Angle Grinder Disc Types Explained: Which Disc for Which Job

An angle grinder will cut, grind, sand and strip metal, but only with the right disc fitted. Cutting discs slice steel and must never be used for surface grinding, grinding discs remove stock and dress welds, flap discs blend and finish, wire brushes strip rust and paint, and diamond blades cut tile, brick and block. Get the family right and the tool is predictable and safe. Get it wrong and you either ruin the workpiece or throw abrasive across the workshop.

This guide covers every disc type you can fit to a UK DIY grinder, how the size and speed markings work, and which disc to reach for on the most common jobs.

The five disc families at a glance

Almost every disc sold for a hand-held grinder falls into one of five groups. The thickness or grit tells you which is which, and that number is printed on the label and stamped on the metal ring.

The logic behind the label is simple. Cutting is a slicing job, so the disc needs to be thin, sharp and reinforced. Grinding is a surface job, so the disc needs mass and a bonded face that wears away slowly. Everything else, from blending to stripping paint, sits somewhere between those two jobs.

Cutting discs: thin, thick, and what the numbers mean

A cutting disc is marked with three numbers, for example 115 x 1.0 x 22.23. That is diameter, thickness and bore in millimetres. For most UK grinders the diameter is 115 or 125mm and the bore is 22.23mm, which is the standard spindle size.

Thickness is where the real choice sits:

• 1.0mm and 1.2mm (ultra thin). Less material to remove means a faster cut and much less heat pushed into the workpiece. This matters on stainless steel and thin sheet, where heat discolours and warps the metal. The trade-off is that a very thin disc is unforgiving: twist it in the cut and it cracks.
• 1.6mm. The middle ground, and the safest starting point if you only keep one cutting disc on the shelf. It copes with a bit of flex and still cuts quickly.
• 2.5mm and 3.0mm. Slower and hotter, but far tougher. These suit heavy box section, site work and cuts where you cannot keep the grinder perfectly square.

Two labelling details catch people out. First, a disc marked INOX is made without iron, sulphur or chlorine fillers. Those additives are harmless on mild steel but contaminate stainless steel, which then rusts at the cut edge. Keep an INOX disc for stainless work only. Second, type 41 discs are flat and type 42 have a depressed centre; both fit the same spindle, but flat discs are the usual choice on a 115mm grinder.

Bosch's PRO Rapido Inox range is a good example of a thin stainless disc. It comes in both the 115mm and 125mm sizes that fit most UK grinders, and the 1mm version is the one to reach for on thin sheet and tube where heat control matters.

One rule matters more than any spec: a cutting disc is for slicing only. Pressing the face of a thin disc into a surface, or levering the grinder sideways in a cut, is what turns a disc into shrapnel. Use a grinding disc for that job, or a flap disc for lighter work.

Grinding discs: stock removal and weld dressing

Grinding discs are roughly 6mm thick with a depressed centre, and they are built for flat work: knocking down a weld bead, squaring a cut edge, cleaning up spatter or removing pitting from steel. They remove material quickly and wear down as they work, which keeps the face fresh.

Use one face-on with light pressure and let the disc do the work. Grinding discs are not for cutting, and because they are so much thicker they will burn and wander if you try. If you need a surface finish rather than bulk removal, a flap disc gives you far more control. If you are dressing welds regularly, our guide to getting started with welding covers the finishing sequence from tack to blend, and a bench grinder handles the smaller tidy-up jobs, as we set out in our roundup of bench grinders.

Flap discs: blending, finishing and paint prep

A flap disc is a fan of abrasive cloth on a backing plate. As the flaps wear they expose fresh abrasive, so the disc keeps cutting instead of clogging the way sandpaper does. That makes it the most useful disc in the workshop after a basic cutting disc.

