MRO Today - Wireless brushes: Radial activity

Radial activity

'Wireless' brushes increase workpiece quality, and operator performance and safety

by Rick Pihl

They're always there, attached to the bench motor. Some get used a little, some a lot, but no one thinks much about them - wire brushes. You know you'll catch a flying wire now and then, but that's the price you pay to get the speed and performance needed to handle a tough cleaning or deburring job.

With the recent introduction of "wireless" bristle brushes, the above scenario is rapidly changing. New bristle technology has created individual "radial" discs that, when ganged together and held between face plates, form a safe and effective bristle brush.

These brushes consist of abrasive-filled bristles in a molded, one-piece construction, so there is virtually no danger of wires disengaging from the hub. These colorful discs (each of three grades is a different color) may not have the tough appearance of wire, but premium Cubitron abrasive grain, one of the most durable, longest-lasting abrasive grains available, fills each bristle.

Consistent finish with no surface damage
The abrasive-filled, three-dimensional radial bristle design offers unique cutting properties. These flexible bristles constantly apply sharp mineral to the workpiece. The concentration of abrasive gives the workpiece an incredibly consistent finish without gouging the base material.

In contrast, wire brushes can have a peening effect, leaving small indentations where the bristles hit the piece. This becomes more noticeable as wire brushes wear. Since they wear at an angle, the rotation needs to be reversed periodically to get back to a sharp bristle tip. When this reversal doesn't occur, the wire bristles tend to gouge instead of cut. Brush rotation reversal is not necessary with radial bristle brushes.

Another advantage to radial bristle brushes is less concern about cross-metal contamination. Certain metals collect and bond to the tips of wire bristles. These enlarged tips can lead to gouging or metal transfer when using the same brush on a different material.

The radial brush's flexibility also allows for easy cleaning in hard-to-reach spaces. Accomplish critical applications, such as cleaning threads where the surface dimensions must remain unchanged, quickly and without damage. Remove corrosion and paint easily. Clean and blend welds in a single step.

An easy touch is all it takes
Wire brush users normally lean into the brushes to maximize cutting performance. For heavy users, this leads not only to operator fatigue but adds unnecessary stress to the bench motor. Too much amperage draw rapidly burns up a motor.

Radial bristle brushes draw less amperage because they require only low-pressure contact to maximize performance. Increased pressure places drag on the motor and slows the RPMs. Operating at a higher number of revolutions (between 1,750 and 3,450 RPMs), combined with the continuous supply of fast-cutting abrasives delivered evenly across the work surface, optimizes performance of both the abrasive and bench motor.

Color coding
Radial brushes are ideal for maintenance and repair operations, utility applications, coating removal, weld cleaning, deburring and finishing. Discs come in three grades and are color-coded for easy identification:
36 Grit (brown): Use this grade for your toughest jobs. It provides the most aggressive cut and a coarse finish.
50 Grit (green): This grade is ideal for rust removal, deburring and removal of paint and other surface coatings.
80 Grit (yellow): Use this grade when you need less aggressive removal, but a finer finish.
Bristle brush users should always use goggles, face shields and appropriate protection for hands, arms and body.

Rick Pihl is senior product development engineer for 3M's abrasive systems division.

This article appeared in the October/November 2000 issue of MRO Today magazine. Copyright, 2000.