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The Essential Guide to Concrete Grinding Cup Wheels

The Essential Guide to Concrete Grinding Cup Wheels

13th Jan 2025

On almost every project that entails surface preparation or polishing, there will be areas that a large grinder or shot blaster will not reach. Edges, inside corners, and recessed toe kicks are all areas that need to be ground with a smaller piece of equipment. When polishing a countertop, the smallest walk-behind grinder will be exceedingly difficult to use safely. Even if it can be lifted and set on the surface, the intersection of the horizontal working surface and backsplash will still need to be ground.

All the areas listed above will need to be addressed with a hand grinder. Hand grinders are small, maneuverable tools that have diamond tooling available that emulate what can be fitted on a large grinder.

The diamond tooling for a hand grinder is called a cup wheel or diamond cup wheel. These are attached to a 5” or 7” hand grinder. They attach to the grinder with a threaded or nonthreaded fitting. 

What are Concrete Diamond Cup Wheels?

Diamond cup wheels consist of 3 main parts. There is a tool holder, made from a durable metal alloy, which attaches to the hand grinder. There are two methods of attachment available, threaded and nonthreaded. Before buying a grinding wheel, you need to decide which one will fit on your grinder.

Cutting segments consist of a metal alloy, ceramic, or resin bonding material holding industrial diamonds. When in use, bonding material wears away exposing fresh diamonds. This continues until the bonding material has completely worn away.

The cutting segments having the industrial diamonds are attached to the tool holder. Segments come in different configurations. Each shape has its own use.

  • Turbo
  • Continuous Rim
  • Double Row
  • Arrow Seg
  • Ceramic Shine

The manufactured industrial diamonds are what is doing the work. Taking a closer look at a diamond particle, you will see they are angular in shape. They have very sharp edges that will do the cutting. The diamond particles come in multitude of sizes. The larger the diamond particle (lower the grit number) the more aggressive it will be. If the aim is to remove a large amount of concrete, selecting a coarse diamond will be your best bet.

Types of Cup Wheels

Cup wheels can be used to perform diverse levels of work. One can be selected to grind down a ¼’ concrete lip. Another can be used to put a high gloss shine on a concrete countertop.

Three basic levels of cutting can be achieved. The first level is used to grind the surface. The shape of the segment has sharp cutting edges that have a coarse diamond abrasive. Care should be taken when using this type of grinding wheel. Ease the grinder onto the surface allowing it to do the work. By applying too much pressure when grinding, it might cut a bit faster, but it also overstresses the motor. This will dramatically shorten the service life of the grinder. Too much pressure will also leave a deep scratch pattern that might not be able to be removed with the next step.  

The second level is the honing phase. This process will remove the coarse grinding wheel scratches. The only time this will be used is if the surface is to be polished or a thin mil coating will be applied. It leaves the surface smooth with a highly absorptive open profile. On surfaces where only a fine aggregate is to be exposed, this could be used as the first step.

The final level is to polish. This will produce a smooth, glossy appearance. Polishing wheels are typically fine diamonds encapsulated in a resin-bonding material. They are not designed to remove much stock. They only remove the fine scratches produced during the honing phase. When polishing, the speed of the grinder is set slower than when grinding and performed with a 5” grinder with variable speed.   

Choosing the Right Cup Wheel

During the selection process, the outcome needs to match the grinding wheel. Will a coating be removed, will you need an aggressive scratch pattern for bonding purposes, or will it be the first step of the polishing process? The right tool is the most efficient tool.

  • Turbo
    • o   Ideal for leveling, removing coating, and grinding concrete.
    • o   Aggressive scratch pattern
    • o   Removes thin set, thin glues, epoxies, and urethanes.
  • Continuous Rim
    • o   Ideal when multiple grits are needed.
    • o   Best cup wheel for concrete polishing
    • o   Provides easy grinding and shaping of rounded surfaces, corners, angles, and edges.
    • Double Row
      • o   Ideal for opening hard concrete.
      • o   Overall great general-purpose cup wheel
      • o   Grinds around drains and uneven surfaces without excessive gouging.
      • Arrow Seg
        • o   Extremely aggressive segment shape for grinding
        • o   Use for coatings, adhesive, thin set, and grout bed removal!
        • o   Segment design splits and lifts materials from the surface!
        • Ceramic Shine
          • o   Reduces the scratches and gouging metal bond cup wheels can cause.
          • o   Fast, lightweight and easy to use resulting in a superior edge.

Best Practices for Using Concrete Grinding Cup Wheels

The first thing that needs to be discussed when using any power tool is safety. Not only the safety of the operator but also the people in the surrounding area. Hand grinders spin the diamond grinding wheel at high speeds. They can range from 500 rpm to 7,000 rpm. Wearing safety glasses, gloves, and leather footwear are the most obvious. Correct clothing also needs to be considered.

When working with a power tool that spins, tight fitting clothing needs to be worn. You might think flying debris is the only danger, but having a shirt sleeve getting wrapped around the spinning arbor can cause a huge issue. Loose fitting shirts, pants, and gloves are also a working hazard. Always select tighter fitting attire that will protect the operator from flying objects and not get wrapped up in the equipment.

When selecting a diamond wheel, always start with a less aggressive style or higher diamond grit. If it isn’t cutting the way you want, it can always be changed. If it is too aggressive, the concrete you just removed cannot be put back in place.

If the hand grinder you are using has a speed adjustment feature, start at a slower speed. The faster the aggressive wheel spins, the more it will cut. This will give you a bit more time to get used to the grinding process.

The amount of force that is put on the grinder only reduces the grinder’s life. Let the tool do its thing. It is designed not to be forced when grinding. If it isn’t grinding enough or at the speed you feel it should be, change the grinding wheel to a more aggressive one.

Grinders have vent slots to draw in cool air reducing heat buildup. These need to be free of dust and debris providing good air flow. Dust can also compact in and around the motor. Regularly vacuum all dust from on and from within the housing. Once vacuumed, compressed air can also be used to remove the remaining debris. When using compressed air, be aware the dust will go airborne. Wearing protective glasses and a dust mask is the right thing to do.

After each use, check the power cord for cracks and breaks. If an issue arises, change the cord. Don’t just tape it. 

Conclusion

Diamond grinding wheels are a necessity when performing surface preparation for a coating system, polishing, or just removing an unwanted concrete lip. They can be very efficient if used correctly and fitted with the proper cup wheel.

Grinder cup wheels can be used to remove coatings or grind a surface down exposing the coarse aggregate. When paging through all the wheels offered on the internet, stop and give Niagara Machinea call. We carry almost every type available and can guide you to the best one suited to your project. There is no sense in buying one that doesn’t fulfill your needs. Contacting Niagara first will save you time and money.