“What most people do, they’ll take a scale, a ruler let’s say, and they’ll say ‘I’ve got this sticking out 4"’,” Holden said. “They’ll put a magic marker mark on the shank of the cutting tool (and use that to set the tool). And that’s good enough. They might bring it to a standalone presetter at that point and take their final Z dimension and that’s all they’re looking for. Now that’s not very sophisticated, admittedly.”

“Presetters are another expense, though, so it’s a tradeoff,” he said. “Are you saving more money by saving that time or are you not able to offset that?”

“With a lot of the harder materials, Inconels and titanium, a higher grip force is needed so the tool doesn’t spin inside the holder,” said Matt Brothers, Industry 4.0 Tech Center manager for Zoller Inc., Ann Arbor, Mich.Consistency in setup among operators is the No. 1 draw for shrink-fit toolholding, according to Holden. “To put a cutting tool in a toolholder in a shrink-fit chuck [is the same] if you are working in a shop for two weeks or 20 years,” Holden said. “Whereas if you’re using a collet chuck or other systems, the guy who’s been working there forever, he’s an expert. He knows how to clean out the collets, he knows exactly what to do to get the runout and the better performance while the new guy needs time to get up to speed. In the meantime, you have inconsistent production.”

The brazed ceramic tip end mill is capable of machining five to 10 times faster than a carbide tool when machining heat-resistant superalloys like Inconel 718. For example, while a solid-carbide tool might reach 100 to 150 sfm, the new brazed tip tool can reach speeds of 400 to 900 sfm. “Of course because it’s a brazed tip rather than solid ceramic, the cost of the tool is much lower,” Strauchen pointed out.

Forget about using the blow torch to get the holder hot enough to accept the tool, said the experts. The common method for applying the kind of heat needed is to use the electromagnetism of an induction coil.

One big problem that all-in-one machines can create, however, is a line of idle workers. “Sometimes having two machines in one might not be advantageous if someone is clogging up the machine and all you need is a quick in and out of a shrink-fit drill,” Holden said. “It’s holding you up.”

“The biggest challenges our customers face are location and part variation, which can occur for a variety of reasons, including tool and process failure, uneven surfaces or drilling difficult configurations or drilling at angles,” said Gary Brown, president of Heule Tool. “The majority of our tools are compensation tools, meaning they are spring loaded or activated by centrifugal force. They perform processes like back boring, back machining, back chamfering, compensating, counter sinking and combination drilling. Products are available to handle all types of materials, including nickel-alloys all the way down to brass, bronze and composites.”

In addition to using height indicators and risky touch-offs that can damage the tool in lieu of a presetter machine, Janson said he’s seen one operator place a piece of paper between the tool tip and workpiece. As he lowers the tool, he knows he’s reached the correct height when he can’t pull the paper away.

Yet another reason for using shrink-fit toolholding is its compatibility with automated operations, said Ron West, senior product manager, marketing for Kennametal Inc., Pittsburgh. As a result, he sees customers using shrink-fit to facilitate lights-out operations.

One factor behind the rise in the popularity of shrink-fit toolholding is high-speed machining, also known as high-velocity milling, said Olivier Branget, application engineer for tooling systems, Seco Tools LLC, Troy, Mich.

Along with advanced technology for heating and chilling, some operators favor using a shrink-fit unit that is designed for presetting. And presetters are favored by shops running specific types of machine tools. “The people who really gravitate to those machines (presetters) are those with multi-spindle machines,” Holden said, noting there are milling machines with two or four spindles as well as single-spindle machine tools. “All four spindles are running the same program at the same time. So, they need to make sure all four of the tool angles are the same on the Z axis.”

“I know places do that, but I’d be concerned about changing the material structure of the holder,” said Alec Janson, product engineer II, OSG USA Inc., Irving, Texas, about quenching the holder. “Not that it would be too much but you’re dealing with something that’s supposed to be precision equipment.”

Janson said his criteria for whether to use a presetter depends on the application, the tool size, the level of precision required and the need for speed in production.

