To select blades or bits for cutting concrete, a contractor doesn't need to know how they are made, but he should know how they will be used--the type of concrete he has to cut and the machine he plans to cut with. A manufacturer of concrete cutting equipment can then recommend a blade or bit that will match the concrete and the machine.


Diamond bits and blades are made by brazing diamond segments to the end of a steel tube or the perimeter of a steel disc. Each diamond segment consists of several diamond particles held together by a metal bond. To make segments that will cut different types of concrete, manufacturers vary the composition of this metal bond and the type, size and concentration of diamonds. Most contractors prefer to use wet-cutting diamond blades whenever possible, because the water used to cool the blade also eliminates dust. The slurry that's produced can easily be vacuumed up.


Type of Aggregate--Hard aggregates shorten blade life and slow the cutting rate, so cutting concrete with a hard aggregate such as quartz will cost much more than cutting concrete with a soft aggregate such as limestone. Size of aggregate is also important.

Reinforcing steel--It costs more to cut concrete that contains reinforcing steel because blade life or bit life is shorter and cutting rates are slower.

Operating speed--To keep blades from distorting at high speeds, they are manufactured in the form of a dish that will straighten when the blade is rotated at optimum speed. If the design speed is not achieved, the blade will tend to wander as cutting commences.

Depth of cut--Making deep cuts will generally cost less than making two or three shallow cuts.