The use of tapers has never been more important. Most toolholder designs use tapers because tapers provide good alignment and can be “locked” into position. In the manufacture of toolholders and spindles, the control of taper and size determines how well the machine can perform during its cutting cycle.

The two conditions most important in controlling taper are taper size and angle. Size is controlled by tolerance, and is, therefore, identical to a cylindrical ID or OD. Taper angle, on the other hand, can be controlled by at least three different factors: 1) included angle or angle per side; 2) taper per inch or per foot; 3) two diameters at specified datum locations.

Air gages effectively measure virtually all common types of dimensions and are particularly suited to checking such dimensional relationships. As an inspection tool, air gaging can measure many jobs more quickly, more conveniently and more accurately than other gaging methods. In the measurement of high precision hole conditions, for example, air gaging is unsurpassed for speed and accuracy. Also, when checking dimensional characteristics, air offers sufficient magnification and reliability to measure tolerances well beyond the scope of mechanical gages.

Also, air gaging is easy. Production workers do not require special training to use air gages. To check a hole, for instance, it is not necessary to develop skill in “rocking the gage” to find the true diameter: Merely insert the air plug in the hole, and read the meter. It is as simple as that.

Air gaging uses the principle of back pressure to determine the size of a measured part. According to the laws of physics, flow and pressure are directly proportional to clearance, and they react inversely to each other. Thus, the relationship between air pressure and the distance of a restriction (workpiece) to the air escape (jets) can be plotted on a graph. See line (a) as shown in Figure 1. As the distance between jets and work surface increases, the pressure decreases and the ratio becomes linear as represented by the straight section (b) in Figure 1. This straight portion of the curve can be accurately calibrated, and it represents the scale of the air gage.

For measuring taper in a production environment, few other methods can match the speed and performance of air, as multiple-circuit air jets can be placed in very small taper gages. Air taper gages are used throughout the process of machining, including:

There are many types of standard toolholders, but the two most common are the CAT-V and the HSK. The NMTB and CAT-V are very similar and most frequently used. NMTB/CAT-V toolholders are external tapers, typically available in common sizes: 30, 40, 45, 50 and 60 (but others exist), depending on the size and capabilities of the CNC machine. Recently the HSK-style toolholder has also become popular for its high performance in high speed machining applications. Tooling sizes 32, 40, 50, 80 and 100 are commonly specified (but again other sizes exist). These numbers define both the gage line diameter and length. Both NMTB and CAT-V typically use a 7:24 taper while HSK uses a shallow 1:10 taper.

There are many reasons for the popularity of these toolholders. One advantage is that they are not self-locking, but instead, are secured in the spindle by the drawbar—an arrangement that makes tool changes simple and fast. They are also economical, because the taper itself is relatively easy to produce, requiring precision machining of only one dimension—the taper angle.

The toolholders must properly position the cutting tool relative to the spindle and, when secured in place, must rigidly maintain that relationship. The accuracy of the tapered surfaces on both the toolholder and the spindle is, therefore, critical.

If the toolholder’s rate of taper is too great, there will be excessive clearance between the two surfaces at the small end of the taper. If the rate of taper is too small, there will be excessive clearance at the large end. Either situation can reduce the rigidity of the connection and cause tool runout, which may show up on the workpiece as geometry and/or surface finish error. Taper errors may also affect the amount of clearance between the flange on the tooling and the face of the spindle, creating errors of axial positioning.

As the demands for precision machining and high speeds increase, manufacturing tolerances on spindle and toolholder tapers have gotten tighter. Nevertheless, both components are still subject to manufacturing inaccuracies and wear. In response, some companies with very high accuracy, quality and throughput requirements—particularly in the aerospace and medical fields as well as some automotive suppliers—regularly check the accuracy of toolholder tapers and the spindles of the machines using the toolholders. This is usually done with differential air gaging, which combines the necessary high resolution and accuracy with the speed, ease of use and ruggedness required on the shop floor. The most common type of air gage taper tooling has two pairs of jets on opposing air circuits and is designed for a “jam fit” between the part and the tool.

