Not sure which abrasive disc to buy? Start here.
Picking the wrong disc costs you time, money, and finish quality. This guide walks you through every variable so you can choose with confidence — whether you're cutting mild steel on a construction site or finishing stainless in a fabrication shop.
1. Match the Disc to Your Material
This is the single most important decision. Using the wrong disc on the wrong material leads to poor results, premature wear, or disc failure.
| Material | Choose | Avoid |
|---|---|---|
| Mild steel / structural steel | Standard aluminium oxide discs | — |
| Stainless steel | Discs marked inox or stainless (iron- and sulphur-free) | Standard discs — they contaminate and cause rust pits |
| Cast iron | Silicon carbide or aluminium oxide | — |
| Aluminium & non-ferrous metals | Open-structure aluminium oxide; zirconia for harder alloys | Standard closed-structure discs (clog quickly) |
| Masonry / stone / tile | Diamond or silicon carbide | Metal-specific discs |
| Fibreglass / composites | Silicon carbide or dedicated composite discs | — |
A note on stainless steel
This comes up constantly: yes, stainless-steel discs are different. Standard abrasive discs contain iron and sulphur compounds that transfer into stainless during grinding and cause corrosion from the inside out — even on grade 304 or 316. Always use discs that are explicitly labelled inox, stainless, or iron/sulphur-free when working on stainless. The small price difference is far less than the cost of reworking contaminated welds.
2. Cutting vs Grinding: Choose the Right Disc Type
Cutting discs and grinding discs look similar but are engineered for completely different forces. Never use a cutting disc to grind or vice versa.
| Cutting Discs | Grinding Discs | |
|---|---|---|
| Thickness | 1.0 mm – 2.0 mm (thin) | 6 mm – 8 mm (thick) |
| Profile | Flat (Type 41) | Depressed centre (Type 27) |
| Action | Slices through material | Removes material across a surface |
| Side grinding? | No — disc can shatter | Yes — designed for it |
| Best for | Pipes, bar, sheet, angle iron | Weld dressing, deburring, surface prep |
Browse our Cutting Discs and Grinding Discs collections.
3. Diameter — Match Your Grinder Guard
Disc diameter must match the maximum rated size of your angle grinder. Common sizes:
- 100 mm (4") — compact / light-duty grinders; good for pipework and tight spaces
- 115 mm (4½") — the most common workshop size; versatile
- 125 mm (5") — popular mid-size; widely available
- 180 mm (7") — heavier grinders; structural and fabrication work
- 230 mm (9") — large grinders; heavy stock removal and cutting thick section
Never mount a larger disc than your grinder's rated maximum. The guard exists for a reason — an over-speeded disc can fail catastrophically.
4. Bore Size — The Centre Hole
The bore (centre hole) must fit your grinder's spindle. The two most common bores are:
- 22.23 mm — standard for most angle grinders worldwide
- 16 mm — used on some smaller or older machines
Reducers are available but fitting a disc with the wrong bore size on a makeshift adapter is a common cause of disc failure. Always match bore to spindle.
5. Grain Type — What the Abrasive Is Made Of
| Grain | Best for | Characteristic |
|---|---|---|
| Aluminium oxide (AO) | Steel, stainless, general metal | Long-lasting, cost-effective |
| Zirconia alumina | Hard steels, heavy stock removal | Self-sharpening; aggressive cut rate |
| Silicon carbide (SC) | Non-ferrous metals, masonry, stone | Sharper but more brittle than AO |
| Ceramic alumina | High-alloy, hardened steels, titanium | Premium life; cool cutting reduces heat discolouration |
6. Grit / Grain Size — Coarseness
Lower grit numbers cut faster and leave a rougher finish. Higher numbers leave a finer finish but remove material more slowly. For discs used on angle grinders:
- 24 – 36 grit — aggressive stock removal, weld dressing
- 40 – 60 grit — general grinding, surface prep
- 80 – 120 grit — blending, lighter finishing
Flap wheels and flap discs typically range from 40 to 120 grit and are ideal when you need both stock removal and a refined finish in one pass. See our Flap Wheels collection.
7. Specialised Abrasives
Grinding Wheels
Bench and pedestal grinding wheels are used on fixed machines rather than angle grinders. They're rated for a specific RPM — always check the wheel's stated maximum speed against your machine's spindle speed before mounting. Browse Grinding Wheels.
Burrs
Carbide and abrasive burrs are used in die grinders and rotary tools for deburring, porting, and intricate shaping work where an angle grinder is too large. Browse Burrs.
Full Abrasives Range
View the complete Abrasives collection to see everything in one place.
Quick-Reference Selector
| Job | Disc type | Grain | Grit |
|---|---|---|---|
| Cut mild steel pipe / bar | Cutting disc (1.0 – 1.6 mm) | Aluminium oxide | N/A |
| Cut stainless steel | Cutting disc — inox rated | AO iron/sulphur-free | N/A |
| Dress welds on mild steel | Grinding disc (6 mm) | Aluminium oxide / zirconia | 24 – 36 |
| Dress welds on stainless | Grinding disc — inox rated | AO iron/sulphur-free | 24 – 36 |
| Blend and finish | Flap wheel / flap disc | Zirconia or ceramic | 60 – 120 |
| Deburr / shape (die grinder) | Burr | Carbide or abrasive | — |
| Surface prep — masonry | Grinding / cutting disc | Silicon carbide / diamond | — |
If you're unsure which disc is right for your job, contact us — we're happy to help you spec the correct abrasive before you buy.