Abrasive-Nylon Wheel Brushes Deburr Hard Metal Parts

May 15, 2020


2-Brush-Research-Finishing-burrsA wheel brush often is the ideal solution for applications calling for surface finishing, cleaning, polishing, deburring, edge blending or removal of paint, rust or other contamination. A type of power brush, motor-driven wheel brushes, circular in shape with uniform distribution of the fill materials extending radially from the center core to the periphery, may feature an arbor hole or keyway that supports their use with grinding equipment or CNC machinery.

When employing metal-wire filaments, wheel brushes prove ideal for light deburring, edge blending and general surface finishing. The brushing action occurs at the edge or face of the tool.

However, when used on harder materials, wire filaments can break off, or deform―even if crimped. Although knotted-wire options are available for more aggressive deburring, for today’s hardened steels and alloys, even this type of wheel brush is not sufficient.

Instead, for the most aggressive deburring or surface finishing, a wheel brush using abrasive-nylon filaments made of silicon carbide offer a solution. Taking it one step further, diamond grit can be used for the hardest metals and alloys in use today.

For JR Precision & Welding, a Houston, TX, machine shop specializing in welding, 3D printing and three- and five-axis CNC manufacturing, removing large burrs from holes in a hard 4140 steel-alloy part proved challenging.

The part in question, a muzzle brake, or compensator, connects to the barrel of a rifle or pistol to help control recoil and the rising of the barrel that normally occurs after firing. Muzzle brakes utilize slots, vents, holes, baffles and similar devices to redirect a portion of propellant gases to counter recoil and unwanted muzzle rise. Where and how these holes are placed in the muzzle brake has a tremendous effect on the influence of the brake in terms of recoil and muzzle movement. 

When machining these holes at JR Precision & Welding, large burrs formed at the oval-shaped gas ports. The Type 410 muzzle-brake cylinder, hardened and tempered to a tensile strength of 850-1000 Mpa, was machined in an elliptical path, which increased the size of the burrs created.

“The burrs that were created were razor sharp and thicker than we wanted them to be on each of the four main ports in the part,” says James Mawazeb, director of operations and lead engineer at JR Precision & Welding.

This led him to reach out to a local tooling representative from Bass Tool & Supply, a supplier of CNC machine tools, for wheel-brush options to remove the burrs in one automated operation. The rep, in turn, suggested he contact Los Angeles-based Brush Research Mfg., known for its Flex-Hone tool, characterized by abrasive globules permanently mounted to flexible filaments that attach to a center shaft. With its low-pressure, low-temperature abrading process, the tool can remove work hardened layers and deburr parts without disturbing the underlying metallurgical structure.

The engineers at Brush Research suggested that Mawazeb send in several sample parts for testing in its Los Angeles, CA, surface-finishing laboratory.

“After testing out disc brush with different depths and speeds, we decided to try an abrasive nylon wheel brush,” says Elysha Cole, product support specialist at Brush Research. “It was able to easily get into the slots, push the burrs out and remove them.”

1-Brush-Research-Finishing-productThe abrasive-filled nylon filaments are set into molded cores, allowing higher filament densities and putting more cutting tips at the point of attack, according to company officials, who note that the durable, self-sharpening filaments provide excellent wear life.

Tested extensively in the lab: a 6-in.-dia. tool with silicon-carbide filaments that can be automated via attachment to CNC equipment or employed offline in a secondary operation. JR Precision & Welding opted for 80 grit to provide the desired surface finish. The tool fit well in the magazine of the shop’s five-axis machine and existing toolholders, according to Mawazeb, who noted the tool’s exceptional performance. In addition to removing the large burrs, he offers, the brush also provided a soft edge break to the muzzle cylinder’s four ports, removing the razor sharpness without affecting the surface finish.

“The abrasive nylon brush removes just the right amount of material,” says Mawazeb, “and the surface finish  matched what the customer wanted.”

With the concept proven, JR Precision & Welding ultimately decided to purchase a smaller 3-in.-dia. version of the wheel brush. This brush’s shorter trim fill has less give, thus delivering a more aggressive action. 

The machine shop has installed the abrasive nylon brushes, with equipment programmed for upcoming orders of muzzle brakes. 

Industry-Related Terms: Grinding, Abrasive, Alloys, Center, CNC, Core, Edge, Grit, Periphery, Polishing, Surface
View Glossary of Metalforming Terms

 

See also: Brush Research Mfg Co

Technologies: Finishing

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