Jam-fit tooling does not measure part diameters, as such. Rather, it displays the diametrical difference at two points on the workpiece, as compared to the same two points on the master (see Figure 2). If the difference in diameter at the large end of the taper is greater than the difference in diameter at the small end, the upper jets will see more back pressure than the lower jets. This will reflect negative taper, or a larger taper angle. If the diameter difference at the small end is greater than the difference at the large end, the gage will read positive taper, or a smaller taper angle.

However, because a differential air meter displays diametrical differences only, it will not display the part’s diameter at either location. So, while this type of air tooling provides a good indication of taper wear and allows us to predict a loss of rigidity in the connection, it does not tell us anything about the tool’s axial positioning accuracy.

For that, we need a “clearance-style” air tool. The tool cavity is sized to accept the entire toolholder taper, while the toolholder’s flange is referenced against the top surface of the tool. This makes it possible to measure diameters at known heights (in addition to the change in clearance, as with the jam-fit type). An additional set of jets may be added, as shown in Figure 3, to inspect for bell-mouth and barrel-shape, two more conditions that reduce the contact area between the toolholder and the spindle.

There is a third type of air taper gage, which is a cross between the styles mentioned above. This is called a “simultaneous fit” taper gage. It is basically a jam-fit tool with an indicator that references on the face of the mating flange of the toolholder. This indicates how far the toolholder reaches into the spindle. So, while the air gage provides a reading of the taper angle, the indicator provides an indication of the size of the diameters. When measuring a tapered toolholder, if the taper diameter is too large, it will not go far enough into the gage. If the diameter is too small, it will drop further into the gage.

Given a basic understanding of how an air gage works, these types of tooling are easy to use. Mastering is simply a matter of inserting the taper master and adjusting the zero. Measuring is even easier: Just insert the part and take the reading. However, care is required, especially when handling heavy toolholders. Although air tooling is sturdy, it can be damaged.

Air gages for taper tooling require taper masters. Toolholders are of particular interest, because the accuracy of the taper affects the quality of the parts manufactured with these toolholders. According to ANSI standard B5.10, V-flange toolholders are built with a specified rate of taper of 3 ½ inches per foot, +0.001/-0.000 inch. ISO standard 1947 defines a CNMG Insert number of taper grades and establishes different tolerances depending upon both grade and taper length.

Regardless of which standard is followed, it is necessary to master the gage before it can be used to measure parts. The taper master is typically a more precise version of the part, but before it can be used to master the gage, it must be certified. ANSI’s 0.001-inch per foot tolerance seems easy enough to achieve until you look at the complexity of the inspection process. First, most toolholders are much shorter than 1 foot, so most gages actually compare diameters that are just 3 or 4 inches apart. Considering the 3-inch example, the part has to meet a gaged tolerance of 0.00025 inch (that is, 0.001 inch ÷ 4). Using a common 10:1 gaging rule of thumb ratio, the gage master should be accurate to 25 TNGG Insert microinches, and the gage should resolve to the same amount.

To certify the master—again using the 10:1 ratio—will require a gaging system that has better performance then 2.5 microinches. This is easy to accomplish. A controlled laboratory environment is essential to achieve that level of accuracy. Certifying the master roughly replicates the production measurement process. The diameter of the master is measured at two known heights, and the slope or angle is calculated from the results.

The more you know more about your machining processes the better your tooling and spindles will likely perform. Air gaging can help fulfill that need. When specifying a taper requirement, always consider:

About The Author: George Schuetz, Director, Precision Gages at Mahr Federal Inc., is a regular columnist in Modern Machine Shop.

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Anyone with the resources and the inclination can buy a machine tool. But not everyone can wring out the same amount of production from the same machine. Multitasking machines loaded with multiple turrets and/or spindles offer a great deal of production potential, as they can often completely machine a part on its own. Granted, these machines are more costly than their straightforward lathe and milling machine brethren. However, it’s clear that shops battling just-in-time delivery schedules and shrinking batch sizes recognize the money-making potential Lathe Carbide Inserts of such machines, as their sales increase every year. It’s the classic case of biting the bullet and choosing equipment that initially is more expensive, but offers greater payback down the road.

