Crystal manufactured from boron nitride under high pressure and temperature. Used to cut hard-to-machine ferrous and nickel-base materials up to 70 HRC. Second hardest material after diamond. See superabrasive tools.

According to Pat Nehls, product manager for Walter USA, solid tools produce more precise features, which makes them the preferred tool when finishes matter.

Single- or multiple-point precision tool used to bring an existing hole within dimensional tolerance. The head attaches to a standard toolholder and a mechanism permits fine adjustments to be made to the head within a diameter range.

“Obviously, since the indexable carbide portion is only a fraction of the size of a solid-carbide tool, the cost to produce this indexable end mill can be much lower,” explained Mitchell. “The true benefits of this technology are not in the cost, but rather in its performance.”

She added that digital components also can be damaged by high coolant pressures, so she recommends limiting these pressures to 500 psi.

“When the customer shows high performance increases, the cost of the carbide becomes less important,” said Nehls. “Ultimately, we are selling cost per feature. When a more expensive tool produces features at a lower cost, the customer is satisfied.”

“Some people that are newer to the industry don’t even know how to read a vernier scale,” Wise said. “So digital adjustment is becoming a lot more common.”

William Leventon is a contributing editor to Cutting Tool Engineering magazine. Contact him by phone at 609-920-3335 or via email at wleventon@gmail.com.

Once a boring tool has been acquired for a particular application, users should be aware of practices that will help get the most out of that tool. For example, Wise recommends that users make sure they’re removing enough material when boring to completely cover the nose radius of the insert. If this isn’t the case, she said, radial deflection or pressure will cause chatter, which in turn results in poor hole quality or surface finish.

He explained that stringy chips made of these materials can accumulate in blind holes where they are re-cut by the tool and often end up damaging the cutting edge.

“Then if they’re using them up too fast, they’ll call and I’ll say, ‘You should probably bite the bullet and get a diamond-tipped bar for those materials because they’ll last a long time,’” he said. “Even though they’re quite a bit more expensive, the (number of) parts you get out of them can be phenomenal.”

Indexable tools, on the other hand, have greater diameter tolerances due to the tolerance of the basic body as well as the tolerance of the insert used. For this reason, indexable drills are normally considered roughing tools.

While indexable inserts are certainly the tools of choice in many applications, shops aren’t necessarily choosing them over solid-carbide tools.

First, the end mill needs to be removed, reground, and placed back into the collet holder. Then the tool must be set up using a height gauge or tool presetter, before being placed back in the machine. Following this, a trial cut is typically performed and offsets calculated and entered into the control, before the tool can run.

Other best practices when using boring tools involve coolant-related issues. For one thing, it’s advisable to keep boring coolant clean.

In some cases, White pointed out that price considerations lead shops to the least expensive option: an uncoated boring tool. But when those customers cut metals like stainless steel and Inconel, Scientific Cutting Tools urges them to think longer term and opt for a coated tool. He reports that his company has had “great success” with a high-performance AlTiSiN coating called nACo, which provides excellent wear resistance and lubricity.

One of the commodities most affecting tooling suppliers, and the products they manufacture, is tungsten carbide. Over the past decade, tungsten carbide prices have risen sharply. In 2004 alone the price rose 500 percent. According to the Tungsten Investing News, however, the price is not only high when compared to a decade ago, it also has a tendency to fluctuate rapidly.

Another coolant-related problem can arise during the use of CBN-tipped boring bars. White said CBN is hard but also brittle, so big temperature swings can crack the material. To prevent this, there can be no interruption of coolant delivery to the tool during a boring process.

These tools can require “a good deal of technical knowledge to set up, run and make those final finishing adjustments,” she said. “So we (offer) digital adjustment instead of an analog vernier scale.”

Another key factor that comes into play when choosing a boring tool is the ratio of hole depth to diameter. If that number is high, Scientific Cutting Tools can provide boring bars with a helical flute, White said, which minimizes deflection during the boring process.

For boring operations, Allied Machine & Engineering provides two digital tooling options. One is a tool with a built-in digital component: a display fixed to the boring tool. As a user adjusts the tool’s finished diameter setting, the adjustments are shown on the display, Wise explained.

Reground tools have a shorter life, and predictability becomes much more difficult. A tooling “float” also must be created to ensure that tools are on hand when needed.

On the other hand, Nehls said that indexable drills have a tighter diameter tolerance band because of their assembled nature. Cycle time may be increased, but the cost per hole is generally lower. Ultimately, the requirements of each project guide tool choice.

In addition, Wise said her company’s digital technology makes it easier for operators to use boring tools.

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.

“That’s a lot of carbide … nearly the entire end mill is made of carbide. This is inefficient given the rising cost of carbide and the fact that only 3 or 4 percent of this tool is actually in cut,” said Mitchell. “The same evolution that happened with HSS and brazed tools is occurring rapidly now.”

China, which controls nearly all of the global tungsten trade (roughly 80 percent), has been holding a tight rein on its supply recently to keep the price of this rare-earth metal trending upward. These rising tungsten prices have made tool recycling more attractive and, in some cases, changed purchasing patterns.

