ANGLE GRINDER DISCS EXPLAINED: CUTTING, GRINDING, FLAP AND WIRE BRUSH DISCS
Angle grinder discs fall into four main types: cutting discs, grinding discs, flap discs and wire brushes. Choose by the job first, then the material, and always confirm that the disc size and speed rating suit the grinder.
The disc does the work, so the wrong one is slow at best and dangerous at worst. This guide explains each type, what it is for and how to read the label.
IN THIS ARTICLE
- The four main types of angle grinder disc
- Which disc for which material?
- Cutting discs vs grinding discs
- Flap discs and grit
- Wire brushes for rust and paint
- How to read an angle grinder disc label
- Are angle grinder discs universal?
- When to replace an angle grinder disc
- Matching discs to M7 angle grinders
- Sources and specification notes
- Frequently asked questions
THE FOUR MAIN TYPES OF ANGLE GRINDER DISC
The four main types are cutting discs, grinding discs, flap discs and wire brushes. For cutting and grinding discs, the abrasive grain helps decide which materials they handle best.
| Disc and abrasive grain | Typical materials | Advantages | Limitations |
|---|---|---|---|
| Brown aluminium oxide (A), resin-bonded cutting disc | Iron, steel, rebar, carbon steel and angle iron | Low cost, tough and versatile | Can wear faster, produce sparks and leave burrs |
| White aluminium oxide (WA), resin-bonded cutting disc | Stainless steel, alloy steel and harder steels | Strong cutting action; can run cooler | More brittle if twisted or used incorrectly |
| Silicon carbide, black (C) or green (GC), resin-bonded disc | Cast iron, non-ferrous metals, glass and stone | Sharp grains for hard, brittle materials | Wears quickly |
A and C are abrasive codes in ISO 525; WA and GC are commonly used manufacturer codes. Flap discs and wire brushes are covered below.
WHICH DISC FOR WHICH MATERIAL?
Start from the material, because the same job needs a different disc on mild steel, stainless steel or wood.
Can you use an angle grinder disc on wood?
Only with an accessory made for wood and rated for the grinder’s speed; a saw is usually the safer choice. Toothed wood-cutting attachments raise kickback risk. Keep the guard fitted and both hands on the tool.
CUTTING DISCS VS GRINDING DISCS
Never swap them: a thin cutting disc is not built for side pressure, and a thick grinding disc is not built for cutting.
- Cutting discs: thin for fast cuts with little waste. oSa safety recommendations say not to grind with their sides or put side pressure on them.
- Grinding discs: thicker, commonly Type 27 with a depressed centre, and worked at a shallow angle.
- Rule: use cutting discs for cutting and grinding discs for grinding unless a disc is explicitly marked for both.
FLAP DISCS AND GRIT
A flap disc grinds and finishes in one step, so it often replaces a grinding disc for weld blending.
Its overlapping abrasive flaps expose fresh abrasive as they wear. Use around 40 grit for fast stock and weld removal, 60–80 grit for general blending and edge work, and around 120 grit for finishing before paint or coating. A flat flap disc suits broad surfaces; a conical one suits edges and heavier work at an angle.
WIRE BRUSHES FOR RUST AND PAINT
Use a wire cup brush for flat surfaces and a wire wheel brush for edges, corners and weld seams.
- Crimped wire: flexible, for lighter cleaning.
- Knotted wire: stiffer, for heavier rust, scale and weld spatter.
Wires can break off during use. Wear eye and face protection, and confirm the brush maximum speed is compatible with the grinder.
HOW TO READ AN ANGLE GRINDER DISC LABEL
Check maximum speed, size and expiry date before fitting any disc. FEPA guidance identifies markings on bonded discs made to EN 12413, including maximum RPM, dimensions, restrictions of use, expiry date or traceability code, EN 12413 marking and manufacturer or supplier details.
The disc’s RPM rating must be at or above the grinder speed. HSE Northern Ireland guidance states that the spindle speed must never exceed the maximum speed marked on the disc.
