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Tooling: cutting edge takes on new shape.

Tooling: Cutting edge takes on new shape

There is a definite trend toward consolidation in the cutting-tool industry. This isn't too much of a surprise considering overall cutbacks in the credit markets (which tend to inhibit inventory levels of distributors), pressure from overseas competitors, cutbacks in defense contracts, and the overall reduction in industry output due to a weak recovery and general US manufacturing decline.

That's the opinion of Tim Wyman, chairman of Talbot Holdings Ltd, Atlanta, whose cutting-tool companies include Weldon Tool, Brubaker Tool Corp, Fastcut Tool Corp, and the New England Tap Co.

Though it is a tough market, there will always be the need for cutting-tool producers (and their products) who have made the right investments in modern manufacturing equipment, says Mr Wyman, adding that US companies have a greater capacity to produce quality tools than at any time in our history.

There is a trend toward new geometries and families of tools based on these geometries to meet the requirements of speed, feed, and depth of cut (DOC) in removing metal faster, cleaner, and more manageably. And the best may still be coming as new materials and coatings help extend performance at the cutting edge.

Coating developments have extended the range and performance of high-speed steels and solid-carbide tooling. Other materials such as PCD (polycrystalline diamond) and CBN (cubic boron nitride) are finding application in specific and difficult machining applications; PCDs for nonferrous and nonmetallic materials and CBN for machining hardened steels.

At the same time, carbide indexable cutting-tool inserts continue to show their versatility and ability to combine machining operations in one tool, i.e. plunging, face turning, slotting, threading, grooving, and the like. According to one major distributor, demand for certain types of carbide-tipped cutting tools such as reamers, drills, end mills, and boring bars has dropped because of the impact of carbide inserts.

Other trends among buyers noted by the distributor include:

* A distinct "Buy American" feeling, especially for superior quality of US-made tools, if they are price competitive;

* Continuing inroads of foreign-produced tools because of price;

* Growing demand for TiN-coated materials for taps, drills, and end mills;

* Growing use of indexable carbide inserts;

"Everyone is looking for predictability . . . knowing how long the tooling is going to last (resistance to wear), how it is going to perform in our modern untended machine operations (chip control)," says Charles Carter, vice president of technology, AMT--The Association For Manufacturing Technology, Washington.

CNC machine tools certainly bring with them their own unique tooling requirements. Running untended machines means that chip making and breaking must be more efficient and not injurious to the process. James L Hunt, director-product management for the Metal-working Systems Div of Kennametal Inc, calls consistency and predictability of tool life "crucial qualities in unmanned or minimally manned machining operations."

One thrust in increasing productivity comes from developments in materials for high-speed machining. (See exhibit "How materials affect high-speed machining" from LeBlond Makino Corp, Mason, OH.)

"One of the reasons carbide performs so well over steel milling cutters is that carbide can run at higher speeds," says John Krawood, president, ABC Tool Inc, Middletown, CT. "Those higher speeds generate heat. . . At slow speeds, around 70 sfm, the speed at which steel mills cut, the tool is fighting the full strength of the steel. But as the speed increases, so does the heat generated at the cutting edge, lowering the tensile strength of the steel at that point. So generally, the faster you spin the cutting tool, the less strength (resistance) the workpiece will have. But remember, if you spin too fast, the generated heat will break down the strength of the carbide edge, and the tool will fail prematurely."

Pushing the envelope

ABC Tool has combined the solid-carbide material of its Turbo-Mill with the geometry of as many as 16 flutes for profile-milling steel, stainless, and Inconel. The Turbo-Mill runs on any of the fast CNC machines. Priced three times cobalt and twice carbide mills, it reportedly increased tool life 500% and feedrates 1000% vs a conventional six-flute carbide mill in cutting steel weldments at 60-62 Rc for TDM Corp, Fletcher, NC. Leading cutting-tool manufacturers are finding new ways to push the envelope in product performance, even in mature product segments like drills and taps, where price alone has tended to dominate the consumer's attention, according to SKF Tools Corp, Milford, CT.

