Imagine burying a roughing tool in a block of Ti-6Al-4V titanium and ripping away more than 1,000 cm3 (61 cubic inches) of material in just one minute. If you’d been at a recent test of Kennametal’s new HARVITM Ultra 8X helical milling cutter, you’d have seen exactly that. Using a 95 mm (3.74 in.) axial depth of cut, 20 mm (0.78 in.) radially, and a feed rate of 423 mm/min. (16.65 ipm), the 80 mm (3.15 in.) diameter HARVI Ultra 8X plowed through this difficult aerospace superalloy for nearly 3 minutes straight without flinching.
Tim Marshall, 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) and seeing outstanding results with each.
“Kennametal developed the HARVI Ultra 8X to meet two distinct needs,” Marshall says. “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 still achieving excellent tool life. At the same time, machine tool builders and users alike 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. The new HARVI Ultra 8X does all that, and a lot more besides.”
Massive piles of chips notwithstanding, your shop almost certainly wants its tools to stay in the cut far longer than 3 minutes. Marshall agrees, saying the HARVI Ultra 8X was designed to predictably remove 20 cu. in. (328 cm3) of Ti-6Al-4V each minute while attaining 60 minutes of tool life per cutting edge. To do this, Kennametal combined a number of innovative technologies in this highly engineered cutting tool solution:
-A double-sided yet positive rake insert that delivers the lowest cost per edge possible and simultaneously reduces power consumption by up to 50 percent.
-Thanks to a unique AlTiN+TiN PVD coating that provides robust resistance to thermal fatigue, Kennametal’s high-performance KCSM40 carbide grade enjoys much longer tool life than competing solutions.
-The HARVI Ultra 8X cutter body is constructed of a higher quality steel than competing solutions for improved stiffness and rigidity under high cutting forces.
-In addition, a unique BTF46 (bolt taper flange) connection provides the ultimate in deflection resistance compared to traditional shell mill-type holders.
-The variable-helix design of HARVI Ultra 8X breaks up the harmonics that lead to chatter, further improving tool life, part quality, and throughput.
This last point is particularly important. A variable-helix geometry greatly reduces carbide-killing vibration. Using 12 mm 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.
Yet the HARVI Ultra 8X has even more tricks up its sleeve. Precision through-the-tool coolant nozzles direct cutting fluid where it’s needed most. An enhanced flute design assures maximum chip evacuation. Oversize M4 Torx Plus screws for greater insert stability. The option with a KM4X adaptor brings greater toolholding stability. Specially-prepared insert edges optimized for the KCSM40 grade greatly extend tool life. Corner radii from 0.8mm to 6.4mm, in both inch and metric, means there’s little you can’t machine.
“We’ve optimized everything about the HARVI Ultra 8X,” says Marshall. “The flutes and the coolant nozzles assure maximum chip flow, something that’s very important when you’re removing this much material—without it, the chips get jammed up and you’re facing catastrophic failure. Our KCSM40 grade has proven to be a top performer in high-temp alloys, but we also offer several equally excellent grades for other work piece materials. And eight cutting edges per insert? Nobody else has that in a helical cutter.”
Double sided inserts not only means lower cost per edge but the ability to increase speeds and feeds beyond what was previously possible, Marshall notes. And because the HARVI Ultra 8X is available with an integral shank or the “crazy strong” BTF46 mount, users can adapt the cutter to virtually any machine tool spindle with no loss of rigidity. “We go up against our competitors’ and sometimes even our own helical cutters and are blown away by the performance improvement,” he says. “For anyone who’s looking for the highest productivity at the lowest possible cost per edge, this is the cutter for them.”
Related Glossary Terms
Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.
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.
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.
- cutting fluid
Liquid used to improve workpiece machinability, enhance tool life, flush out chips and machining debris, and cool the workpiece and tool. Three basic types are: straight oils; soluble oils, which emulsify in water; and synthetic fluids, which are water-based chemical solutions having no oil. See coolant; 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.
Phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the tensile strength of the material. Fatigue fractures are progressive, beginning as minute cracks that grow under the action of the fluctuating stress.
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
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.
- helical cutter
Endmill or other cutter with spiral or helical flutes. May be right- or left-hand.
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.
- milling cutter
Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.
- physical vapor deposition ( PVD)
physical vapor deposition ( PVD)
Tool-coating process performed at low temperature (500° C), compared to chemical vapor deposition (1,000° C). Employs electric field to generate necessary heat for depositing coating on a tool’s surface. See CVD, chemical vapor deposition.
Angle of inclination between the face of the cutting tool and the workpiece. If the face of the tool lies in a plane through the axis of the workpiece, the tool is said to have a neutral, or zero, rake. If the inclination of the tool face makes the cutting edge more acute than when the rake angle is zero, the rake is positive. If the inclination of the tool face makes the cutting edge less acute or more blunt than when the rake angle is zero, the rake is negative.
Main body of a tool; the portion of a drill or similar end-held tool that fits into a collet, chuck or similar mounting device.
1. Ability of a material or part to resist elastic deflection. 2. The rate of stress with respect to strain; the greater the stress required to produce a given strain, the stiffer the material is said to be. See dynamic stiffness; static stiffness.