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What are the Different Types of Collets?

6/7/2023

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Technical Blog excerpt courtesy of  Techniks USA
Collets come in many different types and sizes. Here is an overview of three of the more popular types of collets, along with the pros and cons of each system.

ER Collets

ER collets have between a 0.020” and 0.040” holding range
ER collets have between a 0.020” and 0.040” holding range
The ER collet system has become very popular due to the flexibility of the system to hold a variety of cutting tool shank types including drills, end mills, and taps. Also, ER collets provide several solutions for increasingly popular coolant-through cutting tools.

Most standard ER collets have between a 0.020” and 0.040” holding range, making them a good choice when needing to hold odd-sized cutting tool shanks. This holding range also means fewer ER collets are required to hold a range of cutting tool shank diameters as opposed to other collet systems like TG.

The popularity of the ER collet system has led to several variations to hold a wide assortment of cutting tool shanks. Some ER collets have been modified with squares at the bottom to hold taps. Others have been modified to provide quick-change capabilities or compensation, also called “float”, for rigid tapping cycles as shown in the images below.

Specialized ER Collets

Other modifications include special slotting designs that seal around the cutting tool shank and force coolant through channels in coolant-through tooling, as well as modifications to include coolant ports in the collet that direct coolant to the cutting area.

TG Collets

Techniks Parlec TG PG collet 75 100
TG collets have about the same accuracy as DA collets, but because there are more slots, and therefore more faces clamping on the cutting tool shank, they tend to deliver greater holding power.

TG can be a good solution for larger shank diameter cutting tools, but they generally limit how far down into a pocket you can reach due to interference with the collet nut, as TG collet nuts tend to be quite large.
TG collets are not as popular as ER collets for several reasons. Most notably, the larger diameter collet nuts can require the use of extended end mills to avoid interference from the collet nut when milling pockets.

Also, since TG collets have a very small collapse range, they are intended for use with one size cutting tool shank.

ER collets, by contrast, offer a large collapse range that can be helpful when clamping odd-shank diameter tools.
On the flip side, TG collets tend to have a bit more holding power than ER collets due to the collet base having a 4° taper as opposed to the 8° taper found in ER collets. This can make TG collets a good choice when machining with longer-length cutting tools.

Double-Angle (DA) Collets

Stop using DA collets in CNC Machining
Please stop using DA collets in CNC Machining
Double-Angle (DA) collets have been around for a long time and continue to be used in the market. There are, however, many issues associated with DA collets of which users should be aware.

Let's just clear the air and say it: Don't use them. If you have them in your shop, replace them with ER Collets and ER Collet Chucks as soon as possible and you will recoup the cost of the new holders and collets in your tool life probably within a month or two.

One of the primary issues with DA collets is that they essentially clamp on the cutting tool shank with only two opposing faces in the I.D. bore.

DA collets have four slots in the front of the collet and four slots in the back of the collet creating four clamping faces.

However, when DA collets are tightened towards the lower end of their collapse range, two of the faces tend to be pushed out of the way so only two of the faces are clamping on the cutting tool shank. This may cause some runout at the nose when the tool is inspected in a presetter.

Additionally, when the tool begins cutting and side forces are applied to the cutting tool, the cutting tool tends to deflect into the area where the faces are not clamping on the tool shank.

This results in excessive chatter that dramatically reduces tool life and results in rough surface finishes. You will be hard-pressed to find a quality end mill holder manufacturer endorsing the performance of their tooling in DA collets.
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P3 Coated ER Collet Reduces Friction & Improves Tool Life

3/23/2022

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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.
As the collet nut presses down and turns against the 30° face of the collet, the collet face will tend to twist with the collet nut, distorting the shape of the collet.

​This radial distortion negatively affects tool run-out sine the collet bore is not longer straight.

