Short answer: For the odd cut, a thin abrasive cut-off wheel is the cheapest way in. For regular metal cutting, a diamond blade with a turbo rim wins on cost per cut, because it keeps its diameter instead of grinding itself away. A flap disc is not a cutting blade at all: it sands and blends. Whichever you choose, it must match your grinder in diameter, arbor and speed rating.
What are the options?
| Disc | How it works | What happens over time | Best for |
|---|---|---|---|
| Abrasive cut-off wheel (Type 1, flat) | Bonded grit grinds itself away to cut | Shrinks with every cut, gets slower and more fragile | Occasional cuts where price per disc matters more than lifespan |
| Grinding wheel (Type 27, depressed center) | Thick abrasive for grinding on the face | Wears slowly | Grinding welds and bevels. Too thick to cut with. |
| Flap disc | Overlapping abrasive flaps sand the surface | Wears layer by layer | Blending welds, deburring, rust removal. Not cutting. |
| Diamond metal blade (turbo rim) | Diamond grit on a steel body cuts, the body stays | Keeps its diameter for thousands of cuts | Regular cutting in steel, rebar, aluminum, copper and brass |
What thickness of cut-off wheel should I buy?
Thin wheels, around 0.040 to 0.045 inch, cut fastest with the least heat and the least material removed. They are also the most fragile: side pressure or a twist in the cut snaps them. Thicker wheels tolerate more abuse and cut slower.
For most work on a 4 or 4.5 inch grinder, thin is right. Just keep the wheel square in the cut and let the speed do the work, never your arm.
Does a diamond blade really cut metal?
Yes, if it was built for it. An ordinary tile blade glazes on steel within a few cuts. A metal-rated diamond blade uses a turbo rim that bites into steel and stays sharp, and a body that keeps its 4 inch diameter cut after cut.
That is the design of the Indestructible Disc 2.0, the metal cutting disc for angle grinders: a turbo rim with cooling holes on a diamond steel body, made for steel, rebar, pipe, aluminum, copper and brass. It keeps its diameter for around 5,000 cuts, so the last cut runs at the same speed as the first, and there is no shrinking wheel to shatter once it gets thin.
The honest trade-off: a diamond blade costs more per disc than an abrasive wheel. It costs less per cut once you cut more than a couple of times a year, because one replaces a whole box.
Which blade for which metal?
| Metal | What to expect | Blade notes |
|---|---|---|
| Mild steel, rebar, angle iron | Straightforward, lots of sparks | Any thin cut-off wheel or a metal diamond blade. Support both sides of the cut. |
| Stainless steel | Runs hot, work-hardens where you dwell | Keep the blade moving. A stainless-rated abrasive wheel, or a diamond blade with light passes. |
| Aluminum, copper, brass | Soft and gummy, loads up abrasive wheels | Light passes, back out to clear the cut. A diamond blade does not load up the way an abrasive wheel does. |
| Sheet metal | Flexes, grabs and warps from heat | Thin blade, clamp close to the line, short cuts with pauses. |
Technique for each is in How to Cut Metal With an Angle Grinder.
What size do I need?
Match three numbers to your grinder: diameter (4 inch and 4.5 inch are the common small sizes, 100 mm and 115 mm), arbor hole (5/8 inch or 7/8 inch, 16 mm or 22 mm) and maximum RPM. The blade's speed rating must be above your tool's speed. Our discs are 4 inch (100 mm), 5/8 inch (16 mm) arbor, 0.04 inch (1 mm) thick and rated to 12,225 RPM. If you are unsure what your grinder takes, Will This Disc Fit My Grinder? shows where to look.
What makes a metal cut safe?
- Guard on, always. If a wheel comes apart at 10,000 RPM, the guard decides where the pieces go.
- No side load. Cutting wheels are strong in the direction they spin and weak sideways. Twisting in the cut is the most common way to break one. Why Do Cutting Discs Break? covers the rest.
- Support both sides of the cut so the offcut cannot sag and pinch the blade.
- Gear: safety glasses for the sparks, cut resistant gloves because a fresh steel edge is a blade, ear protection because a grinder on steel runs well past 100 dB.
What does it cost per cut?
Hardware store cut-off wheels are typically gone after 30 to 50 cuts, and the last dozen of those are slower and more fragile than the first. Add up a year of wheels for a busy shop and the box costs more than one diamond disc that is still at full diameter. For two cuts a year, buy the box. For everything else, buy the blade that does not shrink.
The short version
Occasional cuts: thin abrasive cut-off wheel. Regular cuts: diamond blade with a turbo rim. Flap discs are for finishing, not cutting. Match diameter, arbor and RPM, keep the blade square, and keep the guard on.
Get the disc built for metal: Indestructible Disc 2.0, the metal cutting disc for angle grinders