SKF Tools has designed and manufactured drills and taps to handle high production rates in the difficult-to-machine or "exotic" materials as well as the typical ferrous materials. The new geometry of the TiN-coated HSS ADX drill line features a modified 130-deg split point which eliminates chip packing on soft materials and spiraling or rifling of the drilled hole. A higher helix angle and a changed flute geometry increase the rate and efficiency of chip removal for machining carbon steel, alloy steel, ductile iron, stainless steels, and die steels.

Similar design changes have been made in SKF Tools' TiN-coated micrograin solid-carbide line of CDX drills for carbon, structural, and alloy steels, as well as tempered and hardened steel, cast iron, titanium, copper, bronze, and aluminum. For a hand-tool manufacturer, using CDX drills simplified a spotting, drilling, and reaming operation for two holes in 4340 steel. The new tools eliminated the spotting operation, improved penetration rates by 40%, and produced a hole finish that eliminated the need for reaming.

One way to provide versatility is to develop a family of cutting tools based on variations in both material and geometry. Brubaker Tool's Starchip end-mill line features five variations in material and geometry that are aimed at specific machining applications. Starchip I is a cobalt tool with special geometry designed for use in machining titanium and free-machining stainless; Starchip II is high-speed steel with a blue finish for machining low- and medium-hardness steels; Starchip III is a bright-finish cobalt for hard-to-machine materials such as nickel-based alloys (Inconel, Hastelloy, Waspaloy), with a special hook-angle chipbreaker flute; Starchip IV is a HSS tool with a 38-deg helix angle for use on aluminum; and Starchip V is a cobalt tool with a coolant hole and 38-deg spiral for machining aluminum.

New coatings

Coatings continue to extend the range of high-speed tool steels and solid carbides for users. (See T&P, September 1991, Pg 30). According to Balzers Tool Coating Inc, North Tonawanda, NY, new high-performance PVD thin-film wear-resistant coatings are expected to selectively replace TiN coatings which have grown in popularity since their introduction 10 years ago.

The next generation of coatings includes titanium carbonitride (TiCN) and chromium carbide (CrC), which will improve performance in niche areas where TiN has found limited success or where additional performance is desired.

In general, says Balzers, the more abrasive workpiece materials such as cast irons, stainless steels, and aerospace alloys, where abrasive wear is a major factor in tooling wear, may benefit from the new higher-performance coatings. Also, the softer workpiece materials, such as brass and aluminum, where the key destructive wear mechanism is adhesive welding, appear promising. TiCN is well suited for cutting highly abrasive and gummy materials such as cast iron, brass, and aluminum alloys; CrC coatings are well suited for machining of titanium and titanium alloys and aluminum die castings.

Indexable-carbide cutters

Trends in the use of carbide cutting inserts have followed a similar path with emphasis on geometry and coatings for productivity improvements in machining operations. One goal, however difficult to achieve, is to combine several machining operations in one insert when possible. Another trend is to create a simplified family of inserts to cover a range of machining applications.

Chip breaking and chip control, of course, are of paramount importance. Over the last decade, according to Gregory J Moreland, manager-marketing, Teledyne Firth Sterling, La Vergne, TN, the benefits of improved chip control include: 1) better part finishes and the elimination of sanding or polishing operations; 2) safety and production improvements through the elimination of downtime to reduce "bird's nests"; 3) extended tool life as better chip control reduces the propensity of tools to fail due to edge buildup (chip welding).

One by-product of this trend is that many new designs enhanced for specific and very narrow applications entered the market. "Users were soon confronted with the dilemma of selecting an appropriate design from a confusing array of slashes, grooves, and dimples," Mr Moreland claims. TFS, for example, was offering 22 separate designs at one time. The solution: simplify and consolidate designs. TFS has developed a three-groove system which, in combination with its coated grades, covers a wide range of machining applications.

To simplify insert selection and help users choose the optimum tool, Carboloy Inc, Detroit, developed its Secolor guide to turning inserts and a slide-rule selector. These simplify selection of a wide variety of geometries for producing the most acceptable chip length. Material coatings include alumina, TiC, TiN, and compositions of titanium with nitrogen, carbon, and oxygen.

Controlling chips

Chips are acceptable if they are short enough to simplify disposal, assure safety for the operator, and do not degrade surface finish, explains Kennametal's Mr Hunt.

