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It’s been estimated that a tool with a run-out of 50% of the tool’s chip load will reduce its tool-life by 40%. That means that a 1/8” tool with a 0.00019” chip load per tooth will lose 40% of its tool-life with a run-out of less than 0.0001”. Excessive and inconsistent run-out from a properly setup ER collet chuck assembly typically occurs due to friction build-up between the 30° face of the collet and the collet nut.
 The result?
Other Parlec P3 collet advantages:
Don’t throw away you ER collet chucks to improve accuracy Try Parlec P3 collets and supercharge your ER collet system.
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Written and edited by Bernard Martin PowerCOAT Collet Nuts provide up to a 75% increase in holding power!  One of the most important elements of the toolholding 'system' is the collet nut. Each toolholder "system" consists of a precision ER tool holder that comes with a special "Power Coated" high power nut that holds tighter than any other nuts. According to Techniks, the 'Power Coat' nut is the secret to their high holding power. Because it holds so tight, the 'Power Coat' nut improves T.I.R., extends carbide tool life, and improves finish in heavy milling operations. Techniks recommends that for best results always tighten the nut to the proper torque using a torque wrench with a tightening stand, and never over-tighten the nut because this can damage both the collet and the collet pocket. To demonstrate the difference between an uncoated and coated collet nut, Mike Eneix, from Techniks did some testing. He took an uncoated, imported nut and put it to the test against the Parlec PowerCOAT nut. Mike took them to the limit to see which one gives you more holding power. Check out the video below! What makes the difference?As anyone knows who has changed a flat tire on their car, tightening down a nut on a 60 degree thread involves some friction as the mating metal surfaces interact. That's why nuts can be a bit 'hot' to the touch when you take them off. The objective with the "Power Coated" nuts was multifold:
First Techniks needed to reduce the coefficient of friction on the thread angle to enable more lubricity for the nut to tighten down farther. As we all know 'heat' causes metal to "grow" so what may at first appear to be tight, in fact, loosens, as soon as you stop tightening it. Second they needed to make sure that the front surface of the collet that engages the shorter 30 degree taper on the front of an ER collet did not 'twist' as the night tightened down. Both problems really involved reducing friction and through a combination of engineering tolerances and unique coating process we believe that we've found the most economical solution to eliminate the use of cheater bars and collet over torque. Here's what they've found out in testing the "Power Coated" Nuts:
“Power Coat” is an innovative, permanent coating that increases clamping pressure of the nut up to 75% compared to standard ER nuts. More holding power reduces the chance of spinning the shank of the tool inside the collet, which can cause premature failure of the collet.  The four critical requirements for tool holders are clamping force, concentricity, rigidity, and balance for high-spindle speeds. When these factors are dialed in just right, there’s nearly no chance of holder error and considerable cost reduction is achieved thanks to longer tool life and reduction of down-time due to tool changes. Easier said than done, our experts shared some of their best, quick-hitting advice for top tool holder performance in different situations. 1. Balance holders as a complete assembly Long-reach milling has some unique demands; when setting up this type of job, always balance tool holders as a complete assembly. While many tooling providers pre-balance their holders at the factory, it’s often inadequate, especially for long-reach applications. 2. Holder damage can go from bad to worse quickly Wear and tear on holders can be costly in the end, but there are ways to protect against it. Inspect and care for your holders. Trauma on a holder or spindle—dings, scratches, gouges, etc.—can magnify quickly. One bad holder can spread its problems like an illness. If you’re seeing disruptions like these on your holders, get them out of the rotation. 3. The rule of thumb on holder dimensions Looking for affordable ways to avoid vibration? Start by opting for a holder with a combination of the largest diameter and shortest length possible. 4. Rigidity can harm tapping operations What many don’t realize about tapping operations is that a perceived strength of collet chucks—their rigidity—can actually be detrimental. Rigidity does very little to counteract the dramatic thrust loads imposed on the tap and part, exacerbating the already difficult challenge of weathering the stop/reverse and maintaining synchronization. 