ARE ANGLE GRINDER DISCS UNIVERSAL?
No. A disc must match the grinder in diameter, bore, speed rating and guard coverage.
- Diameter: match the tool size—100 mm, 115 mm, 125 mm or 230 mm. Never fit a larger disc.
- Bore: most 115 mm and 125 mm discs use a 22.23 mm (7/8 in.) centre hole with standard M14 flanges.
- Speed: disc RPM must meet or exceed grinder RPM.
- Guard: it must cover the disc correctly.
Can you use a smaller disc on an angle grinder?
Only if the manual allows it, it fits the flanges and its speed rating is sufficient. See 115 mm vs 125 mm Angle Grinder: Which Size Should You Choose? for the full comparison.
WHEN TO REPLACE AN ANGLE GRINDER DISC
Replace a disc when it is worn, damaged, past its expiry date, dropped or badly stored.
- Worn: do not use grinding and cutting discs down to the flanges.
- Damaged: cracks, chips, missing segments or a bent disc mean replacement.
- Expired: check resin-bonded disc dates.
- Stored badly: keep discs dry, frost-free and away from large temperature changes.
After fitting a new disc, oSa recommends running it at operating speed for at least 30 seconds while standing out of its line before starting work.
MATCHING DISCS TO M7 ANGLE GRINDERS
Choose a disc rated at least for the grinder speed, and match the diameter and spindle. The following speeds come from M7 product pages.
| M7 grinder | Disc size | Grinder speed | Disc must be rated at least |
|---|---|---|---|
| QB-7245 (S/M), air | 115 mm | 11,000 RPM | 11,000 RPM |
| QB-7215 (S/M), air | 125 mm | 11,000 RPM | 11,000 RPM |
| QB-7315 (S/M), air | 125 mm | 10,000 RPM | 10,000 RPM |
| DG-502, cordless | 125 mm | Up to 8,500 RPM | 8,500 RPM |
| DG-501 / DG-585, cordless | 125 mm | 8,000 RPM | 8,000 RPM |
| DG-485, cordless | 100 mm | 8,000 RPM | 8,000 RPM |
Official M7 product data lists a 5/8"-11 / M14 × P2.0 spindle for the air models, M14 × P2.0 for 125 mm cordless models, and M10 × P1.5 for DG-485. For choosing the grinder itself, see How to Choose the Right Angle Grinder: Corded, Cordless or Air.
Contact M7Find a Local Distributor
SOURCES AND SPECIFICATION NOTES
Disc safety rules come from industry safety bodies and UK guidance; grinder speeds and spindle data are from M7 official product pages, verified 2 November 2026.
- FEPA: safety leaflet for bonded abrasives.
- oSa: do’s and don’ts for bonded abrasive wheels.
- HSE Northern Ireland: abrasive wheels information sheet.
- ISO 525: abrasive designations.
- M7 official pages: QB-7245, QB-7215, QB-7315, DG-502, DG-501, DG-585 and DG-485.
Follow the exact disc maker’s markings and instructions for the disc in use.
FREQUENTLY ASKED QUESTIONS
What are the different types of angle grinder discs?
The four main types are cutting discs, grinding discs, flap discs and wire brushes. Cutting discs cut metal, grinding and flap discs remove and finish material, and wire brushes clean rust and paint.
Can I use a cutting disc for grinding?
No. Cutting discs are thin and are not designed for side pressure. Use a grinding disc or flap disc for grinding unless the disc is marked as suitable for both.
What angle grinder disc cuts metal?
A thin cutting disc made for metal. For stainless steel, choose one marked for stainless (inox) to avoid contaminating the surface.
Can I use a flap disc instead of a grinding disc?
Often, yes. A flap disc grinds and finishes in one step, so it is a common choice for weld blending. For heavy stock removal, a grinding disc is the usual choice.
Do angle grinder discs expire?
Resin-bonded cutting and grinding discs carry an expiry date or traceability code, often stamped on the metal centre ring. Do not use a disc past its expiry date.