“The real limitation in machining efficiency is that when you produce a chip it has to go someplace,” he said. “If the volume of the chip is more than the flute can handle, pressure will build behind the cutting edge and breakage or crashes can result.”

GWS Tool Group, Tavares, Fla., has introduced a new Ti Feed mill specifically for machining titanium. Not yet released but coming in the fall is a combination solid-carbide tool with brazed ceramic milling head for high-feed milling of high-temperature alloys like Inconel 718, according to Drew Strauchen, executive vice president.

Solid-carbide round tools cover a wide range of applications, including drilling, milling, as well as reaming and threading. The newest product innovations, however, are opening eyes in job shops and production shops to their capabilities in finish machining. New end mill and drill product lines are coming out almost daily that improve machining processes for the more mundane applications in cast iron and steel to the increasingly complex demands of titanium, stainless steel and heat-resistant superalloys (HRSA). Following are suggested approaches by leading suppliers to finding the right tooling match for a variety of applications.

“You can’t walk into an aerospace shop without seeing titanium and stainless steel everywhere,” Clynch continued. “Our new carbide grades allow us to run much faster for machining those material types. For example, the Ti-Turbo end mill machines titanium at 250-300 sfm, compared to normal cutting speeds of 140-160 sfm. Heat is a critical consideration when machining with carbide. When we engineer new carbide substrates, we’re looking for ways to remove as much cobalt content as possible within the substrate because cobalt melts at high temperatures and studies have shown that wear rates increase as cobalt content is increased.”

“Like many industries, the aircraft industry has transitioned to using more five-axis machining centers to produce parts like turbine blades,” Strauchen continued. “The combination of five-axis machines and fixturing is often not conducive to certain types of roughing, where you would traditionally take the whole length of the cut of the tool and use a trochoidal milling path to rough out the material. That’s a very efficient way to rough but a lot of machining environments, especially five-axis, don’t permit that style of machining and require Z-level machining tool paths instead.”

“Presetting is especially important when using reconditioned tooling because the reconditioning process takes a little off the length. Having a good tool management system that uses reconditioning creates the possibility there could be duplicate cutting tools in different reconditioning cycles and therefore different tool heights. Presetting the tool heights eliminates the differences and promotes accuracy.”— Ron West, senior project manager, marketing, Kennametal Inc.

Some manufacturers make machines that combine shrink-fitting with presetting. There are pros and at least one con to these. A combination machine requires only one cost justification to the bean counters vs. having to justify the price of two machines. A combination machine can also take up less floor space than a standalone shrink-fit unit and presetter would.

Horn’s multi-flute end mills for machining titanium, Inconel, stainless and other high-temperature resistant metals benefit from high-speed and high-efficiency strategies. The highest MRR possible in high-speed machining with multi-flute tools happens when the process engages the full flute length of the tool. “The more flutes, the larger the core diameter of the tool needs to be for rigidity,” he said.

Changing the material properties of the toolholder isn’t the only concern. “What we found is [that with] unevenly cooling the tool, shocking the tool, there could be some negative effects,” Holden said, adding that he’s also seen operators pick up a heated toolholder and place it in sand to cool. “[It] could actually induce runout. You want to have even cooling. It’s important.”

If the same tool is going to be used over and over and there is concern about clearance, shops should shrink-fit and preset the holder, then insert a backup screw for a repeatable Z axis, Holden advised. Haimer, Seco and Zoller machines also have a rod the operator can insert through the center of the toolholder that functions just like the backup screw.

Advanced CAM programming enables milling strategies that include high-speed milling, high-efficiency milling, optimized roughing and proprietary CAM software. “In the past, for a pocketing application you might use a two- or three-flute end mill. Now you can use a high-performance drill to start the hole and trochoidal milling to complete the pocket. You couldn’t do that before the control system and CAM were up to snuff,” Tonne explained.

Chip evacuation is a major limiting factor in drilling that is being addressed by twisted coolant-through holes, according to Cline. “The twisted coolant holes allow for deep chip gullets with plenty of room to evacuate chips while maintaining a very large and strong core,” he said. “The rigidity of solid carbide allows increasing the length-to-diameter ratios of solid-carbide tools to 20, 30, 40 and even 50 times diameter—ratios unimagined in the past. You wouldn’t see this in the past because if the carbide was tough, it had no wear resistance and if it had wear resistance it was so brittle that it would deflect and break.