5. Balancing is crucial to five-axis machining Five-axis machining introduces a whole new set of tooling challenges. While important in any type of machine, balance may be of most importance in full five-axis work. A well-balanced holder helps ensure the cutting edge of the end mill must be consistently engaged with the material in order to prevent chatter and poor surface finish quality. 6. Consider spindle speed requirements when choosing between shrink-fit and hydraulic holders If you have to choose between shrink-fit and hydraulic holders in a long-reach application, consider the spindle speed required. If a hydraulic chuck exceeds its rated RPM, fluid is pulled away from the holder’s internal gripping gland, causing loss of clamping force. But when used within its recommended operating range, a hydraulic tool holder offers superior runout and repeatability. On average, a good shrink-fit holder has about 0.0003-inch runout, while a hydraulic chuck offers 0.0001 inch or better. 7. Don’t overlook the tool’s effect on holder performance The cutting tool affects holding ability more than most machinists and engineers realize:
8. Not all dual-contact tooling is the same Anyone in the market for BIG-PLUS dual-contact tooling should consider this simple statement: Only a licensed supplier of BIG-PLUS has master gages that are traceable to the BIG grand master gages and have the dimensions and tolerances provided to make holders right. Everyone else is guessing and using a sample BIG-PLUS tool holder as their own master gage—a practice that any quality expert will advise against. Look for the marking: “BIG-PLUS Spindle System-License BIG DAISHOWA SEIKI.” 9. You may have a BIG-PLUS spindle and not even know it You’d be surprised how often we hear from our certified regrinders or engineers in the field about folks that didn’t realize their machine had a BIG-PLUS spindle—the message can get lost in the supply chain or during the sales process. The easiest way to know if an interface is BIG-PLUS is to place a standard tool into the spindle and see how much of a gap there is between the tool holder flange face and spindle face. Without BIG-PLUS, the standard gap should be visible, or about 0.12 in. If it is BIG-PLUS, the gap is half of this amount, or only 0.06 in. These values change depending on 30 taper, 40 taper or 50 taper sizes, but the gap is visibly less than usual. 10. Use positive offsets during holder setup It may be how it’s traditionally been done but touching off holder assemblies in each machine to establish negative tool offsets based on the zero-point surface—the vise, machine table, workpiece, etc.—is not the most efficient process. We think the choice is pretty clear: adapting machines to a single presetter so they can receive positive gage lengths is superior to using all types of machine-specific negative offsets.
This is a change to “the way things have always been done” that can be met with some resistance, but in the grand scheme of things, it’s a relatively small and simple step that makes life much easier. It’s a relatively low-cost opportunity to introduce more standardization of holder setup to the shop floor. Holders are the bridge between the machine and the part. That’s a lot of pressure—literally and figuratively. It’s important to select, care for and use holders carefully from the day they are purchased until they’re tossed into the recycling bin. From collet chucks to coolant inducers, BIG KAISER is North America’s source for standard-bearing tool holders that guarantees high performance. Explore the full lineup. A REVIEW OF THIS MACHINING METHOD, THE BASIC CONCEPTS AND SOME EXCITING DEVELOPMENTS IN THE TECHNOLOGY by Preben Hansen, President, Platinum Tooling Technologies Inc.  Universal style adjustable tool might be the ideal solution for families of parts. Live tooling, as a component on a lathe, is specifically manipulated by the CNC to perform various milling, drilling and other operations while the workpiece is being held in position by the main or sub spindle. These components, whether BMT or VDI, are also called driven tools, as opposed to static tools, that are used during turning operations. All live and static tools are built per the machine tool builder’s specification for each of the various models they produce. A key to running a successful job shop or production department is to partner with a supplier who can meet the tooling needs for all or most of the machines on your floor.  