Custom Cup Brushes

A cup brush runs face-on. The tool, usually an angle grinder or a machine spindle, holds it at a shallow angle to the work, and the ring of filament tips sweeps a wide circle at each pass. A wheel brush runs edge-on, like a grinding wheel, and touches the work along a narrow band at its rim. So a cup covers area, and a wheel follows edges, grooves and profiles.

An end brush is the small cousin: a tight tuft at the end of a shank, for holes, pockets and corners where the cup body would block access.

In our range, the 65 mm SS304 crimped cup and the 75 mm knotted high-carbon steel cup are made for angle grinders. The 100 mm P120 silicon carbide and 120 mm P320 aluminum oxide abrasive nylon cups, the latter on a 6061 aluminum hub, handle deburring and finishing. These and the drill brush attachments start at 500 pieces per design. Built-to-order cast iron cleaning cups and high-temperature PPS mold brushes start at 100.

• Carbon steel wire: the most aggressive and the lowest cost, for ferrous parts where traces of carbon steel left on the surface do not matter.
• Stainless steel wire (304, 316): for stainless steel and aluminum, so no carbon steel is embedded to rust later; also for weld discoloration on stainless.
• Brass wire: softer, for lighter cleaning and softer metals, and where sparks must be limited.
• Abrasive nylon: silicon carbide for hard materials and a fast cut, aluminum oxide for steel and a finer, even finish. Grits run from coarse, around P80, to fine, around P320.
• High-temperature filament: PPS for cleaning hot molds and die-casting tools without melting.

Never move a brush from carbon steel to stainless work. The carbon steel picked up in the wire is enough to start rust on the stainless.

Grinder cup brushes are usually 65–150 mm across, with a fill length of about 25–40 mm. Larger cups and drill brushes are built to the tool. The fitting must match the spindle: a threaded center for the grinder thread, such as M14 or 5/8-11, an arbor hole, or a shank for a drill. Check the guard clearance; a cup that is too big for the guard should not be used with the guard removed.

No faster than the maximum speed it was made for. Wire cups are rated by their maximum operating speed, and the tool’s no-load speed must not exceed it. Running faster flings wires and can break the brush. Too much pressure is the other common fault: it bends the wire over, heats it, and leaves the brush cutting with the sides of the wire instead of the tips. Let the tips do the work with light pressure, and let a slower, larger cup cover area rather than pushing hard on a small one.

Wear eye and face protection, gloves and close-fitting clothing; loose wires leave a brush at speed. Keep the guard on. Run a new brush for a moment in a safe direction before touching the work, to throw off any loose wire. Keep bystanders out of the plane of the brush. These are the site’s rules first; the brush is built to support them.

• The surface material and area, and what has to come off: rust, scale, paint, weld discoloration, burrs.
• The finish you need after brushing.
• The tool, its spindle thread or arbor and its no-load speed, and guard clearance.
• Cup diameter and form: crimped, knotted, abrasive or polymer.
• Your brand and packaging, and the quantity per design.