| June 12, 2007 |
Selecting the right concrete saw for the application at hand is important, but in most cases, matching the diamond blade to the material you’re cutting is an even more daunting task. Both decisions can impact worker safety as well as profits.
“As a general rule, you may say if a saw runs, it will cut,” says Bill Glynn, product manager for Sawtec. “However, if the wrong blade is used or the saw is used for the wrong application, these machines can not only become less productive, they can be dangerous.”
To prevent an accident, Glynn suggests relying on the knowledge base of blade and saw manufacturers when choosing tools or blades. Counter personnel at rental houses or dealerships that carry concrete saws and blades can help you make the right choices if you know the hardness and composition of the material you will be cutting, the cut depth and length and factors such as whether rebar is present in the slab.
Because of the multitude of diamond blades available and the confusion this creates, a contractors’ group and saw manufacturers’ association worked together last year to produce an application code for diamond blades. For more information on the project, read the sidebar at the end of this article.
After you have selected the right saw for your job and the correct blade for the material you will be cutting, you can maximize productivity and ensure safety through proper operating techniques.
Quick checks can keep you safe
If you’re using a cut-off saw, check that the guard is in position and fits properly before you operate the saw. Make sure the arbor and arbor flange are in good shape and are locking together correctly before you operate the saw. If the pieces don’t fit together properly, the saw blade is not installed right. “It takes two minutes, max,” to check those things, says Lodema Erbacher, technical support manager for RGC Products. “There’s no way on earth I’d want 4,100 rpms of 14-inch saw blade coming at me.”
Always wear safety goggles, gloves, steel-toed shoes, hearing and head protection and a dust mask if you are dry cutting. Don’t wear loose-fitting clothing and do not operate gasoline- or diesel-powered machines inside a building or other enclosed area. Someone else should be in the vicinity while you are sawing in case of accident or injury.
Don’t change the way your concrete saw is put together. “There’s a lot of people who want to make their own homemade alterations to them,” says Bruce Coleman, product manager for Multiquip. “If people start taking off pieces and modifying it to their own requirements, this can lend itself to safety hazards.”
Before each use of a walk-behind saw, make sure all blade guards are down and belt guards are in place, says Richard Tremain, product manager for Target. Also check the tightness of the bolt or nut that holds the blade on the collar.
If you are working in an area where slurry will not run off or be vacuumed up, take extra care when walking near the slippery, sludgy material that might end up on the floor or a walkway.
More brawn doesn’t equal faster cutting
You should always step cut – make a 1-inch guide cut – instead of cutting full depth on the first pass, says Thom Fisher, marketing director for Diamond Products. You must guide the saw as well; it will not follow the cut by itself.
When working with a handheld saw, let it do as much of the work as possible. “If you lean on the saw too much, you’re going to end up not being productive,” says Mark Michaels, product manager, Husqvarna. “Just because you’re pushing on the saw and you’re working harder doesn’t mean you’re going to cut more.”
Many operators think saws will cut faster if they push on them, but that only slows down the rpms of engine-driven tools when they should stay at maximum rpm for optimal cutting.
Never exceed the maximum operating speed of the blade, says Rita Moore, marketing product manager for Ingersoll-Rand. The blade speed rating must match the arbor shaft speed on the machine. Running a blade at higher than recommended speed is dangerous. At worst the blade could fly apart and at best it reduces cutting efficiency.
If you are wet sawing, you can achieve maximum performance by keeping the water pressure elevated. Optimum water pressures vary by manufacturer, but you can find this information in your owner’s manual. Proper water pressure is particularly important when you are using a chain saw. “If you’re cutting through 18 or 20 inches of concrete or brick, that’s a long way to plunge in before you get to the opposite side of the wall where some of the slurry can be flushed out,” Erbacher says. “So what happens is it all has to be flushed out back toward the operator. And without adequate water pressure and flow, it just doesn’t happen.” If you don’t flush away the sandy material in the slurry, it will wear the chain or blade inappropriately.
Chain saw operators sometimes tension the chain improperly or install the chain backwards, Erbacher says. Chain tension should be checked periodically throughout the day, depending on usage. If you use a saw nonstop for eight hours, tensioning should be checked every 20 to 30 minutes. You can find instructions on chain tensioning and installation in your operator’s manual.
Never use a chain saw where you do not have sure footing and cannot face the cut without overextending your reach. Plan chain saw cuts by outlining them with a marker for a visual guide. For long cuts, score a line first for a guide.
If you are using a hydraulic power source, make sure the hydraulic pressure and flow meet the saw’s requirements. Hydraulic saws can be run off excavation equipment that uses up to 3,000 psi and 25 gallons per minute flow, but you may need a flow diverter. The small box, which costs about $450, hooks into the hydraulics between the pressure and return lines of the saw and the pressure and return lines of the excavating machine. The flow diverter reduces hydraulic pressure so you don’t overpower the saw.
Scott MacKay, marketing manager for Partner, advises keeping extra belts and starter ropes with you at the jobsite in case one breaks.
Don’t put straight gasoline in an engine-driven saw. Always use the correct oil/gas mixture. If raw gas gets into the unit, you may need to replace the cylinder assembly, which will cost 35 percent of a new saw.
When operating large, walk-behind saws, make sure the front pointer is adjusted correctly. Pay attention to the tracking of both small and large walk-behind saws. Most of the time, the blade is mounted on the right-hand side of the machine, causing the saw to pull to the right. Large saws have a rear-wheel adjustment that offsets the right pull, but you still need to watch the tracking to make sure it is working properly, Tremain says.