Parlec’s new  P3 ER collets have a special anti-friction coating on the 30° face that dramatically reduces friction at this critical connection.
ER Collet face area of Friction
Parlec P3 Collet coating area
The result?
  • Improved tool runout
  • Longer tool-life
  • Less frequent tool changes
  • Improved surface finishes

Other Parlec P3 collet advantages:
  • 3 micron T.I.R
  • Fewer slots that standard collets making them more rigid – in the cut!
  • Special slotting seal for coolant up to 2,000 PSI

​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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The Different Types of Boring Tools

2/16/2022

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different-types-of-boring-tools
Put simply, the manufacturing process of boring is enlarging a hole in a piece of metal. There are quite a few different pieces of machinery or approaches that can be used to make holes from lathes and mills to line boring or interpolation. We wanted to do a quick break down of the different kinds of boring tools available to bore holes and/or secondary boring operations.

Boring Bars

Boring deep holes can involve extreme length-to-diameter ratios, or overhang, when it comes to tooling assemblies. Since it can be difficult to maintain accuracy and stability in these scenarios, we need boring bars to extend tooling assemblies and while maintaining the rigidity to make perfect circles with on-spec finishes.

Solid boring bars
Typically made of carbide for finishing or heavy metal for roughing, solid boring bars have dense structures that make for a more stable cut as axial force is applied.

Damping bars
When cutting speeds are compromised, or surface finishes show chatter in a long-reach boring operation, damping bars are an option. They have integrated damping systems. Our version, the Smart Damper, works as both a counter damper and friction damper so that chatter is essentially absorbed.
different-types-of-boring-tools-2

Boring Heads

Boring heads are specifically designed to enlarge an existing hole. They hold cutters in position so they can rotate and gradually remove material until the hole is at the desired diameter.

Rough boring heads
Once a bore is started with a drill or by another method, rough boring heads are the choice for removing larger amounts of material. They are built more rigid, to handle the increased depths of cut, torque and axial forces needed to efficiently and consistently make the passes to remove materials.

Fine boring heads
Fine boring heads are best used for more delicate and precise removal of material that finishes the work the rough boring head started. They are often balanced for high-speed cutting since that’s the best approach for reaching exact specifications.

Twin cutter boring heads
Most boring heads feature one cutter that cuts as its feed diameter is adjusted by the machine. There are twin cutter boring heads that can speed up cutting and add versatility. For example, the Series 319 and other BIG KAISER twin cutter boring heads include two cutters that can perform balanced or stepped cutting without additional accessories or adjustments by switching the mounting locations of the insert holders that have varied heights.

Digital boring heads
Traditionally, adjusting boring heads has been painstaking and time-consuming, especially when it’s done in the machine. It’s easy to make mistakes when maneuvering to read the diameter dial and adjusting it to the right diameter. Digital boring heads have a LED that makes precise adjustments much easier.
different-types-of-boring-tools-4

Starter Drills

Since cutters are on diameter of boring heads and not their face, they are not able to initiate a hole on a flat surface or raw material. Especially in smaller bores, fluted drills called starter drills can be used to get the hole started before rough boring.

Specialty boring heads
Back boring and face grooving heads, as well as chamfering insert holders, are available for some of the most common secondary operations, after a hole is bored. We produce specific heads with cutters at the appropriate angles so each of these operations can be done without manually moving the part, changing the tool or adjusting the cutter angle.

Modular boring tools
Since limiting length-to-diameter ratios is so crucial to boring success, it’s extremely valuable to be able to make your tooling assembly as short as possible. Our modular components are based on a cylindrical connection with radial locking screw that allows for the ideal combination of different kinds of shanks, reductions and extensions, bars, ER collet adapters and coolant inducers.

Looking for some help finding the right boring equipment for your next job or new machine? Our engineers are here to help. Get in touch with us here.
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Micromachining: What to Know About Toolholders, Drills, End Mills, and CNC Machines.

9/21/2021

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About the author: Jack Burley, Vice President of Sales and Engineering and Big Kaiser Precision Tooling Inc.
Micromachining, cutting where the volume of chips produced with each tool path is very small, is not a high-speed operation in relation to chip load per tooth. Rather, it involves a high spindle speed relative to cutter diameter. The part may be physically larger, but details of the part require ultra-small profiles achieved only by micromachining. In other words, micromachining is not limited in scope to only miniature parts.
Big Kaiser considers tools with <3mm to be micro tools with unique geometric considerations.
Big Kaiser considers tools with <3mm to be micro tools with unique geometric considerations.
TOOLHOLDING
In medical work, where tight tolerances are standard, dynamic runout; the measurement of the spindle at high speeds, performed using laser or capacitance resistance technology, and balance must be controlled to deliver and maintain viable tool life.
Much of this burden falls on the holder. Balance doesn’t change as spindle speed increases, however the forces it creates increase exponentially alongside speed. The impacting results appear quickly in micromachining.

