Diamond Grinding Discs

A 250 mm single-disc grinder can be tooled two ways, and that is the first decision a buyer makes. Both reach the same concrete, but they spread the cost differently and limit the job differently.

The disc: one set of segments, fixed for life

Segments sit on the body and cannot be taken off individually. A disc therefore keeps one grit for its whole life and performs one stage of work; when the segments are gone, the whole tool is replaced. What you get in return is a four-bolt fitting and nothing to match up: the tool is balanced at the factory and the operator has nothing to get wrong.

Our concrete discs carry 20 segments measuring 10 × 10 × 40 mm. Contact area with the floor is 80 cm² — roughly 16% of the 250 mm disc face, which measures 491 cm². The rest is clearance for spoil; if diamond covered the whole circle, the tool would skate over the laitance instead of lifting it.

The segment head: grits change mid-job

A head holds segments magnetically or in the RediLock system and lets you step through grits without taking the tooling off the machine. It is the only route if the floor is going to be polished: grits 20, 30, 80 and 120 in segments and 50–1000 in pads are covered in diamond pads and segments. There, only the segment wears out and the head stays.

The GX 250 takes both

Our single-disc Toolsa GX 250 grinder ships with a grit 30 disc for hard concrete and a diamond segment head, plus a wall dust guard. The head is removable, so one machine strips with a disc and polishes with segments — buying a disc does not close off the other route.

TSC, TMC and THC — the code names the concrete, not the bond

The letters describe the floor the disc is built for: TSC for soft, abrasive concrete and screeds, TMC for medium-hard, THC for hard concrete and industrial floors. The bond was chosen at the factory — inversely to the material, because the matrix has to wear away to expose fresh diamond crystals. The mechanism and the full hardness scale are set out under diamond segments; with a disc, judging the floor is enough.

All three come in grit 30 — the grain for opening concrete, taking off laitance and exposing aggregate. There is no finishing-grit disc in the range, and that is not an oversight: with one permanent set of segments, a polishing tool would be useful for one stage in a hundred.

PCD — stripping resin and adhesive with nothing holding it back

Polycrystalline diamond gets under a layer and tears it off in sheets rather than grinding it down. This is the tool for epoxy resin, carpet adhesive and thick coatings that kill an ordinary diamond segment within minutes. The PCD 250 disc carries PCD cutters only, with no element limiting how deep it goes — it can take several millimetres in a single pass. On a thin layer and a level floor, that is too much.

PCD Hybrid — same bite, with depth under control

The PCD Hybrid 250 disc adds an ordinary grit 30 grinding segment. It rides on the concrete and supports the tool, so the PCD cutters cannot sink deeper than they need to. The hybrid works more slowly than full PCD but leaves the substrate flat — this is the version for paint, thin adhesive and any coating under which the concrete has to stay level.

Every disc has a 250 mm body and a four-bolt hole pattern, so it fits the Toolsa GX 250, the Norton Clipper CG 252 and other machines of that class.

Start from what you are taking off

If a layer of foreign material sits on the floor — resin, adhesive, paint — a diamond disc will clog with it before it lifts anything. Coatings go to PCD or PCD Hybrid; bare concrete goes to TSC, TMC or THC. The line is sharp: PCD tears, diamond grinds, and neither tool substitutes for the other. Once the coating is off, you go back to a diamond disc to level the exposed concrete.

The floor tells you its hardness through the tool

Concrete with no paperwork is judged in use. If the disc still looks new after a dozen square metres and progress is slow, the floor is hard and the segment is not opening — go one code up next time. If segments vanish in front of you and dense dust pours out from under the machine, the concrete is soft and abrasive, which is TSC territory. Cement screeds and fresh slabs almost always behave as soft material, even though they feel hard to the hand.

Down-pressure does half the work

A disc does not cut by itself — the mass of the machine presses it down. The GX 250 weighs 60 kg, and a 2 × 7 kg weight kit brings it to 74 kg, close to a quarter more. On hard concrete that is often the difference between grinding and burnishing the surface with no result. The inverter gives 350–1500 rpm, which at the rim of a 250 mm disc means a peripheral speed of 4.6 to 19.6 m/s — one range that covers both sticky adhesive and hard screed.

Very hard concrete: no disc, but there is a segment

The disc scale stops at THC. Very hard floors — power-trowelled, surface-hardened, quartz-broadcast — call for the XHC code, which exists only as a segment for a head. A disc will work there, but THC will cut slowly and wear unevenly. Machines built for that kind of work are in planetary concrete grinders.

Extraction is part of the set-up, not an accessory

Dry grinding releases respirable silica dust, and the GX 250 carries a Ø 50 mm vacuum port and a wall dust guard precisely to capture it at source. Without extraction the dust settles on the disc and acts like grease between diamond and concrete: the tool stops biting although it is not worn. Vacuums matched to this work are in vacuum cleaners for grinders and scarifiers.

Machines for these discs are in concrete grinders and planetary concrete grinders. Replaceable tooling — segments in grits 20–120, PCD segments and polishing pads — is in diamond pads and segments. Dust extraction, without which dry work makes no sense, is in vacuum cleaners for grinders and scarifiers.