Kennametal has focused its insert development in response to an increasingly prevalent situation in the metalcutting industry, where operational parameters and speed/feed performance are basically fixed. The user is, however, still looking for continuing improvement in terms of lower operating costs.

The result has been the extension of the Kennametal's MG family of insert geometry with the addition of the MG-MG insert. It is designed with a 5-deg, positive, medium-force profile to meet strict performance criteria in machining steel and stainless steel to lower the cost per piece.

For example, in machining an automotive gear blank--SAE 5128 forging, 182 BHN--the new 5-deg positive-profile geometry improved tool life 84% vs the conventional MG geometry and the high-positive MG-P, Kennametal claims. Operations included chamfer, face, turn, and chamfer.

The chipbreaker

According to Greenleaf Corp, Saegertown, PA, there is a direct relationship in molded chipbreaker designs between the width of land and the depth and angle of the edge. However, the function of other features such as bumps, waves, and similar surface irregularities, is difficult or impossible to determine by any of the normal criteria. "In fact, when replaced by inserts without these features, as often as not, the insert performed as well," explains Keith H Smith, marketing manager.

"No doubt a good case can be made for some of the inserts in specific installations and also, without doubt, there is an element of gimmicking in many of them," he claims.

Because Greenleaf felt that from the consumer's viewpoint, "the picture has become confusing and perhaps misleading," it has introduced a range of chip-control inserts which is easy to understand and "yet effective." Greenleaf's CNMG series of inserts carries the designations FF (fine finishing), GP (general purpose), MR (medium roughing), and HR (heavy roughing). FF is intended for light DOC and feedrates to 0.015 ipr. GP for semi-finishing to light roughing and feedrates above 0.008 ipr. MR for medium roughing at feedrates over 0.015 ipr. And, for heavy roughing, the HR double-sided for feedrates above 0.030 ipr. For more aggressive heavy roughing, a single-sided CNMM insert is recommended for feedrates over 0.030 ipr.

Geometry continues to play a central role in insert developments from Iscar Ltd, Tefen, Israel. Just being introduced in the US market is its Heliface insert for deep face grooving and face turning. Designated HFMR/L, Heliface molded-sintered types provide right- and left-hand positions, and the system has the ability to reach larger depths and turn in all directions.

Face-grooving is normally limited in depth, in diameter, or in width of cut. The limitation depends on the insert and tool geometry, minimum groove diameter, and problems with chip flow. The new double-ended Heliface insert embodies nonparallel, opposite-end cutting edges. The rear edge is slanted in relation to the frontal edge to lessen the effective width in the cutting direction. Depth of cut at the frontal edge is unlimited. As the tool penetrates deeply into the workpiece, the rear side does not come in contact with the machined grooved surface. Standard maximum depth of groove on the outside is 1". Machining operations are unlimited along the central axis.

The Heliface insert can turn in either direction so that, after the first groove is made, the cut can be continued toward center or toward the outer diameter. Such a combination handles face grooving and turning, precision grooving, and face turning to any required profile.

The new Heliface insert joins the Cut-Grip, [TM] Top-Grip, [TM] and Self-Grip [TM] families of inserts that Iscar has developed to meet the demand for accuracy, higher surface quality, improved chip flow, smaller insert size, lower forces and power, and less tool variety. [Exhibit Omitted]

PHOTO : Above: Cutting a good "9" chip with Kennametal's MG-P insert. Left: CDX drill with 130-deg point design from SKF.

PHOTO : Finishing cut of 0.015" was successfully done along the periphery of an Inconel 718 part that was 3/8" thick at 27" per minute using 16-flute Turbo-Mill solid-carbide end mill.

PHOTO : Brubaker Tool's Starchip end-mill line features five variations in material and geometry.

PHOTO : Heliface insert for deep face grooving and face turning features rear edge that is slanted to clear newly made cut.
COPYRIGHT 1992 Nelson Publishing
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Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:includes related article on machining speed and information exchange
Author:Lorincz, James A.
Publication:Tooling & Production
Date:Jan 1, 1992
Previous Article:Doctor downtime with diagnostics?
Next Article:Shear spinning for the pressroom.

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