Masonry Magazine June 2002 Page. 18
Cover
STORY
If time is money, and it is, then you want to cut and place masonry units as fast as possible. That means cutting dry and that means dust. Everywhere.
Electric motors are more common and here again, there are choices to make. Lundberg explains, "If you are going to be cutting brick all the time, you don't need a five horsepower motor, a 1.5 or 2 horse is sufficient. If you are only working in residential areas, pick a 1.5 horsepower, 110 Volt motor; it's adequate. But if you know that 220 is going to be available sometimes, get a dual-voltage unit where you can switch from 110 to 220 by throwing a switch. Usually, 220 runs more efficiently but watch your extension cord the wrong size for the length of the run will cut the available current."
The current draw of the saw varies from start-up to continuous run. When you use a portable generator, for example, to run the electric saw, be aware that you might have to use an over-rated generator. MK Diamond Products, Torrance, Calif., makes multiple lines of masonry saws. Their literature states: "These motors require approximately two to three times the normal running requirement for startup. For example, a saw motor with a stated power requirement of 1426 watts and a startup factor of 3x the normal running load will require a generator rated at approximately 4278 watts."
In addition, if a water pump is being used with the saw, this will increase your startup load approximately 138 watts for a total of 4416 watts. Another factor that must be kept in mind is that the normal running requirements are a baseline rating and are easily exceeded if a motor is placed under a greater load (ie. pushing a thicker material through the saw at a faster rate).
Wet or dry?
IF TIME IS MONEY, and it is, then you want to cut and place masonry units as fast as possible. That means cutting dry and that means dust. Everywhere.
Brian Delahaut of MK Diamond Products says, "One concern masons have is that they have to let that water dry off a brick or block; they can't go right from the cut to putting it in place. With dry cutting, because you don't need water, you can just cut and place, cut and place."
And, he adds, "A lot of the materials supplied today have a tremendous amount of acid or coloring or other types of materials in them. The more you cut these products wet, the more the concentration of the chemicals will be in the water in the pan. What ends up happening is you can get a staining action on those units as the day goes on, making those bricks or blocks look different than the ones you started with in the morning. Many engineers are calling out in the specs that they don't want any of the materials cut wet, only cut dry. But with silicosis being a big issue, you must remember that wet cutting will decrease the dust from the bricks or masonry block."
Wet is messy but healthier, it seems. As Lundberg says, "Slurry is not as big a problem. Wet sawing minimizes airborne particles. Slurry goes down into the water pan and it can be collected and disposed of safely. The problem with cutting brick and block dry is the inhalation of the dust. When you cut dry, you've got to be able to filter out all that dust to keep it from workers lungs. The contractor is supposed to be sure everyone on the jobsite has dust protection. But when you cut wet there is no dust."
Brock, the mason super at J. E. Dunn, agrees that wet is better. "I'd rather cut wet, to keep the dust down. Architects are getting away from that, not letting me book wet units. That makes it a lot more difficult-we end up having to cut a lot of units dry because of the specs."
Another reason for cutting wet is to extend the life of the blade. Keith Branoff, Detroit area sales representative for Diamond Products of Elyria, Ohio, explains it this way. "The value of a wet application is that you'll extend your diamond blade life, anywhere from 20 percent to 30 percent by adding water as a lubricant and also as an agent to flush out the dust. All saws in a masonry application today come with a water hookup. The downside to the water is that it's messy. In northern areas, in the middle of winter, it's next to impossible to get a mason contractor to use water. For indoor work, you would have to go with water to keep the dust down so everybody would be able to see what they're doing inside of an enclosed area."
MK Diamond makes this additional distinction: "Dry cutting blades require sufficient airflow about the blade to prevent overheating of the steel core. This is best accomplished by shallow, intermittent cuts of the material along with periods of "free-spinning" for several seconds to maximize the cooling process. For wet cutting applications, liberal amounts of water act as a coolant to support the cutting effectiveness and longevity of the wet blade."
Picking the blade
BESIDES THE LUBRICATING effect of water on the blade, picking the right blade for the job, whether wet or dry, is important. Lundberg notes, "You've got to decide if you're going to cut wet or dry. Today, you can cut wet with a dry blade. It used to be all the blades were wet cutting but now we can laser weld segments on to the core that allows you to cut dry."
Diamond cutting disks-blades in other words come in many sizes and special materials much like the bricks and blocks they are designed to cut. "You have to select the blade based on the material you are cutting," comments Branoff.