When runout occurs, the edge most affected takes over the bulk of the cutting. Uneven wear causes the tool to fail more quickly than if the tool rotates about the centerline as intended. In one customer application, we found that drilling into a steel workpiece 0.590" deep with a 0.118" diameter carbide drill in a holder with 0.00008" runout accuracy produced 2,300 holes.
BIG KAISER HSK-E32, E25, or E20
Micro milling machines, ideally suited for small tools and small workpieces, are characterized by spindle speeds of more than 50,000rpm using small HSK tool holders such as HSK-E32, E25, or E20.
A holder with 0.00060" runout accuracy produced nearly two-thirds fewer holes, only 800. In this scenario, the shop could save hundreds of dollars a month in carbide costs – as well as labor costs due to less tool changing – by making one smart tool holder choice.

Holder attributes that can boost production include symmetrical design, a perfectly concentric collapse of the collet around the cutter, and a ball-bearing raceway nut with precision-ground threads.

CHALLENGES
While these characteristics are good rules of thumb, things change fast in this field and, like our customers, we must adapt as trends emerge.

Batch sizes are getting smaller. Bone screws, for example, were typically run on multi-axis, Swiss-type lathes where the same tools and programs ran for days at a time. Traditionally, prototyping in this arrangement was not an option because of the complexity and time involved in programming and setup. Today’s need for customized sizes demands flexibility and quick changeover to remain productive.

We are investing a large portion of our research and development (R&D) in tackling this challenge. We are working on hydro-clamping tool holder systems that could make the decades-long approach of using ER collets obsolete. It would make it possible, for example, to perform a simple drill change on a gang slide in seconds.

COOLANTS
Another trend in medical manufacturing being driven by the U.S. Food and Drug Administration (FDA) is clean machining without the use of water-soluble coolants.
Super-chilled CO2 or cryogenic machining with liquid nitrogen are considered possible replacements. Protecting small holder parts at the nose from coolant has always been a concern, but using gas requires more attention for holders to be effective.
Mega Micro Coolant Nut for Mega Micro Chuck 6S
The Mega Micro Coolant Nut for Mega Micro Chuck 6S provides a more efficient coolant supply for micro cutting tools and is designed for high-speed micro machining up to 6mm.
We are focusing on two features:
  • Holders that remain completely sealed to outside atmosphere
  • Very small delivery holes in collet faces or clamping nuts that properly restrict gas flow
Big Kaiser hydro- clamping tool holder system for Swiss-type lathes
Matching medical components to each patient demands flexibility. This hydro- clamping tool holder system for Swiss-type lathes would make the decades-long approach of using ER collets obsolete by making it possible to perform a simple drill change on a gang slide in seconds.
TOOLING
Tool considerations also must be taken into account to keep up with the demanding medical field. Better results often cannot be achieved by simply increasing spindle speeds or using smaller tools; a deeper understanding of cutters is necessary.

We consider tools with diameters <3mm to be micro tools. These aren’t simply smaller versions of their macro counterparts. They have geometric considerations all their own. For example, the 1mm Sphinx drill can run at 80xD. But this is only possible because the cylindrical shaping extends further down the tool, closer to the tip, to facilitate pecking and maintain strength.

Tool carbide should be ultra-fine grain (nano or submicron grain size) to ensure high abrasion resistance and good toughness. Coatings are valuable too, but it’s important to understand how coatings can negatively impact micro tool performance. Micro tools have extremely fine surface finishes and sharp cutting edges. Coatings can fill in valuable space – a flute on a drill, for example – needed for proper chip evacuation, which is critical in these applications.