Most often, live tooling is offered in standard straight and 90º angle head configurations with a wide range of tool output clamping systems, including ER collet chuck, arbor, Weldon, Capto, whistle notch, hydraulic, HSK, CAT, ABS and a variety of custom or proprietary systems developed by the many suppliers to the industry. When the need arises for a new machine tool, careful consideration should be made to determine which live tools are appropriate for your application. While a standard machine tool package will help you get started, it is important to anticipate job and volume changes, as well any unforeseen machining challenges from the beginning, in order to avoid machine downtime. This short article is meant to give you a set of parameters to consider when evaluating the live and static tooling to use in your shop or production department. Simply stated, you need to do as much evaluation of your process, when determining the proper tooling to be used, as you did when you evaluated the various machines available for purchase. This fact is often overlooked and that can be a critical error, in the long run. Your examination can range from the simple (external vs. internal coolant, for example) to the sublime (adjustable or multi-spindle configurations) to the custom tool, that may be required and built to suit your special application. Finding a supplier who has an in-house machine shop for the preparation of special tools is a great value-add. Tool life is the product of cutting intensity, materials processed, machine stability and, of course, piece parts produced. Two seemingly identical job shops can have vastly different tooling needs because one is automotive and one is medical, or one specializes in the one-off and low-volume work, while the other has a greater occurrence of longer running jobs. The totality of your operation determines the best tooling for the machines being purchased. Bearing construction and the resulting spindle concentricity drive the life of any tool. You might find that just a 10-15% greater investment in a better design can yield both longer lasting cutters and consistently superior finish on your products. Of course, the stability and rigidity of the machine tool are always critical factors. Bevel and spur gears that are hardened, ground and lapped in sets are best for smooth transition and maximum torque output. Taper roller bearings are consistently superior to spindle bearings in live tool milling applications, so look for a combination system to get the highest rigidity possible. Also, look for an internal vs. external collet nut, so the cutting tool seats more deeply in the tool, as superior performance will result.  Likewise, high pressure internal coolant might be desirable. Look for 2000 psi capabilities in 90º tools and 1000 psi in straight tools.You need to ask another question, namely, is the turret RPM sufficient to handle the work to be done? It’s possible that a live tool with a built-in speed increaser, often called a speed multiplier, would be helpful. Would it be beneficial to move secondary operations to your lathe? Gear hobbing can be accomplished in this manner, as can producing squares or flats, through the use of polygon machining. Standard live tooling most often is best suited to production work, where the finish, tolerances and cutter life are critical, while quick-change systems may be better suited to the shop producing families of products and other applications where the tool presetting offline is a key factor in keeping the shop at maximum productivity. It’s a given in our industry that when the machine isn’t running, the money isn’t coming.
Dedicated tools for large families of products may often be desirable for some applications, but do consider whether a flexible changing system would be more appropriate. Talk to your tooling supplier for the various options, before making that determination. If standard ER tooling is suitable for the work, there are many good suppliers. It is important though, to pay close attention to the construction aspects noted above. For a quick-change or changeable adapter system, there are fewer suppliers in the market, so seek them out and be sure they can supply the product styles you need for all your lathe brands.  Now, an application example showing clear evidence of the value of testing live tool performance... One company was performing a cross-milling application using an ER 32 output tool on a Eurotech lathe, running 10 ipm at 4000 rpm. They were making three passes with a cycle time of 262 seconds and were having difficulties with chatter on the finish, while producing 20,000 pieces per year. The annual cost of the machining was over $130,000. By using an alternative live tool with an ER 32AX output, internal collet nut design, with the same parameters, they were able to produce the part in a single pass with a smooth finish and cycle time of just 172 seconds. Over the course of the year, this yielded a cost savings of $45,000, approximately 20x the cost of the tool. The bottom line is the bottom line, as the accountants tell us. In the end, you may not need a universal adjustable tool or a multi-spindle live holder or even a quick-change adapter system but do consider all these options. Talk to your machine builder and several tool suppliers, plus the most important people in this equation, your shop personnel, as their input is invaluable to keeping you up and running in a profitable, customer-satisfying scenario. The author welcomes questions, comments and additional input from readers. Please contact Preben Hansen at 847-749-0633 or phansen@platinumtooling.com. Mr. Hansen has over 30 years in tooling and is considered a leading authority on the topic in the North American machine tool market.
