by Alan Miller
Originally published in Fabricating & Metalworking Oct 24, 2018
Shrink-fit and hydraulic holders are both useful in low clearance, tight work envelopes found in moldmaking and multi-axis machining applications. When deciding which one to use, their differences will guide your choice. Here are some of the fundamental contrasts to help you decide which holder type is best for your work.
Hydraulic holders (shown here) and shrink-fit holders share a middle-of-the-road gripping strength: about half that of a milling chuck and about double that of collet chucks. The superior vibration control of hydraulic chucks makes them good choices for finish milling, reaming and drilling work. While they may not be as precise, the rigidity of shrink-fit holders makes them effective in moderate to heavy milling work where clearance is an issue, and in many high speed scenarios.
Shrink-fit and hydraulic holders are especially useful in low clearance, tight work envelopes because of their relatively slim design. This has made them effective in moldmaking applications and more coveted since the widespread adoption of multi-axis machinery. Hydraulic and shrink-fit holders also share a middle-of-the-road gripping strength: about half that of a milling chuck and about double that of collet chucks.
These similarities are why we’re taking the time to compare the two. When it comes to deciding between one or the other, it’s the differences that will guide the choice. So let’s dig into some of the fundamental contrasts that may help you decide which holder type is best for you and your work.
When it comes to the holders themselves, shrink-fit is generally a slightly lower cost. The delicate hydraulic clamping systems built into the holders add cost when compared to the simple and solid bodies of shrink-fit holders. Where the major difference lies is in the equipment needed to heat the shrink-fit holders.
When heated to the proper temperature, the resulting growth of the ID allows the tool to be slipped into the bore. Once cooled, the holder expands, gripping the tool. This process, especially the induction heating, involves cost. Shrink-fit heating systems start at around $5,000 and go up from there. They also require fairly significant power, adding a slight ongoing expense.
If you want to see a full return on your shrink-fit investment and then some, maintenance is critical. When dealing with temperatures that can approach 600 deg F, the stakes are heightened.
This is why we recommend using dry cutting tools without oil on them. From there, diligent attention must be paid to the cleanliness of holder bores and tool shanks. Any contamination will be baked onto the metal and progressively deteriorate performance.
When it comes to hydraulic chucks, maintenance is straightforward as long as the hydraulic chamber stays sealed. To ensure the hydraulic system performs consistently, we recommend using test pins to gauge its force over time.
Training, Handling and Safety
Hydraulic chucks are infinitely simple. A turn of a wrench locks the tool in place. When it comes to shrink-fit systems, there are a few more factors to consider when getting the team up to speed, including safety considerations. Aside from the operators who handle the tooling and heating system directly, others on the floor need to be made aware of the risk of burns.
Heating stations are usually benchtop arrangements because of the power requirements. This means hot metal will need to be transported across the floor in one form or another. Another training consideration is that tools can be overcooked, so to speak. This will cause permanent damage that harms performance. Operators must understand, know how to prevent and diagnose this.
As mentioned earlier, hydraulic chucks use a simple wrench to lock in the tool. Tools can also be swapped at the machine or offline. When it comes to shrink-fit setups, they must be done exclusively offline where the heating and cooling can be powered. Most heating cycles can be as fast as 15 seconds.
Cooling can take several minutes, even with assistance like air. Having extra compatible holders is a viable solution to speed concerns, if you’re comfortable with the additional investment. All that being said, there are significant time-saving opportunities to be found setting up tools offline. We believe strongly in tool measuring systems and recommend offline setup when and where applicable.
Hydraulic chucks have two specific advantages in terms of vibration and accuracy. The first is that shrink-fit tools and holders are dependent on the heating and cooling processes being consistent. This brings us back to the maintenance section above; the slightest imperfection in the holder bore, not to mention the natural inconsistencies in the heating and cooling processes, can be multiplied at the cutting edge in the form of vibration or runout.
There is also the chance of some variation from operator to operator. Hydraulic chucks are less reliant on these variables and their production is imminently consistent. Once a master bore is established during manufacturing and assembly, it’s a repeatable process over thousands of cycles.