There are three features of OSG’s AE-H ball nose end mills that make them ideal for machining hardened steels and die/mold applications, according to Minhas. “The first feature is the high precision radius tolerance of two-tenths that is very important for surface finish and reduces polishing time. The second feature is its unequal index, which reduces vibration. And the third feature is the variable rake angle, meaning that it’s not the same rake angle from the tip to the main diameter.”

“It certainly is growing in popularity,” said Brendt Holden, president of Haimer USA, Villa Park, Illinois. “We’re seeing more and more companies adopt the shrink-fit technology. Initially it started with [some] die mold [and] some high-speed machining applications that aligned with aerospace or medical-type work. What we’re seeing now is shrink-fit in the general machining markets.” This includes automotive production facilities, sub-suppliers of parts and the general market. “Shrink-fit is fast and reliable but if it wasn’t providing better toolholding in the machine tool, where the machine tool can run more efficiently, we wouldn’t even be talking about it,” he said.

The following are tips and tricks of the trade, shared with Manufacturing Engineering by the experts.

For those who operate single-spindle machines, 90 percent of them just want to make sure when they put the cutting tool in that they have clearance between the nose of the toolholder and the tip of the cutting tool edge, Holden said.

Ti Feed end mills are available in coolant-through and solid configurations in 3/8-1" (9.53-25.4 mm) sizes with the most popular being ½" (12.7 mm). “Z-level processing engine parts with the Ti Feed mill taking a lot of light cuts doesn’t produce a lot of torque or load on the workpiece,” Strauchen said. “Ti Feed end mills take advantage of radial chip thinning, wherein higher feed rates can be realized with lighter depths of cut to rough parts to near net shape. The optional coolant-through capability dramatically improves thermal resistance, which is critical in machining titanium alloys.”

“With longer drills the designs are changing,” Cline continued. “For our 20×D, we’ll have four margins down on the bottom. When the first part of the drill is engaged, it has four margins and two of the margins will drop off as you go up the drill body and it’ll be a double-margin drill. Also, you’ll see designs where the gullets have been increased due to the strength of the substrates. The helix ratios will change and the core diameters will change when drilling really deep (20×D). The chips come up the body and we’ll alter the inside diameter of the core to facilitate ejecting them.”

OSG also has a laser mounted in one of its machines that will do automatic tool touch-offs. “It’s kind of like the presetter we have, it’s just within the machine,” Janson said. “It’s used in the same way but a little bit quicker and less manual.”

What are the main drivers in milling? “That is the first question we ask and one that has multiple answers,” he said. “Machining costs (productivity), tooling costs (cost per edge), and tool change costs (tool life) are three considerations for determining the impact that a cutting tool can have on cost per unit (CPU) in a manufacturing environment. We simply inform the end user to pick two of the three drivers because achieving all three simultaneously is practically impossible. Once we know the drivers that the end user needs, we choose specific tooling from three product areas: high-performance; standard (or legacy type, standard flute/helix design); and a newly introduced general-purpose product.”

“This is a really important aspect of shrink-fit,” said Kennametal’s West. “The rapid, controlled heating of the toolholder has to stay within the limits of the material from which the adapter is made. Exceeding the maximum temperature will jeopardize the integrity of the adapter, which in turn reduces grip and runout. It takes its toll on tool life.”

The two-in-one machines may also be a boon to speed, accuracy and safety. “You’re going to get more setting accuracy in the tools, you’re going to have a faster preset cycle time, and it’s also a safety thing as well because you’re not handling any sharp objects,” said Zoller’s Brothers. You’re not taking the chance of dropping these heavy tools if one was to have shrinking and presetting done separately.”

Haimer and Zoller have an intelligent coil that can sense the distance from the inside of the coil to the outside of the chuck so it doesn’t exert any more power than needed to heat the holder.

