Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.

“It’s important that we keep those two things related,” he said. “So if we’re talking about 14" of reach and the tool diameter is only ½", we have a ratio of 28 times the diameter. But a 2"-dia. tool at 14" length is only a 7-1 ratio, which is not particularly extended length.”

“But even though the instinct is to slow down when something vibrates, there are certain situations where if you go faster, you also run into a sweet zone that (doesn’t) get the chatter,” Burley said. “And extended-reach toolholders have these bands just as much as the shorter ones. They’re narrower but still exist.”

“The cutting tool chosen could be more positive or high shearing,” he said. “Or we can apply toolpaths, such as high-efficiency or high-feed milling, which are different approaches to speeds and feeds and depth of cut.”

Emuge also produces an extensive line of tapping toolholders. The Softsynchro rigid tap holder, with minimal length compensation, is said to reduce axial force to a fraction of that required in typical tapping applications, improving thread quality and extending tool life by up to 300%. Patented elastomer springs separate the spindle from the tap, absorbing excessive axial forces and providing the tap with a significant boost in tool life and performance. Torque from the spindle is transferred to the tap via ball bearings in precision-ground grooves, promoting precision micro-correction of lead errors in a rigid tapping cycle. The modular system is adaptable to any application requiring a length adjustment screw and interchangeability for different size taps.

TIR is less than 0.0001″ (0.0025 mm) even after thousands of tool changes, and powRgrip’s rigidity and high mass minimizes harmonics, extending tool life and reducing consumable costs, according to the company. The system has five sizes, resulting in only five machine inserts the operator would ever need to use every holder, and eliminating the need to purchase machine taper mounts.

Form of milling that produces a flat surface generally at right angles to the rotating axis of a cutter having teeth or inserts both on its periphery and on its end face.

Haimer is best known for its extensive line of shrink-fit toolholding. This system is a simple one-piece, highly rigid design with no moving or wearable parts. Benefits include runout accuracy up to 0.00012″ (0.00305 mm), superior repeatability, minimum vibration and chatter and excellent balance, according to the company.

Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.

The aerospace industry in particular has a big stake in secure toolholding, notes Jack Burley, vice president, sales and engineering for BIG Kaiser Precision Tooling Inc. (Hoffman Estates, IL). “A number of critical components are made from titanium, which is expensive and difficult to machine. If a cutting tool slips or pulls out, the results are extremely costly, in terms of both downtime and material loss,” Burley said.

The advantage of the modular concept, according to Burley, is that there are hundreds of different components that can be assembled together. A CAD/CAM programmer can choose from these to create the optimal tool configuration to fit into the reach and meet the needs of the program.

“At least 90% of the time, catalog toolholders typically in the range of 2" to 6" or 8" are more than long enough to overcome these minimum strokes, dead zones or any other problems with machine limits,” Burley said. “It gets down to 10% of the problems—where either the parts are just so small or so close to the table or it’s on a horizontal where you have to reach across to the opposite side because of the feature that you’re trying to get to—where you need extended-reach toolholders.”

Shops should be aware that heavy-duty machining is not the only cause of tool pullout, said Ryan Krolak, technical sales specialist for Schunk Inc. (Morrisville, NC): “It can also be the result of toolholders that do not offer concentric clamping,” Krolak said. “This often causes excessive runout, creating an uneven chip load on the cutter and premature tool failure. This shouldn’t have to be said, but it is important to make sure that all the running parameters are within the range of the material and the cutting tool being used.”'

Coromant Capto by Sandvik is another modular system that can be used to create extended-length toolholders. “You can use a Coromant Capto adapter on the machine spindle side and then put different types of milling cutters, drills or boring heads on the machining side of the assembly end of the adapter,” Backus said. “You can add more extensions to make it longer and stack them out as far as you need. On the same tool assembly, you can have different diameters, which gives you a lot of versatility. You usually would start with a larger diameter at the base and then reduce it to whatever you need or just keep it all the same diameter for the entire assembly.”

For high production tapping, the Speedsynchro tap holder features a programmable integrated transmission of 1:4.412 to optimize thread production on CNC machines with synchronous spindles. Combined with Softsynchro’s minimum length compensation, this allows high cutting speeds at a relatively low synchronous machine tool speed, compensating for synchronization errors during the threading process. Thread production cycle time is reduced by up to 40%, and the lower spindle speed can result in significant savings in energy costs.

As machining speeds increase and more difficult-to-machines alloys are introduced, machine shops need to continually re-evaluate their toolholding options. While highly secure toolholders typically cost more than their standard counterparts, the payback—in terms of the ability to machine at higher speeds and fewer scrapped parts and tools—can be substantial.