This translates to consistent clamping tolerances and forces over the life of the holder. The second advantage is the natural damping characteristics that hydraulics provide. That’s not to say shrink-fit holders are ineffective in terms of vibration management. Their runout is five times better than side-lock holders.
Roughing and Finishing
That brings us to some application talk. While they may not be as precise, shrink-fit holders’ rigidity makes them effective in moderate to heavy milling work where clearance is an issue, and in many high speed scenarios. The superior vibration control of hydraulic chucks makes them good choices for finish milling, reaming and drilling work.
Roughing and Finishing
Up to this point, you may think I’m an advocate of hydraulic chucks over shrink-fit holders, but that’s not the case. We offer both products. In fact, shrink-fit holders are fundamentally the perfect tool holder. From an engineering perspective, there are no moving parts, no additional components, they use the properties of the holder itself to grip the tool and they’re symmetrically round. But as we all know, a manufacturing floor is not a perfect environment. Variables must be considered when choosing equipment.
Should the choice between hydraulic chucks and shrink-fit holders come up, the factors discussed here will help guide your choice.
With this innovative centering tool from Big Kaiser, spindles and tools can be centered quickly and easily. It's ideal for limited spaces within small lathes. The Centering Tool is a static dial gauge for easy centering.
Carmex Mini Tools feature BLU submicron grade carbide with advanced PVD triple layer coating for high heat resistance
The Mini Tools line from Carmex, combining long-reach carbide shank toolholders, through tool coolant, with a wide selection of quick indexing coated inserts, are designed for high performance threading, turning, grooving, boring, and chamfering in conventional and hard materials.
Applications include threading – threads with large pitch/profile, long thread generation, and applications requiring over-hang.
The carbide shank toolholder with through coolant provides excellent vibration resistance combined with long reach.
Inserts feature BLU submicron grade carbide with advanced PVD triple layer coating for high heat resistance and smooth cutting operation. Inserts are available in a variety of sizes and configurations.
According to Jeff Dei, president of Carmex USA, “The new Mini Tools line is another example of Carmex’s emphasis on top quality tooling for smaller parts. The increasing market for Swiss-style machining on smaller complex parts includes multiple applications in fields such as aerospace, medical tools and implants, the energy industries, and others. The Carmex combination of innovative product design and superior quality is helping our customers meet these new challenges and maintain a competitive edge.”
Kurt Machining Utilizes Live Tool Speed Increaser, Realizes 9x Tool Cost Savings in Less Than a Year
Minnesota CNC shop, and manufacturer of Kurt Vises, uses Heimatec speed increaser to up RPM and feed rate; significantly reduces cycle time on aluminum engraving application.
Kurt Machining (Minneapolis, Minnesota) specializes in providing precision CNC machined parts, using state-of-the-art technologies and up to 5-axis machining. Since 1952, this 110,000 sq. ft. shop has provided its customers in a variety of high-quality demand markets with components and welded assemblies. These include aerospace, defense, semiconductor, energy, automotive and more.
Eisenshank turned to his local tooling distributor, Abrasive Specialists, Inc. (ASI) and their tooling partner, Platinum Tooling, for suggestions. Leigh Kinnan of ASI worked with the local Platinum Tooling representative, Cody Papenfus, to test run a Heimatec speed increaser, with the goal of increasing RPM on the machine and decrease part cycle time, with a documentation of the potential savings.
After performing the calculations in consultation with Preben Hansen, president of Platinum Tooling and exclusive importer for Heimatec products in North America, it was determined a significant savings could be realized.
Detailing the application, ASI demonstrated that a 1:3 speeder, increased the spindle RPM enough that when coupled with the nearly 3X increase in the feed rate on the machine, would produce a significant improvement to the current machining cycle.
Calculating the reduction in machining cost per part and factoring the cost of the speed increaser, it was determined the use of the Heimatec product onboard the Hwacheon turning center would result in a 9X cost saving for the customer, in the first year’s production run on this engraved aluminum component.