Horn’s DSFT end mills—part of the DS line of high-DOC, low-radial-engagement tools—are designed for the consistent chip thinning required to get the maximum advantage out of these strategies. “With an end mill, you are normally looking at radial chip thinning, unless it’s a ball nose where you have radial chip thinning and an approach angle,” said Tonne. “Radial chip thinning requires a very accurate system or you’ll lose your advantage and chip or destroy the tool. There’s a balance between how many flutes you put on a tool, how fast you need to go, and the volume of chips that are going to reside in that flute. Typical for a half-inch mill, you would look for a five-flute end mill for trochoidal milling of gummy materials.”

Another failsafe method uses RFID tags. “We check the tool, we write the information to the chip,” Brothers said. “Then we place the unit into the machine tool and it transfers the information when it’s ready to use the tool. Usually in high production [applications], companies use RFIDs just for the sake of repeatability and to decrease errors. So, they don’t have to come back after making a few parts and quality control comes and says ‘this part’s oversized.’”

Solid-carbide round tools have seemingly been around forever; before them, high-speed steel (HSS) tools ruled the roost, and after them a growing selection of alternative processes like indexables, EDM, waterjet and now additive manufacturing emerged as competition.

Today’s advanced solid-carbide drills feature modern carbide substrates, coatings, edge preps and updated software for grinding machine capability that allows putting different styles of grinds on the drills, according to Patrick Cline, national holemaking product manager, Iscar USA. “The trend with solid-carbide drills is to machine materials in the hardened rather than in the soft state before heat treating,” he said.

“If your toolholder loses its shine and becomes black and dull instead after repeated shrinking, it was probably made of inferior material.” — Brendt Holden, president, Haimer USA

The AE-H ball nose end mill has OSG’s Durorey multi-layer coating on the substrate. Coatings are super heat resistant with an ultrafine nano structure and a special strength medium for long life, fine finish, and process stability, according to Minhas.

Brothers’ company also has another product option called »zidCode«, which prints out a QR code that the operator can scan for the offsets that will input the information in the table as well. “That’s growing in popularity,” he said. “It’s quick data input and you’re eliminating data transfer errors.”

Not only could runout be induced with uneven cooling, the tool also could be sentenced to an early death. “You’re changing some of the makeup of the holder and you could decrease the life of the tool,” Brothers said.

Enabling high-speed machining, in addition to holders with stronger clamping forces and reduced runout, are more complex algorithms in computer-aided machining software, Ball said.

Induction coils solved a problem at Seco in the early 2000s, Branget said. At the time, some tools—typically those with smaller diameters and also ones made of solid-carbide inserts in steel shafts—were getting stuck in shrink-fit holders because the method used to expand the internal bore was so slow that it heated the tool at the same time. The thermal coefficient of the holder and the shank was the same. Today, induction systems are so powerful you can heat up the holder enough to expand it before the tool gets hot, said Branget.

Having trouble with your tapping process? If so, Bill Minhas, applications engineer-II for OSG USA Inc., Irving, Texas, advises checking the drilled hole for straightness and other defects that can destroy hole quality. “When I’m called into a shop that is having trouble with their tapping process, I usually find that most of the time it isn’t the tap, it’s the drilling process. If the drill is dull and not drilling straight, there are a number of defects that can destroy hole quality. I suggest checking the hole with a pin gage and replacing the drill with a new one.”

Brothers described how room for error is introduced when using a separate shrink-fit unit and presetter. “In the touch-off method, the procedure is to zero out the encoders, bring it down, touch it off and look at the distance that it traveled,” he said. “Then, you’ll go to the table and type in the value. But there is the risk of typing in the wrong number.”

That problem is solved with automated data transmission. Zoller has an option, data output, where if there’s a networked or USB port or if the machine is capable of accepting a file from a post-processor, the operator can do the presetting and generate the same machine code with the offsets. It inputs all the right information into the proper pockets. As a result, the operator doesn’t need to type anything.

Another method for cooling uses a spray of water on the heated toolholder followed by air blown over it or cooled solely with forced air, which Seco shrink fit units do.

