Because the diamonds fracture and wear down quickly on hard material, the hard 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 segmented edge. It will feel smooth.

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 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. Overheating can cause segment loss (the solder holding the segment onto the core melts), severe blade damage and safety problems. Water also reduces dust and helps remove cuttings from the bottom of the cut.

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-temperature 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.

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. Let’s look at this grinding process step by step.

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 to 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 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.

When diamond 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 fracture and break 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 for them to do the maximum amount of grinding before being replaced by “new” diamonds.