Diamond Saw Blades & Cutting Tools

The diamond crystal used is manufactured or man-made diamond. Manufactured diamond is preferred over natural diamond because crystal shape, size, and strength can be more closely controlled. Various crystal sizes and types of diamond are used, depending on the specific application.
The matrix, or bond is a metal alloy made of iron, cobalt, nickel, bronze or other metals used in various combinations. The matrix holds the diamond grit in place, evenly dispersed throughout the segment. On the edge and sides of the segment or rim, individual diamond crystals are exposed, partially embedded in the metal matrix, or bond. Bond tails which trail behind each exposed diamond, help support the crystals. The steel core is a high grade heat-treated, tempered steel disc, which is precision ground to size. These cores are manufactured exclusively for diamond blade applications. All blades have centre holes, sized according to the saw shaft they will be used on. Centre hole sizes are generally standardized. Hand held grinding and high speed saws may have several different shaft sizes.

Types of Diamond Saw Blades

Blades for use on concrete saws also have drive pin holes. Blades subjected to the higher horsepower and torque exerted by concrete saws require a drive pin to keep the blade from spinning on the shaft. You may find some masonry saw blades or other type blades with a drive pin hole, but the hole is not functional. Segmented blades have gullets or slots between the segments. These gullets serve to help cool the blade during sawing by allowing water (wet cutting) or air (dry cutting) to flow through the edge of the blade. They also allow some flexing and help reduce cracks at the edge of the blade. Diamond blades are mounted onto the blade shaft of a saw and clamped tightly into place between two collars or flanges. When power is applied to the shaft, the blade spins. The saw operator then begins pushing the blade into the material. Now the cutting begins – but a diamond blade does not really “cut” like a knife – it grinds.

Remember, the diamond segment is made up of diamond crystals embedded in a metal matrix or bond. During the factory “break in” process individual diamond crystals are exposed on the face and sides of the diamond segment, with supporting bond tails trailing behind them. Note the direction of rotation of the blade. You can feel the diamond exposure by running your fingernail along the edge of the segment. As the blade segment contacts the material, the exposed diamond crystals on the segment face grind through the material. The exposed crystals on the sides of the segment provide relief so that the blade core will “clear” the sides of the cut.

While diamond crystals are grinding away the material, the material is wearing away the segment. The hardness of the material causes the diamonds to fracture and break apart as they cut. The abrasiveness of the material wears away the metal bond. Eventually, as the bond continues to wear, it releases the “used” diamond. Another “new” diamond then begins its grinding work. From the first cut, this continuous exposing, grinding and wearing process continues all around the blade until the diamond segment is completely worn away. Also notice that the steel core wears thinner as the segment wears down. To further understand how the blade interacts with the material, let’s see how the blades work on different materials.

Soft and Hard Bonds

When diamond saw blades are used to saw hard materials, (like tile, brick or cured concrete with hard aggregate) the hardness of the material will cause the exposed diamonds to 6 fracture and break down quickly. For the blade to keep cutting, the metal bond must also wear down quickly, to keep “new” sharp diamonds exposed on the segment surface. Therefore, blades designed to cut hard materials, generally have relatively soft metal bonds. The soft bond allows the blade to cut freely and stay “sharp”. Now, for sawing relatively soft, abrasive materials, (like masonry block, “green” concrete or asphalt) the metal bond must be hard. The hard bond resists the abrasion and holds the exposed diamond crystals long enough, so that they can do the maximum amount of grinding before being replaced by “new” diamonds. Let’s use two examples to help illustrate the grinding/wearing principle:

What happens if a HARD bonded blade is used to saw hard materials?

Because the diamonds fracture and wear down quickly on hard material, the metal bond segment will not wear away fast enough to expose new diamonds and the blade stops cutting, becoming dull. You can easily identify a “dull” blade by running your fingernail along the segment edge. It will feel smooth.

What will happen if a SOFT bonded blade is used to saw soft/abrasive material?

The abrasiveness of the material will wear away the metal bond so quickly that good, usable exposed diamonds will be lost. The blade segments will wear down too fast, resulting in poor blade life.

The most important principle to understand is that the blade and the material INTERACT to make the sawing process work. For the blade to cut freely and fast, it is important to get the right blade for the job.

Wet Cutting Diamond Blades

Wet cutting diamond blades must be used with water. Concrete, masonry, tile and high speed saws have water tubes which spray water onto the blade. Water is required as a coolant to keep the blade from overheating through friction during cutting. Over-heating can cause segment loss (the solder holding the segment onto the core melts), and severe blade damage and safety problems. Water also reduces dust and helps remove cuttings from the bottom of the cut.

Dry Cutting Diamond Blades

Until a few years ago, water had to be used on all diamond blades. Advances in blade technology, specifically the laser-welding process, now allow some blades to be used dry. The strong laser-weld which fuses the segment to the core is designed to withstand the heat and pressure of dry cutting. High temperatures solder bonds and other processes are used on some dry cutting blades. Dry cutting blades are “air-cooled” and should be used only for “intermittent” or shallow sawing, to allow the air flow around the blades to dissipate the heat. Wet cutting blades are still recommended for continuous cutting or deep sawing.