide range of other uses, as well.
- Grinding is, of course, the main reason for having an angle grinder. The right grinding wheel lets you take an angle grinder and grind down metal weld lumps, sharp corners, and similar things into a smooth finish that’s safe to handle.
- Sanding and surface preparation is the most common use of an angle grinder. With the right sanding pad attached, angle grinders are very effective at stripping off old paint, dealing with rough spots and defects.
Sanding pads are much cheaper to replace than planer blades, so it’s common to give old lumber a pass with an angle grinder before sending them out for thickness planing. - Cutting is another area that the angle grinder excels in, with the right cutting disc installed. Various cutting attachments will let you cut through masonry, tile, concrete, and metal, along with the softer stuff like plastic, wood, and PVC.
- Polishing discs with a bit of polishing compound turn angle grinders into efficient finishing tools.
- They are also used with wire brushes for removing rust or adding a matte finish to a shiny surface.
- They can also be used to quickly sharpen a blade with the right sharpening disc, as well.
Choosing The Right Angle Grinder
Angle grinders are relatively inexpensive tools, and at first glance, they all look very similar to one another that there is a temptation to just go with the first cheap one you can find and get right to work.
Despite the many similarities of angle grinder brands, however, you also have to consider that most of the work you will do with the angle grinder requires you to run it for extended amounts of time.
Unlike, say a drill where you use it to place your hole and fastener and you’re done, using an angle grinder means making several passes on your workpiece with a small handheld tool – and often for hours at a time.
Durability is important in choosing an angle grinder, so make sure you are getting the right size of angle grinder with the right amount of power suitable for your project.
Small Angle Grinders:
Generally, a small angle grinder is a unit that takes discs of sizes seven inches or less. They are useful for a wide variety of cutting and grinding applications, especially when portability and maneuverability are important.
These are the most common types of angle grinders that are used today. The two most popular sizes are a 4" or 4 1/2" grinder.
They typically measure just a bit over 12 inches long at the most and have the widest range of options when it comes to power sources. These can be found in electric versions (corded), cordless versions and pneumatic (compressed air) versions.
Small angle grinders can take wheel diameters of up to 7 inches, with the smallest units able to take just the 3-inch discs, for more detailed work.
Features To Look For In Smaller Angle Grinders:
- Brushless motors on angle grinders take out the need for brush changes, and they let the cordless models run more efficiently, cooler and prolong the motor life of the tool.
- Kickback brakes stop the wheel dead in its track when the tool senses that a bind has happened, stopping the tool from wrenching itself free of your grip.
- Two-stage triggers require you to flip a safety switch off first before the trigger can start the tool, lowering the risk of accidental starts especially when you are changing discs.
- Vibration control helps to keep your hand from going numb and eases the uncomfortable feeling of the tool, especially if you are using it for longer periods of time.
- Variable speed lets you control the disc speed with the trigger, letting you ease off in case of heat buildup or go slow with the polishing disc.
Corded, Cordless And Pneumatic Angle Grinders
Corded Angle Grinders: Corded angle grinders are those that need to be plugged into a power outlet before they can work. Their advantage is clear – indefinite running time and consistent power whenever you need it. They are also more lightweight as well compared to the cordless models and are generally more inexpensive to own.
Of course, you have to be within range of a suitable outlet if you are to use a corded angle grinder and there is also the slight risk of you sawing into the power cord by accident, as well.
Cordless Angle Grinders: Cordless, or battery-powered angle grinders, take their power supply with them. For onsite jobs that require you to use a grinder up a ladder or on scaffolding, a cordless grinder can be incredibly handy to have. With modern brushless electric motors and lithium-ion batteries, they last for a good amount of time between recharges, as well.
Like most cordless models, though, quick-charge technology has only come so far in minimizing the downtime when charging up your tool. Expect at least half an hour to get a decent charge on a drained 6 Ah battery. They also weigh at least two pounds more than the equivalent corded small angle grinder.
Pneumatic Angle Grinders: Pneumatic angle grinders take the idea of the corded electric angle grinder to a whole new level. They need to be plugged into a suitable air compressor unit in order to function, but once you do, they are the lightest angle grinders you can have. With no batteries and no electric motors, the action is all powered by air pressure.