Coatings must be ultra-thin (<1µm) and smooth; our experience shows that misapplied coatings result in poor tool life due to breakage; the coating reduces cutting edge sharpness, increasing torque force on the drill. When coating is necessary, consult with the cutting tool manufacturer to provide this directly.

Chips and small tooling naturally do not get along well. Compensating for low spindle speeds with tools that have more flutes support an ideal feed rate, but chip evacuation may suffer. Determining the appropriate chip load – as close to the cutting edge as possible – allows operations at the highest possible spindle speed, accelerating the cycle and improving surface finish.
Optimal conditions exist when the chip load is relatively equal to the cutting edge radius.

Many micro end mills are designed so the cutting edge radius has a positive rake angle to create a shearing action. A chip load less than the cutting edge radius often results in a negative rake angle where the tool rubs rather than cuts. This increases the force required and generates more heat which can result in built-up edges and poor tool life. A chip load significantly bigger than the cutting edge radius often leads to premature failure because the tool is not robust enough to withstand such forces.

MACHINE TOOLS
Micromachining requires machine tools with very high sensitivity, fine resolution in the feed axis, and very precise spindles capable of high speed with low dynamic runout. For micro-drilling operations, specialized micro machines are best.

Micro milling machines are suited for small tools and small workpieces. They are characterized by spindle speeds faster than 50,000rpm using small HSK tool holders such as HSK-E32, E25, or E20. With the right holder, tool runout can be controlled to less than 1µm (0.000040") at the cutting edge, ensuring sub-micron accuracy.

In medical micromachining, understanding each piece of the equipment puzzle is critical. It’s also important not to make assumptions based on other tools or parts you may have worked with, especially in more standard sizes. Invest the right time and energy in gearing up for the next medical job and you’ll get more parts done right faster.

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10 Tips for Improving Tool Holder Performance

8/19/2021

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10 Tips for Improving cnc rotary ToolHolder Performance
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:
  1. Polished shanks reduce friction, as does the cleanliness.
  2. Oil and coolants reduce gripping power.
  3. Cutter shank roundness is often assumed to be close enough to perfect to ignore, but in reality, a 25 millionths tolerance is necessary for high-speed performance.

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. 

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INDICATION MARKS ON PULL STUDS ​IS NOT NORMAL

5/25/2021

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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.
Picture
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.

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Don't Take Your Retention Knobs for Granted

2/16/2021

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​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. 
1 Retention knob pull stud casues of failure

Retention knobs go through thousands of tool changes which means that they are subjected to the very high pulling forces from the spindle’s drawbar.

This force can be up to 2300 ft. lbs. for 40 taper toolholders and up to 5000 ft. lbs. for 50 taper toolholders.
​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 FAIL

Pull 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 threads on your retention knob will stretch slightly when load is applied and the loading borne on each thread is different.

When you apply a tensile load on a threaded pull stud, the first thread at the point of connection sees the highest percentage of the load.
Percentage of Load on a Retention Knob Thread
Percentage of Load on each thread of a Retention Knob.
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 DESIGN

Repetitive 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?  ​
For the same reason we put corner radiuses on end mills, sharp corners are a common area of failure for any mechanical device.

​The same holds true with your pull studs:  The sharp angles on the head of the retention knob and at the minor diameter of the threads are common locations of catastrophic material failure.
Retention Knob Metal Fatigue
These are the two weakest points of any 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 Retention Knob for Rotary Toolholders
Styles of MegaFORCE Retention Knobs

MATERIAL

Not 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

5. Cut thread vs rolled thread retention knob
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%.  
6. LMT Fette - Thread rolling with F2 Rolling head on CNC lathe
Shown here is a Fette head cold forming a thread. Note how the three roller forms center and maintain near perfect concentricity of the pull stud shaft.
In cold forming, the thread rolls are pressed into the component, stressing the material beyond its yield point. This causes the component material to be deformed plastically, and thus, permanently.

There are three rollers in the typical thread rolling head that maintain better concentricity by default than single point cutting of the threads.

Also, unlike thread cutting, the grain structure of the material is displaced not removed.
Rolled threads produce grain flows that follow the contour of the threads making for a stronger thread at the pitch diameter which is the highest point of wear. 