As Shawn Eisenshank notes, “This is one of those classic scenarios, where the theoretical has proven out in practice, as we’ve seen exactly the results ASI and Platinum Tooling proposed in their test calculations.”
Cody Papenfus of Hexis in Plymouth, Minnesota, who is the area rep for Platinum Tooling adds, “We say we put our expertise to work at the spindle of the machine and, in this case, that’s exactly what happened. The speed increaser performed as expected, the customer got the results promised and it was a win-win, for all. We serve our customers for the long haul and successes like this one are the big reason.”
Kurt Machining performs both vertical and horizontal milling and turning, complex assemblies and weldments, delivering with rapid lead times. CAD compatibility is offered for web-based communications and fully interactive manufacturing engagement for its customers.
The company performs contract manufacturing in high quantity as well as prototyping for new designs. Kurt also performs impact extrusion, heat treating and cleanroom operations including ultrasonic cleaning of stainless steel and aluminum components and assemblies, with cleaning to Class 1000 with 100 protocol.
The company is ISO 9001:2015 and AS9100D plus NADCAP Certified. Kurt Machining is quality certified by the U.S. Government to MIL-Q-9858 and MIL-I-45208.
Accu is the message that is displayed when the battery needs to be changed.
This message does not mean there is an error or accuracy malfunction with the boring head. The head should still continue to function for a few more adjustments. If this message appears on the EWE heads, the wireless connectivity to the App and history functions are deactivated until the battery is replaced.
NTK offers an extensive line of high precision boring tooling designed for Swiss machines. One of these produce lines is called “Mogul Bar”. The Mogul Bar system provides the user outstanding chip control and higher rigidity than most conventional tooling on the market.
Outstanding chip evacuationThe most notable characteristics of the Mogul Bar is excellent chip evacuation and chip control. Mogul Bars outfitted with NTK’s “F” or “FG” chipbreaker inserts will evacuate chips backwards.
This means that when a Mogul Bar machines an I.D. bore, chips comes out towards the bore entrance. The major-ity of boring processes on Swiss machines are done on the main spindle side and thus the bore itself is a blind hole. This machining process creates many issues if you use conventional boring bars designed for CnC lathes.
Typical difficulties incurred during a boring process on Swiss machines are either chips remaining in the bore and rough surfaces caused by inconsistent chip control. However, Mogul Bars equipped with nTK uniquely designed chipbreakers, evacuate chips straight backwards and solves both of these problems at once.
Another important feature of the Mogul Bar series is high rigidity. Mogul Bars increased rigidity is a result of a newly designed bar head configuration and a minimal flat width on the bar.
Steel shank Mogul Bars can machine as deep as L/D=5, a depth which nor-mally requires expensive carbide shank boring bars.
NTK carbide shank Mogul Bars can machine up to L/D=7 depth and this gives users flexibility of machin-ing deeper bores in a single process. rigidly and mini-mal flat widths reduce vibration.
Variety of Insert Grades
NTK offers both coated carbide grades and cermet insert grades for Mogul Bars. As most tooling engineers know, cermet grades can machine at faster speeds with higher productivity, provide better sur-face finishes and can achieve more accurate dimen-sion control, than carbide grades. These benefits come from the fact that the primary substrate of cermet grades, Tin /TiC, are chemically stable compared with WC of carbide grades and have better adhesion resistance.
Mogul Bars are available from a minimum machining diameter of 5mm. With the combination of NTK unique chipbreakers, you can enjoy better chip control and highly rigid boring bars. In comparison with solid carbide boring tools, Mogul Bars has cost advantage as well.
If you are facing chip control or chattering issues, NTK believes that Mogul Bars can be the answer to your problems.
Over the years, many of our customers have come to us because they were regularly breaking taps.
This meant that the holes had to go from a depth of .150" to .190". The 2-56UN thread’s major diameter was .086", and the drill diameter .070".