Grit choice follows the same order as sandpaper:

• 40 grit. Fast removal, for stripping heavy rust, mill scale or a rough weld.
• 60 grit. General cleaning and blending after a grinding disc.
• 80 grit. The best all-round starting point for weld blending and deburring.
• 120 grit. Finishing, and as far as most DIY work needs to go before primer.

Type 27 flap discs are flat and suit edge work and blending. Type 29 discs are slightly conical and take a more aggressive angle, which is handy on flat plate. Both work on the same grinder, so the choice comes down to how you hold the tool.

Wire brushes, diamond blades and the rest

Wire brushes come in two styles. Crimped brushes have wavy wires and are gentler, which suits light rust, loose paint and cleaning before welding. Knotted or twisted brushes are dense and aggressive and will chew through heavy rust, thick scale and old paint. Cup brushes for flat surfaces, wheel brushes for edges, corners and inside fillets. If you are working on stainless, use a stainless wire brush, because a carbon steel brush leaves particles that rust.

Diamond blades cut masonry and tile rather than metal. A continuous rim blade gives a clean edge on porcelain and stone, so it is the one to choose for tiling. A segmented rim blade cuts faster on brick, block and concrete because the slots clear the dust, but it chips the edge. Neither is for metal. Neither is a good idea on wood either: dry diamond cutting throws fine dust, and you should run dust extraction or a mask.

Two other discs are worth knowing. A poly or strip disc removes paint and rust without gouging the steel underneath, which makes it useful for restoration work. A backing pad with a fibre or sanding disc is for blending curves and shaping, but it wears out fast compared with a flap disc.

Matching the disc to your grinder

Three things have to line up before a disc is safe to fit: diameter, speed rating and bore.

Diameter. A disc must never be larger than the grinder is rated for. A 115mm grinder takes 115mm discs, full stop. A bigger disc will not sit inside the guard and it will run faster at the rim than it was designed to survive. This is the single most dangerous mistake you can make.

Speed rating. Hand-held grinders run fast and the disc has to be rated at least as fast as the tool spins with no load. The usual figures are below.

Bore. 22.23mm covers almost every UK DIY grinder. If you have a machine with a 16mm spindle, use the reducing ring supplied with the disc rather than fitting it loose.

On the tool side, 115mm and 125mm cordless grinders cover nearly all home jobs. The Einhell TC-AG 18/115 is a straightforward budget starting point, the Makita DGA504Z and Bosch GWS 18V-7 are the brushless mid-range options, and the flat-head Einhell TP-AG 18/125 F gets into tight corners. If you are already on a battery platform, the Ryobi R18AG-0 and the DeWalt DCG407N are the obvious additions. We compared all of them in more detail in our guide to the best cordless angle grinders.

For heavier work, corded 180mm and 230mm machines take the bigger discs. A Makita GA7070X1 in 180mm or a GA9071X1 in 230mm, both 240V, is the sort of tool that earns its place on a bench when you are cutting thick box section all afternoon.

How to read the markings on a disc

Bonded abrasive discs sold in the UK are marked to EN 12413, the European standard for safety requirements on bonded abrasives. The HSE guidance on the safe use of abrasive wheels sets out what those markings mean in practice, and a grinding wheel chart is a useful decode for the grain and bond codes.

The fields worth checking before every fit are:

• Dimensions in the format D x T x H, so you can confirm the disc matches your grinder.
• Maximum speed in both m/s and rpm. Hand-held discs are normally rated at 80 m/s. That number must be at or above your grinder's no-load speed.
• Expiry date. Resin bonds absorb moisture from the air and weaken, which is why discs carry a use-by date. A disc that has sat in a damp garage for years is not worth the risk.
• The EN 12413 mark plus a safety pictogram, and often an oSa or MPA certification logo.

Before mounting any wheel, look for cracks or chips and run a ring test: hold the disc by the bore and tap it lightly with a screwdriver handle. A sound disc rings clear. A dull thud means it is damaged, and it goes in the bin.