“Modern shrink fit machines use preprogrammed heating cycles that are based on the nose diameter of the holder. This ensures uniform heating and consistent holder life by not overheating the holder, which can change the molecular properties, causing the holder to lose its gripping force.”— Jay Ball, product manager for solid milling, Seco Tools

Edwin Tonne, training and technical specialist for Horn USA Inc., Franklin, Tenn, puts a little bit of a different twist on the evolution of solid-carbide round tools and looks into the background of machine technology to determine “which came first, improved tools or improved machines. Better precision of all components, more sophisticated electronics and control systems have produced superior machine technology,” said Tonne. “Advanced machining centers with the required acceleration and deceleration in combination with advanced CAM programming have set the stage for serious improvements in solid-carbide round tools. End mills, for example, are able to be designed with more flutes, as many as 16, and with chip gullets to facilitate chip removal.”

“That’s a tried and true practice that works great,” said Janson. “The issue is if you get a tool that’s less than 1 mm in diameter, especially end mills and square end mills, you start to have concerns about the potential of chipping from that. That’s the concern we have when we’re dealing with stuff of that size. So, we typically use a presetter.”

Minhas explained the advantage of having the variable rake angle on the AE-H end mill: “Ball end mills always start cutting at the tip, which is not rotating. The variable rake angle is very strong at the tip to avoid chipping. Then, as you go further up to the diameter of the tool, it’s sharper so that you can cut the material lightly.”

According to Cline, a drill can be produced with a larger gullet area without sacrificing the strength and integrity of the tool. “In the past, if you wanted to make a drill with a large gullet, you would either make it stubby or sacrifice some of the penetration rate since you would run slower to reduce force,” he said. “For faster drilling, we have a line of three-flute solid-carbide drills for a higher penetration rate in order to reduce cycle times.”

“Even touching off … some people will shrink the tool then bring it down and touch the tool off, but you could damage the part if you don’t have an experienced operator and it could come down and chip the tool,” Brothers continued. “Again, not using the tool to make chips.”

While the basic concepts behind shrink-fit toolholding—heating expands and cooling contracts—have remained the same since its inception in the 1990s, companies responsible for the technology behind it have improved their machinery and processes. Apocryphal stories remain about using a blow torch to expand the inner bore, and some shops still quench a heated tool holder in a bucket of water and coolant to prompt contraction, but now there are much safer and more controlled ways to do both.

Micrograin carbides continue to be a key element of the tools. They represent the best way to achieve the middle ground between a tough, coarse carbide grade with lower cutting speed or a higher speed but brittle cutting grade. “A coarse-grain end mill can take more abuse without chipping but its speed and productivity are lower. You can have a tough carbide grade or a higher-speed carbide grade or something in the middle. Our grade is durable with higher speed capability,” Tonne said.

Brothers said he’s even seen some people do presetting with calipers. “There’s even some ways of doing it on the machine tool where they have different gages, touch-off probes and lasers,” he said. “But then all you’re using the machine tool for is a presetter, not making chips. [That’s why] it’s always nice to have that done offline.

Heule’s products are used for new materials and processes such as dry machining or minimum mist, as well as drilling holes in small motors and medical applications. “Our products are used anywhere holes are drilled that have burrs that have to be removed. They eliminate a lot of manual operations, making it possible to manufacture products from beginning to end without touching them or with minimal manual intervention.”

Both tools are designed for machining aerospace engine components for the substantial backlog of aircraft engines, which is challenging to the supply chain. According to Strauchen, it’s critical for the supply chain to be able to increase throughput and reduce cycle times. “Engine and engine component manufacturers place a significant premium on productivity,” he said. “With backlogs being what they are, the value of time trumps tool cost and tool life every time.

Before you can pick the right tool, you need to first determine what it will be used for. “In order to select the correct solid-carbide round tool for a given milling application, we must understand the end user’s main driver,” said Matt Clynch, national product specialist-milling at Iscar USA, Arlington, Texas.

Deburring drilled holes and bores in production quantities represents a challenge to companies in virtually every industry. To deal with these challenges, deburring products and processes from Heule Tool Corp., Loveland, Ohio, are being used by manufacturers in aerospace, automotive, heavy equipment, energy, medical and precision machining for their finishing operations.