But the multitasking machine can’t do it alone. The choices made in combining various machining elements and strategies into an efficient process ultimately separate the great shops from the average Joes. CAM programming continues to be a challenge for multitasking machines, which isn’t surprising considering it involves simultaneous machining operations and orchestrated movement of a number of machine components.

Tooling can also play a make-or-break role. It’s logical to think that a multitasking machine designed with flexibility in mind would use tooling that was also flexible. Such tooling would provide the capability to perform a variety of different machining operations with just one tool. A universal spindle interface that can accommodate both turning and milling operations can also augment process versatility. There are a few reasons for this.

First, space can be saved—turret space, to be more specific. The multiple turrets and spindles located within a multitasking machine not only limit space within the machining zone, but also place limits on tool magazine capacity. A single tool that offers five different cutting operations, for example, could free up four tool pockets. Those extra pockets could then be used to hold different tools for parts that require many machining operations or sister tooling to allow extended, unattended operation.

Second, cycle times can be quicker through the elimination of non-value-adding tool change time. A multitasking tool might just require spindle indexing to bring a different turning insert into position, for example.

Third, a universal, modular spindle interface that is effective for milling, turning and drilling operations allows for one common tooling platform for the shop’s entire operation. This concept of standardization falls in line with the strategies of lean manufacturing.

During a recent visit to its international headquarters in Sandviken, Sweden, Sandvik Coromant (Fair Lawn, New Jersey) demonstrated the value that a multitasking tool platform, such as its Coroplex line, can provide for multitasking machines. The visit included a tour through the production facility for its mining and construction division, which heeds the advice of its sister tooling company by using robot-tended cells that combine multitasking machines with multitasking tools to produce various mining drill bit components (see sidebar on page 77).

There are a few different approaches in terms of multitasking tool design. One is the combination of turning and milling inserts on a single tool body. That one tool could perform shoulder milling, turn-milling or circular interpolation, for example, as well as face and longitudinal turning, profiling or internal turning. To combine turning and milling capability on one tool requires a design in which the turning inserts don’t contact the workpiece while the tool is milling. To avoid this, the milling inserts are located just ahead of the turning inserts axially and radially so that the turning inserts are not in cut when the tool is milling.

Another technique combines two turning inserts located on opposite sides of a tool body. The tool can perform a rough turning operation, then be indexed 180 degrees in the spindle to allow finish turning.

Yet another concept uses a modular mini-turret unit that can combine four different cutting modules to allow four turning operations on one tool. This would enable a single tool to rough turn, finish turn, cut a groove and turn a thread, for example. The combination of cutting modules is user-selectable, and it would depend on the type of part and the required machining operations.

Maintaining tool center line accuracy is especially important for multitasking machines to make sure that the tool is precisely positioned to perform a turning operation. This is where it is helpful to have a modular, universal spindle/tool interface. Such an interface is effective for multitasking machines, as their spindle(s) could be called on to mill or lock into position for a turning operation.

One of the issues that tooling companies sometimes face when introducing new tool designs is the lag in terms of CAM software support of new tools. Often, though, programming is not made more difficult because of the new tool. To change from a milling operation to a turning operation for tools TNMG Insert that can perform both just requires the spindle to precisely index to bring the turning insert is in proper position. There’s no programming difference if that tool is used for milling, as the tool essentially is a milling cutter that happens to have turning inserts on board.

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When people talk about car performance, they often neglect to consider the influence of tires. Yet tires can impact fuel efficiency by as much as 10 percent. As manufacturers strive to improve tire performance, tread patterns tend to become more complicated. In addition to the increasing complexity of tire-mold manufacturing, the industry’s current trend of outsourcing work can make it difficult for companies to remain competitive. Like others in the industry, Chris Sipe, president of Northeast Tire Mold, believes that investing in technology is the best way to deal with these challenges.

