How Diamond Grit Affects Concrete Grinding Performance

When it comes to concrete grinding and polishing, selecting the correct diamond grit is just as important as choosing the right bond hardness. Diamond grit directly affects how aggressively a tool cuts, how much material it removes, and the quality of the surface finish left behind.

Understanding diamond grit and its purpose throughout the grinding and polishing process can help contractors improve productivity, achieve better floor finishes, and reduce unnecessary tooling costs.

What Is Diamond Grit?

Diamond grit refers to the size of the diamond particles embedded within a metal bond, ceramic bond, or resin bond tool.

The grit number indicates the size of the diamond particles:

• Lower grit numbers contain larger diamond particles.
• Higher grit numbers contain smaller diamond particles.

As a general rule, larger diamonds cut more aggressively and remove material faster, while smaller diamonds produce finer scratch patterns and smoother finishes.

This progression allows contractors to gradually refine the concrete surface, removing scratches from the previous grit before moving to finer polishing stages.

Why Diamond Grit Matters

Each grit size serves a specific purpose within the grinding and polishing process.

Using the correct grit at the appropriate stage helps:

• Remove coatings and contaminants efficiently.
• Level uneven floors.
• Expose aggregate.
• Eliminate scratches from previous grinding stages.
• Prepare the surface for densification.
• Develop clarity and gloss.
• Achieve a high-quality polished concrete finish.

Skipping grit stages or using the wrong grit can leave visible scratches that become increasingly difficult to remove later in the polishing process.

Understanding Metal Bond Grits

Metal bond diamonds perform the heavy cutting and grinding stages of concrete preparation.

25/30 Grit Metals

The most aggressive metal bond option.

Best used for:

• Very hard concrete.
• Heavy stock removal.
• Aggregate exposure.
• Floor levelling.
• Surface correction.

Because of their aggressive nature, 25/30 grit metals leave a deep scratch pattern that requires subsequent refinement.

30/40 Grit Metals

A slightly finer grinding option that still delivers excellent cutting performance.

Best used for:

• Hard concrete surfaces.
• Aggregate exposure.
• Floor levelling.
• Removing scratches left by 25/30 grit metals on very hard concrete.

40/60 Grit Metals

Often considered the transition grit between aggressive grinding and scratch refinement.

Best used for:

• Scratch removal.
• Minimal to medium aggregate exposure.
• Refining floors after coarse grinding.
• Preparing the floor for higher grit stages.

60/80 Grit Metals

A refinement-focused grinding stage.

Best used for:

• Removing scratches left by coarser metals.
• Creating a smoother surface profile.
• Preparing the floor for polishing stages.

120 Grit Metals

A specialised grit often used on softer concrete.

Best used for:

• Final scratch removal on soft concrete.
• Surface refinement before transitioning into ceramics or resins.
• Reducing visible metal bond scratches.

50 Grit Round Metals

Designed specifically for refinement and scratch removal.

Best used for:

• Removing residual scratch patterns.
• Surface preparation before ceramics or resins.
• Achieving a more uniform finish.

Understanding Ceramic Grits

Ceramic tools bridge the gap between metal grinding and resin polishing.

50 Grit Ceramics

Ceramics help remove fine metal bond scratches while beginning to close the surface profile.

Best used for:

• Refining metal bond scratch patterns.
• Preparing floors for resin polishing.
• Assisting with grouting and clear-coat preparation.
• Reducing resin consumption during polishing stages.

Many contractors consider ceramics one of the most valuable steps in achieving a high-quality polished concrete finish.

Understanding Resin Grits

Resin polishing pads are designed to progressively refine the surface and increase clarity, reflectivity, and gloss.

50 Grit Resins

The first resin stage used after grinding.

Best used for:

• Wet polishing applications.
• Removing 30 grit scratch patterns.
• Grouting operations.
• Refining 60 grit metal floors.

100 Grit Resins

A key transition stage in polishing.

Best used for:

• Wet polishing.
• Removing grout and densifier residue.
• D-rubbing floors.
• Surface refinement before higher polishing stages.

200 Grit Resins

The stage where the floor begins developing noticeable clarity.

Best used for:

• D-rubbing operations.
• Scratch refinement.
• Preparing the floor for fine polishing.

400 Grit Resins

The beginning of true polishing.

Best used for:

• Fine polishing.
• Removing 200 grit D-rub scratch patterns.
• Increasing surface clarity.
• Preparing for high-gloss polishing.

800 Grit Resins

A significant gloss-building stage.

Best used for:

• Fine polishing.
• Improving light reflectivity.
• Producing a noticeable polished appearance.

1500 Grit Resins

Used to achieve premium polished concrete finishes.

Best used for:

• High-gloss polishing.
• Increased image clarity.
• Decorative polished concrete applications.

3000 Grit Resins

The final stage of ultra-fine polishing.

Best used for:

• Maximum gloss development.
• Premium architectural finishes.
• High-reflectivity polished concrete floors.

A Typical Diamond Grit Progression

While every project is different, a common polishing sequence may include:

1. 25/30 or 30/40 Grit Metals – Surface preparation and aggregate exposure.
2. 40/60 Grit Metals – Scratch refinement.
3. 60/80 or 120 Grit Metals – Final metal grinding.
4. 50 Grit Ceramics – Transition stage.
5. 50 Grit Resins – Initial polishing.
6. 100 Grit Resins – Densifier and grout refinement.
7. 200 Grit Resins – Surface clarification.
8. 400 Grit Resins – Fine polishing.
9. 800 Grit Resins – Gloss development.
10. 1500 Grit Resins – High-gloss polishing.
11. 3000 Grit Resins – Premium finish.

The exact sequence will vary depending on the floor condition, aggregate exposure requirements, and desired finish level.

Common Mistakes When Selecting Diamond Grit

Many polishing issues can be traced back to improper grit selection or progression.

Common mistakes include:

• Skipping grit stages to save time.
• Advancing before scratches are fully removed.
• Using overly aggressive grits unnecessarily.
• Transitioning to resins too early.
• Failing to inspect the floor between stages.

A successful polishing process relies on removing the scratch pattern from the previous stage before moving forward.

Final Thoughts

Diamond grit is the foundation of every successful concrete grinding and polishing project. From aggressive stock removal to mirror-like finishes, each grit serves a specific purpose in creating a smooth, refined, and visually appealing floor.

Understanding when and where to use each grit allows contractors to improve efficiency, maximise tooling performance, and consistently achieve professional results.

At Unicorn Diamond Co, our range of metal bonds, ceramics, and polishing resins has been developed to provide reliable performance across every stage of the grinding and polishing process. Choosing the correct grit progression is one of the most important steps in achieving exceptional polished concrete results.