Read the speed and the date
Every disc is marked with a maximum permitted speed, which must exceed your grinder’s no-load speed. It also carries an expiry date: resin-bonded abrasives absorb moisture over years and lose strength. Neither marking is decoration on a component spinning at that rate.
Never side-load a cutting disc
A thin cutting disc is strong in its plane and weak across it. Grinding with the face of a cutting disc, or twisting the grinder in the cut, is how they shatter. Use a grinding disc or a flap disc for dressing, and keep the cut open so the kerf cannot close on the blade.
Thin cuts better
A 1 mm (0.04 in) disc removes a third of the metal a 2.5 mm (0.10 in) one does, so it cuts faster for the same power and puts less heat into the work. Thicker discs survive rough handling better. For steel section, 1 mm (0.04 in) is the modern default.
Discard dropped discs
A disc dropped onto a concrete floor may have invisible cracks. It costs less than a euro. Nobody in the history of workshops has regretted throwing one away.
The questions welders ask
Do I need iron-free discs for stainless?
For anything that will stay stainless, yes. Ordinary discs shed iron particles that embed in the surface and rust, leaving brown speckles. Discs marked free of iron, sulfur and chlorine avoid it — and a disc used on mild steel should never be used on stainless afterwards.
Why does my disc wear unevenly?
Usually because it is being used at an angle, or because the guard is forcing an approach that loads one side. An evenly worn disc stays circular and gets smaller; one that develops a taper or a lip is being side-loaded, which is the failure mode to avoid.
Last reviewed 2026-08-14