Live tooling increases a manufacturer’s cutting options and enables machinists to perform operations other than turning. Here’s what you need to know to maximize your investment.

Traditional, 2-axis CNC lathes are slowly going the way of whitewall tires, only to be replaced by evermore capable mill-turn and multitasking machines. 

Because of this trend, live tool attachments (synonymous with driven tool attachments) are becoming increasingly important members of the turning department, responsible for cutting slots, drilling cross holes and milling part features that previously required secondary operations on one of the shop’s machining centers.

“It’s a bit like bolting an attachment to the front of a Toyota Camry and using it to plow the fields. You can do it, but if you don’t take good care of the engine and transmission, you’re going to experience unexpected downtime much earlier than you’d like.”
Tom Dang

Most live tools come from third-party suppliers, however, rather than the machine builder. You might be left wondering: whose should you buy? Which manufacturer uses the best gears, bearings and seals? What brand is most accurate and rigid, able to spin true year after year? And once your new driven toolholders arrive, what maintenance procedures should you follow to avoid dishing out even more hard-earned cash on what is admittedly a significant tooling investment? 

Finding Your Best Live Tooling Options

These are all excellent questions, of course, and ones that Scott Leitch can help answer. 

The sales and marketing manager at EXSYS Tool Inc., Leitch explains that, even though there are plenty of high-quality live tool options available, shops are limited to those that fit their specific lathe and its turret or turrets—unlike the CAT and BT spindles common to most machining centers these days (although these are evolving to include HSK and other dual-contact designs), machine tool builders have largely gone their own way in turret design. 

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Without naming names or offering a preference, Leitch says the majority of live tool lathes are equipped with either VDI or BMT turrets. The first of these acronyms stands for Verein Deutscher Ingenieure, which Google translates as “Association of German Engineers.” As you might have guessed, VDI originated in Europe. The toolholder body has a serrated shaft that slides into a hole in the turret’s face or periphery and mates to a toothed, cam-lock drawbar mechanism within. Cutting tool rotation is achieved via a spline gear on the end of the shaft, which engages with a servo motor located inside the turret. 

Depending on whom you ask, BMT is short for “base-mounted turret” or “bolt-mounted tooling.” It uses a frustratingly nonstandard pattern of four bolt-holes and keyways to align and secure the driven tool to the turret’s outer faces. As with VDI tooling, BMT is powered by a servo motor within the turret, although the coupling itself varies between a splined interface—common on Sauter brand disc turrets—or the more common tang-style drive. 

VDI proponents argue that, because driven toolholders can often be mounted on either turret face, their solution is more flexible and cost-effective. VDI might also be a bit more accurate, especially on lathes with turret misalignment problems, because the toolholders are easily aligned through the use of a dial indicator and some gentle taps with a brass hammer.

Taking It Easy

This adjustability, however, is also VDI’s Achilles’ heel. Because of it, some suggest that VDI is less rigid and requires more setup time. By comparison, BMT’s four keyways mean no adjustment is needed—drop them in, bolt them down, and get machining. 

“In my experience, tang-style BMT is gradually replacing VDI as the first choice in driven toolholders, although both styles are capable of doing an excellent job, provided the CNC machinist follows some best practices,” Leitch says.

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Chief among these is the secret behind long-term, hassle-free and productive milling operations on a live tool CNC lathe: Don’t treat it like a machining center. The smaller spindles in these toolholders require that lighter depths of cut be used than with dedicated milling machines. Keep feed rates moderate, and try to engage multiple flutes to reduce harmonics and chatter. 

Similarly, tool stick-out should be kept to a minimum. If not, a tool extending three to four times its diameter can overburden the relatively small spindle bearings within the toolholder itself. Worse, a cutting tool hanging out too far in the radial direction might hit the sheet metal when indexing the turret, a fairly catastrophic event.

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Plowing Fields with a Camry

Tom Dang, vice president of Lyndex-Nikken Inc., agrees with the need for sound machining practices in live tool applications. And as with EXSYS Tool’s Scott Leitch, he suggests that shops can go a long way toward maximizing their live tool lathes investment by sticking with routine preventive maintenance procedures. 

“Because you’re asking them to do more with less, live tool lathes basically cheat the traditional approach to machining,” he says. “It’s a bit like bolting an attachment to the front of a Toyota Camry and using it to plow the fields. You can do it, but if you don’t take good care of the engine and transmission, you’re going to experience unexpected downtime much earlier than you’d like.”

Read more: Managing Downtime: A Guide to Improving Shop Productivity During Manufacturing Slowdowns

That means keeping toolholders clean and well-lubricated. Inspect them between teardowns for wear. Look for live tools able to run either wet or dry, as these eliminate the chance that the programmer forgets to turn on the internal coolant, thereby burning up the seals and bearings. Also, keep track of how many hours of use each live tool has seen. This will avoid the all-too-common problem of pushing a tool past the point of no return, turning what should be routine maintenance into a complete rebuild, or worse. 

Maintenance aside, each supplier has its own unique selling features. Dang says most live tools on the market rely on ER-style collet systems but suggests Lyndex-Nikken’s SK collets are more rigid and have greater gripping strength, primarily due to their steep, 8-degree taper. And Leitch notes that tool changeover-related downtime is increasingly critical for shops of all sizes, which is why he recommends EXSYS Tool’s Preci-Flex modular adapters, which use either a standard ER collet, or Preci-Flex adapter with cone and face contact. The quick-change system supports offline tool presetting, simplifies tool changes for less experienced operators, and is far faster than traditional collet-style holders.

Live Tooling: Here’s How to Maximize Your Investment

Live tooling increases a manufacturer’s cutting options, allowing you to perform operations other than turning.

If you’re already using live tooling, there are steps you can take to maximize your investment.

Take our poll to share your insights and discover what others are doing.

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It's great that you mentioned that to achieve maximum utilization of your live tool attachments, you should opt for routine maintenance to expect decade use. My dad would benefit from this information because he plans to open a machining shop soon. He would most probably buy live tooling fo it, so I'll show this article to him. Thanks!


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