Repeatability was nearly impossible on his CNC equipment, and he literally came in every Saturday to tap the holes by hand. When he started talking with us, he was breaking his taps after only 20 holes — an extraordinarily short tool life.
By re-examining his technology, and switching to Carmex Precision thread milling, he was able to accomplish the threading of 683 holes with a single thread-mill on his CNC equipment.
Despite the number of passes, the wear factor between the first and the last holes could only be measured in tenths, and the customer was able to get the thread detail back to its original .150" full thread depth. Perhaps just as important, his Saturdays are now “tap-free.”
Ohio manufacturer of oil field equipment saves 184 hours on one high-precision cutting tool head made of Nitralloy®
PMC-Colinet has a long history in the pipe and tube market, having started in 1912 and introduced the world’s first carbide-tooled pipe threading machine in 1958. Today, the company is established as a primary supplier of machines to the OCTG sector. Its customers include integrated steel mills that sell finished pipe and couplings to the oil and gas industries, specifically using the company’s machines for threading products for downhole drilling applications. PMC-Colinet also supplies cutting tools, consumable tooling, aftermarket parts and field service to the industry.
Recently, PMC-Colinet did an assessment on one very challenging job, namely, cutting keyways into large sections on a high-precision cutting tool head made of Nitralloy. For many years, the production had involved the use of a shaper to produce the keyway in the bore of the die head. Typically, the bore ranged from 6” to 13” in diameter and more than 12’ in length. These keyways have extremely tight tolerances, with location at +/- 0.0005”, width at +/- 0.001” and depth to +/- 0.0025”.
One style of cut is a 3-step keyway that does not run all the way through the bore, stopping at a window that is milled from the outside diameter. This situation prevented the PMC machining department from using a ram EDM to produce the keyway. The only options previously used were to rough the keyway on an old shaping machine, then send it out for ram EDM. This process required 50 hours on the shaper, plus approximately a week for the ram EDM. Another option was to do the job entirely on the shaping machine. Roughing the keyway had to be much more precise and usually required about 61 hours. Plus, an additional 145 hours were required to finish the part, normally. These times included 10-12 hours for set-up.
The team at PMC, led by Milling Foreman Rick Kokish, decided to explore other methods to produce this part on its Monarch 175B VMC. They conducted an exhaustive search on the Internet, turning up over 133,000 hits for 90º angle heads. After more than 30 hours of gleaning out the unsuitable products, they narrowed the search to just two vendors. Both manufacturers visited the facility and brought out their standard angle head designs. One of the companies, Heimatec, quickly realized this job would require a custom 90º head design to satisfy all the requirements.
One competitor brought a standard 40 taper tool, while Heimatec presented a larger, heavier 50 taper unit.
A week later, Preben Hansen, Heimatec’s president, supplied a drawing for the proposed custom product. PMC engineering reviewed both the standard and custom designs and awarded the project to Heimatec.
The angle head supplied was designed to perform a wide variety of cutting tasks on the various end products produced by PMC. On the keyway in a bore 6” in diameter and 12” in length, using the Heimatec 90º head, PMC spent 6 hours in setup, 3 for roughing and 3 for finishing, plus 12 to 16 hours of actual cutting time. This represented a total savings of 184 hours on a single part. Though the head appeared too slender to remain rigid during the entire cutting cycle, according to PMC sources, the performance was deemed very successful.
Heimatec’s head design for this custom radial drilling and milling head features an adjustable tool stop, 3 support pins for stabilizing the tool, CAT 50 taper style, 360º indexable pivot on the angle head and inclined tooth gear design for maximum rigidity.
During the project, Preben Hansen from Heimatecc supervised the installation. After the stop block attachment and grinding of the supports pins for the head were accomplished in just one day, the head was mounted and several experimental cuts were performed. Hansen spent time with Rick Kokish as well as CNC programmer Barry Spence at PMC, discussing various options for programming the head on the Monarch VMC. The very next morning, the setup was performed and an actual keyway was roughed.
Results ongoing have continued to satisfy all requirements, according to PMC sources.
Technical Support Blog
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