Tim Marshall, Kennametal’s senior global product manager for indexable milling, has tested the Harvi Ultra 8X with a variety of customers, pushing the limits of the new cutter on everything from 15-5 PH to cast iron to Aermet 100 (high-strength steel), reporting outstanding results with each.
“Kennametal developed the Harvi Ultra 8X to meet two distinct needs,” he explains. “The first came from the aerospace industry, which thanks to the large numbers of aircraft being built today requires the highest metal removal rates possible, but with excellent tool life. At the same time, machine tool builders and users are asking for tools able to withstand higher cutting speeds but generate lower machining forces, so as to reduce wear and tear on machine components during extreme cutting conditions.”
Large piles of chips notwithstanding, machine shops almost certainly wants their tools to stay in-cut for much longer than three minutes. Marshall agrees, saying the Harvi Ultra 8X was designed to predictably remove 328 cm3 of Ti-6Al-4V each minute, while attaining 60 minutes of tool life per cutting edge.
To achieve these results, Kennametal has combined a number of technologies in this engineered cutting tool solution, including: a double-sided yet positive rake insert that delivers low cost per edge while simultaneously reducing power consumption by up to 50%; a proprietary AlTiN+TiN PVD coating that provides robust resistance to thermal fatigue; Kennametal’s KCSM40 carbide grade that delivers long tool life; a cutter body constructed of high quality steel for improved stiffness and rigidity under high cutting forces; a special BTF46 (bolt taper flange) connection for high deflection resistance compared with traditional shell mill type holders; and a variable helix design that breaks up the harmonics which lead to chatter, further improving tool life, part quality and throughput.
The last point is particularly important. A variable helix geometry greatly reduces carbide-killing vibration. Using 12 and 10 mm inserts also helps, as their smaller size means more inserts in the cutter body, more inserts engaged in the workpiece, and more inserts to absorb the pounding of a heavy machining operation.
Harvi Ultra 8X cutters also feature precision through-the-tool coolant nozzles that direct cutting fluid to where it is needed most. An enhanced flute design ensures maximum chip evacuation, while oversize M4 Torx Plus screws provide greater insert stability. Corner radii are available from 0.8 to 6.4 mm.
“We’ve optimised everything about the Harvi Ultra 8X,” says Marshall. “The flutes and the coolant nozzles facilitate maximum chip flow, something that’s very important when removing this much material. Without it, the chips get jammed up and you are facing catastrophic failure. Our KCSM40 grade has proven to be a top performer in high-temperature alloys, but we also offer several equally excellent grades for other workpiece materials. And eight cutting edges per insert? Nobody else has that in a helical cutter.”
Double-sided inserts not only mean lower cost per edge but the ability to increase speeds and feeds beyond what was previously possible. And because the Harvi Ultra 8X is available with an integral shank or the BTF46 mount, users can adapt the cutter to virtually any machine tool spindle with no loss of rigidity.