The cold forming process also cold works the material which takes advantage of the nickel work hardening properties of 8620.
7. Fette Turning Concepts Thread Rolling Magnaflux
Photo courtesy Mike Roden at Fette Tool. www.turningconcepts.com
By comparison, cut threads interrupt the grain flow creating weak points.

MEGAFORCE GEOMETRIC DESIGN

MegaForce Retention Knob features vs standard pull stud
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.
Blended Radii
With the new Techniks MegaFORCE pull studs, stress risers of sharp angles have been eliminated through the blended radii on the neck where the gripper engages under the head of the pull stud.
9. Techniks MegaFORCE Pull Studs
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.
MegaFORCE Technical Specs
  • Material: SAE8620
  • All knobs are case carbrized, hardened, and tempered to:
    • Case depth: 0.025” – 0.030”
    • Surface hardness: HRc 56-60
    • Core hardness: HRc 44 minimum
Torque Specs
The following are the guidelines for torquing your pull studs according to Techniks.
  • BT 30 36 ft. lbs.
  • ISO 30 - 36 ft. lbs.
  • 40 taper - 76 ft. lbs.
  • 50 Taper - 100 ft. lbs.

RETENTION KNOB BEST PRACTICES

In 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.
  • Regularly inspect retention knobs for signs of wear. Wear may appear as dimples or grooves under the head or visible corrosion anywhere on the retention knob. 
Picture
  • If the retention knob demonstrates any signs of wear replace it immediately
  • Make sure to properly torque the retention knob to the manufacturer’s specifications. Use a torque wrench and retention knob adapter to ensure proper torque. 
  • Overtightening can overly stress the retention knob leading to premature failure and can cause the tool holder taper to swell leading to a poor fit between the machine spindle and the tool holder.
  • Apply a light coat of grease to the retention knob MONTHLY to lubricate the drawbar. If you use through-spindle coolant (TSC), apply grease to the retention knobs WEEKLY.

Special thanks for Greg Webb at Techniks and Mike Roden from Fette Tools/ Turning Concepts, for providing technical insights. 
1 Comment

Spindle Maintenance Tips to Ensure Top Machining Performance

11/11/2020

2 Comments

 
A machine’s spindle is one of the key links in the machining chain. In other words, if there are irregularities inside or at the face, they can show up on your part.

It makes regular inspection and spindle maintenance critical to getting the most out of your equipment and maintain process efficiency. These three accessories, the Dyna Contact Taper Gage, the Dyna Test Bar and the Dyna Force Measurement Tool, can help you perform this maintenance easily without eating into valuable spindle time.

Dyna Contact Taper Gage

Dyna Contact CNC Spindle taper gage
Dyna Contact CNC Spindle Taper Gage
Spindle taper protection
The Dyna Contact taper gage makes verifying taper accuracy simple. All the operator must do is apply blue dye to the ceramic gage, insert it in the machine spindle and remove it. A quick visual check will reveal any improper contact points inside the taper.

Dyna Test Bar

Dyna CNC Spindle Test bar
Dyna CNC Spindle Test Bar
Static accuracy inspection
Another way to ensure your spindle bearings are good and ensure quality control is to measure its static accuracy. Using something like our Dyna Test bar, which inserts into the taper and extends out, is one way to do this.
With the help of a dial indicator, you can uncover any runout while safely spinning the spindle at a very low RPM and verify the parallelism of Z-axis motion.

Dyna Force Measurement Tool

Dyna Force CNC Spindle force measurement tool
Dyna Force CNC Spindle Force Measurement Tool
Retention force verification
Finally, in the machinery category, let’s talk retention force. The clamping mechanism in your spindle reduces chatter while ensuring rigidity and reliability. Like any other mechanism this can wear, making regular inspection a smart idea.
The Dyna Force measurement tool provides a precise digital reading that reveals reduction in retention force in increments of 0.1kN.
If you would like a demonstration for any of these tools contact us or set up an appointment for one of our Next Generation Tooling engineers to visit you!
2 Comments
<<Previous

    Technical Support Blog

    At 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.
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    Authorship

    Our 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.

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