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There are several types of miniature brushes available today that 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.
GENERAL PARAMETERS
"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," states Mike Miller of Brush Research Manufacturing.
Miller explains that there are 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. One new 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.
Another brush, the Flex-Hone®, is available in miniature sizes as small as 4 mm (0.156 in). Sometimes referred to as the "dingleberry hone," this ball-style hone features globules or balls of abrasive grit permanently laminated to the end of nylon filaments.
"For any application with a bore size of 4 mm or greater, this is almost always the preferred tool," says Miller. "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 percent 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.
ON THE OTHER HAND
Sizes that are 1/16 in and smaller clean up best by hand, using 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, though there are holders and pin vises available to grip small diameter brushes.
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 popular miniature all-stainless steel brush features stainless steel filaments and a stainless steel stem. It is available in diameters down to 0.024 in and is ideal for clearing chips out of holes or clearing protruding and break-through burrs."