by Bernard Martin There have been some who claim that drawbar gripper fingers and/or ball marks that appear on retention knob head after several tool changes is normal.  It is NOT.
THAT IS FALSE. According to Haas CNC, ball or gripper marks on the edge of the pull stud indicate that the drawbar does not open completely. If you see these indication marks you should check your drawbar and replace these pull studs immediately. It’s time for machine tool builders and machining companies to shelf the long-standing ISO 1940-1 standard in favor of ISO 16084:2017. Not only is balancing tools rarely necessary, it can also be risky. A lot of conflicting information has circulated over the years about balancing tools. As an author of the new standard for calculating permissible static and dynamic residual unbalances of rotating single tools and tool systems – ISO 16084:2017 – allow me to clear some things up and, hopefully, make life a little easier for you.
Since its institution in 1940, the G2.5 balance specification has been widely accepted across the industry; i.e., “it’s how things have always been done.” However, machines were much slower 80 years ago. Back then, the most advanced machines would have spun larger, heavier tools at a maximum speed of about 4,000 RPM. If you applied the math from those days to today, you’d get unachievable values. For example, the tolerances defined by G2.5 for tools with a mass of less than 1 pound rated for 40,000 RPM calculates to 0.2 gram millimeters (gm.mm.) of permissible unbalance and eccentricity of 0.6 micron. This isn’t within the repeatable range for any balance machine on the market. Similarly, application-specific assemblies, for operations like back boring and small, lightweight, high-speed toolholders, can’t be accurately balanced for G2.5. Machine tool builders rely on an outdated number, too, often basing spindle warranty coverage on using balanced tools at very specific close tolerances. While it’s true that poorly balanced tools run at high speeds wear a spindle faster, decently balanced tools performing common operations won’t wear spindles or tools drastically and deliver the results you’re looking for. While it’s true that poorly balanced tools run at high speeds wear a spindle faster, decently balanced tools performing common operations won’t wear spindles or tools drastically and deliver the results you’re looking for. A Little Lesson About ForcesThis all begs the question: When do you need to take the time to balance holders? I would argue that tools require balancing only if they’re notably asymmetrical or being used for high-speed fine finishing. Here’s a rule I’ve long followed: If cutting forces exceed centrifugal forces due to unbalance, high-precision balancing isn’t needed because the force required to balance the tool will most likely be less than cutting forces.