They are also some of the cheapest angle grinders you can get, too – after you invest in a proper air compressor unit, that is.
Medium & Larger Angle Grinders
Angle grinders that take just the 7-inch discs are considered to be medium-sized, while those that can take 7-inch and 9-inch discs belong in the large category. These grinders are designed more for deep cuts and going over larger surfaces in one pass, and they have the horsepower to match.
The majority of medium to large angle grinders are the corded type, with powerful motors for such a small package. A good medium angle grinder, for example, comes with electric motors rated for 3 horsepower (3 HP) or more – the same rating you would expect from an industrial planer, for example.
The large angle grinders come with motors exceeding 5 HP, and these things can be on the heavy side. A small angle grinder might weigh a bit more than 5 pounds – in contrast, a large angle grinder can weigh almost 15 pounds and measure more than 20 inches in length.
Features To Look For:
- Overload protection keeps the powerful grinder motor safe as it operates under heavy load.
- Since larger angle grinders only come with brush motors, an auto shut-off feature to let you know that the motor brushes need changing helps protect the motor from damage
- Adjustable or removable side handles lets you use your tool in tight spaces.
- Vacuum attachment lets you connect the grinder to a vacuum to cut down on the debris and dust flying around.
How To Compare Angle Grinders:
There are a few things to look for when comparing different angle grinders and some of these talking points include:
DISC SIZE
Disc size determines which discs you can use with your angle grinder, and how deep of a cut you can make with it. 7-inch discs or more lets you work on more surface area with each pass as well, but you need to invest in a heavier and more expensive angle grinder.
POWER
The power for angle grinder is usually given in Watts (W) and is usually stated as max watts out – the maximum power your grinder can put out of its business end.
For corded models, input power is rated in terms of Amps (A) while cordless models specify input in Volts (V). The input for pneumatic angle grinders are given in CFM (cubic feet per minute), often with a recommended operating pressure in pounds per square inch (PSI) specified alongside that.
Medium and large angle grinders also specify power in terms of horsepower (HP) as well, for easier comparison using smaller figures. 1,000 Watts or 1 kW is around 1.34 HP.
SPEED
When comparing speed between angle grinder models, keep in mind that those that can take smaller discs can put out faster RPM than larger models. The rotation per minute (RPM) of an angle grinder is often given in terms of “no load speed” – that is, the fastest rotation it can do with no disc installed.
Medium angle grinders have motors that can go faster than 8,000 RPM, while large angle grinders have a slower pace of around 6,000 RPM, but for more power.
A Quick Look At The Different Grinder Wheels Out There:
Most angle grinders can use any type of disc or wheel if it’s the right size. Certain wheels, like polishing and buffing wheels, are designed to be used at a low speed.
*** Do not use discs and wheels other than for their intended purpose – using cutting discs to grind, for example. When you do, you run the risk of shattering the disk and having shards shooting off everywhere.
- Silicon Carbide Discs: are used for shaping metal in general. They can grind down welding, clean sheet metal, around the edges of steel pipes, and quickly sharpen metal tools like hoes and wood axes.
- Cutoff Discs: are designed to cut the harder stuff like rods, bolts, rebars and metal pipes.
- Sanding Pads: can clear old paint as a surface preparation step and can be used for coarse and fine sanding as well.
- Grinding Discs: are well suited for quickly shaping edges and rough sharpening of garden tools.
- Wire brush Wheels: are used for stripping off paint and rust and taking off the burrs from rough-cut metal surfaces.
- Diamond Cutting Blades: are best used when cutting concrete, tile, masonry or granite. Make sure you are using the proper diamond cutting blade for your technique – there are diamond blades designed for dry cutting as well as those used for wet cutting, where water is used.
- Aluminum Oxide Wheels: are versatile discs that can be used for woodworking and in cutting crumbly material like particle boards.
- A Flap Disk: works very much like a wire brush, but with flaps instead of wires. They are ideal for blending a weld bead into the rest of the metal.
They also work well for deburring rough cuts and finishing metal in general and can also be great for removing larger amounts of wood, like an aggressive sanding pad would.
