Should I buy a 125 mm or a 230 mm grinder?

Most daily work is done with 125 mm: light, controllable and served by the widest range of discs. A 230 mm machine is a second tool for heavy sections and construction cutting.

Can I grind with a cutting disc?

No. A thin cutting disc will not carry side loads and can shatter, causing serious injury. Use a thick grinding disc to remove material.

What does the speed marked on a disc mean?

It is the maximum speed the disc withstands, and it must be higher than the machine's. Fitting a lower-rated disc to a faster machine can burst it.

What does a kickback clutch do?

It limits the machine's reaction when the disc jams in the workpiece by briefly releasing the drive between motor and spindle. Jamming is the most common cause of a grinder being thrown from the hand.

Can a cordless grinder replace a corded one?

For short cutting and grinding, yes — especially on 18 V high-output packs. For long, continuous grinding a corded machine is better on both heat and cost.

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Angle Grinders & Cutters

Grinders are classified by disc diameter, and that diameter sets both cut depth and speed: a small disc spins fast and stays controllable, a large one turns slower but cuts deeper. This page covers the difference between angle grinders, large grinders and chop saws, how to choose a disc, and what safety features to look for. The catalogue holds over 190 models.

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Disc diameter and speed

Peripheral speed at the rim is limited, so as the disc grows the machine's rpm comes down. A 115-125 mm angle grinder runs at around 11,000 rpm, a 230 mm machine at around 6,500. You choose the larger machine because it cuts deeper, not because it is "stronger".

Disc	Typical speed	Cut depth	Use
115 mm	~11,000 rpm	~28 mm	Thin sheet, sections, assembly work
125 mm	~11,000 rpm	~33 mm	General purpose, the most common size
180 mm	~8,500 rpm	~50 mm	Heavy sections, concrete
230 mm	~6,500 rpm	~68 mm	Thick material, construction cutting

Cutting discs, grinding discs and flap discs

The disc decides the job, and the wrong disc is both unsafe and slow. A thin cutting disc is for cutting only; pressing it sideways to grind will shatter it. A thick grinding disc removes material, and a flap disc sands and dresses weld beads.

Every disc carries a maximum permitted speed, and it must exceed the machine's. The disc size must match the machine's guard, and the guard must never be removed.

Cutting disc: cutting only, never side loads.
Grinding disc: removing material, dressing edges.
Flap disc: sanding, dressing weld beads.
Diamond disc: concrete, tile, stone — dry and wet types differ.

Safety features

Look for three on a modern grinder: a kickback clutch that releases the drive when the disc jams, restart protection so the tool does not run on when power returns, and a side handle that damps vibration. The guard is mandatory for cutting work.

Cordless grinders often add an electronic brake that stops the disc in under a second when the trigger is released — a real safety gain where cutting is frequent.

Frequently Asked Questions

Should I buy a 125 mm or a 230 mm grinder?
Most daily work is done with 125 mm: light, controllable and served by the widest range of discs. A 230 mm machine is a second tool for heavy sections and construction cutting.
Can I grind with a cutting disc?
No. A thin cutting disc will not carry side loads and can shatter, causing serious injury. Use a thick grinding disc to remove material.
What does the speed marked on a disc mean?
It is the maximum speed the disc withstands, and it must be higher than the machine's. Fitting a lower-rated disc to a faster machine can burst it.
What does a kickback clutch do?
It limits the machine's reaction when the disc jams in the workpiece by briefly releasing the drive between motor and spindle. Jamming is the most common cause of a grinder being thrown from the hand.
Can a cordless grinder replace a corded one?
For short cutting and grinding, yes — especially on 18 V high-output packs. For long, continuous grinding a corded machine is better on both heat and cost.