Quick Answer: Replace a concrete grinding disc when the segments wear below about 2 mm, cutting speed drops noticeably, the disc glazes or smokes, or the machine vibrates. A worn disc cuts slowly, burns the concrete, and can damage the tool holder, so check segment height before every job.

Measuring Segment Wear

The most reliable sign is segment height. New segments stand several millimetres proud of the steel core; once they wear down to about 2 mm or level with the core, the steel starts touching the concrete and the disc stops cutting. Lay the disc flat and slide a coin or feeler gauge beside the segment, or simply look at the profile. Segments that wear unevenly, with one side nearly gone, also need replacing because the disc will wobble and cut a taper.

Performance Signs: Speed, Glaze, and Heat

If the same disc that used to cut fast now polishes the surface and skips, the diamonds are exposed and dull or the bond is too hard for the concrete. Glazing looks like a smooth, shiny segment face; it cuts nothing and smokes under pressure. A disc that smells hot, smokes, or turns the concrete dark. double-row cup wheel is burning instead of cutting. Slow progress on the same concrete you ground yesterday means the disc is either glazed or worn, and dressing only fixes the glaze.

Wobble, Balance, and Structure Checks

Hold the disc by the arbor and spin it. single-row cup wheel; a visible wobble means a warped core or uneven segment wear. Check for cracks near the mounting holes or segment joints, and for segments that have loosened or shed. A damaged core can shed segments at speed, so inspect before every use and retire any disc with cracks. If the machine vibrates with a fresh disc but not with the old one, the old disc was the source of the shake.

Replacement and Matching Rules

When a disc is done, replace it with the same type and bond suited to the next stage of the job. A 12-segment 180 mm cup wheel for coarse removal, then step to medium metal bond for the flattening pass, and never skip from coarse straight to resin pads. Keep spare discs on site so you are not tempted to squeeze one more pass out of a worn wheel.

How many square metres does a cup wheel last?

A 180 mm cup wheel on an angle grinder typically lasts 50 to 200 square metres of light grinding depending on concrete hardness and pressure. Floor machine discs last longer per area because the machine runs more evenly.

Can a glazed disc be saved?

Sometimes. Dress it on a soft concrete block or a dressing stone to expose fresh diamonds. If it still glazes after two dressings, the bond is wrong for the concrete and the disc should be swapped for a softer bond.

Conclusion

Check segment height, cutting speed, glaze, and wobble before each job, and replace discs at about 2 mm of segment left. A worn or glazed disc slows the job and damages the floor, so retiring it early is always cheaper than burning the surface.