An introduction to handheld concrete grindersPublished 14/11 at 14:47
A handheld concrete grinder has a wide range of applications, from renovation work to levelling and remediation and can also be used to supplement the work of a large, walk behind floor grinder.
A well designed concrete grinder will make a difficult job much easier. Although there are a lot of budget concrete grinders on the market, these are simply metalworking angle grinders with a diamond cup wheel mounted, not having important features and characteristics that make purpose built concrete grinders such as the AGP machines so effective. They have many uses for tasks in renovation of old construction, such as grinding off old screed, plaster, grout, or concrete. They are also great for grinding off crests and generally levelling uneven concrete surfaces.
Types of cup wheels and other factors
There are three main types of cup wheels available to be used for specific tasks. Cup wheels for grinding hard concrete will have diamond segments designed for this purpose with softer bond, allowing more aggressive diamond exposure. These diamond segments will stay sharp but will not last as long. Cup wheels for grinding abrasive materials such as soft concrete, screed, tile mortar, etc. have diamond segments made to resist the abrasiveness of the work material, thus lasting longer. PCD cup wheels are suited to aggressively scraping away adhesives and soft coatings such as bitumen and elastomeric roof coating without smearing.
Due to dry grinding, dust containment is very important meaning that the dust skirt must be as effective as possible. This also provides the additional function of keeping the cup wheel properly aligned to the surface. Therefore, it needs to have the ability conform to the surface shape by way of a spring suspension. In addition, to allow grinding up to the edge, the skirt needs to have a half-moon door which can be temporarily opened.
Since the grinding of vastly different surfaces is possible, it is important that the rotation speed may be adjusted to best suit the application. In addition, having constant speed electronics allows the set rotation speed to be kept consistent during operation, which will result in a much more even surface. Unlike most of the concrete grinders in the market, AGP grinders are all equipped with variable constant speed.
Selecting a concrete grinder
AGP has a full line of concrete grinders and so one can find the exact tool needed for the job. The three main criteria for choosing a concrete grinder are handle style, cup wheel size, and motor type. The two main handle designs are angle and vertical style being a matter of operator preference which type to use. The technique employed with either involves a light touch, with the operator guiding the tool quickly over the surface to grind a small depth at a time.
The vertical style, such as used on the G5, G7, and BG5 AGP models, puts the weight of the motor directly over the cup wheel, making them especially suited to grinding horizontal surfaces. These are also suitable to be used with the floor grinding trolley. The angle style, such as used on the AGP G125, G180, and BG125 is more general purpose. The most common sizes for cup wheels are 125mm and 180mm. 125mm usually have a wider variety of consumables available and tend to be more economical. 180mm, such as the G7 and G180, are more suited to grinding larger areas.
Universal motors use conventional carbon brush design used in most power tools. These motors offer good power to weight ratios, simplicity, reliability, and economy of operation. The motor’s carbon brushes are a wearing part and thus maintenance involves replacing them when worn. Brushless high frequency motors, such as used on the BG5 and BG125, have the advantage of having much higher efficiency and thus output, as well as not needing to replace brushes, thus making them virtually maintenance free. Although their initial cost is much higher, they tend to last many times longer than universal motors, have higher efficiency, and have a higher ingress protection rating.