Krolak agreed that machining aerospace parts is particularly challenging. “Aircraft manufacturers have many applications with materials costing thousands of dollars and individual part cycle times exceeding 12 hours,” he said. “With this much invested in each machined component, tool failure is absolutely not an option.” To meet this need, Schunk recently introduced the Tendo Aviation toolholder for applications that require a secure tool that will not pull out.

For example, he said if a 6"-long tool chatters at 2,000 rpm, a 7"-long tool might not because the 6"-long holder at that rpm is coincident to the natural frequency of the system while the 7"-long holder is out of phase.

The Tendo holder contains an internal clamping piston that compresses hydraulic fluid into the oil chamber. The piston is manually actuated by an external clamping screw turned to a dead stop by an Allen key. A flexible sleeve immediately expands evenly against the tool shank, first centering the tool, then powerfully gripping it on the full surface. A length-setting screw can be actuated radially or axially for tool presetting.

In response to demand, Ultra-Dex developed a chatter-free line of boring bars with up to a 14-1 ratio. These long-overhang ratios are made possible by an internal damping technology based on a high-density alloy that provides optimal dynamic stability.

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.

Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.

Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.

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.

Ultra-Dex USA offers chatter-free boring bars with an internal damping technology based on a high-density alloy. Image courtesy of Ultra-Dex USA

“You will sacrifice a little bit of accuracy when you start building up these components, but they’re designed in such a way as to remove the inaccuracy of each connection,” Burley said. “We’ve actually stacked together four or five parts and measured the (total indicator runout) at almost 12" and seen runouts that are less than 0.0005", which is extremely good for any tool.”

For maximum tool security, the Pin-Lock Collet system is available as an option. This feature works with any Weldon shank tool and guarantees pullout protection.

This modular toolholder system for larger, heavier tools includes a lightweight aluminum insert for extended-length toolholders. Image courtesy of BIG KAISER Precision Tooling

An integrated damping system for extended-reach facemilling eliminates vibration for higher productivity, better surface finishes and higher removal rates. Image courtesy of BIG KAISER Precision Tooling

As an option to a single-piece, extended-length holder, several companies offer modular systems that can be built to longer lengths as needed.

All the recent investment in multiple-axis machines, with their increased accessibility to workpieces, has made many people believe that the need for extended-reach toolholders is greatly reduced if not eliminated.

“Extended reach is not just how long it is but how long it is in relation to the tool diameter,” said Gregg Bishop, general manager of Ultra-Dex USA, Flushing, Michigan.

Anti-vibration technologies typically are based on a damping mass, which is often a heavy metal, a fluid or both inside a holder to offset vibrations.

“It’s kind of like Legos where you start with a basic holder and you can extend it and taper it and do all kinds of things to make it the way you want it to look using standard components,” Burley said. “And the beauty of that is, because you’re using a pool of common components, you can take it apart whenever the job is over and reuse the parts for other builds.”

Holly B. Martin is a science writer and technical copywriter based in Winchester, Va. For more information, visit www.hollybmartin.com.

Because of interference, such as from a machine spindle snout, getting into certain features on a vertical machining center sometimes requires toolholders with long gauge lengths, said Jack Burley, vice president of sales and engineering at BIG KAISER Precision Tooling Inc., Hoffman Estates, Illinois. The minimum Z-axis, which is the closest distance a spindle can be to the worktable, has to be made up by the length of the toolholder. In the case of a horizontal machining center, the shortest distance a spindle can be to the center of the table is also a dead zone that has to be made up by the toolholder, he said.

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

Coromant Capto is a completely modular system supporting machine adapters, extensions and facemill adapters. Image courtesy of Sandvik Coromant

Shrink-fit is based on the thermal expansion and contraction of metal, and uses an induction heating unit for assembly. The bore of the holder is initially slightly smaller than the outside diameter of the tool shank. When heated, the holder expands sufficiently to allow tool insertion. After cooling, contraction of the holder grips the cutting tool with up to 10,000 lb (4536 kg) of force. Tools can be changed in seconds, and operator training is minimal. As noted above, the Safe-Lock feature can be incorporated into Haimer shrink-fit toolholders.

“In many cases,” Backus said, “with our vibration-damping toolholders for turning, boring or milling, it can be a great productivity booster without needing to make reductions to the cutting data.”

“The further the overhang of the tool assembly, the more vibration will be introduced,” Backus said. “If they’re taking a light cut with a milling cutter or they’re drilling, they may get by with a pretty long assembly. But if they’re doing a heavier cut with the milling cutter, they need something like our Silent Tools milling adapter to dampen the vibration.”

Sandvik Coromant’s Coromant Capto is available in various length extensions to optimize applications and with dampened extensions to minimize vibration. Image courtesy of Sandvik Coromant

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For many generations, machining was a largely manual process with relatively slow speeds and shallow cutting depths. The most common toolholders were Weldon/sidelock chucks and ER collets, and, under these comparatively benign machining conditions, cutting tool slippage or pullout was not a serious issue.

