Cut metal with an angle grinder by fitting a thin (1 mm) abrasive cut-off disc rated at or above the grinder’s free speed, clamping the work on both sides of the line so it can’t sag and pinch the disc, and letting the disc’s own speed do the cutting rather than leaning on it. That’s the method. Everything below is the disc choice, the setup, and the two failure modes — a bound disc and a wrong disc — that account for almost every metal-cutting injury with this tool.
- Angle grinder with the guard fitted
- Thin abrasive cutting disc(s), sized to the grinder
- Face shield over safety glasses
- Leather or cut-resistant gloves
- Ear protection
- Two C-clamps or a vise
- Scriber or marker for the cut line
The two failure modes that account for almost every injury here
Cutting metal fails in one of two ways, and both have a mechanism worth knowing rather than just a warning to heed.
- The wrong disc. A grinding disc (thick, depressed-center) is built to take load on its face. A cutting disc is thin and built to take load on its edge only. Using a grinding disc to cut, or twisting a cutting disc sideways in the kerf, loads it in the direction it has no strength in — that’s how a disc shatters rather than wears down.
- The pinched cut. Metal bridged between two supports sags as you cut through the middle. The kerf closes on the disc, the disc binds, and a bound disc at 11,000 rpm kicks back instantly — there is no reacting to it once it happens. Support and clamp both sides of the line before you start, not just one.
- Check the disc’s rpm stamp against the grinder’s plate, every time you swap discs between tools. A disc rated below the grinder’s free speed can burst in normal use.
- Face shield, not just glasses. Metal sparks are hotter and more numerous than the dust from wood or masonry, and they come off in a stream toward wherever you’re standing.
What’s Inside!
How to Use an Angle Grinder to Cut Metal — Video
Cutting Metal, Step by Step
- Mark the line and clamp the workSupport the metal on both sides of the cut, not just one end. This is the step people skip, and it’s the one that prevents a pinch.
- Fit the cutting discFlat face of the clamping nut against the disc, label facing outward so you can still read the rpm rating without removing it.
- Set your stanceBoth hands on the grinder, side handle fitted, body out of the disc’s cutting plane so sparks stream past you rather than across you.
- Bring it to full speed before it touches the metalLoading a disc while it’s still spinning up stresses it unevenly.
- Let the disc cut, not your armLight, steady forward pressure along the marked line. Leaning on it doesn’t cut faster — it heats the disc and wears it unevenly.
- Keep it in one planeTwisting the disc inside the kerf is the most common way to bind and shatter one. If it starts to bind, back out along the same line rather than forcing through.
- Ease off through the last few millimetersSlow down as the offcut is about to separate, so it doesn’t drop suddenly and snag the disc.
Which Disc, and the Diamond-Disc Claim You’ll See Repeated Everywhere
Most sites selling diamond discs claim they last 30 to 50 times longer than an abrasive cutting disc. That’s true for concrete and tile. It is not generally true for steel, and the mechanism explains why: a standard diamond disc’s bond is engineered to erode gradually and expose fresh diamond as it works through masonry.
Steel doesn’t erode that bond the same way — tradespeople on welding and machining forums consistently report standard diamond discs clogging, glazing over, and overheating on steel rather than cutting it (MIG Welding Forum, diamond discs on metal). A separate category — metal-specific diamond cut-off discs with a different bond, sold under names like Lenox METALMAX — is built for steel. It’s rated by its manufacturer for over a thousand cuts, but that’s a distinct, considerably more expensive product, not the tile-and-stone diamond disc from the same aisle. For ordinary shop cutting, the thin abrasive disc remains the standard tool, and this guide is written around it.
| Disc | Good for cutting metal? | Why |
|---|---|---|
| Thin abrasive cut-off disc (1 mm) | Yes — the standard choice | Cheap, interchangeable across brands and grinders, wears predictably |
| Standard diamond disc (masonry-bonded) | No | Bond is designed to erode into stone, not steel — clogs and overheats instead of cutting |
| Metal-specific diamond disc | Yes, for high-volume repeat cutting | Different bond entirely; manufacturer-rated for hundreds of cuts, priced to match |
| Grinding disc (any type) | No — not a cutting disc | Built for face-load grinding; using it edge-on to cut is how discs shatter |
Metal Cutting Disks
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Where This Goes Wrong
- Cutting with a grinding disc. It’s thick and depressed-center for a reason — edge-on into a cut, it can grab and shatter rather than slice.
- Only clamping one end. The unsupported end sags as the cut progresses and pinches the disc from the other side. Support both sides of the line.
- Forcing a slow cut. If the disc isn’t cutting cleanly, it’s worn, glazed, or the wrong disc for the metal — not something more pressure fixes.
- Skipping the face shield for “just a quick cut.” The cuts that go wrong are rarely the long ones; they’re the ones nobody bothered to gear up for.
Metal-Cutting Questions People Actually Ask
What size cutting disc do I need for metal?
Match the disc diameter to the grinder — most commonly 115 mm (4.5 in) or 125 mm (5 in) for handheld work. Within that size, a thin 1 mm disc cuts faster and wanders slightly more; a thicker disc tracks straighter but cuts slower. For most sheet and section steel, the thin disc is the better default.
Can I use a diamond disc instead of abrasive to cut metal?
A standard masonry diamond disc, no — its bond clogs and overheats on steel instead of cutting it. A metal-specific diamond disc (a different, more expensive product) can outlast abrasive discs by a wide margin on high-volume work, but for occasional shop cutting a thin abrasive disc is still the practical choice.
Why does my cut keep binding or wandering?
Binding is almost always an unsupported workpiece — the kerf closes as the metal sags and grips the disc. Wandering is usually the disc twisting sideways instead of tracking straight through the marked line. Clamp both sides of the cut and keep the grinder in one plane and both problems mostly disappear.
Can an angle grinder cut rebar or cast iron pipe?
Yes, with a thin abrasive disc rated for metal. Secure the piece in a clamp or vise first — round stock rolls under load — and expect a cast iron pipe thicker than your disc’s cutting depth to need a second pass from the other side.
What should I do if the grinder overheats mid-cut?
Stop and let it cool. A hot motor is losing insulation life every minute it keeps running, and a hot disc is more likely to glaze over and grab. Neither problem is fixed by pushing through it.
The One Thing Not to Get Wrong
Almost every bad outcome in metal cutting traces back to one of two choices: the wrong disc, or an unsupported workpiece. Get those two right — a thin abrasive disc rated for the grinder, and the metal clamped on both sides of the line — and the rest is just letting the tool do the job it’s built for. For the tool itself, disc types, and the safety rules that apply beyond cutting, the full beginner’s guide covers it.
