Imagine for a moment that you’re sitting in the cockpit of a modern jet. You’re surrounded by buttons, dials, and controls whose function you don’t understand. Behind you, a plane full of passengers anxiously waits for you to safely transport them to their destination. 

Now, trying to fly a jet without proper training is absurd; yet, we do many things in our personal and professional lives without adequate training or knowledge. The potential fatal consequences of making an error when flying a plane stops us from attempting such a task
(not to mention aviation laws), but should we require extreme danger to force us to be skilled at a task?

Achieving competence in any field starts with the basics; they’re the foundation on which everything else is built. Before you can fly that plane, you must learn about the plane’s mechanics.

I’m not a pilot, so I can’t teach you how to fly a plane, but I am an expert on concrete grinding diamond tools. In this post, you’ll learn about the individual components and their purposes before I get into the grinding tools themselves and how to choose the correct one. 

 I. Learning the Basics

The Diamond

When using a grinder, all the grinding or cutting is done by the diamond. Synthetic diamonds are predominantly used for modern diamond tools because they provide a large selection of sizes, shapes, and strengths. Diamond tool manufacturers can then optimize tools for a wide range of applications. Diamond size is sorted by mesh or grit size, and there’s an inverse relationship between the size of the diamond and the size of the grit number. This means a large diamond has a small number (e.g., 18/20, 30/40) and a small diamond has a large number (e.g., 80/100, 170/200). Large diamonds are used for aggressive removal while small diamonds are used for honing and polishing applications. 

The Bond

The sole purpose of the bond is to hold the diamond. It is commonly made from metal or plastic resin but can be made from any material that is suitable for the tool’s application. The bond is designed to wear away at a predetermined rate to allow for new diamonds to be exposed before all the surface diamond has broken down. 

A bond must be matched to the material it is intended to grind, or the tool will not function well. For example, if a soft concrete floor is ground with a tool designed for medium concrete, the tool will only have a fraction of the intended life and will wear out prematurely. This is because the wear resistance of the bond is too low for the concrete, which results in the tool needlessly wearing away and releasing new diamonds before the surface diamonds have broken down. 

If a tool for soft concrete tool is used on a hard concrete floor, the surface diamond will break down and the tool will stop cutting before new diamonds are released. This is because the wear resistance of the bond is too high and, therefore, the bond is not releasing diamonds fast enough to replenish the diamonds on the surface. 

Understanding diamond tool basics will help you make the correct tool selection and avoid these problems.

It seems counterintuitive, but a hard concrete floor requires a low wear resistance or “soft bond,” while a soft concrete floor requires a high wear resistance or “hard bond.” (Note: Using the terms hard and soft bond aren’t technically correct, but for the purpose of simplicity, they are acceptable.) 

The best way to understand bonds is to consider how much concrete is being removed from a soft versus a hard concrete floor. On a soft floor, you could produce 5+ bags of concrete dust by grinding 1000 sq ft, while a similarly sized hard floor may only yield 1 bag of dust. This means the soft floor is wearing the bond with 5 times as much dust as the hard floor, which is why it needs to have a much higher wear resistance bond. The hard concrete tool needs to have a correspondingly low wear resistance bond to match the low amount of concrete being removed; otherwise, it will not release new diamonds fast enough. 

II. Choosing the Correct Tool

Understand your requirements.

Do you need an aggressive tool to remove a heavy coating? Or a fine grit to remove scratches during a polishing process? The grit size is going to determine how aggressive the tool is, so this should be your starting point.

• 30/40 grit: the jack of all trades prep tool
• 18/20 grit: aggressive removal
• 80/100 grit: concrete polishing. 

Don’t be afraid to try a few different tools to see how they differ and to determine which one provides the best result.

Select the correct bond. It’s often difficult to know the hardness of the concrete before you start grinding, so you’ll have to make an educated guess, and then monitor the tool wear and performance to determine if your choice was correct. Check the tool wear regularly, and don’t hesitate to try another bond if you’re unsure about your selection. Some obvious red flags to watch for are poor cutting performance, which means the bond is too hard, and excessive tool wear, which would indicate that your bond is too soft. 