At that point, aggressive cutting – not unbalance – is going to damage the spindle. Unbalanced tools are also blamed for issues that turn out to be misunderstandings about a machine’s spindle. I’ve visited shops with new high-speed spindles that had trouble running micro tools over 15,000 RPM. They rebalanced all the tools on the advice of their machine tool supplier, but to no avail. It turned out the machine was tuned for higher torque and higher cutting forces. Before going to the effort of balancing toolholders, work with your machine builder to understand where a spindle is tuned. Not only is balancing tools rarely necessary, it can also be risky. Our inherently asymmetrical fine-boring heads are a good example. Because we balance them at the center, a neutral position of the work range, you lose that balance if you adjust out or in. To adjust, you’d typically add weight to the light side, which can be a problem for chip evacuation and an obstructor. Or you can remove weight from the heavy side, but that means you have to put some big cuts on the same axis of the insert and insert holder, ultimately weakening the tool. In longer tool assemblies, common corrections made for static unbalance can also cause issues. It happens when a toolholder is corrected for static unbalance in the wrong plane; i.e., adding or removing weight somewhere on the assembly that’s not 180 degrees across from the area where there’s a surplus or deficit. Once the tool is spun at full speed, those weights pull in opposite directions and create a couple unbalance that often worsens the situation.  All the components of Big Kaiser's Mega ER Grip Series - Body, Collet and Collet nut - Are all balanced for high speed machining A Cautionary TaleIf you do go down the balancing road, you’d better know where you can modify tools, what’s inside, how deep you can go, and at what angles. Whether you’re adding or removing material on a holder, I highly recommend consulting the tool manufacturer for guidance first. As a cautionary tale, consider a customer who was attempting to balance a batch of our coolant-fed holders. Based on the balancing machine, the operator drilled ¼-inch holes at the prescribed angle into the body of the holders. Not realizing what was inside, he drilled into cross holes connecting coolant flow and ruined several holders. Tooling manufacturers are doing their part to avert disasters like this. For most, simple tools like collet chucks or hydraulic chucks are fairly easy to balance during manufacturing. We account for any asymmetrical features while machining and grinding holders and pilot each moving part, ensuring they’ll locate concentrically during assembly. These measures ensure the residual unbalance of the assemblies is very, very low and eliminate the need for balancing.
Decades of the same standards have conditioned us to think a certain way about balancing tools. While it seems logical that every tool must be balanced, it’s just not the case: Many issues attributed to unbalance aren’t caused by unbalance, and the risks of balancing every single tool often aren’t worth the reward.
Save your balancing time and resources for high-speed fine finishing. If you do have work where balance is crucial, consider how the tools you buy are balanced and piloted out of the box and/or consult your partners before making any modifications. by Bernard Martin Retention Knobs are the critical connection between your machine tool and the tool holder and they are the only thing holding a steep taper tool holder in the machine’s spindle. Techniks has recently introduced their MegaFORCE retention knobs that have some rather unique features when compared to standard pull studs. Before delving into the features of the MegaFORCE pull studs, let's review some things that you may not know, or think about, on a daily basis.
According to Haas, you should expect a service life of about 6000-8000 hours for a retention knob. Most all rotary toolholder manufacturers state that you should be replacing your pull studs at least every three years. However, if you're running multiple shifts, 24-7, making lots of tool changes, making very heavy cuts with long reach or heavy cutting tools, and/or have ball lock style grippers instead of collet type grippers used on the retention knob, you will probably need to replace your studs at least every six months. Given the spindle speeds that we are running at to remain competitive, retention knobs are not an item that you want to take a chance on breaking. I can tell you firsthand that 5 pound toolholder with a drill in it flying out of the spindle at 23,000 RPM is not something you want to experience. METAL FATIGUE: WHY THEY FAILPull studs encounter catastrophic failure as a result of metal fatigue. The metal fatigue can be caused by a number of reasons including poor choice of base material, engineering design, machining process, poor heat treatment, and, sometimes, they have just met or exceeded their service life. We're going to dig into each of these reasons below but first let's look at some threading fundamentals.
The load on each subsequent thread decreases from there, as show in the table. Any threads beyond the first six are purely cosmetic and provide no mechanical advantage. Additional threads beyond the sixth thread will not further distribute the load and will not make the connection any stronger. That is why the length of engagement of the thread on a pull stud is generally limited to approximately one to one & a half nominal diameter. After that, there is no appreciable increase in strength. Once the applied load has exceeded the first thread's capacity, it will fail and subsequently cause the remaining threads to fail in succession. RETENTION KNOB DESIGNRepetitive cycles of loading and unloading subject the retention knob to stress that can cause fatigue and cracking at weak areas of the pull stud. What are the weak areas of a standard retention knob?
