The Most Complete Introduction To Milling Inserts - milling cutter insert

A good place to start is by learning the ISO 1832 standard, which, according to the International Organization for Standardization, “establishes a code for the designation of the usual types of indexable inserts for cutting tools in hard cutting materials or any other cutting materials, in order to simplify orders and specifications for such inserts.”

Ready for a quick ISO introduction? Pick up a “typical” box of turning inserts—some CNMG432 roughers, for example, or VPGR331 profiling tools—and follow along:

Iscar USA, a member of the IMC Group, is another cutting tool manufacturer pursuing continuous improvement opportunities for its customers, which is why the company isn’t afraid of setting aside the ISO 1832 standard when it makes sense.

Hitting a home run might require thinking outside the ISO box, he says. “If you’re striving for consistent 15 percent to 25 percent increases in productivity, you should look at changing your whole process. Using trochoidal toolpaths during roughing operations is one such approach.”

Winter and the other experts are happy to help customers decode the ISO standard and find the optimal insert for a given application, but as Winter points out, even the perfect grade, shape and coating will often bring only small gains.

“One of the drawbacks of ISO standard tools is that they typically rely on a top clamp, eccentric screw or some combination of the two to hold the insert in place,” says Robert Navarrete, national product specialist for parting, grooving and turning. “Yet these can allow a microscopic amount of insert lift, leading to vibration and reduced tool life. A dovetail-style geometry and on-edge clamping system eliminate this by taking pressure off the screw and redirecting it into the pocket.”

Kip Hanson is a freelance writer and manufacturing consultant. Hanson, who is the proprietor of KAHMCO LLC, has more than 40 years experience in manufacturing, machine tools, fabrication and ERP systems. In addition, Hanson is a contributing editor at Manufacturing Engineering​, Shop Metalworking Technology and others. He has been writing about manufacturing technology since 1998.

Unfortunately, you’ll also find it chock-full of exceptions. In their ongoing effort to address the machining world’s ever-evolving landscape, cutting tool manufacturers continue to develop novel, often proprietary solutions that don’t fit neatly into any standardized set of guidelines.

Keeping an assortment of brazed carbide tool bits and solid carbide rounds in the tool crib is probably a good idea. You never know when you may need to hand-grind a special tool for an oddly shaped part or hard-to-reach area.

Trochoidal turning (also known by the trade names Dynamic Turning and VoluTurn) can be done with ISO-standard round inserts, but it’s more effective when the insert has a rail interface for graduated indexing, as with the company’s CoroTurn 107 RCMT.

Navarrete is talking about Iscar’s HELITURN line of tangentially clamped turning tools. As he explains, these offer greater stability in the pocket, not only improving tool life and surface quality but also significantly increasing the tool’s metal removal capabilities. “It also provides much better predictability, an attribute that’s particularly relevant to shops that wish to run lights-out,” he says.

“Proper insert selection depends on many factors,” says John Winter, a turning product specialist at Sandvik Coromant. “Workpiece material and geometry are high on the list, but choosing an insert with adequate edge line security for the operation—a tool that can handle interrupted cuts, for instance—is equally important.”

While choosing the right turning insert and toolholding system is critical, so is proper process development, says Seco Tools Indexable Product Specialist Jay McCord. Too often, shops don’t follow the manufacturer’s feed and speed recommendations and fail to use a scientific approach to troubleshooting, including documenting one change at a time.

There’s just one caveat, though, and it applies to each of the proprietary solutions described here and elsewhere: Machine shops must invest in new toolholders, followed by reprogramming and process optimization.

But considering that a new toolholder and box of inserts sell for a few hundred bucks or so, it’s a small price to pay for the potential benefits.

“We’re also seeing great success with our PrimeTurning offering, which uses a similar chip-thinning strategy, as well as the eight-sided CoroTurn 800,” Winter says. “Yes, these solutions require some changes to your turning strategy but are well worth the time investment for shops that are working with difficult materials or looking for ways to leapfrog their competition.”

For most turning operations, though, indexable carbide tools make machine setups both faster and easier while significantly reducing the downtime associated with tool changes. Which still leaves one problem: deciding which insert is right for the job.

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Peruse a supplier’s tooling catalog or website and you’ll quickly find an overwhelming variety of indexable tooling. Profiling tools, groovers and threaders, boring inserts, indexable and modular drills, cutoff tools—there’s no shortage of high-quality turning tools out there, all designed to make lathe turning operations more profitable and part quality more consistent.

“If we see that a shop can enjoy a 20 percent improvement in either tool life or productivity, we’re happy to present that to them in a written pre-sales test report and then prove it to them on the production floor,” Navarrete says. “Return on investment is generally quite fast when adopting a new tooling technology like this, with some customers saving tens or even hundreds of thousands of dollars. It’s pretty much a no-brainer.”

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That was a very abbreviated tour through the ISO 1832 standard, now on its sixth edition and spanning 24 pages. You’ll find it a helpful starting point on your road to insert selection.

“Our 3D-printed Jetstream coolant clamps deliver cutting fluid to the correct location for different turning applications like heavy roughing, roughing and finishing,” he says. “They can also be used with our Steadyline brand of modular boring bars, which have an internal dampening mechanism to eliminate chatter, improve surface finish and increase productivity.”

Indexable tools make machine setups faster and easier while significantly reducing the downtime associated with tool changes, but choosing the best insert can be tricky. Here’s what you need to know.

“The flip side of the FIX8 is that you can take much heavier cuts than with a WNMG- or CNMG-style rougher, and do so even on lighter-duty machines,” he says. “And since you have eight cutting edges to work with, the cost per part is generally lower as well.”

“There’s a lot to consider during insert selection,” says Robert Keilmann, marketing portfolio manager at the company. “ISO turning tools are suitable for a great many applications, but given the huge variety of parts and materials in this landscape, not to mention the evolution of CNC machine tools, we’ve found it necessary to develop turning tools that provide effective chip formation and extended tool life on lower-horsepower machinery. Our FIX8 line does exactly that.”

Sandvik Coromant is not alone. Abhay Chaubal, product manager for the Americas at Seco Tools, is quick to point out that the company’s MF2 chipbreaker and RCMT insert solve the all-too-common chip control problem encountered when using round inserts.

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“That’s one of the reasons why we’ve begun marking our inserts with QR codes, which allow the user to scan the code with a smartphone and pull up the product page showing the correct cutting parameters for the material you’re currently turning,” McCord says. “They also provide traceability back to the manufacturing process in case of a problem and make it easier to dispense individual inserts from a vending machine. As with many of our customers, Seco Tools is very focused on continuous improvement, and this is just one more example of that.”

Like Winter, he encourages shops to explore alternative toolpaths, with ISO inserts or otherwise. He also notes that recent innovations in toolholding can bring significant results.