A general rule you can follow when choosing your starting tool is that new, well-finished concrete floors will be hard and older, beat-up floors will be soft. Medium concrete floors will fall somewhere between the two extremes. Contractors should carry their most commonly used grit sizes in three bonds matching the three most common types of concrete they encounter. 

III. Factors to Consider when Selecting Diamond Tools

a) Performance. The first element, performance, outweighs the other two elements combined. Performance drives not just your profitability but also your competitiveness, which will determine if you win bids and grow your business or sit at home. There’s a lot riding on the performance of your tools. So, how do you know which ones to choose? 

The best way to understand diamond tools, and, as a result, make informed decisions is by calculating and monitoring your tool performance. 

To calculate the performance of your tools: 

Step 1: Measure the area ground (never estimate)

Step 2: Calculate the grinding time by subtracting any stoppage time from the total shift time

Step 3: Divide the square feet ground by the total grinding time

So, if you ground 5,000 sq ft in 7 hours, you would have a production rate of 714 sqft/hr. Write the date, location, job, tool, grinder, and floor condition next to the production rate, so you have a complete picture. This information should be kept in a log book that you bring to all your jobs. It’s important to calculate this data on every job, even when it seems unnecessary. 

Understanding your tool performance will not only help you choose the right brand of tools, but it will also help you choose the correct tool from that brand’s product line. Rossi Abrasives has an exceptional product line, but sometimes a customer will not see good results because they used an incorrect tool. Your data will make that clear because the tool will not reach its normal production rate. You will have measurable targets for every step in your grinding process, which will make managing your grinding operations easier. 

Once you have a few months of data, I recommend trying another brand of tools, so you have a reference point. You may not see weaknesses in your tools without seeing other products. We all get attached to specific tools, but try not to let your preferences and emotions muddle the process. Instead, let the data guide you through all your tool selection. It’s a good idea to try a new tool at least once a year because the market is always changing and evolving. 

b) Cost. If you looked at the purchasing criteria for most contractors, you might think that diamond tool cost is not only the most important criteria, it's the only criteria. 

Cost is only relevant in the context of the tool’s performance. 

I can't stress this enough. If a tool doesn’t have consistently high production rates, it’s irrelevant how much it costs. There can also be a substantial difference between the price of the tool and the actual cost. Some tools may be cheap to buy but expensive to use. It’s easy to sort fools gold from the real deal by simply calculating your actual tool cost. This is something you should do on every job, and the numbers should be kept in the same log book where you track your tool performance.

Calculating your diamond tool cost is as simple as taking the cost of a set of tools and dividing it by the total square feet you got from the set. 

For example, if you paid $427.50 for your set of tools and ground 12,000 sq ft, your cost would be $0.0356 or 3.6 cents per square foot. When compared to labor and other costs, diamond tool cost is relatively small, so if you’re trying to save money, you should target a larger expense. Your diamond tools are a critical investment—you can’t expect to get a lot out of them if you’re not willing to put some money into them. 

c) Inventory. The best tools in the industry won’t help you if you show up to your job without them. It’s essential to carry your most commonly used grit sizes in at least 3 different bonds so that your crew has the ability to find the best match. Your productivity and cost effectiveness rely on having the right tool, but it also helps your crew learn by seeing and measuring the performance of the different tools. Attempting to save money by carrying a minimal diamond tool inventory will result in higher overall cost and lower productivity. Like the previous two points, it’s about understanding what will bring your business real cost savings, not perceived savings. Once you establish a basic inventory, refill it automatically as you use the tools.

Lock and Load

Now that you’re equipped with the basic knowledge to get started, all you need is a little patience and curiosity to experiment with different tools and the understanding that mistakes will be your greatest source of knowledge.

We have an excellent Concrete Grinding Starter Bundle to ensure you get started on the right foot. 

Knowledge is power, success is a result of the effort you put in, and comfort zones are for retirement. Today is the day. Advance your business. Outthink the competition. Don’t sit idle. 

If you have questions or comments, I encourage you to email me. 

Carpe Diem.

Mark Rossi

Rossi Abrasives

*This article was published in the 2018 May/June issue of Concrete Construction Magazine, in the Concrete Surfaces section.