The most common failure point for a retention knob is at the top of the first thread and the underside of the pull stud where the grippers or ball bearings of the drawbar engage and draw the toolholder into the spindle. Remember, bigger Radii are stronger than sharp corners. More on that soon.  Styles of MegaFORCE Retention Knobs MATERIALNot all retention knobs are made from the same material, however, material alone does not make for a superior retention knob. Careful attention to design and manufacturing methods must be followed to avoid introducing potential areas of failure. Techniks MegaFORCE retention knobs are made from 8620H. AISI 8620 is a hardenable chromium, molybdenum, nickel low alloy steel often used for carburizing to develop a case-hardened part. This case-hardening will result in good wear characteristics. 8620 has high hardenability, no tempering brittleness, good weldability, little tendency to form a cold crack, good maintainability, and cold strain plasticity. There are some companies making retention knobs from 9310. The main difference is the lower carbon content in the 9310. 9310 has a tad more Chromium, while 8620 has a tad more nickel. Ultimate Tensile Strength (UTS) is the force at which a material will break. The UTS of 8620H is 650 Mpa (megapascals: a measure of force). The UTS of 9310H is 820 Mpa. So, 9310H does have a UTS that is 26% greater than 8620H. That said, Techniks chose 8620 as their material of choice because of the higher nickel content. Nickel tends to work harden more readily and age harden over time which brings the core hardness higher as the pull stud gets older. The work hardening property of 8620 makes it ideally suited for cold forming of threads on the MegaFORCE retention knobs. It should be noted that some companies are using H13. H13 shares 93% of their average alloy composition in common with 9310. ROLLED THREADS VS. CUT THREADS A cut thread, image 1, has a higher coefficient of friction due the the cutting process, while a roll formed thread, image 2, has a lower coefficient of friction which means that it engages deeper into the toolholder bore when subjected to the same torque. You will notice that Cutting threads tears at the material and creates small fractures that become points of weakness that can lead to failure. Rolled threads have burnished roots and crests that are smooth and absent of the fractures common in cut threads. Rolled threads produce a radiused root and crest of the thread and exhibit between a 40% and 300% increase in tensile strength over a cut thread. The Techniks MegaFORCE retention knobs feature rolled threads that improve the strength of the knob by 40%.
Also, unlike thread cutting, the grain structure of the material is displaced not removed.
By comparison, cut threads interrupt the grain flow creating weak points. MEGAFORCE GEOMETRIC DESIGN Overall Length There are some claims that a longer projection engages threads deeper in the tool holder preventing taper swelling. While a deeper thread engagement can help prevent taper swelling, applying proper torque to the retention knob is an effective way to reduce taper swelling. An over-tightened retention knob may still cause taper swelling regardless of how deep it engages the threads of the tool holder. Additionally, the longer undercut section above the threads presents a weak point in the retention knob.
Ground Pilot There is a ground pilot, underneath the flange, which provides greater stability. The pilot means the center line of the tool holder and pull stud are perfectly aligned. Magnetic Particle Tested Each Techniks MegaFORCE retention knob is magnetic particle tested to ensure material integrity and physical soundness. MegaFORCE retention knobs are tested at 2.5X the pulling forces of the drawbar.
RETENTION KNOB BEST PRACTICESIn order to maximize the life of your retention knob and prevent catastrophic failure here are some technical tips to keep your shop productive and safe.
Special thanks for Greg Webb at Techniks and Mike Roden from Fette Tools/ Turning Concepts, for providing technical insights.