“If you’ve got to go around the side of a workpiece but the first 6" is in the dead zone, then we’re going to make that zone as beefy as we can,” Burley said. “Compared to a one-piece holder of exactly the same length and the same exact shape, the rigidity wouldn’t be as good as the solid tool, but I would put it within about 10% of the same range.”

“There’s a ton of demand in the oil and gas industry to get much deeper into a bore for ID turning,” said Gregg Bishop of Ultra-Dex USA. “They’re always trying to push that envelope to reach size and finish limits we never thought were possible. Imagine a 40" bore with a standard 4" bar. You can’t do that with a traditional carbide shank boring bar.”

Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.

One of BIG Kaiser’s newest products, the Mega Perfect Grip milling chuck, is designed specifically to prevent cutter failure. The high-accuracy milling chuck has fully concentric clamping and runout of less than 0.0004″ (0.0102 mm) @ 4×D. It accepts standard Weldon flat end mills and requires no special grinding of the milling cutter.

In addition to the characteristics inherent the hydraulic expansion design, the Aviation toolholder employs a locking mechanism. A cutting tool with a standard Weldon shank is inserted into a special sleeve with a ball lock. The tool/sleeve assembly is then locked into place via set screws in the base of the toolholder. Finally, the holder is hydraulically actuated. As with other Tendo models, this process can be accomplished in seconds.

“The idea for a 1"-wide slot is to use a smaller-diameter cutting tool, like a ½" milling cutter instead of a 1" cutter, and then feed the cutter forward in a circular toolpath opening the slot to the 1" width instead of creating it with one big hog pass that’s 1" wide,” said Mark Backus, product specialist for machine integration and tooling systems at Sandvik Coromant Co., Fair Lawn, New Jersey.

CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.

Distance between the bottom of the cut and the uncut surface of the workpiece, measured in a direction at right angles to the machined surface of the workpiece.

Engineers at Rego-Fix agree that even with the highest clamping forces available, there are applications that require additional cutter retention measures. At IMTS 2012, Rego-Fix introduced the secuRgrip anti-pullout system, available for powRgrip, ER collet holders and milling chucks. A small, profiled steel locking key insert is installed in the ground flat of standard Weldon-shank cutting tools, locking the tool to the collet. A threaded friction bearing cap secures the collet in the holder and provides increased clamping force to prevent the collet from spinning.

”After more than four years, there have been no documented cases of a tool pullout with a secuRgrip holder,” said Chris Herdman, technical field support engineer for Rego-Fix. “The only mode of failure is that of the cutting tool itself.” Unlike other systems, secuRgrip does not require purchase of specially modified end mills, but rather can accept standard 0.5–1″ (12.7–25.4-mm) carbide or HSS end mills. The system maintains 0.0001″ runout and allows users to preset tool heights.

“They can run at higher speeds and feeds versus a plain carbide or steel boring bar with the same hangout ratios,” Bishop said. “It’s a productivity booster, so the (return on investment) on the added cost is found where the customer takes into consideration the increased throughput.”

There are secure toolholders for a variety of cutting operations, including milling, drilling and tapping. For example, Emuge Corp. (West Boylston, MA) offers its highly rigid FPC Mill/Drill Chuck with three tons of traction force to hold a tool securely. This is the world’s only chuck with a 1:16 wormgear, according to Emuge. The collet-cone assembly absorbs virtually all vibration, for maximum vibration dampening. With a 3×D tool length, variation in concentricity is less than 3 µm, which extends tool life and substantially improves workpiece surface finishes. All models are balanced to G2.5, 20,000 rpm. In a speed comparison with four competing chuck designs, the FPC chuck enabled the feed rate to be increased by 30% with no loss in performance.

A modular system normally consists of basic holders with extensions, reductions and toolholder components that fit into them, such as shell mill, collet chuck or endmill holders.

Several years ago, Haimer developed and patented an anti-pullout system, Safe-Lock, as an optional feature on its shrink-fit holders and power collet chucks. Safe-Lock employs special drive keys in the holder and mating grooves in the tool shank, ensuring positive locking in place of the cutter and preventing spinning and pullout. Unlike Weldon flats, the mating ground grooves are perfectly symmetrical, thus eliminating issues associated with unbalance and uneven side loads. The system also provides users with the ability to adjust the axial position of the cutting tool in the holder. With 14 of the largest round tool companies as official licensed partners, tools from any number of global suppliers are readily available.

“With the 5-axis, I can tilt things around to get into those places using a standard toolholder, but you’re always working off the center of the table,” Burley said. “So everywhere around it, there are going to be certain tilts that make it difficult to reach, like the B-axis all the way at 90° to the spindle, and some features down by the table itself.”

