Achieve the Perfect Slice

Dec. 1, 2001
Selecting the right diamond blade to run on concrete saws is the best way to maximize your equipment investment. More and more companies offer diamond

Selecting the right diamond blade to run on concrete saws is the best way to maximize your equipment investment. More and more companies offer diamond blades. But how does a rental customer choose the right blade for the right saw?

Blade performance is a combination of the material being cut, cutting speed and blade life. Changing one variable affects the others. Aggregate hardness and size, amount of steel reinforcing (rebar) and whether the concrete is green or cured affects blade selection. The diamond blade segments are made up of a mixture of diamonds and metal powders. The composition of the bond that holds the diamonds must be matched to the hardness or softness of the material being cut. The simple rule of thumb to remember when selecting a blade is to use something hard to cut something soft and something soft to cut something hard.

Know your concrete

The size of the aggregate affects blade performance. Large aggregate makes the blade cut slower, while smaller aggregate makes the blade cut faster. Heavy reinforcing with rebar also tends to slow the blade and make it wear faster. The time the concrete has had to cure greatly affects how the material will interact with the blade. Freshly poured or green concrete is softer and more abrasive than cured concrete. The blade will need a harder bond with undercut protection to cut green concrete and a softer bond for cured concrete. Undercutting is a condition in which the steel core of the blade wears faster than the diamond segments. It is caused by highly abrasive material grinding against the core. The best remedy is to choose a blade with undercut protectors on the core or poly-arc segments.

Know your saw

You must know the blade specifications required by your saw. Do not use blades not recommended by the manufacturer on your saw. You can control cutting by adjusting spindle speed. Increasing spindle speed makes the diamond blade cut harder, decreasing the spindle speed makes the blade cut faster. Harder, less abrasive materials require slower spindle speeds and softer, more abrasive materials need faster spindle speeds. Never operate blades at rotational speeds greater than the maximum RPM listed on the blade. Over speeding can damage the blade or cause serious injury.

Know the differences between blades

There are several types of diamond blades from which to choose. High-speed segmented blades are the most competitively priced on the market and make fast, smooth cuts in many materials. They provide a constant depth of cut and fewer blade changes. Most of these blades come with a 1-inch arbor with a drive pinhole or a 20mm arbor.

Dry walk-behind concrete saw blades are ideal for intermittent cuts in concrete, green concrete and asphalt. They cut without water and are often used in patch/repair work or expansion joints. Dry and wet masonry blades provide a consistent depth of cut with less dust than abrasives. Segmented dry small-diameter blades are used on hand-held circular saws and most right angle grinders.

Use them on concrete block, marble, soft granite, stone, tile and other materials. Dry tuck-pointing blades are used on hand-held circular saws and small, right angle grinders. Dry tuck-pointing pins can be used on routers to clean out mortar from mortar joints and butt (vertical) joints. Dry tile blades are continuous-rim blades used for chip-free cutting on tile saws, right-angle grinders and circular saws. Dry segmented cup grinders, used on right-angle grinders, grind all types of concrete, masonry, brick, block and stone.

Abrasive wheels

A much less expensive cutting tool is the abrasive wheel. Abrasives are more disposable and do not last nearly as long as a diamond blade. They are made of bonded materials (silicon carbide and aluminum oxide) and are designed for smaller cutting, sharpening and grinding jobs. Typical abrasive products include high-speed wheels for masonry and concrete, wheels for walk behind, chop and power hand saws, cup grinding wheels and grinding stones. Abrasives can break if improperly used and there are a variety of safety precautions to follow when using them.

Identifying the type of concrete in the application, knowing the specifications of your saw and understanding the differences in the types of diamond blades will all help rental customers choose the right blade for their concrete saw.

Thom Fisher is advertising and trade show manager for Diamond Products, Elyria, Ohio.