 Spindles and tool holders are in a constant battle with the forces of nature, with this battle becoming more and more difficult with heavier cuts and longer projections. Chattering and deflection have always been the bane of machinists’ existence, so much so that the sight of a long and slender toolholder will immediately cause goosebumps. If you understand why a long tool holder behaves the way it does, you’ll know that there are ways to fight back against this bending. Every machinist knows that short and stubby holders are more resistant to deflection than long and slender holders. You’ve also probably heard that, if possible, you’ll want most of your cutting forces to be axial rather than radial. Not only does this fight chatter in operations like boring, but your spindle also is better equipped to handle loads in this axis. However, these options aren’t always going to be on the table, especially in unavoidable long-reach situations and many milling operations. In this constant battle with tool deflection, much time and effort has been spent designing shorter holders, stiffer tools, and clever anti-vibration geometry and materials. But oftentimes, the body diameter(s) of the holder can be overlooked as a means of increasing rigidity, especially in situations where it is all you have to work with. This is a serious shame, as you’ll soon discover. The concept of dual-contact technology has been around for years, existing in many different forms but always with the same goal of capitalizing on this untapped potential of rigidity. For those who don’t know, dual contact refers to the shank contacting the spindle taper and the spindle face simultaneously. Oftentimes, the solution involved ex post facto alterations to the spindle or tool holder, such as using ground spacers or shims to close the gap, for example. In other words, there was no standard solution, and if you wanted dual contact, you would have to be prepared to spend time and money either buying modified tool holders or modifying them yourself to adapt them to your spindle. BIG-PLUS emerged as a solution to this issue. Essentially, both the spindle and tool holder were ground to precise specifications so that they closed the gap between spindle face and flange in unison (while depending on very small elastic deformation in the spindle). What this meant is that operators were able to confidently switch BIG-PLUS tooling in and out of a BIG-PLUS spindle and achieve guaranteed dual contact. Not only that, but standard tooling could still be used in a BIG-PLUS spindle if necessary, and vice versa. Though not technically an international standard, it’s been adopted by many machine tool builders because of the clear performance improvements and simplicity. In fact, BIG-PLUS spindles come standard on more machines than you would think. We often come across operators that have machines with BIG-PLUS spindles and don’t even realize it.  How exactly does dual contact help with tool rigidity? The torque (or moment) exerted by the cutting forces is maximized at the point where the holder and spindle meet, the base of the tool holder. With standard CAT40 tool holders, this would be the gage line diameter. When the holder contacts the spindle face via BIG-PLUS, the effective diameter would be the larger diameter of the v-flange, since this is the new anchoring point of the holder and spindle. So, you are beefing up the diameter at the point where the reactionary force is greatest. It’s not too much of a leap to conclude that a larger effective diameter will give you more rigidity. That being said, you may still be asking yourself: does such a seemingly small increase in diameter really make a difference? To understand the effect of BIG-PLUS, you must understand the physics behind it. Imagine a simple scenario in which a tool holder is represented by a cylindrical bar that is fixed at one end and free-floating at the other. In other words, a cantilever beam. If you think about it, this is essentially what a tool holder becomes once it’s secure in the spindle. Now, let’s introduce a radial force F that acts downward at the suspended end of the bar, which represents a cutting force you would encounter when milling or boring, for example. The bar, as you might expect, will want to bend downward. It’s similar to how a diving board bends when someone stands at the end, though less exaggerated.  It’s possible to predict the amount of deflection (or inversely, bending stiffness) at the end of this hypothetical bar if you know its length, diameter and material. The expression below represents the stiffness k at the end of the bar where d=diameter, L=Length and E=Modulus of Elasticity
