Diamond Dos and Don'ts

Diamond blade manufacturers see evidence of their blades getting beat up in different ways. Blades get burned, stuck (and then hit with a hammer), bent and broken. It's not pretty and it's not good for business.

Whether a customer is renting a diamond blade or using a diamond blade on a gas-powered saw, electric hand saw, stationary saw or walk-behind saw, a few words of wisdom can help save blades from misuse and abuse. To maximize the life of a blade, educate your customers on blade basics. Give them a list of dos and don'ts so they can avoid making common mistakes.

Many variables impact blade life, which can vary greatly. Key factors impacting blade life include:

The quality of the blade (diamond quality and concentration, and segment bond and width) makes a difference in blade life.

Two blades with the same diameter could have different diamond depths, different amounts of diamond in the blade segment and different segment heights, for example.

Just as there are different grades of diamonds for jewelry, there are different grades of synthetic diamonds for saw blades.

"A higher-quality diamond is going to perform better and definitely last longer," says Ted Skaff of Pearl Abrasive Co. Sometimes it also may grind or cut faster, he adds.

Another very key factor is the material that needs to be cut.

Concrete is harder than asphalt, which is a very soft, abrasive material. Cutting a harder material like concrete requires diamonds to be exposed more quickly (and a softer bond to hold the diamonds to the segment).

"You could use a blade designed for concrete to cut asphalt and it will cut really fast - but it won't last very long," says Thom Fisher with Diamond Products.

How concrete will impact blade life depends on aggregate size, sand type (sharp and abrasive, or round and non-abrasive), aggregate hardness (determined by rock type), and reinforcing steel (amount, grade and gauge).

For example, a courser aggregate with a lot of sand will wear a blade faster than concrete with less sand, less aggregate, Skaff says.

Softer and more abrasive green concrete will require a harder bond with undercut protection, Fisher says.

How long a blade can be used on a job depends on the amount of cutting that needs to be done.

Using a blade to cut a driveway is different than using a blade to cut a long stretch of highway, Fisher points out.

The tool used with the blade affects blade life, too.

A tool with high rpm will wear a blade faster than a tool with low rpm, Skaff says.

And lastly, the operator can shorten the life of a blade.

An operator applying more pressure will tend to wear out a blade faster than someone applying less pressure, Skaff says.

Given these variables, manufacturers offer the following dos and don'ts to maximize blade life.

Do use the right blade for the job.

There are blades designed specifically to cut concrete, masonry and green concrete.

While general-purpose blades can cover a variety of applications, application-specific blades are engineered with a specific bond to meet the needs of a specific application. They do the best job and blades will last longer, Skaff says.

To help find the right blade for the job, ask about the job, says Hobie Smith of MK Diamond Products Inc.

The first questions should be:

  • What material are you cutting?
  • What type of machine will be used?

Follow-up questions should include:

  • How much cutting will be done?
  • How fast do you need to do the job?

Once customers have the right blade and tool in hand, they need to know how to use the blade on a concrete saw properly. Determine their level of expertise and provide instruction as needed.

Do use a wet blade only when wet.

A common mistake renters make is using a wet blade dry. "A wet blade should never be used dry," Skaff says. But, he points out, dry blades can be used wet and that might actually increase production and blade life. Heat and dust are enemies of a blade, he explains. Using a blade wet eliminates both enemies.

"We get blades back all the time that are fried because water wasn't used," Fisher says. "It doesn't take very long for the friction of concrete (or even asphalt) to burn up a blade."

Smith was in a rental yard when a customer returned in less than an hour. The customer was using a wet blade to cut cured concrete but he was cutting dry. He nearly destroyed a diamond blade, and both he and the rental store owner were unhappy.

Don't bury the blade.

Another common mistake is burying the blade all the way to the flange, or forcing the blade through the material being cut.

Forcing the blade through the material will damage the saw by increasing the amperage, burning up the motor and overheating the blade, which causes premature wear and damage, explains Skaff, who has seen blades burned so badly they have a purple rainbow around the rim.

Metal in the diamond rim can get so hot that it covers the diamonds. Glazing over diamonds on the rim can cause blades to dull and stop cutting even though there's a lot of life left on the diamond rim of the blade, he continues, noting this can be solved in the field by dressing the blade.

"You always want to let the blade do the cutting, whether you're using a handsaw, stationary saw or walk-behind saw," he says. "That will increase the life of the blade and the life of the tool being rented."

Fisher adds, "In reality, you shouldn't even use half of the diameter of a blade." Instead, he says you want to make several passes with the blade.

In other words, Smith says, customers need to be using a step-cutting technique.

Don't be pushy.

No one likes to be pushed beyond his or her limits, the same is true of tools and blades. A customer should not push a blade too hard just to get a job done fast.

Don't spin in the wrong direction.

Often renters will spin a blade in the wrong direction. Arrows labeled on the blade show the right direction to put the blade on a saw. Blades need to be installed and spin the way the directional arrow is pointing.

A blade will still cut if it's spinning the wrong way, but the diamonds will be eaten up quickly, Fisher says.

Do remember the drive-behind pinhole.

When mounting blades to walk-behind saws, Fisher says not to forget the drive-behind pinhole. In addition to the center arbor, he says that the second hole on the flange steadies the blade and prevents wobbling.

Do use caution when changing directions.

Skaff offers another word of caution for walk-behind saws: "If your blade is an inch deep into a cut and you want to turn, don't rotate the saw while the blade is still in the cut," he says. "I've seen segments of blade bend and break because a machine changes directions while the blade is still in the cut."

He adds, "If you're going to change directions, make sure your machine is off and the blade is up out of the cut and the machine is unplugged."

Final words of advice

Manufacturers offer manuals that cover diamond blade basics (how to use water, how to mount blades, how fast to spin blades, how to determine the proper size saw for the proper blade). Make sure customers have access to all the information they need to operate efficiently - and of course, safely.

If a customer destroys a blade, he usually is responsible for paying for it, and he's not going to be happy.

"You want to keep your customers coming back," Smith says. "If you can identify the material they're cutting, the operator's expertise, and educate renters about the basics, then everyone is happy."

Skaff adds the renter gets more bang for his buck, the rental yard increases its return on investment, and the blade supplier or manufacturer gets good brand recognition.

When blades are not misused or abused, he says, everyone wins.