How to Select Abrasives and Grits for Flex-Hone® Tools

Flexible cylinder honing is a low-pressure, low-temperature abrading process that removes burrs and improves surface finish at the same time. Unlike rigid hones, which have only two or three stones, flexible cylinder hones have hundreds of cutting points for a full 360° of cutting action. As the abrasive globules on a flexible honing tool wear, fresh cutting particles are continuously exposed.

Brush Research Manufacturing (BRM) supplies Flex-Hone® tools in 10 different abrasive types and 11 different grit sizes. Eight of the abrasives are standard, and two are available by special order. The base material of the workpiece determines which abrasive to choose. The amount of work to perform and the degree of surface improvement that’s required determines which grit size to select.

Depending upon the application, Flex-Hone® tools in several different grits may be required.  If a surface requires significant improvement, start with a lower-grit Flex-Hone® and then use one or more higher-grit tools until the final finish is achieved. The use of a fine-grit deburring tool on a coarse starting finish is less effective than a coarse-grit tool followed by a fine-grit tool. 

Standard Abrasive Types

Standard Flex-Hone® tools are available in the following abrasive types: silicon carbide, aluminum oxide, zirconia alumina (No. 1525 and No. 1549), boron carbide, tungsten carbide, levigated alumina, and diamond. BRM ball hones with cubic boron nitride or ceramic abrasive are available by special order only. The Flex-Hone® Resource Guide lists the available grit sizes for each standard abrasive type.

Silicon carbide (SC) is used with cast iron, mild steel, or stainless steel. For deburring and surface finishing aluminum, brass, bronze, or softer metals, choose aluminum oxide (AO) abrasive. 240-AO Flex-Hone® tools are recommended for Nikasil cylinders. An extremely hard material that’s used to line the surfaces of engine components, Nikasil reduces friction and wear, especially in aluminum engines.

Zirconia alumina (ZA) abrasive provides longer tool life than silicon carbide, but is suitable for many of the same materials. Z-grain No. 1525 consist of 25% zirconia and 75% alumina. Z-grain No. 1549 consist of 40% zirconia and 60% alumina. Both types of ZA Flex-Hone® tools are designed for use with cast iron, low carbon steels, medium carbon steels, and stainless steel. 

Boron carbide (BC) abrasive is used with medium carbon steels, high carbon steels, heat-treated steels to 50 Rc, and titanium. Tungsten carbide (WC) is for high carbon steel alloys and more exotic space age alloys. Choose either 100% WC Flex-Hone® tools, or BRM flexible cylinder hones with a 50/50 blend. Levigated alumina is available in extra fine grit only, and ideal for a final polish on many materials.

Diamond Flex-Hone® Tools and Specialty Abrasives 

Diamond Flex-Hone® tools are recommended for deburring, surface finishing, and edge-blending carbide, ceramic, hardened tool steels, heat-treated steels, and other hard materials. Made with nickel-coated abrasive, these diamond honing tools offer excellent heat dissipation and bond retention. As the Diamond Flex-Hone® brochure explains, applications include aerospace components and medical parts.

Brush Research Manufacturing (BRM) also supplies Flex-Hone® tools with cubic born nitride (CBN) CBN and ceramic abrasive. Available by special order only, these flexible honing tools combine the proven benefits of Flex-Hone® technology with specialty abrasives for demanding applications. To learn more about BRM’s full-line of surface finishing solutions, contact us today.