HARVI III Endmill

Contact Details

Kennametal Inc.
Address
525 William Penn Place, Suite 3300
Pittsburgh
15219
PA
United States
Phone
724-539-5000
Toll Free Phone
800-446-7738
Fax
724-539-5022

40.2831882, -79.3943748

November 02,2017
HARVI III Endmill

It started in 2015, when engineers at a major U.S.-based aircraft manufacturer kicked-off a challenge to determine which cutting tool manufacturer offers the best products for milling forged Ti-6Al-4V titanium. The company invited Kennametal and 10 other global tooling suppliers to the University of Sheffield’s Advanced Manufacturing Research Centre (AMRC) in the U.K., where the different teams competed in the challenge. The event required months to complete, but the winning tool from Kennametal outperformed its competitors, gave added value in productivity and tool life to the company, and ultimately ended up in the aerospace giant’s internal tooling catalog.


The aircraft manufacturer supplied three sets of cutting parameters for both the “traditional milling” and "high velocity” approaches. These were designated as current, meets and exceeds expectations. In the traditional testing rounds a 0.1 in. (2.54 mm) radial depth of cut (DOC) was used, with cutting speeds ranging from 150 sfm (46 m/min) for the “current” values, 200 sfm (61 m/min) for “meets,” to 250 sfm (76 m/min) for “exceeds.”

“We went straight into the 'exceeds' range in the first test round setting the bar for others to follow,” says Kennametal Staff Engineer Danny Davis, who participated in the testing, In the following high-velocity testing approach the DOC was decreased to 0.02 in. (0.508 mm) but with increased surface speeds to 400 sfm (122 m/min), 450 sfm (137 m/min), and 500 sfm (152 m/min), respectively.

Both approaches imposed strict guidelines on tool geometry: participants must use a 1.25 in. (31.75 mm) diameter endmill, one with a flute length of 4 inches (101.6 mm), corner radii of 0.09 in. (2.29 mm), and a flute count of 5 or 6 flutes. “Kennametal was the only participant that dared using a 6-fluted tool right from the start” adds Davis, “we were told ‘no holds barred!’ by management, so we had to start always from the top range.”

During the testing, tools were required to achieve Z-axis cut depths of 2 inches (50.8 mm), and extend from the holder exactly 4.5 inches (114.3 mm). Only imperial unit tools were allowed (no metric equivalent). It was left to the tooling supplier to determine the tool coating, carbide substrates and best cutting geometry for the test.

Needless to say, engineers at the company provided a clearly defined set of rules for all, and each participant engaged their best and brightest people for the testing. In Kennametal’s case, multiple substrates, geometries, coatings and edge preps were evaluated. High and low pressure coolant was tried, sometimes with coolant through the tool, other times without. Kennametal also performed its own internal testing at facilities in Fuerth, Germany, and LaVergne, Tenn., and Asheboro, N.C., using five different machining centers and filing three patents during this endeavor. Chip flow and formation were analyzed using high speed cameras and new tool grinding processes developed as a result. In all, nearly 300 different tools were produced for the project, and 15,000 cubic inches (246,000 cm3) of titanium machined.

During its final round of testing, Kennametal used a shrink fit Safe-Lock-style holder and operated its tools in the “exceeds” category in all cases. With the traditional milling approach, less than 0.001 in. (0.025 mm) of tool wear was observed after one hour, with a surface finish of 23 μin. Ra (0.6 μm). The high-velocity approach provided comparable results, with tool wear measured at less than 0.0014 in. (0.035 mm) and surface roughness better than 27.5 μin Ra (0.7 μm). Both met the aircraft manufacturer’s requirements, and also delivered a 20 percent greater metal removal rate than its competitors because Kennametal choose to supply a 6-flute tool instead of a 5-flute tool.

While the tests were being conducted for the challenge, company engineers were also conducting tests of the Kennametal tools internally, validating them against criteria used for any tools under consideration for production use. They tested multiple tools and were able to run for 2,000 minutes with no more than 0.00157” (0.039 mm) wear.

What’s this mean to other customers? Kennametal has recently released the results of its months of testing, under a name you might be familiar with. The HARVI III Aerospace Expansion line of solid-carbide endmills is based on much of the cutting tool technology that made the HARVI III popular. It offers six unequally spaced flutes to break up chatter even at higher feed rates. Its lower cutting forces and eccentric relief design provides improves tool life, and has a tapered core that increases stability during heavy cutting conditions. “Interestingly, whatever modifications to the existing HARVI III were tested, we always came back very close to the existing design we’ve had for the past five years,” says Davis. “The final modification was so minor that we plan to simply upgrade the old HARVI III design.”

The new HARVI is available in KCSM15 Beyond grade, which is designed for exceptional performance in titanium and stainless steels, and its center cutting design gives you the flexibility to use it for roughing and finishing operations alike. “In total, 303 standard catalog line items were created,” Davis notes. “This includes ball nose and square end mills with various radii in different overall lengths. The standard offering comprises diameter 1/2 in. up to 1-1/4 in. off the shelf and even 1-1/2 in. made-to-order with very short lead times. This illustrates how serious we take the new product line, which is much larger than any HARVI line launched in the past.”

“The HARVI III Aerospace Expansion line is now part of the aerospace leader’s internal tooling catalog,” adds Kennametal Key Account Manager Peter Lawson. “That’s good for them, but it’s even better for those shops that struggle to achieve tool life in titanium, who can now leverage the results of our combined testing. The HARVI III line not only produces more parts, more predictably and in less time than the competition, it also offers better chip control and tool life, a win-win for any shop. It was both a privilege and an honor to be chosen for this competition, and it’s gratifying to deliver a product that perfectly addresses so many of our customers’ needs.”

Related Glossary Terms

  • centers

    centers

    Cone-shaped pins that support a workpiece by one or two ends during machining. The centers fit into holes drilled in the workpiece ends. Centers that turn with the workpiece are called “live” centers; those that do not are called “dead” centers.

  • chatter

    chatter

    Condition of vibration involving the machine, workpiece and cutting tool. Once this condition arises, it is often self-sustaining until the problem is corrected. Chatter can be identified when lines or grooves appear at regular intervals in the workpiece. These lines or grooves are caused by the teeth of the cutter as they vibrate in and out of the workpiece and their spacing depends on the frequency of vibration.

  • 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.

  • depth of cut

    depth of cut

    Distance between the bottom of the cut and the uncut surface of the workpiece, measured in a direction at right angles to the machined surface of the workpiece.

  • endmill

    endmill

    Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.

  • feed

    feed

    Rate of change of position of the tool as a whole, relative to the workpiece while cutting.

  • filing

    filing

    Operation in which a tool with numerous small teeth is applied manually to round off sharp corners and shoulders and remove burrs and nicks. Although often a manual operation, filing on a power filer or contour band machine with a special filing attachment can be an intermediate step in machining low-volume or one-of-a-kind parts.

  • flutes

    flutes

    Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.

  • gang cutting ( milling)

    gang cutting ( milling)

    Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.

  • grinding

    grinding

    Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.

  • milling

    milling

    Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

  • relief

    relief

    Space provided behind the cutting edges to prevent rubbing. Sometimes called primary relief. Secondary relief provides additional space behind primary relief. Relief on end teeth is axial relief; relief on side teeth is peripheral relief.

  • 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.