Small parts requiring deburring, edge blending or other surface finishing can present several production challenges to manufacturers. When handheld tools are used to perform intricate secondary finishing off the production line, this can slow productivity and produce inconsistent results. Even when the process is fully automated, specifying the appropriate finishing brush for the application plays an integral role in improving the tool’s overall performance and lifespan. For these reasons, the appropriate selection of deburring tool often requires engineering assistance from the tool manufacturer.
Fortunately, there are several types of miniature deburring brushes available today that can solve the productivity and quality challenges involved when manufacturing parts of various small sizes, contours and materials.
These miniature brushes vary not just in size, but also in filament type. Carbon steel, stainless steel, brass, nylon and abrasive filled nylon are commonly used. Abrasive filled nylon can contain silicon carbide, aluminum oxide or diamond abrasive. Appropriately selected, these tools address tight tolerances, edge blending, deburring and other finishing requirements that have a direct impact on overall product functionality.
Naturally, the specific application affects the choice of miniature brush. Variables include contours required, the type of material, and the amount of material to be removed. Other factors that apply to brushes used in automated applications include RPM of the machine tool, feed rates, and optimum wear-life of the brushes.
“Overall, the specification of a brush involves the task at hand, (e.g., deburring or surface finishing) the speed at which it must be accomplished, the size of the feature being worked, and the material the brush is working on,” explains Mike Miller of Brush Research Manufacturing (Los Angeles, CA, USA), a company that designs and produces miniature finishing brushes in an assortment of designs, sizes and materials.
Miller says his firm manufactures miniature brushes for bores ranging in size from as small as 0.024 in. and varying in lengths and tip styles. Filaments options include nylon, carbon steel, stainless steel, brass and abrasive filled nylon. Brush Research Manufacturing’s newest brush is filled with diamond abrasive nylon and will cut harder materials, deburr faster and last longer, providing a unique level of flexibility and longer tool life.
The popular Brush Research Manufacturing Flex-Hone® is also available in miniature sizes as small as 4 mm. (0.156 in.). Sometimes referred to as the “dingleberry hone,” the Flex-Hone is a ball-style hone that features globules or balls of abrasive grit permanently laminated to the end of nylon filaments.
“For any application with a bore size of 4 millimeters or greater, this is almost always the preferred tool,” Miller says. “One reason is that it is more abrasive at the point of attack, whereas an abrasive nylon brush will have abrasive grit particles interspersed throughout the filament. The ball-style hone is about 95% pure grain abrasive right at the point of need, so it really does an effective job.”
Miller adds that the ball-style hone is not recommended for working on threads, whereas abrasive nylon is very effective for removing burrs and polishing thread peaks and flank angles, particularly in tapped aluminum holes.
“This type of operation can be automated,” Miller says, “although sizes 1/16 in. and smaller may best be cleaned up by hand with an abrasive nylon or stainless steel brush. Small diameter brushes are not usually rotated under power because the brush stem wires are very fine and may bend. However, there is a series of holders and pin vises that is commercially available to grip the small diameter brushes.”
Abrasive nylon brushes have gained in popularity. To begin with, nylon is not reactive, Miller explains, so the brush will not impart carbon impurities onto the surface of the product. Nylon doesn’t oxidize, and therefore doesn’t rust or cause rust. Safety is another issue because metal filaments can develop wire fatigue over a period of time. If you are using a wire brush incorrectly, that could happen in a short period of time.
Grit selection is another important variable that may require supplier technical support. For example, products that have very fine finish requirements may benefit from brushes with finer grit material. Hard materials such as ceramics and glass may require diamond grit.
“That is not to discount the effectiveness of metal brush filaments,” Miller adds. “One of the popular miniature models is our all stainless steel brush, which features stainless steel filaments and a stainless steel stem. This model is available in diameters down to 0.024 in. and is very popular for clearing chips out of holes or clearing protruding and break-through burrs.”
“It depends on the surface finish spec or whether they have an issue where they need a little more aggressive brush for more deburring power,” Miller advises. “Sometimes you have a combination of needs such as cross-hole deburring and achieving a fine surface finish. It is not always best to try to accomplish both with the same brush. You may want to use a coarser Flex-Hone or brush first to remove the burr and a second, finer brush to achieve the required finish or contour.”
According to Miller, customers may have several concerns about specifying brushes. Whether to automate the brush operation is a primary concern, although it quickly becomes obvious to most users that automating a process and avoiding secondary operations are significant benefits in terms of both productivity and consistency.
“With a very broad selection of miniature brushes available, there are customers who have a lot of questions about the operating parameters, particularly the first time,” he says. “So we encourage them to get assistance from our engineering department. Also, we have a surface-finishing laboratory, and we encourage customers to send the parts in question to us—the parts they would like to deburr or finish with our products. We analyze the parts and then select the tools we think will provide the best solution, and then we run tests. We then return the part to them with our best recommendations regarding the selection of the tool, the operating parameters, and surface finishing measurements, if required. This has been an important resource for a lot of our customers.”