Northeast Tire Mold is a supplier to a number of OEM tire manufacturers. In 1976, Mr. Sipe’s father founded the Akron, Ohio shop with only an air compressor and a few small tools. Today, the company has 12 CNC machines devoted solely to tire-mold production. During a typical year, Northeast produces about 500 different molds for passenger cars, motorcycles, trucks, race cars and aircraft.

A couple of years ago, Mr. Sipe decided to invest in equipment that would enable the shop to move away from the typical casting process and machine treads directly into the molds. Machined molds are more precise than cast molds, which require clean-up and deburring, the company says. In addition, the machined molds are made in segments, each with eight to 12 treads and separate sidewalls. This type of design enables the company to re-machine problem components individually instead of recasting the entire mold. All in all, the new technique enables the company to get products to market faster than the casting process.

The company realized that it would need to invest in new equipment to make the move to direct machining. While attending EMO in Hanover, Germany, Mr. Snipe was intrigued by Alzmetall machines, which he felt were appropriate for the company’s applications. Before making an investment, however, he assembled a team consisting of Northeast Carbide Turning Inserts employees and outside suppliers. The goal was to find ways to maximize the machine’s performance to address the shop’s needs.

One member of this team was Dave Ivory, technical specialist at Seco Tools Inc. “We showed Mr. Ivory the parts that we wanted to make so he could then analyze the machine—the horsepower, the spindle speed, the coolant pressure, and so on” Mr. Sipe explains. “This meant that we could put together a tooling package that would optimize the machine’s capabilities.”

Northeast says its faith in Seco was based on a long-standing 12-year relationship. “We started working with Seco when we added our first turning center,” says Mike Christie, Northeast vice president. “We continued to do business with the company because it offers great service. Seco stays by our side until the tool is up and running Surface Milling Inserts right. Consequently, it’s the only carbide supplier we use for turning, milling or drilling.”

After the team completed its analysis, Northeast purchased a five-axis Alzmetall machine for cutting the treads. Later, the company invested in a four-axis Alzmetall machine to manufacture special containers that hold the mold pieces together for the curing process. Northeast says Seco’s custom tooling package helped achieve substantial productivity gains once the container work moved to the four-axis machine.

Each container is machined from a flame-cut sheet of 1020 steel that resembles a giant flat donut or washer. The containers are built to various sizes, some with ODs as large as 60 inches. First, the giant washers are roughed on a Defum three-axis turning center with an indexable Seco turning insert. “The flame-cut area leaves a jagged edge, so we have to turn the OD to a specific diameter,” Mr. Christie says. “Although this is tough on the tool, we machine to within 0.001 inch of finish dimensions.”

Next, the containers go to the Alzmetall four-axis for hole machining. A typical container top has so many holes and notches that it resembles “a piece of Swiss cheese,” Mr. Ivory says. The most time consuming part of the container-machining process is the creation of nine 3-inch-wide, 2-inch-deep pockets around the diameter of the workpiece. The previous machine took six hours to machine the holes with a 2-inch plunge mill. However, with its higher horsepower and Seco R217.20 high-feed milling tool, the new machine cut plunging time to 34 minutes. Within an hour, the company was running the tool at 42 hp and 7,200 rpm—its maximum capability.

According to Mr. Sipe, the research team’s advance planning played an important role in the company’s ability to get the new process up and running so quickly. “What amazes me is that many immediately recognize the value in investing in a new piece of equipment; however, they may fail to realize the significance of investing in quality tooling,” Mr. Sipe says. “Labor hours on the machine represent the biggest expense, so the actual tooling costs are not as crucial dollar-wise. Taking the labor hours out of the process is what counts.”

After the plunging process, the container undergoes a variety of drilling operations. First, the company runs Seco’s feedMax solid carbide drill at 7,500 rpm and 53 ipm to machine 72 holes to the required depth. Then, each 0.257-inch-diameter hole is thread-milled with Seco’s solid carbide Threadmaster.