Ryan Grey, sales manager for Crown Construction Equipment, advises cutting in passes when using small walk-behind saws that aren’t self-propelled. Concrete should be cut 2 inches at a time, and asphalt can be cut 3 inches or more in a single pass, depending on the aggregate mixture.
And finally, listen to the engine, if your saw has one. “A good operator should be able to tell when a blade is bouncing, the belts are slapping or the blade is lifting out of the cut,” Fisher says.
Cleanup and attention to air filters key to longevity
When you finish using a concrete saw, clean the machine with water so the slurry doesn’t reharden. This should be done daily or as needed, depending on use. “Maintenance to me is also cleaning,” MacKay says. “It’s not so much that it needs to look pretty, but you get a lot of that grime off there. It won’t cause you complications down the road.”
Erbacher suggests spraying a water displacement product on both cut-off and chain saws to keep water from adhering to small areas that might be prone to corrosion. Put the oil near the saw shaft or blade on a cut-off saw. If you have a chain saw, disconnect the water supply and shoot some pressurized air through the saw to rinse the water and slurry out. Then spray the oil through the opening where the water hose connects, followed by a quick burst of air to get it through the bar.
Inspect the nose sprocket on a chain saw every time you put on a new chain and any time you do a lot of plunge cutting. If the nose sprocket is worn, replace it immediately – otherwise the bar could be damaged. Check the drive sprocket for wear daily.
If you have an engine-driven saw, changing the air filters and oil according to the manufacturer’s recommendations is imperative. “They’re in a very dusty, abrasive environment,” Coleman says. “Because of the caustic nature of concrete cutting, it’s highly recommended that you even increase what is considered a normal service cycle for the engine.
You need to rember that the air filter’s job is to stop that dirt from entering and damaging the combustion chamber, says David Schwartz, product manager, industrial & assessories, for Stihl.
Take care, however, that you don’t change air filters too often. Manufacturers’ recommendations on this topic vary. MacKay of Partner suggests checking air filters weekly even though filters in the company’s machines generally last two to four weeks. He recommends inspecting air filters on Fridays. If a filter is almost at the end of its life, it should be changed if it won’t make it through the next week.
Lennart Gustafsson, president of Partner, advises customers to perform scheduled maintenance on concrete saws every two to four weeks, depending on use, in the shop instead of at the jobsite. “Don’t touch the saw in the field,” he says. “Bring it back to the supervisor on scheduled maintenance. Have it serviced by a technician who knows what he is doing.”
Starters in the past needed to be maintained once a month, but will run eight to 12 months today before requiring service, Gustafsson says.
Grease bearings according to the manufacturer’s recommendations, usually once a day, says Jerry Boehmke, customer service manager for Cimline. Also check for loose components and belt wear daily. If you are using a handheld cutoff machine with a semiautomatic belt tensioner, use it at the end of the day to quickly ensure the drive belt is correctly tensioned, Schwartz says.
Check belt tensioning on walk-behind saws every morning before use. “If the belts become loose, you’re not transmitting all the horsepower from the engine to the blade shaft,” Tremain says. “The belts will slip a little bit, and it just slows down productivity.”
Every time you change a blade on a walk-behind saw, make sure the blade collars that clamp the blade on are clean.
Concrete saws get a lot of vibration, so you should conduct daily checks of major screws and bolts, as well as bolts that hold on the arm and guard and screws in the top cover that protects the air filter. A loose cover could let dirt in around the filter. “Once something starts to get loose, the vibration these saws are subjected to is severe and it’ll only get worse,” Michaels says. “The preventive maintenance of checking these things out daily is going to save you time rather than being out there in the middle of the day breaking a belt or losing something. That’s a lot more costly than a short check in the morning.”
Application code makes blade selection easier
A national saw manufacturers’ group announced in November it had created a diamond blade application code to help contractors differentiate product capabilities and applications.
Diamond saw blades more than 12 inches in diameter made by the group’s members would bear a Masonry and Concrete Saw Manufacturers Institute certification mark and a blade application code. The code specifies three factors: whether the blade is intended for wet or dry use; the type of material the blade is intended to cut; and the types and power ratings of saws the blade is intended for.
Russ Hutchinson, director of product safety and technical services for the Association of Equipment Manufacturers, of which the saw manufacturers institute is a part, says several members are already using the codes, others are fine tuning the process to permanently etch the code into their blades and more have plans to use the code in the near future.
The Concrete Sawing and Drilling Association, a contractor group, came to the manufacturers and asked them to come up with an application code and a permanent way to mount it to the blades. “There was a need to help the person out in the field,” Hutchinson says. Contractors told the institute that when an operator has a variety of diamond blades stored in a truck, he doesn’t know what applications they are meant for just by looking at them.
Profit was a concern for the contractors as well since expensive blades can wear out quickly if they are used in the wrong application.
The general applications the code denotes are: cured concrete; green concrete; asphalt; asphalt over concrete; block, brick or masonry refractories; and tile, ceramic or stone. In telling consumers which types of saws blades may be used on, the code covers flat saws in four horsepower groupings; three horsepower ranges of wall saws; several handheld gasoline-, hydraulic-, electric- and air-powered saws; three horsepower ranges of stationary saws and three horsepower classes of masonry or tile saws.
To view code information online, go to www.aem.org/CBC/Groups/ProdSpecific/SMI/Pubs.asp#blade.