There are so many different accessories for stripping coatings, and grinding or polishing concrete slabs, that it can be very confusing as you decide which tooling is right for the job with the machine you own.
To complicate matters, it goes beyond matching the accessory to the machine. It also includes the properties of the coatings, the properties of the concrete slab, and jobsite conditions. Variables change from jobsite to jobsite or even from one part to another on the same job.
The diamond tooling market is constantly changing, with new and improved products, different types of bonds, new means of attaching the accessories to the machine, and many unique products that may or may not be better. To understand the accessories, you must understand the fundamental basics of the tools.
The accessories can be defined by two key areas: how they attach to the machine and the type of cutting action or bond. These two areas overlap because they have nothing to do with each other except that some propriety attachments usually claim to be engineered to ideally match the machine.
But the propriety attachments also might limit the choices for an accessory with a specific cutting action or bond. This is because there might only be a single manufacturer making these types of accessories. This limits the competitive innovation that comes from numerous suppliers trying to build a better mousetrap.
The heart of the accessory is not how it attaches to the machine, but how it performs. The bond or the type of accessory is the key area defining the performance of the accessory, which is completely independent of how it attaches to the machine.
The grinding, honing, or polishing action is accomplished through a mutually abrading action where both the accessory and the slab surface are wearing. To keep the accessory from abrading too quickly, the abrasive media is usually a diamond. The abrading activity occurs at the diamond crystal so it leaves troughs or scratches in the slab surface as the diamond scrapes across it. The accessory contains many of the diamond crystals based on the size of the accessory and the diamond concentration.
The diamond itself is classified and graded by many parameters, including size, shape, and toughness. Think of these diamond crystals as a miniature plow removing the material from the slab surface by scraping the hard crust off so the soft loose material can be cleared away.
Each single diamond crystal is held in place by a bond. As the diamonds fracture or wear out, it is important for the bond to wear enough to release the old diamond crystal and expose a new sharp crystal. Ideally, the quality of the diamond will match the bond so the diamond will have microfractures to keep sharp edges throughout the effective life of the crystal as the bond wears away to expose new crystals.
If the bond wears away too quickly, the diamond crystals simply fall out prematurely. If the bond is too strong and the diamonds break off or wear enough to have very dull surfaces before the bond releases the old diamond, then the performance of the accessory will suffer.
The bonds are classified by many types, including a metal bond, resin bond, and semi-metal (hybrid) bond. Newer technologies, such as coated-fiber (diamond maintenance pads), electroplated (EP), or vacuum-brazed (VB) accessories, and polycrystalline diamonds also are appearing.
The main difference between the bonds is how strong they hold the diamond and how much the diamond protrudes from the surface of the bond media. The physical size of the exposed diamond is equivalent to the size of the plow.
Metal bond. The metal bond is exactly as it sounds. Each diamond crystal is cradled in metal so the bond is very strong and the individual crystal can protrude far above the surface of the tool. The protruding diamond crystal (the miniature plow) must be large enough to penetrate the coatings or slab surface to abrade the skin of the slab. If it protrudes too far, it will leave deep scratches in the slab surface.
Softer bond. The softer bond is typically a resin or polymer material. The resin is not nearly as strong as the metal bond, therefore the resin must encompass more of the crystal to retain it from prematurely pulling out of the bond. Therefore, the equivalent size diamond in both a metal bond and resin bond will be drastically different, enough so that it is common practice to step back one grit size in the transition from a metal to resin bonded accessory.
Hybrid bonds. The semi-metal or hybrid bonded accessories are basically a resin material where the diamond itself is coated with a metal so it becomes physically larger. This creates a stronger retention in a resin bond and can protrude more than an uncoated crystal in a standard resin bond.
Maintenance pad. Another common type of bond is a diamond maintenance pad, which is a fiber pad with the fibers of the pad coated in a diamond epoxy-type media.
EP, VB accessories. EP or VB accessories are a means of attaching a diamond crystal directly to a metal plate by either an electroplating process or through brazing in a vacuum. The advantage is that the protrusion of the diamond is really at a maximum. So for an equivalent grit diamond, these type of tools will be the most aggressive. There is no bond interference. Although the EP and VB accessories are very aggressive, they are typically very short on life. Also, the EP and VB accessories do not directly sequence with the metal bonded accessories. An equivalent grit EP or VB will leave a much deeper scratch than a metal bond accessory
Mike Orzechowski is chairman of the Concrete Sawing and Drilling Association’s Standards and Specifications Committee. He also is vice chairman of the Association of Equipment Manufacturers’ Saw Manufacturers Institute. Email firstname.lastname@example.org.