Simple, Effective Crosshole Deburring of Complex Metal Parts

In automated machining, the removal of burrs and sharp edges in cross-drilled holes and other difficult-to-access areas, such as undercuts, grooves, slots, or internal holes, can be tedious and time consuming. One particular challenge is deburring the intersection of cross-drilled holes that are frequently found in engine and transmission components. Despite the challenges, the removal of burrs from this production process is an absolute must for high quality, precision parts. In many applications, cross-drilled holes act as conduits for fluids, lubricants and gases. Failing to remove burrs can cause blockage of these critical passages or create turbulence in the flow. Burrs can also lead to part misalignments, affect dimensional tolerances, and limit the overall efficiency of machined components.

“Getting rid of burrs is really important because if there is any loose material that gets dislodged when the component is in use, it can cause major problems,” says Anthony Scott, the lead machinist at Orange Vise Company LLC (Placentia, CA), a manufacturer of machine vises and quick change fixturing components. Although there are many techniques for deburring internal passages at crossholes, the majority require sending out parts or investing in equipment to complete the work in-house that can cost tens of thousands of dollars. These options, which include thermal, abrasive flow, electrochemical, and high pressure water, effectively remove excess material, but they also build time into the manufacturing process and add to costs.

The more ideal option for many machining operations is to integrate deburring into the automated process with a simple, effective crosshole deburring tool, such as a flexible hone (Flex-Hone) from Brush Research Manufacturing Co., Inc. (BRM; Los Angeles, CA). By doing so, operators can speed up the manufacturing process and ensure uniform quality for precision parts. According to Scott, flexible hones are ideal because they cost effectively smooth edges and produce a blended radius for crosshole deburring. “It is really about accessibility, because there aren’t really any other tools that can do what a flexible hone can,” he says.  “Whether it is internal grooves or multiple crossholes, there is really no way to reach those areas with any sort of other tool.”

For engineers in the automotive, aerospace, manufacturing and machining industries, the ball-style hone is a highly specialized abrasive tool that is instantly recognizable by its unique appearance. Characterized by the small, abrasive globules that are permanently mounted to flexible filaments, the product is a flexible, low cost tool utilized for sophisticated surfacing, deburring and edge blending. Available in sizes ranging from very small diameter hones (4 mm) to those up to 36 in diameter or more (a size appropriate for large engine cylinder bores), these deburring tools can be custom designed to the size, shape and abrasive grit to fit any application’s needs.

“I used the Flex-Hone quite a bit when I was working in aerospace,” explains Ken Spaulding of Zodiac Engineering, a contract manufacturer in California. “We did a lot of parts that involved tubes with multiple crossholes and slots. Getting inside there to reach the burrs, particularly if the walls were thick, is extremely difficult.” With a background in aerospace parts as well as mold making, Spaulding is currently focused on creating products of his own design, such as high-end pocket knives and cycling components for BMX, road and mountain bikes. He also continues to perform contract manufacturing work and particularly appreciates how the flexible hone’s abrasive globules each have independent suspension that is self-centering, self-aligning to the bore and self-compensating for wear, all of which facilitate close tolerance finishing work.

“The hone conforms to whatever you are working with, even if it’s irregular,” notes Spaulding. “For example, if the back side of the part is not flat or not on consistent level plane in Z, the tool is flexible enough to still remove any burrs.” For best results, the deburring tool is typically rotated into the main bore into which the crossholes break. After a few clockwise strokes, the tool is removed and the spindle reversed to rotate and stroke the flexible hone in a counterclockwise direction for a few more strokes. The forward and reverse rotation creates a symmetrical deburring pattern. Coolant should be used to keep metal cuttings and deburred metal in suspension.

According to Scott, although the Flex-Hone is often used with automated production equipment, it can also be used for secondary deburring options offline as needed. “This tool can be used in CNC machines and also with a cordless drill,” he says. “So if you manage to deburr 90 percent of the holes in a machine but have a few left you can’t access easily, you can use it with a handheld drill and maintain the uniformity in surface finish and process.” Additional customization from BRM in a variety of shapes is also possible to meet the requirements of non-traditional applications. This includes spherical-end configurations, stepped or multi-diameter configurations for double diameters and counterbores, tapered or cone shapes, segmented shapes, or combining Flex-Hone globules with other filament materials.

Brush Research Manufacturing Co., Inc., 4642 Floral Drive, Los Angeles, CA 90022, 323-261-2193, Fax: 323-268-6587, info@brushresearch.com, www.brushresearch.com.