Safe use: five rules that prevent most injuries

Angle grinders cause a large share of DIY injuries, and the causes are predictable. These five habits remove most of the risk.

1. Keep the guard on and adjust it. The guard should sit between the spinning disc and your hands. Rotate it to cover the side you are working from.
2. Never overspeed a disc. Match the rpm rating to the tool, and check the expiry date.
3. No side-loading, no toothed blades. Cutting discs slice, they do not grind. Toothed circular saw blades sold for angle grinders were banned in the UK by the Office for Product Safety and Standards because of the kickback risk, and that ban is worth respecting.
4. Two hands, side handle fitted, work clamped. A grinder that grabs has enormous torque. Clamp the workpiece so both hands stay on the tool.
5. Wear the right protection. Sealed goggles beat open specs for metal work, because fine particles travel around the edges of a lens. Add an FFP3 mask for dust when cutting masonry, and ear defenders.

For eye protection, 3M 2890SA sealed goggles sit against the face and keep debris out, while 3M 2840 safety glasses are the lighter option for short jobs. A JSP M632 FFP3 mask covers cutting brick, block and tile, and 3M Peltor ear defenders handle the noise.

Gloves need a caveat. Leather gloves protect your hands when you handle freshly cut metal, but take them off while the grinder is running, because a glove can catch on the spinning spindle and pull your hand in. On dust, a wet and dry vacuum such as the Karcher WD 4 connected to the guard keeps the worst of the cloud down, and our guide to workshop air quality covers the rest. The full gear list sits in our workshop safety guide. If the grinder is only part of the job and you need to drill or tap after cutting, a little cutting and tapping fluid keeps the drill bit cool and the hole accurate.

Frequently asked questions

Can I use a grinding disc to cut metal?

No. A grinding disc is about 6mm thick and built for surface work, so it cuts slowly, overheats the metal and loads up with swarf. Cutting discs are thin and reinforced for slicing only. Mixing the two up is the most common cause of angle grinder accidents in home workshops.

What size disc does a 115mm angle grinder take?

A 115mm grinder takes 115mm discs with a 22.23mm bore, the standard UK spindle size. Never fit a larger disc than the grinder is rated for, because it will not sit inside the guard and it will run above the speed the disc was built to survive.

What is the difference between a 1mm and a 3mm cutting disc?

A 1.0mm or 1.2mm disc removes less material, so it cuts faster and puts far less heat into the workpiece. That matters on stainless steel and thin sheet, where heat discolours the metal. A 3.0mm disc cuts slower and hotter but survives rough handling and slight twisting much better, so it suits heavy stock and site work.

Do angle grinder discs expire?

Yes. Bonded discs use a resin bond that absorbs moisture from the air and weakens over time, which is why EN 12413 requires an expiry date on every disc. Check the date stamp before you fit it, and store discs flat in a dry place rather than loose in a damp drawer.

What does INOX mean on a cutting disc?

INOX discs are made without iron, sulphur or chlorine fillers. Those additives are harmless on mild steel, but on stainless steel they can contaminate the cut edge, which then rusts. If you are cutting stainless, use an INOX disc kept only for stainless work.

What grit flap disc should I buy first?

An 80 grit flap disc is the best general starting point for blending welds and cleaning up cut edges on steel. Add 40 grit if you need to remove material quickly, and 120 grit if you want a finish ready for paint.

Whichever disc you fit, treat it as a consumable with a job to do: match the family to the task, match the rating to the tool, and replace it when it wears or expires. For more workshop guides, visit MakerUK.

Related Articles

Best Cordless Angle Grinders UK 2026 Essential UK Workshop Safety Guide Best Safety Glasses for Woodworking UK 2026 How to Start Welding: UK Beginner Guide Best Bench Grinders UK 2026

As an Amazon Associate we earn from qualifying purchases.

Last reviewed: 10 September 2026 · Workshop-tested guidance · Contains affiliate links