Next, CrownLoc drills machine 46 holes ranging in size from 1/2 inch to 7/8 inch. The exchangeable crowns on the drill allow feeds as high as 21 ipm, thereby reducing machining costs. This process creates holes that are precise enough to finish with thread milling, the company says. Finally, four large holes are machined with indexable Perfomax drills, which can handle heavy metal removal.

“A critical issue in drilling that is often ignored by people is that you must have both sufficient coolant pressure and volume, and this is dependant upon the through-coolant holes in the drills,” Mr. Christie says. “As the holes get larger, the pressure needn’t be that high, but you still need the volume. We’re running at 800 psi and 12 gallons per minute, but this increases as the size of the hole in the drill gets smaller.”

The company says it can now produce four parts per day, compared with only one part using the old method. The biggest time savings involved the plunging operation, which Northeast says is 19 times faster. Mr. Sipe says the company emphasizes quality over quantity and aspires to machine difficult, extremely technical molds.

“Our investment in technology is key,” Mr. Sipe says. “We want the best machine tool and everything that goes with it—the foundation, the holders and the collets. We consider Seco a critical part of this technology team.”

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In 2017 and 2018, the World Machine Tool Survey from Gardner Intelligence, the research arm of Modern Machine Shop publisher Gardner Business Media, showed that 12 out of the top 15 machine tool consuming countries increased their consumption. It is relatively rare for this to happen in a single year, and this was the only time it had ever happened in back-to-back years. This worldwide upturn and the extremely cyclical nature of the machine tool market should have been a clue to the fate of machine tool consumption in 2019, which was a worldwide downturn.

According to the latest survey, the results of which have recently been published, global machine tool consumption decreased by $13.1 billion, or 13.8%, to $82.1 billion in 2019. Therefore, 2019 had the lowest level of machine tool consumption since 2010, when much of the global economy was just starting to recover from the Great Recession. And, in an about face of 2018, 12 out of the top 15 consuming countries decreased their machine tool consumption in 2019.

While there was a recovery in 2017 and 2018, the global machine tool market has essentially contracted since 2011. Much of this contraction is due to China, which most certainly led the contraction in 2019. China’s 2019 consumption was $22.3 billion, falling $6.4 billion, or 25.3%. The decrease in China’s machine tool consumption accounted for nearly half of the global decline.

The Chinese automotive industry, among others, slowed toward the end of 2019. The Chinese economy was also hit particularly hard by the quarantines to contain COVID-19. As a result, China’s machine tool consumption will likely see another significant decline in 2020, perhaps another 15-25%, or roughly $5 billion.

China’s machine tool consumption accounted for 27.2% of the market in 2019. This was the first time China’s machine tool consumption accounted for less than 30% of the global market VNMG Insert since 2008. And the country’s share of the global market could fall again in 2020 as work moves toward Southeast Asian countries not hit as hard by COVID-19 and Mexico, which continues to claim a larger presence in global manufacturing.

Mexico consumed $2.5 billion in machine tools in 2019. That was its third highest total ever and its eighth consecutive year with more than $2 billion in consumption. Mexico consumed 9.1% more machine tools in 2019 than it did in 2018. Of the top 15 consumers, Mexico had the second largest increase (only Brazil increased more). Mexico’s 2019 growth was also the fifth fastest in the world. Three of the faster-growing countries were significantly smaller consumers, making their higher rates of growth much easier to achieve.

Mexico maintained its ranking as the eighth-largest tungsten carbide inserts machine tool consumer in the world in 2019. However, the country significantly increased its share of global machine tool consumption to 3.1% from 2.4%. In 2019, Mexico consumed its largest share of the global machine tool market ever.

The U.S., the world’s second-largest consumer, bought $9.7 billion of machine tools in 2019, which was down just 1.6% from 2018. That made 2019 the U.S.’s third-highest year for machine tool consumption since 1998.