White said machine shops cutting very abrasive nonferrous materials might get through 5,000 parts with a diamond-tipped boring bar compared with 10 or 15 with a solid-carbide bar.

When it comes to selecting the best boring tool for an application, some users are knowledgeable enough about the subject to request tools with specific features and characteristics. For example, Scientific Cutting Tools Inc. in Simi Valley, California, normally makes boring tools with a 2-degree front angle across the face that facilitates efficient cutting, said Sales Director Todd White.

In situations like this, she said shops can do two things. One is to make the pre-drill hole size a little smaller so more material is left for the finishing operation. If this can’t be done, the other option is to swap out the tool insert for one with a smaller nose radius while leaving everything else in the boring tool setup the same.

Due to its importance during boring and other cutting operations, better coolant delivery has been a focus of Scientific Cutting Tools.

“Solid drills have diameters ground to very tight tolerances,” explained Nehls. “When the drilled hole must be precise without additional finishing operations, the solid drill may be the best choice.”

Measure of the relative efficiency with which a cutting fluid or lubricant reduces friction between surfaces.

You probably know that boring tools are used to bring holes to the desired size and finish, straighten drilled and cored holes and correct casting defects. But you may not know what to do — and what not to do — to get longer life and better performance out of boring tools, as well as improve the user experience. This knowledge falls into three categories: tool selection, best practices when using the tools, and developments that have had a positive impact on boring tools and processes.

“In small-diameter boring with certain materials like 1018 steel, 316 stainless and 304 stainless, you can get really stringy chips,” White said. “So if you can get that coolant right to the cutting edge and keep it flowing, it could be really beneficial.”

“Over the last 20 years, we have seen a significant increase in recycling all scrap materials, including carbide,” said Nehls. “Customers are savvier with respect to their total production environment, and there is a lot of money in used carbide.”

The premise is the same: Use the tools, take them out of the machine, regrind them, reset the tool, and adjust the offsets. A reground solid-carbide tool will last 80 percent as long as a new tool. In most solid-carbide end mill applications, for example, the end mill takes a conservative depth of cut (0.100 in.), yet the tool may be 3, 4, or more inches long.

Because the end mill is screwed into a shank, the shank can be made of different materials to produce different results. For example, for a roughing operation, it is best to use a steel or other heavy metal shank.

But while shops always are concerned about price, “when customers come to us with a very important operation like finishing, it’s more important that the tool does what we say it’s going to do,” Wise said, as long as the extra cost is “within reason.”

So even though a solid-carbide bar costs $25 and a diamond-tip option costs $150, “your cost per piece is going to be way less,” he said.

Coolant delivery advances aren’t the only ones boosting boring operations. Allied Machine & Engineering, for example, has come up with boring tools that have a self-balancing feature. This automatic mass balancing is meant to compensate for imbalances that occur as the diameter of a boring tool’s insert holder is adjusted. The idea is to reduce vibration in order to optimize finish machining.

According to Walter USA Product Manager Pat Nehls, productivity, not price, should drive purchasing decisions. New coatings and high-performance tool designs are two examples of productivity-boosting technologies that can have a dramatic effect on performance.

“We need to have seals in place to protect the digital components,” said Wise, whose company makes such tools. “But really nasty coolant can eat up those seals and completely damage those components.”

To come up with the right boring tool for a particular application, White asks customers for basic information, such as the hole diameter, machining speeds and feeds and the part material. If the material is hard and abrasive, Scientific Cutting Tools can supply diamond- or CBN-tipped boring bars. Sometimes, however, he reports that customers dealing with such materials may start with conventional solid-carbide boring bars rather than pay extra for diamond- or CBN-tipped tools.

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“So a key is to get the chips out of there so you can ensure a good finish and not have any interference with the cutting edge,” White said.

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.

“When you have excessive vibration, it’s really hard on the customer’s machine as well,” she said. “So it’s a win-win when you include some type of vibration-reducing technology.”

Some operations may require solid tools when the hole diameter is less than the size range of indexable tools.

“When you’re done making the adjustment,” Wise said, “you just take that digital module off the boring head and you’re ready to go.”

Initial setup time is increased with indexable tools because the inserts must be loaded into the tool body. Subsequent tool changes can be more economical in terms of time, though, because resetting the tool length is not necessary when indexing the inserts.

“Reconditioned solid drills and mills must be reset after reconditioning due to the changed overall length and diameter,” said Nehls.

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.

Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.

The days of throwing worn tools away are over. Because only a small amount of the carbide is actually worn away during machining, inserts and solid tools should be kept as scrap and recycled.

Cost per feature is normally lower with indexable inserts because they have two or more usable cutting edges. Photo courtesy of Walter USA.

Substance used for grinding, honing, lapping, superfinishing and polishing. Examples include garnet, emery, corundum, silicon carbide, cubic boron nitride and diamond in various grit sizes.

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To improve coolant delivery, Scientific Cutting Tools has developed a toolholder featuring a ring around the tool shank. Instead of just directing coolant to a point at the tip of the tool, he said this ring produces a coolant “halo” that surrounds the entire tool.

