Quick Answer

On most Brazilian concrete floors — typically 25–40 MPa slabs cast with crushed granite or gneiss aggregate — start with a medium bond trapezoid block in 30/40 grit. Move to a soft bond only when the segment goes shiny and stops cutting on a dense, high-strength slab, and use a hard bond only on soft, sandy screeds that eat diamond too fast. Check the connection before you order: M6 (6 mm) and 9 mm three-hole plates are the common formats on universal grinders sold in Brazil, while Redi Lock, Quick Change, pin/plug and Easy-Fix systems each need dedicated tooling.

What a Grinding Block Actually Is

A grinding block — bloco de moagem in Portuguese — is the trapezoid steel plate that carries diamond segments and mounts on the grinding head of a floor grinder. Three or four blocks sit on one head and do the coarse work: flattening the slab, stripping coating residue, and opening the surface so resin pads can polish. It is not the same tool as a grinding cup wheel for a hand grinder, and it is not a resin polishing pad. Buying the wrong one is the most expensive mistake in floor preparation, because a block that does not cut forces extra passes and wears the machine.

Segment Shape Decides How the Block Cuts

Two blocks with the same grit and bond can behave completely differently if the segment shape changes. The shape controls contact pressure, how the diamond shears the concrete, and how quickly the block glazes over on hard slabs.

Segment shape	How it cuts	Where it fits
Single / double bar	Continuous contact, stable, fast flattening	First cut on flat, medium-hard slabs
S segment	Shearing edge, keeps biting on dense concrete	High-strength slabs that glaze standard blocks
Zigzag	Alternating bite, less vibration, good removal	Hard concrete and rough, patched floors
Round / button	Shallow scratch, low aggression	Bridge passes before transitional and resin steps
Rhombus / shark	Aggressive bite, directional	High spots, coating edges, uneven pours
Oval	Between bar and round: removes without gouging	Mixed or unknown slabs, first pass on soft concrete

Trapezoid Block Specification Table

The table below lists the universal trapezoid blocks we supply for machines with three-hole plates. All of them run the same grit range — 6#, 16#, 30/40#, 60/80#, 100/120#, 150#, 200# — and are available in soft, medium and hard bond.

Model	Segment shape	Connection	Segment size	Bond	Typical use
JOY-TP-R3	Triple round	M6 or 9 mm holes	25 × 12 mm	Soft / medium / hard	Universal trapezoid grinder, general floor prep
JOY-TP-S2	Double S	M6 or 9 mm holes	12 mm	Soft / medium / hard	Hard, dense slabs; resists glazing
JOY-TP-ZG2	Double zigzag	M6 or 9 mm holes	12 mm	Soft / medium / hard	Rough or patched floors, coating residue
JOY-TP-RH2	Double rhombus	M6 or 9 mm holes	12 mm	Soft / medium / hard	Iron Horse / Xingyi heads; high spots and edges
JOY-TP-O2	Double oval	M6 or 9 mm holes	12 mm	Soft / medium / hard	Soft or unknown concrete; low-gouge first pass
JOY-TPF-B1	Single bar	Fast Change System	40 × 12 × 12 mm	Soft / medium / hard	Quick-change heads; high metal removal
JOY-TP-B2	Double bar (Diamatic)	M6 or 9 mm holes	12 mm	Soft / medium / hard	Diamatic plate spacing

Pick the shape from the job, not from stock availability: on a dense 35 MPa slab with granite aggregate, an S or zigzag block keeps cutting where a bar block polishes itself flat. On a soft 20 MPa screed, an oval or round block is safer because it will not cut a visible step in a single pass.

Bond: The Setting That Decides Your Cost per Square Metre

Bond is the metal powder that holds the diamond. It wears away at a controlled rate so fresh diamond is exposed. Get it wrong and the block either polishes itself instead of the floor, or disappears in a few hundred square metres.

• Soft bond — for hard, dense concrete: high fck, river stone or quartz aggregate, slabs that glaze a medium block.
• Medium bond — the default for most Brazilian industrial and commercial floors; the most common specification we ship.
• Hard bond — for soft, sandy or highly abrasive screeds where a medium bond wears out too quickly.

What you see on site	Probable cause	What to change
Segment face is glassy, sparks, barely cuts	Bond too hard for the slab	Step down one bond grade (hard → medium → soft)
Block worn out after 200–300 m²	Bond too soft or grit too coarse	Step up one bond grade and review grit sequence
One side of the block wears faster	Plate rocking, worn head, uneven floor	Check head bearings and plate flatness before blaming the tool
Deep scratches that will not come out at 100/120	Started too coarse or skipped a step	Add a 30/40 pass instead of jumping grit

Grit Sequence for Floor Preparation

A workable sequence on most jobs: 6# or 16# only where there is coating residue or a very rough pour, 30/40 as the first full pass to flatten, 60/80 to remove the coarse scratches, then 100/120 before transitional pads and resin. Overlap each pass by about one third of the head width so the floor stays flat.

Check the Connection Before You Order

Connection mismatch is the single most common reason an order becomes useless. Measure, do not guess:

• Hole count and diameter — 3-hole plates with M6 bolts (6 mm thread) versus 9 mm clearance holes are different products.
• Centre-to-centre spacing — Diamatic plates use their own spacing even though they take M6 bolts.
• Plate thickness — thin plates for quick-change heads will not hold on standard heads, and thick plates jam in magnetic systems.
• Quick-change, pin, E/Z plug, Easy-Fix — each family has its own locking geometry; a Husqvarna Redi Lock tool will not fit a Lavina head without an adapter.

Five Mistakes We See on Brazilian Jobsites

• Ordering a hard bond for a dense slab because "hard sounded stronger" — the block glazes and the job stalls.
• Running 6# on a soft screed to save time, then spending three passes removing the gouges.
• Mixing grits across the heads of one machine, which leaves the floor wavy.
• Grinding wet when the floor is dry-cured — slurry hides the scratches until polishing.
• Never dressing the block: a glazed segment cuts nothing, and dressing with a abrasive block restores it in seconds.

FAQ

How many blocks do I need per machine?

Most floor grinders take three or four blocks per grinding head, and a twin-head machine takes twice that. Always order one spare set: a set that wears out mid-job costs more in downtime than the spare blocks.

Can I use one brand's block on another brand's grinder?

Only if the connection matches. Trapezoid plates with M6 or 9 mm holes are broadly interchangeable between universal heads; Redi Lock, Quick Lock, Quick Change, pin/plug and Easy-Fix tooling is proprietary to its platform.

Dry or wet grinding?

Dry grinding with a HEPA extraction unit is the standard for floor preparation because it keeps the slab visible and the dust controlled. Wet grinding is used for polishing steps and for heat-sensitive coatings.

Get the Right Block the First Time

Send us the machine model, a photo of the plate underside with a ruler across the holes, the slab specification (fck and aggregate if known) and the finish you need. We will match the block, grit and bond, and quote by set so you are not ordering one piece at a time. See the full range of diamond grinding tools or read how to choose trapezoid grinding shoes before you specify.