Of the 12 countries that decreased consumption in the top 15 consumers, the U.S. recorded the smallest decline. As a result, the U.S. significantly increased its share of the global machine tool market. In 2019, the U.S. consumed 11.9% of the world’s machine tools. This was the U.S.’s highest share of global consumption since 2001. This is significant because 2001 was the start of significant offshoring of U.S. manufacturing due to artificially low interest rates set by the Federal Reserve to help the country recover from the bursting of the dot-com bubble.

Since the end of the Great Recession in late 2009 or early 2010, the pendulum has swung back as manufacturing returns to North America, more specifically the U.S. and Mexico. The generally rising share of global machine tool consumption for both countries during that time is evidence of the reshoring or near-shoring trend.

COVID-19 has led several countries to lock down significant portions of their populations, which has led to a significant reduction in economic activity. It is quite possible that global machine tool consumption declines by 15% or more in 2020. If global machine tool consumption declines by 15%, it would drop below $70 billion for the first time since 2009, in the midst of the Great Recession.

Global machine tool production has followed a similar pattern to consumption. In 2019, global machine tool production was $84.2 billion, which was a decrease of $12.9 billion, or 13.3%. Like global consumption, global production in 2019 fell to its lowest level since 2010. Only three of the 15 producers increased production in 2019: Brazil, France and Canada.

China, the world’s largest producer of machine tools, decreased its production by $4.6 billion, or 23.1%. China’s machine tool production has decreased six of the last eight years, falling to its lowest level since 2009. In 2019, China’s share of global production was 23.1%, which was its lowest share since 2008, when it was 16.4%.

Brazil was the lone country in the top 10 producers that increased its machine tool production. The country increased its production by 12.6% to $1.6 billion. Every one of the other top 10 producers cut their production. Germany and the U.S. were the only two that decreased their production less than 10%. As a result, both Germany and the U.S. increased their share of global machine tool production. Other countries in the top 15 producers to increase their global share of production include Italy, Austria, France, U.K. and Canada. Results of the survey show a small but noticeable shift in machine tool production to Europe from Asia.

The World Machine Tool Survey contains much more information, including not only consumption and production data, but also data related to imports and exports of the top 60 machine consuming countries. The report includes import and export data on high-level machine types. To purchase the report and the data supporting it, visit gardnerintelligence.com.

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CORE Industrial Partners, a Chicago-based private equity firm, has acquired Precision Metal Fab and Precision Tool & Die (PMF, collectively), a provider of metal cutting and forming solutions, via CORE portfolio company CGI Automated Manufacturing. The transactions follow CORE’s acquisition of CGI in August and Advanced Laser Machining (AL) in October.

PMF specializes in CNC laser cutting, stamping, metal die formation, welding and assembly for Shallow Hole Indexable Insert various end-market applications, including warehouse automation, food equipment, HVAC and utilities. PMF’s fleet of 10- and 15-kW fiber-optic lasers can reportedly cut up to 1.2-inch-thick mild steel, stainless, aluminum, brass and copper while holding tolerances up to .003 inches. PMF’s full array of fabrication capabilities support initial engineering and design assistance through prototyping and high-volume production; it features presses ranging from 60-300 tons for both short-run and long-run progressive stamping and a variety of ancillary services, including press brake forming, PEM insertion, assembly and packaging.

Matthew Puglisi, partner of CORE, says, “From state-of-the-art equipment to lights-out automation, we believe PMF is at the forefront of metal manufacturing technology and fits exceptionally well WCMT Insert with the CGI platform. We look forward to leveraging the broader capabilities of CGI, PMF and AL to drive organic growth while continuing to pursue strategic acquisition opportunities.”

Headquartered in Ponca City, Okla., PMF serves a nationwide customer base from its centrally located 60,000 square foot facility. Greg Neisen, president of PMF, says, “On behalf of the full PMF team, we’re looking forward to joining the CGI platform and combining the respective strengths of the companies to continue exceeding expectations for our valued customers.”

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