Choosing angle grinder work tools
The list above is what exists. This is how to decide which of it you actually need, what separates a tool worth keeping from one that ends up at the back of a drawer.
Kickback, and which way it throws the tool
Kickback happens when a cutting disc binds in the cut. The disc stops, the motor does not, and the machine is thrown along the line of the cut. Which direction depends on which part of the disc bound, and it happens faster than any reaction.
Prevention is mechanical. Cut with the disc pulling the work into the guard rather than away from it, keep the cut straight so the disc cannot pinch, support the work both sides of the cut so it cannot close, and never cut with the disc's leading edge into a corner.
- Binding causes it
- The disc stops, the motor does not, and the machine goes along the cut line.
- Support both sides
- So the cut cannot close on the disc. An unsupported offcut pinches as it drops.
- Keep the cut straight
- Twisting the grinder in a cut pinches the disc, which is exactly the trigger.
- Stand out of the line
- Not directly behind the cut. That is where the tool goes if it does kick.
Disc speed rating and diameter
Every disc carries a maximum rpm, and it must be at or above the grinder's no load speed. A disc rated slower than the machine can burst, and a bursting abrasive disc sends fragments out at the speed it was spinning.
Diameter matters too. Fitting a 115mm disc to a 230mm grinder means the disc spins far faster at its rim than it is designed for, even though it physically fits. The guard also no longer covers it properly, which compounds the problem.
- Check the rpm rating
- At or above the machine's no load speed. A slower disc can burst.
- Correct diameter only
- A small disc on a big grinder overspeeds at the rim even though it fits.
- Check for damage
- A chipped or cracked disc goes in the bin. A ring test on a bonded disc finds cracks.
- Respect the expiry date
- Bonded abrasive discs have one. The resin degrades and the disc weakens.
Cutting discs and grinding discs are not interchangeable
A cutting disc is thin and designed for load on its edge only. Using its face to grind puts a side load on a thin brittle disc, which is one of the classic ways to shatter one.
A grinding disc is thick and designed for face loading. Trying to cut with it is slow and it wanders. Neither substitutes for the other, and the disc will not tell you which it is once the label has worn off, so keep them separate.
- Cutting disc: edge only
- Thin, and side loading it is a classic way to shatter one.
- Grinding disc: face only
- Thick and designed for the load on its face. Cutting with it is slow and wanders.
- Keep them apart
- An unlabelled thin disc and a thick one look similar in a drawer. They are not.
- One disc per material
- Steel, stone and stainless each have their own bond and abrasive.
The guard is the whole safety case
The guard contains most of a burst disc and directs sparks and fragments away from you. Removing it for access is the single most common thing that turns a grinder incident into a hospital visit, and it is done because it is inconvenient.
Positioned correctly it sits between the disc and your body, and it rotates so it can be set for the cut. If a cut cannot be made with a guard fitted, the answer is a different tool or a different approach rather than a removed guard.
- Never remove it
- It contains a burst disc. This is the difference between a fright and an injury.
- Rotate it for the cut
- It adjusts. Set it between the disc and your body rather than taking it off.
- Two hands, side handle
- The handle gives the leverage to hold a kickback. One handed use gives none.
- If it will not fit, stop
- A cut that needs the guard off needs a different tool. Reciprocating saw, or a hacksaw.
Sparks, dust and what catches fire
Cutting steel throws a stream of hot particles several metres, and they will ignite sawdust, solvent vapour, a dust extractor's bag and fuel residue. Grinder sparks setting light to something behind the operator is a recognised cause of workshop fires.
Cutting masonry produces silica dust rather than sparks, which is a long term rather than immediate hazard and needs water suppression, extraction and an FFP3 mask. So the two materials require completely different precautions from the same tool.
- Sparks travel metres
- And they ignite sawdust, solvent vapour and extractor bags. Clear the area behind you.
- Check for a fire an hour later
- A smouldering start is common and it develops slowly. Do not leave immediately.
- Masonry means silica
- Water, extraction and FFP3, all three. Not the same precautions as steel.
- Let go before it stops
- A disc coasts for seconds after the trigger. Never put it down still spinning.
Frequently asked questions
- What can you use an angle grinder for?
- Cutting steel, reinforcement, bolts, tile and stone; grinding welds and deburring; removing rust and paint with a wire cup; and polishing. The disc decides which, and the machine will do all of them with the right one fitted.
- What causes angle grinder kickback?
- A cutting disc binding in the cut, so the disc stops while the motor does not and the machine is thrown along the cut line. Support the work both sides so the cut cannot close, keep the cut straight, and never lead into a corner with the disc's edge.
- Can you use a cutting disc to grind?
- No. A cutting disc is thin and made for load on its edge only, so grinding with its face applies a side load to a thin brittle disc. That is one of the classic ways to shatter one, and a bursting disc sends fragments out at full speed.
- How do I know if a grinder disc is safe to use?
- Check the rpm rating is at or above the machine's no load speed, the diameter matches the machine, the expiry date has not passed, and there are no chips or cracks. A bonded disc can be ring tested by tapping it and listening for a clear tone.
- Is it ever acceptable to remove an angle grinder guard?
- No. The guard contains most of a burst disc and directs sparks away from you, and removing it is the single commonest factor in serious grinder injuries. If a cut cannot be made with the guard fitted, use a different tool such as a reciprocating saw.
- What size angle grinder should I buy?
- A 115mm or 125mm for general work: light enough to control, and adequate for most cutting and grinding. A 230mm has far more reach and cutting depth and is considerably more dangerous, so it belongs on jobs that genuinely need it.
- Do angle grinders start fires?
- Yes, and it is a recognised cause of workshop and site fires. Cutting steel throws hot particles several metres, and they ignite sawdust, solvent vapour and extractor bags readily. Clear the area behind you and check it again an hour after finishing.
- What protection do I need for angle grinder work?
- A full face shield rather than glasses, because a burst disc sends fragments at the face. Plus ear defenders, gloves, and no loose clothing. For masonry add water suppression, extraction and an FFP3 mask, since the dust contains silica.