I won’t ask you to do any math here, I just want you to look at the equation. We can see that increasing d will increase the value of k, while increasing L will decrease the value of k, since it’s in the denominator of the equation. This certainly makes sense if you think about it: a short and squat bar (large d, small L) will be more rigid than a long and slender bar (small d, large L). Something interesting to note is that d is raised to the 4th power, while L is only raised to the 3rd power. Diameter affects rigidity an entire order of magnitude more than the length does. This is where the power of BIG-PLUS comes from and is why a small increase in diameter can have such a powerful effect on performance.  For a CAT40 tool holder, the gage line diameter is Ø44.45 mm and the flange diameter is Ø63.5 mm. Let’s imagine two bars of identical length and material, so L and E remain unchanged. One bar has a diameter of Ø44.45 mm (standard CAT40) and the other has Ø63.5 mm (BIG-PLUS CAT40). If you were to plug these values into the above equation for comparison, you would find that the BIG-PLUS holder results in a k value that is around 4 times greater than the standard bar. Based on this comparison, you could say that a BIG-PLUS holder is 4 times as rigid as an identical standard CAT40 holder, because it is 4 times as resistant to deflection. Think of the tool life and surface finish improvements you would see with a tool that is 4 times more rigid, not to mention the reduction in fretting and potential for reduced cycle time. You would get similar results if you were to make the same comparison for CAT50, BT40, BT30, etc.  If you’re still not convinced, we can also compare the rigidity in this way: Let’s say there is a Ø63.5 mm BIG-PLUS CAT40 bar of some arbitrary length. One of our more common gage lengths is 105 mm, or just over 4 inches, so let’s use it as an example. You’re probably wondering, at what length would a comparable standard CAT40 holder have an equal stiffness? If we take our stiffness expression and set it equal to itself (one side representing BIG-PLUS, the other non BIG-PLUS), we can plug in this BIG-PLUS holder length and our known diameters to find our unknown non-BIG PLUS length:  What does this mean? A BIG-PLUS holder of around 4 inches or 105 mm in length will have equal rigidity to a standard CAT40 holder of around 2.5 inches or 65 mm in length. Any experienced machinist will know quite well the difference in rigidity between a 4-inch long holder and a 2.5-inch long holder.
If this is true, we can say that implementing BIG-PLUS is equivalent to a 40% reduction in length in terms of rigidity. Theoretically, a BIG-PLUS tool holder will behave like a standard tool holder that is nearly half of its length! Obviously, we’ve used simple and idealized cases here to represent the complicated and dynamic world of metal cutting. Tool holders, of course, don’t have uniform body diameters or materials and the cutting forces usually aren’t acting in one direction in a constant and predictable way. If our holder necks up and down to different body diameters along its length, which is realistically what happens, each of these sections would be its own microcosm of “beam” that would influence the overall behavior (at that point, finite element analysis on a computer becomes the only practical way to predict behavior). So, will the advantage of BIG-PLUS really be as dramatic as our hand-calculated classical beam theory suggests? Probably not, but it depends on the tool holder/tool. Most cases will follow our simple model quite closely in practice; others not so much. If nothing else, we’ve demonstrated how dramatically the flange contact of BIG-PLUS can influence rigidity, at least in a purely mathematical sense. As if you needed any more reasons to be on the BIG-PLUS bandwagon besides increased rigidity, you will also eliminate Z-axis movement at high speeds, improve ATC repeatability and decrease fretting. This means that you will take heavier cuts, scrap less parts, and increase tool and spindle life. BIG-PLUS isn’t a new idea by any means, but with a proven track record of tackling tough jobs, it’s hard to imagine working in a modern machine shop and not taking advantage of what it has to offer. If you’re still not convinced, we can also compare the rigidity in this way: Let’s say there is a Ø63.5 mm BIG-PLUS CAT40 bar of some arbitrary length. One of our more common gage lengths is 105 mm, or just over 4 inches, so let’s use it as an example. You’re probably wondering, at what length would a comparable standard CAT40 holder have an equal stiffness? If we take our stiffness expression and set it equal to itself (one side representing BIG-PLUS, the other non BIG-PLUS), we can plug in this BIG-PLUS holder length and our known diameters to find our unknown non-BIG PLUS length: |
Technical Support BlogAt Next Generation Tool we often run into many of the same technical questions from different customers. This section should answer many of your most common questions.
We set up this special blog for the most commonly asked questions and machinist data tables for your easy reference. If you've got a question that's not answered here, then just send us a quick note via email or reach one of us on our CONTACTS page here on the website AuthorshipOur technical section is written by several different people. Sometimes, it's from our team here at Next Generation Tooling & at other times it's by one of the innovative manufacturer's we represent in California and Nevada. Archives
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