Educational Section

Table of Contents

Diamond Blade Basics
Diamond Tools & Technology
Factors that Affect Cutting Performance
Diamonds - Key to Successful Cutting
Cutting Depth Chart
Operating Speed Chart
Do's and Dont's

Factors that Affect Cutting Performance

The life of a blade or bit and the speed at which it will cut depends on the following application conditions. For a manufacturer or distributor to supply the proper blade, they must be told what the material, project timing, and equipment conditions are for your job. If any of these conditions change, you should know how the change will affect blade performance.

Type of aggregate

The type of aggregate has a pronounced effect. Hard aggregates shorten blade life and slow the cutting rate. Cutting concrete with a hard aggregate, such as quartz, will cost much more than cutting concrete with a soft aggregate, such as limestone. Cutting concrete made with hard aggregates also requires more power.
Blades used to cut hard aggregates should have segments with tough diamonds and soft metal bonds otherwise the diamond particles will wear down even with the bond, and the blade will become glazed and unable to cut. Likewise, segments for cutting soft aggregates should have hard metal bonds, so that the diamond particles are not lost before their cutting life is used up. Aggregate hardness can be measured using the Mohs Scratch Test, the Los Angeles Abrasion-Loss Test, or the Shore Hardness Test. Size of aggregate is also important. Concrete made with two-inch flint aggregate will be extremely difficult to cut, but concrete with; one-half-inch flint aggregate will cut much more easily. This is because there is more aggregate surface per unit volume of concrete in contact with the cutting segments when a larger size aggregate is used.

Reinforcing steel

Diamond blade / bond systems are designed to cut concrete which has an abrasive component present at all times. When diamond blades cut steel there is very limited abrasive material present resulting in slower cutting rates. The ratio of the volume of steel per unit volume of concrete has an impact on blade performance. The higher the ratio is the slower the cutting rate will be. Blade life will generally decrease as well.

Tip: When steel is encountered, reduce blade speed if possible, increase cutting pressure, and decrease water flow.

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. The dishing is small, about five ten-thousandths of an inch per inch of diameter. If the design speed is not achieved, the blade will tend to wander as cutting commences. This dishing is called tensioning. When a blade is said to be out of tension the amount of dish is not correct and the blade wobbles from side to side while out of the cut and wanders in the cut. An out-of-tension blade cannot be made to cut a straight line. It will cut a very regular sinusoidal line.
Manufacturers usually list the recommended operating speed directly on the blade. Recommended operating speeds for diamond blades are based on the blade size and the type of material to be cut. For optimum blade life and cutting speed, the actual operating speed will most likely have to be adjusted for the type of aggregate and the amount of steel encountered.

When in doubt about the correct operating speed for a particular material, choose a lower speed rather than a higher speed. Then, if the blade cuts well, try increasing the speed to improve blade life. To cut softer and more abrasive materials use a faster operating speed, faster forward speed, and more water.
In general, higher operating speeds tend to lengthen blade life and slow cutting.

WARNING: Never operate a blade above the maximum or "Do Not Exceed" RPM stamped on the blade. Failure to comply with this speed will result in injury or death.

(See Chart)

Depth of cut

The depth of cut should be adjusted such that a forward speed of 8 to 10 FPM (feet per minute) can be maintained. This speed has been determined over many years of cutting to be the most economical cutting speed based on labor costs, blade costs, machine costs and operation costs.

Coolant

Water or some other coolant must be used to cool most diamond blades.
If not enough water is used, the swarf (fine particles) will not be removed from the cut quickly. This is a common cause of undercutting: the abrasive particles from the cut wear away that part of the steel core where the diamond segments are attached. Without sufficient water, the core will also overheat, causing cracks and premature loss of segments. To minimize blade wear, an adequate volume of water is essential. The water flow for saw blades should be between 1/2 and 3 gallons per minute. Sawing water systems can deliver a maximum flow of 5 gallons per minute.