By Jack Kohane
It could be a love affair. To paraphrase a line: diamonds are a rental operator’s best friend. And with some lust for learning, choosing the right diamond blade for the task at hand will cement the relationship. But which blade will work the desired magic? It takes a deeper understanding of the marriage between diamonds (the kinds found in circular saws) and steel to create a tool that cuts into all forms of hard material.
By Jack Kohane
Rae Hudson, Canadian sales manager for Diamond Products, says, “The most expensive blade is not always the right blade for the job.” In his opinion, the diamond blades segment is very important to the rental industry. “That’s because one of the more common items to rent is a hand-held cut off saw and each saw is usually rented with a diamond blade or an abrasive blade. As long as the construction market continues to grow so will the demand on rental tools and diamond blades.”
PUT A DIAMOND ON IT
A diamond blade is essentially a wedding of a saw blade with diamonds fixed on its edge for cutting hard or abrasive materials. There are a variety of diamond blades on the market, offering various uses, including cutting stone, concrete, asphalt, bricks, coal balls, glass and ceramics in the construction industry; cutting semiconductor materials in the IT industry; and cutting gemstones, including diamonds, in the gem industry. As the name suggests, there are actual diamonds scattered throughout the blade. However, these are not exactly the diamonds found in engagement rings. They are typically synthetic and produced through high-pressure, high-temperature synthesis in order to produce the most efficiency for cutting.
The diamonds can be bonded to the blade through a variety of different methods — typically with sintered metal powder — and these methods can affect the blade quality, but the bond is the most important thing to understand when it comes to diamond blade makeup. The bond varies between different levels of softness and hardness. In addition to giving a base for the diamonds, the bond allows for a specific wear rate to match the material being cut.
HOW IT WORKS
Diamond blades don’t cut, they grind. The exposed diamond crystals do the grinding work. The metal matrix or bond holds the diamonds in place. As the blade rotates through the material, the exposed surface of the diamonds grinds the material being cut into a fine powder. After several thousand passes through the material being cut, the exposed diamonds begin to crack and fracture. The matrix holding the diamond also begins to wear away. Eventually the diamond completely breaks up and its fragments are swept away with the material that it is grinding. As the diamond wears and fractures, controlled erosion of the metal bond containing the diamond exposes new sharp diamond points. This cycle of erosion and exposure continues until all of the diamond and metal bond section of the segment is gone. Once the cutting section is consumed the blade will no longer grind, letting the operator know it is time for a new blade
GOOD, BETTER, BEST
Working with rental operators across Canada, Hudson and his sales team focus on educating retailers on how to advise their customers about choosing the right diamond blade for their needs (there’s also Diamond Products University at diamondproducts.com). Hudson points out that because diamond blades come in a wide variety of sizes and performance levels, selecting the right blade is not always an easy task. Blade costs can vary widely and stretch into the thousands, depending on quality. “And although it may be tempting to buy a lower-cost blade, in the end it will likely be wiser to buy a more expensive, high-performance blade that’s designed to last longer,” he explains.
How efficiently a blade works can even vary in certain parts of the country. Aggregate hardness (there are different types of rock used as aggregate – for example, granite varies in hardness and friability over a range of medium-soft to hard), which can differ from medium-soft in southern Ontario, to medium across portions of the Prairie provinces, to medium-hard in Quebec and the Maritimes.
MATCH BLADE TO APPLICATION
When cutting concrete, several factors will influence the choice of diamond blades. Concrete slabs vary greatly in comprehensive strength, measured in pounds per square inch (psi). Most concrete roads are 4,000 to 6,000 psi, while typical patios or sidewalks are about 3,000 psi. “Aggregate hardness is one important factor when cutting concrete,” notes Hudson. That is due to the fact that hard aggregate dulls diamond more quickly, so segment bonds (made up of two components: diamond and metal) generally need to be softer when cutting hard aggregate. This allows the segment to wear normally and bring new, sharp diamond grit to the surface. Softer aggregate will not dull diamond grit as quickly, so harder segment bonds are needed to hold the diamonds in place long enough to use their full potential.
Also affecting blade performance are the types of sands in the aggregate. Sand is the component which determines the abrasiveness of the concrete. Sand can either be “sharp” (abrasive) or “round” (non-abrasive). Another factor, reinforcing steel, tends to make a blade cut slower. Less reinforcing steel allows a blade to cut faster.
The drying or curing of concrete also greatly affects how the concrete will interact with a diamond blade. Green concrete is freshly poured concrete that hasn’t yet cured. It is softer and more abrasive than cured concrete. Harder bond with undercut protection should be used in this application until it is cured, at which point a softer bond would be appropriate. Further, the definition of green concrete may vary widely: water, temperature, moisture in the aggregate, time of the year and the amount of water in the mix all influence curing time. It is generally considered “green” for eight to 48 hours after it has set.
Horsepower is one big factor when counselling customers on the best mate for the job they’re doing. If a blade is used with a machine that does not have sufficient horsepower for the diamond/bond system, the blade will not perform well. Diamond particles will polish (forming flat spots) and the blade will become glazed. Typically, flat saws range in power from eight to 75 horsepower. In selecting a blade, manufacturers or distributors should be told what the horsepower of the saw is. Using a blade designed for low horsepower saws on a high horsepower saw will result in a fast cutting rate and a short blade life. Using a blade designed for high horsepower saws on a low horsepower saw will result in slow cutting rates with a long blade life.
WET VERSUS DRY
What’s the skinny on wet versus dry? Blades are available for either wet- or dry-cutting applications. Dry-cutting blades can usually be used with or without water and are designed to work in higher temperatures. Wet-cutting blades, however, should not be used dry, because they’re designed to be operated with a continuous spray of water. Using a wet blade dry can result in flying debris as segments and teeth become disengaged from the blade.
Wet cutting is often considered the best method to use. Water cools the blade, reducing heat build-up and extending blade life. Water also dampens cutting fines and eliminates dust.
Some jobs require dry cutting, like when you’re using an electric saw. Cold weather can make wet cutting impractical as well because of potential freeze problems. Wet-cutting is necessary when using a concrete-cutting chain saw.
When cutting dry, don’t cut more than one to two inches deep in one pass and allow the blade to cool periodically. Doing so will keep the blade from overheating; overheating can shorten the blade’s life.
WHAT TO STOCK
In tackling most concrete cutting projects, Hudson suggests rental operators primarily stock general purpose blades. “It simplifies what to choose,” he nods. As for price, Hudson says there’s a price point for everything. “Determine what the customer is willing to invest in a specific tool. This allows the retailer to recommend the right tool for the job.” So when a customer pops the question about the right diamond, you can say, “I do.”
- Use something hard to cut something soft; use something soft to cut something hard. When cutting concrete (hard material) use a softer bond. When cutting asphalt (soft material) use a hard bond. Many factors change the bonds, but this is the basic concept for using diamond tools.
- Start in the middle; then adjust. Starting with a mid-range, general purpose bond makes it easier to dial-in the correct adjustments for the most effective cutting.
Source – Diamond Products