Rego-Fix Tool Corp. (Indianapolis) markets both a friction fit and a tool locking system. The powRgrip series includes holders, collets, and automatic or manual pressing systems. The collet is pressed into the holder with up to 9 tons (8.16 t) of pressure, which Rego-Fix claims to be the highest clamping force in the industry. The compression contacts the nose of the holder and not the taper.

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Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.

“It’s not as good as a solid tool,” Burley said. “But in some situations, because I can build it based on the configuration that I want, I can make it stiffer and larger than a 12" standard holder that is long and slender.”

CAM software tells a programmer the maximum and minimum gauge length from the spindle to the tip of the tool, Burley said. To determine other toolholder dimensions, a program’s collision detection system would calculate the maximum outside diameter of the toolholder and the optimum lengths to reach the longest conditions.

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.

“We can build specials beyond the normal catalog size or range, which is usually after 8" or 6" on smaller-taper tools,” Burley said. “But my preference is to direct people toward our CKB line of modular mill/turn tools for mill/turn centers.”

Hydraulic expansion toolholders were developed by Schunk more than 35 years ago and have been continually improved to keep pace with advancements in machine technology and carbide tooling, Krolak said. The Tendo line features a high concentric clamping force, excellent vibration dampening and runout of less than 3 µm @ 2.5×D. All commercially available tools, with Weldon, Whistle notch or cylindrical shanks, can be clamped. Micron-accurate tool changes can be made in seconds.

“Every tool system and spindle has a natural frequency,” he said. “And when you run a tool that is coincident to that frequency, you get a lot of vibration.”

That was yesterday. Today, the productivity needed to be globally competitive requires ever increasing metal-removal rates during operations such as roughing and high-speed slotting. Process reliability is paramount, especially when working with difficult-to-machine materials. Conventional toolholders typically do not cope well with the high axial forces generated by aggressive machining, and cutter pullout can occur.

“The tool steel itself, along with the Rockwell hardness of the tool steel and the substrate, all relate to the rigidity of the tool assembly,” Bishop said. “Let’s say you try to reach something out 12". You’ve got to start with good runout, and a shrink-fit holder is the smartest choice for that application. Instead of having a toolholder with setscrews on the side of it that pushes a tool one direction or the other, a shrink-fit holder actually wraps right around it, giving you the optimal runout, which is below a tenth.”

Trochoidal milling, a form of high-efficiency milling, is one option for extended-length toolholders because it exerts less stress on the spindle.

Toolholder manufacturers have responded with a variety of rigid, highly secure systems offering anti-pullout protection. These include shrink-fit, hydraulic expansion and locking toolholders. Each features high gripping torque (clamping force) for a tight friction fit on the tool shank. Many offer proprietary locking mechanisms that can guarantee up to 100% tool retention.

Bishop said customers typically use extended-length holders to reach past fixtures, obstructions or part features to machine other part features beyond. For those applications, he recommends keeping cutting forces light to minimize radial or axial radial deflection.

2-D or 3-D path generated by program code or a CAM system and followed by tool when machining a part.

He said oil and gas applications use threads with a high insert engagement, which creates a lot of deflection when cutting, and therefore vibration occurs even at short bar lengths.

Cone-shaped pins that support a workpiece by one or two ends during machining. The centers fit into holes drilled in the workpiece ends. Centers that turn with the workpiece are called “live” centers; those that do not are called “dead” centers.

Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.

Drew Strauchen, vice president, marketing and business development, Haimer USA LLC (Villa Park, IL), cautioned against total reliance on the ability of friction-fit holders to provide maximum tool security. “High gripping torque by itself does not equal guaranteed pullout protection,” he said. “The incredible cutting forces generated by faster machine spindles and more aggressive toolpath strategies [like full radial engagement trochoidal milling] have exposed the limitations of even the best friction-fit clamping systems.”

With an extended-reach toolholder, end users must contend with physics. Due to bending forces and frequencies, a 12"-long tool never can run as fast or hard as a 2"-long tool, Burley said.

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.

An exclusive Key Grip locking mechanism provides anti-pullout protection. It is placed into the Weldon flat of the end mill shank, which is then inserted into one of the three Key Grip grooves inside the chuck. A spring functions to remove the gap between the Key Grip and the wall of the groove. Tightening a clamping nut secures the Key Grip in place, achieving dual contact between the nut and chuck body for rigidity close to that of an integral cutter.

Flexible-sided device that secures a tool or workpiece. Similar in function to a chuck, but can accommodate only a narrow size range. Typically provides greater gripping force and precision than a chuck. See chuck.

The main challenge with extended-reach toolholders is achieving suitable rigidity. The longer and thinner the holder, the more likely that bending forces will cause runout.