The consistency Holden described helps not only with day-to-day operations, but also when quoting a job, so the shop doesn’t overestimate or underestimate machining time depending on the operator, according to Brothers.

Also new from OSG is the 1 to 2-mm ADO microdrill for medical and dental applications, available in 2×D to 3×D lengths. “The ADO micro features coolant-through for good chip evacuation and, though it’s small, has a double margin that is important for stability in the hole,” said Minhas.

OSG’s ADO SUS drills for titanium and stainless feature the company’s proprietary WXL coating; specially shaped coolant holes for 33 percent more coolant flow to the cutting edge; and cutting forces that are always 90º to the cutting edge. With a wavy cutting edge, there isn’t a large cutting force going in one direction, which minimizes heat producing friction—an important feature in stainless steel and titanium machining.

“The thing I’ve always liked, especially coming from the inspection side of the cutting tool industry, and that a lot of customers like, is doing in-process gaging and in-process inspection with a presetter. There are things that I can qualify—diameters, lengths, runouts, radii, concentricity—and we can do DXF overlay profiles if necessary. If an operator wants to do some verification, it doesn’t take that much longer after presetting the tool. They can then be assured that the tool is qualified and will make a good part.” — Matt Brothers, Industry 4.0 Tech Center manager, Zoller

Where Janson works, operators use a touch-off gage (a gage of a known height equipped with a dial to measure distance) set on the workpiece or on the table in the machine. The operator takes the tool, drops it down and touches it on the top surface of the probe until the dial registers the height.

Iscar’s high-performance line is tailored with specific geometries for various material groups like stainless steel, titanium, and 4000 series alloys. “One of the secrets to high-performance capability is found in the geometries that can be produced with new advanced grinding technology and software,” said Clynch. “If you can imagine a cutting edge geometry, today’s advanced machines and software can grind edge geometry and improve chip gullet designs for ejecting or evacuating chips out of the cutting zone.

Commonly seen in commercially available cooling equipment are sleeves with internal coolant that fit over the heated toolholder and reduce its temperature in a matter of seconds. Instead of sleeves, Seco calls its technology cooling bells.

Iscar’s IC903 coated grade solid carbide, with an AH grind special edge prep, drills materials with hardnesses from 55 to 70 Rc. “In the past, you would have to put the holes in the part while in a soft state, which may not be optimal, but your only other option would be to ram EDM the hole which is a slower process,” said Cline.

Unlike its name, the use of shrink-fit tooling is expanding. A shrink-fit toolholder starts with a slightly undersize bore that is heated to enlarge the inner diameter enough to accept a cutting tool and then grip the cutter as it cools and contracts.

Branget’s colleague Jay Ball, product manager for solid milling at Seco, explained, “There’s this dynamic shift going on in manufacturing as far as how we process parts and as a result, we’re seeing a lot of high-velocity milling strategies. More and more customers are using larger-diameter carbide end mills, say ½", ¾" or 1" (12.7, 19 or 25.4 mm), to replace larger, helical cutters to be able to get high metal removal rates. The cost can be substantially lower.”

“The one caveat that we run into with shrink units is they don’t avoid tool pullout. They’re really good at keeping the tool in place if it’s drilling so you’ve got forces going up into the machine. But in milling, especially aggressive roughing, the way the helix angle on the end mill imparts forces onto the holder you will sometimes see the tool shift by up to 0.015-0.02" (0.381-0.508 mm), which can take you out of tolerance. The tool can get pulled slowly out of the holder. It’s something that all holders can have an issue with. You might be better off with something you don’t have to potentially worry about damaging.”— Alec Janson, product engineer II, OSG USA, Glendale Heights, Illinois

Why do it? It provides the cutting tool with lower runout, stronger gripping torque, greater balance, slimmer profile, and extended reach options. It also decreases the inventory a shop needs to keep track of and store, improves repeatability, and shortens tool change time.

Three flutes are optimal for slotting and five flutes and up for more advanced processes like trochoidal strategies. For finishing operations, tools may have up to 16 flutes or more, according to Tonne.