With the introduction of high-speed diamond grinders in recent years, many contractors have tossed other types of equipment aside, hoping that the new, flashy machines will be a catch-all for concrete polishing and grinding applications. As these new machines burst onto the scene, many hopped on the bandwagon, figuring that if they don’t use the biggest and fastest machines available, then they are falling behind the competition.
However, contractors should be familiar with all items in their inventory, and they must focus on providing the correct solutions for application challenges, rather than being distracted by the latest hype. The answer to the question at hand may not always be the newest machine, but instead old faithful.
High and Low
Over the years, there have been countless instances where one technology was replaced by another…The cassette tape gave way to the compact disc…The pager became virtually obsolete after the invention of the cell phone. But while some may be ready to replace their low-speed surface grinders with high-speed diamond grinders, they must first understand the benefits of both machines.
Let’s start by considering high-speed grinders. They became a huge buzzword within the industry as the growth of concrete polishing jobs exploded. Although the machines came with a steep price tag, many people were impressed by the newfound ability to quickly tackle concrete grinding and polishing jobs. Suddenly, everyone could work like the pros…or could they?
With the development of a quicker machine, some may wonder why anyone would still use a low-speed grinder for concrete grinding and polishing. Can’t a high-speed unit do the same job more quickly? The answer is yes, but quicker isn’t always better. With speed comes the increased risk of inflicting costly damage to the surface, especially when the end user isn’t a well-trained professional. Low-speed grinders, however, work more slowly so the operator does not accidentally remove too much material or lose control.
Although low-speed grinders have been available for almost 50 years, the continuous development of new attachments makes them an extremely versatile machine—even more so than high-speed diamond grinders. Not only are the machines capable of grinding concrete, but new polishing attachments, such as General Equipment’s Pro Polish system, also allow them to complete polishing applications. Additionally, since high rotational speeds make it much more difficult for a machine to penetrate surface coatings, low-speed grinders are the only practical option for removing them. And while concrete polishing is the fad for now, the demand for surface coating removal will always remain high.
Different Strokes for Different Folks
Of course, both types of grinders have their place in the industry. As mentioned, high-speed machines are typically suited for well-trained professionals, while low-speed grinders work well for small contractors and do-it-yourselfers, as well as anyone needing to remove surface coatings.
But since many contractors have reduced their emphasis on the use of low-speed surface grinders, here are a few things that should and shouldn’t be done in regards to these machines. By understanding these tips, you are well on your way toward achieving better results.
Do: Understand the job at hand
Low-speed surface grinders may be versatile, but they are not a solution to all removal applications. For example, as a grinder they are designed to remove a minimal amount of concrete from the surface—as little as a few thousandths of an inch. Therefore, if an end user wishes to remove a half-inch of concrete on a 10,000-square-foot floor, a low-speed surface grinder is not the ideal machine.
Don’t: Use incorrect power sources
As obvious as it may seem, make sure that the unit being used has the correct type of power source for the location. Engine-powered grinders are typically the best option for outdoor applications, since electric-powered units won’t work at an outdoor location that has no electrical outlets. Electric-powered machines also won’t suffice at indoor locations that don’t have the correct electrical power available. In these cases, a propane-powered machine might be the ideal choice.
Since electric-powered units often have high amperage and voltage requirements, it is important to understand whether the machine needs a 115- or 230-volt power source and if it requires a 15- or 20-ampere circuit (This data is stated on the electric motor data plate). Then, if an extension cord is used, it should be rated to allow sufficient electrical flow according to the motor specifications. It should also be no longer than necessary, as cord length affects electrical resistance and voltage loss. If one is unaware of this knowledge, it is common for many to melt an inadequate extension cord that they bought from a big-box retailer.
Do: Understand the operation of the machine
Contractors will have a much more pleasant experience operating their low-speed surface grinders if they are aware of proper operating techniques. For example, extra weight, such as cinder blocks or sandbags, can be added to the machine in order to increase the material removal rate. This applies to almost every attachment configuration with the exception of wire brushes. Since most low-speed grinders are designed for the addition of weights, check the owner’s manual for the manufacturer’s suggestions.
Also, many people try to increase the material removal rate by pushing and pulling the machine back and forth. Instead, a more effective technique is to slowly pivot the machine about its wheels.
Don’t: Use the wrong attachment for the job
Manufacturer customer service representatives receive calls every day from operators who are not satisfied with their surface grinder’s results, and the problem is often caused by the use of an incorrect attachment. For example, one of the most common mistakes is trying to use silicon-carbide stones to remove or grind floor coatings. The stones will work for only a short while before their pores clog with material and stop being effective. In this case, scraper attachments may work best. On the other hand, scrapers will not work when trying to remove concrete.
Over the years, many types of attachments have been developed to meet the needs of various applications, and most manufacturers post information on their websites regarding the proper use of attachments. Unfortunately, many end users fail to educate themselves and, consequently, fail to achieve the desired results.
Do: Dispose materials properly
With today’s strict environmental regulations, contractors must consider the disposal of materials from the grinding process, and it is important to have a plan in place before the job is started. If the surface being removed is contaminated by oil, chemicals, radiation or other hazardous materials, one must dispose of them according to government regulations.
Don’t: Forget to maintain the machine
Low-speed surface grinders are fairly simple machines. Besides regular engine maintenance on gas-powered units, there aren’t many components to service. But because the concrete dust grinders produce is extremely abrasive, there are several important lubrication needs.
One of the most common maintenance items that is overlooked is to lubricate the transmission bearings. The problem exists because maintenance personnel typically do not invest the time to remove excess concrete dust accumulations around the bearings after use. Eventually, the grease fittings become hidden from sight, and dust continues to contaminate the bearings. This results in total bearing failure, which may consequently damage expensive transmission components. To combat this problem, some manufacturers have incorporated a remote lubrication system designed to simplify maintenance, but even this cannot prevent all abuse. Therefore, make sure the bearings are greased according to the maintenance schedule.
Next, keep an eye on the attachments. These are key to operational success, so make sure they wear evenly and replace them as the contact surface approaches the attachment discs. Although the service life of attachments varies based on the application and use, have an idea of how long each specific one might last. For instance, one could estimate that a set silicon carbide grinding stones may last approximately 5,000 square feet, while a diamond system could cover up to 50,000 square feet before replacement is needed.
Tried and True
Although new machines have taken much of the recent attention, low-speed surface grinders will continue to stand the test of time. Thanks to their versatility, they can be a seen as a profitable and productive inventory item, rather than an endangered species. And by understanding the simple tips listed above, more contractors can realize the full potential of these machines.