Double-Row Diamond Cup Wheel for Concrete
Double-row cup wheel
The head that gets into the corner a planetary machine cannot reach
A double-row diamond cup wheel is a grinding disc for an angle grinder, with two rings of diamond segments. On a resin floor it grinds the strip along walls, into corners and around drains that a planetary floor grinder cannot reach, so the coating bonds at the edges as well as across the open floor.
A planetary grinder is a circle, and a room is not. Whatever the big machine leaves (the last hundred millimetres against a wall, the inside of a corner, the lip around a drain or a column base) comes out with a hand grinder and a cup wheel.
This is the double-row cut: two concentric rings of diamond segments on a cast body, hard bond, for green or rough concrete. It is not a finishing head. It is there to take material off fast in the one part of the room where nothing else can.
On your floor
The edge work happens before the open floor, not after. We cut the perimeter first so the planetary machine can run into ground concrete rather than stop short of a raw strip, which is what leaves the line you can see later.
It is slow, it is loud, and it is done on one knee. On a 300 m² warehouse it is the better part of a day on its own.
How it wears
A hard bond on soft concrete glazes over and stops cutting; a soft bond on hard concrete wears away in an afternoon. We carry both and change when the slab tells us to, which is usually within the first ten minutes of the first pass.
Without itThe edges stay high. You see it as a dark border round every room the day the light goes on.
What to ask
Ask whoever is quoting how they intend to grind the last hundred millimetres against your wall. If the answer is that they will not, you already know where the dark border will be.
Where it is used
Day 01 of the job, prep, on every system we lay: decorative epoxy, flake floors, urethane cement, quartz broadcast, heavy industrial and repairs & recoats.
Questions people ask
What is a diamond cup wheel used for on a concrete floor?
Removing material fast where a large floor grinder cannot go: the last hundred millimetres against a wall, inside corners, around columns, drains and door frames. It takes off laitance, old paint and high spots, so the primer has open concrete to key into at the edges too.
Double-row or turbo cup wheel: which one do you need?
Both, in that order. A double-row wheel cuts faster and deeper, which suits rough or coated edges, but it leaves its own scratch. A single-row turbo wheel cuts more smoothly and goes second, bringing the edge to the same finish as the open floor.
What happens if the edges of a floor are not ground?
The coating sits on unprepared concrete in a band around the room. It usually shows as a darker border once the floor is finished, and it is where peeling tends to start, because the edge is also where water, mops and furniture meet the floor.