Cross hole deburring made easy with CNC equipment

Published
February 22,2021 - 06:00am
Cross hole deburring made easy with CNC equipment

The  Delta Machine Co. is a machine shop that specializes in complex, tight tolerance parts made of titanium, nickel alloys, stainless steel, aluminum, plastics and other exotic alloys.

Janos Garaczi, president of the Huntington Beach, California, company, is responsible for overall quality as well as much of the programming, set-ups and purchasing.

In the past decade, the machine shop has relied on a flexible, honing tool for a range of automated CNC machining applications such as cross hole deburring, cylindrical honing, surface finishing, edge-blending and cleaning.

By integrating flexible hones in the machining process, complex parts with cross-drilled holes and other difficult-to-access features can be deburred, honed, and surface finished, in-house, at less cost.

In automated machining, 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 frequently found in engine and transmission components.

In many applications, cross-drilled holes act as conduits for fluids, lubricants and gases and failure 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. 

“Eliminating burrs is critical because if any loose material gets dislodged during use, there can be serious consequences,” said Garaczi.

According to Garaczi, the tool he selected for such applications is the Flex-Hone from Los Angeles-based Brush Research Manufacturing (BRM).  Characterized by the small, abrasive globules that are permanently mounted to flexible filaments, the product is a flexible, low-cost tool utilized for sophisticated cross hole deburring, honing, surfacing, and edge-blending.  The hones are available in a variety of abrasive types, sizes, and grit selections.

“For de-burring holes and honing when we need to clean up a component, it is the easiest tool to use for us.  There is a large variety of grades and sizes and it is very versatile,” says Garaczi,

He added that the company is “making more complex parts, especially when it comes to housings with ports all over the part.  That is where the hone comes in really handy – for de-burring the holes where you drill into it.”

For best results, the deburring tool is typically rotated into the main bore into which the cross holes 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 Garaczi, removing burrs can be particularly problematic when dealing with machined superalloys, such as titanium, Monel, Inconel, Incoloy, Invar, Rene and Hasteloy.

 “Even during ‘grooving,’ if you cut the material from one side, it just pushes the burr to the edge,” said Garaczi. “And, if you approach it from the other side, it just pushes it back.  It doesn’t want to break off the material cleanly. As soon as the tool gets a bit dull it gets a lot worse. So, sharp tools with the right geometry are key.”

Garaczi notes that the Flex-Hone is available with a premium nickel coated diamond abrasive for use on materials like carbide, ceramic and aerospace steel alloys; as well as a CBN option that is even harder and is specifically designed for superalloys. These superalloys can exhibit high ductility and work hardening that produce a gummy machining behavior if the correct abrasive tool is not utilized. He added that Flex-Hone helps deburr superalloys such as titanium or heat treated 13-8 stainless alloy.

Garaczi points out that he is installing the flexible hones into CNC equipment to automate the process and reduce the time required to finish superalloys and stainless steels.

Another advantage of Flex-Hone is that it doesn’t create much dust, important considering the damage contaminants might cause to the CNC equipment. “These are very expensive, very accurate machines,” adds Garaczi. “I wouldn’t do anything to jeopardize the accuracy or lifespan of the equipment.”

He says that when making decisions about what tools to purchase it is often on a project-by-project basis.  However, if the tool can reduce cycle times versus its cost, it is an easy decision.

“There are definitely scenarios where it would be good to be able to perform surface finishing of this type of material on CNCs,” says Garaczi.  “It would really save a lot of time and extra processing cost ... I want to do everything on the CNC machines whenever I can.”

To achieve this, the machine shop incorporates Flex-Hones in a variety of sizes in its tool carousels. 

“For a part, we might use two to three different size hones, depending on the number of cross port intersections and different hole sizes,” says Garaczi.  “However, it is really easy to put a Flex-Hone in a toolholder, give it a simple toolpath cycle and let it run.”

For more information on Flex-Hone, phone 323-261-2193 or visit the web site at www.brushresearch.com.

Related Glossary Terms

  • abrasive

    abrasive

    Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.

  • alloys

    alloys

    Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

  • burr

    burr

    Stringy portions of material formed on workpiece edges during machining. Often sharp. Can be removed with hand files, abrasive wheels or belts, wire wheels, abrasive-fiber brushes, waterjet equipment or other methods.

  • computer numerical control ( CNC)

    computer numerical control ( CNC)

    Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.

  • coolant

    coolant

    Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

  • cubic boron nitride ( CBN)

    cubic boron nitride ( CBN)

    Crystal manufactured from boron nitride under high pressure and temperature. Used to cut hard-to-machine ferrous and nickel-base materials up to 70 HRC. Second hardest material after diamond. See superabrasive tools.

  • ductility

    ductility

    Ability of a material to be bent, formed or stretched without rupturing. Measured by elongation or reduction of area in a tensile test or by other means.

  • hardening

    hardening

    Process of increasing the surface hardness of a part. It is accomplished by heating a piece of steel to a temperature within or above its critical range and then cooling (or quenching) it rapidly. In any heat-treatment operation, the rate of heating is important. Heat flows from the exterior to the interior of steel at a definite rate. If the steel is heated too quickly, the outside becomes hotter than the inside and the desired uniform structure cannot be obtained. If a piece is irregular in shape, a slow heating rate is essential to prevent warping and cracking. The heavier the section, the longer the heating time must be to achieve uniform results. Even after the correct temperature has been reached, the piece should be held at the temperature for a sufficient period of time to permit its thickest section to attain a uniform temperature. See workhardening.

  • stainless steels

    stainless steels

    Stainless steels possess high strength, heat resistance, excellent workability and erosion resistance. Four general classes have been developed to cover a range of mechanical and physical properties for particular applications. The four classes are: the austenitic types of the chromium-nickel-manganese 200 series and the chromium-nickel 300 series; the martensitic types of the chromium, hardenable 400 series; the chromium, nonhardenable 400-series ferritic types; and the precipitation-hardening type of chromium-nickel alloys with additional elements that are hardenable by solution treating and aging.

  • superalloys

    superalloys

    Tough, difficult-to-machine alloys; includes Hastelloy, Inconel and Monel. Many are nickel-base metals.

  • tolerance

    tolerance

    Minimum and maximum amount a workpiece dimension is allowed to vary from a set standard and still be acceptable.

  • toolholder

    toolholder

    Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.

  • toolpath( cutter path)

    toolpath( cutter path)

    2-D or 3-D path generated by program code or a CAM system and followed by tool when machining a part.

  • web

    web

    On a rotating tool, the portion of the tool body that joins the lands. Web is thicker at the shank end, relative to the point end, providing maximum torsional strength.