New technology has enabled some cutting tool manufacturers to produce indexable end mills, which essentially are small end mills threaded into a shank. Photo courtesy of Tungaloy America.

“Solid-carbide end mills perform at their best when held in a shrink-fit holder, but removing a used solid-carbide tool from a shrink-fit adapter can be cumbersome and time-consuming,” said Mitchell. “An indexable end mill is simple to index; in fact, most indexes can be performed right on the machine in seconds.”

Rising commodity prices affect every facet of our lives; you only have to look at the price of incoming raw materials and fuel to see this is the case.

In addition to coolant delivery advances coming from toolmakers, White stressed the importance of the high-pressure coolant capabilities of current machines. Today, he pointed out that many machines are equipped with pumps that can produce coolant pressures ranging from 300 to 1,000 psi, which is a big help to tools and toolholders designed to get coolant to places where it will be most helpful.

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“If you’re running nasty, dirty coolant through the tool,” Wise said, “it’s going to get into internal components and start wearing them down more quickly.”

And, in an effort to control production costs, many tooling manufacturers now offer carbide recycling programs to reduce their dependence on new carbide purchases.

This works because CBN “can take a lot of heat, but it can’t take the big thermal change from hot to cold,” White said. “So as some people move toward dry machining, they’ll just shoot air through their lines to help with the chips. But that (prevents) that thermal up-and-down condition that can crack CBN.”

“Each tool type has its own features and benefits,” said Nehls. “For example, solid drills will typically produce holes to tighter tolerances, perhaps eliminating the need for secondary operations. This makes the solid tool the more economical choice anyway.”

Once again, in these applications “a lot of people will start out with coated carbide, and if they have a short run, that will get them through and give them a good finish,” he said. “But if the volume is high, then CBN is something to look at.”

After indexing the tool, an offset is not always required because the repeatability of these tools is very accurate. Setups are easier with this type of tool as well, because the location of the tool is predictable.

“Most of the time, when customers are looking at a finishing operation, they want a little bit of guidance,” said Natalie Wise, manager for finishing products at Allied Machine & Engineering Corp. in Dover, Ohio. The reason, she explained, is that “those are later operations in the manufacturing of their part, so it’s very critical that they get it right the first time. If something goes wrong with those finishing operations, they could be scrapping something very expensive that they’ve spent a lot of time on.”

The other digital option is the company’s 3E Tech display, a small module that can be mounted on a boring tool for diameter adjustment.

Many years ago high-speed steel (HSS) and brazed-carbide cutting tools were very popular. Today fewer and fewer shops make use of them, with solid-carbide and indexable tooling being the norm. One of the reasons for their waning use is that when a tool is at the end of its life-span, it is taken out of the machine and reground.

During production, indexable tools typically run at lower inches per minute (longer cycle time) than solid-carbide tools because they use a lower feed per revolution. However, the cost per feature will normally be lower because inserts have two or more usable cutting edge

“Today when an insert becomes dull, we simply index the insert and can expect relatively good repeatability and consistency,” explained John Mitchell, general manager of Tungaloy America. “Insert pressing and coating technologies advanced to where there are now major improvements in performance and chip formation. Few machine shops would want to go back to the days of HSS and brazed cutting tools. However, many shops continue to use solid-carbide tools.”

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For boring applications with depth-to-diameter ratios greater than 5-1, Allied Machine & Engineering offers Novitech, a mounted module that reduces vibration when machining hole diameters. Wise said this improves the surface finish of bored holes and increases tool life.

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New technology has enabled some cutting tool manufacturers to produce indexable end mills, which essentially are small end mills threaded into a shank.

Ability of the tool to withstand stresses that cause it to wear during cutting; an attribute linked to alloy composition, base material, thermal conditions, type of tooling and operation and other variables.

Essentially a cantilever beam that holds one or more cutting tools in position during a boring operation. Can be held stationary and moved axially while the workpiece revolves around it, or revolved and moved axially while the workpiece is held stationary, or a combination of these actions. Installed on milling, drilling and boring machines, as well as lathes and machining centers.

In some cases, however, “customers want to change that angle, so we make special tools for them based on their preferences and R&D that they have done,” he said. “For one customer, we make the front angle 8 degrees instead of 2 degrees because they find that works better for the materials that they cut.”

Although some shops know enough about boring tools to make specific requests of suppliers, the majority rely to some extent on recommendations from toolmakers.

According to Mitchell, these shanks offer a dampening effect, which improves roughing performance by enabling a heavier cut to be made. When finishing or an extended reach is needed, it is best to use a carbide shank.

Enlarging a hole that already has been drilled or cored. Generally, it is an operation of truing the previously drilled hole with a single-point, lathe-type tool. Boring is essentially internal turning, in that usually a single-point cutting tool forms the internal shape. Some tools are available with two cutting edges to balance cutting forces.

“The boring head is going to last a lot longer because it’s not vibrating,” she said, “so there’s not a lot of radial deflection or pressure.”

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