A REVIEW OF THIS MACHINING METHOD, THE BASIC CONCEPTS AND SOME EXCITING DEVELOPMENTS IN THE TECHNOLOGY
by Preben Hansen, President, Platinum Tooling Technologies Inc.
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 email@example.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.
Here is a very helpful video on 'how-to' setup a subplate with SpeedLoc by mPower.
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.
compiled & edited by Bernard Martin
As more and more of our customers are using Martindale Gaylee Circular saws we put together this guide to the commonly asked questions such as "Is there a rule-of-thumb for the number of teeth?" or "How much side clearance should I have?" Here we cover a lot of the fundamentals of selecting the right circular saw blade configuration, some tips, tricks, and troubleshooting for when things go wrong.
Circular Saw Feed Rates
These are general cutting speed recommendations for circular saws used in metalcutting from Martindale/Gaylee. The may vary from application to application but are basically some general suggestions starting parameters when using high speed or carbide saws.
Selecting the Proper Number of Teeth in Your Metalcutting Saw
Generally speaking, deep cuts and soft material require fewer teeth for chip clearance and stronger teeth (landed).
Thin material requires more teeth, but keep-in-mind that at least 2 teeth on the blade need to be engaged in cut. Hard materials and narrow slots (under .025”) likewise require more teeth.
Hard Materials require more teeth, and give a smoother cut, but at a much lower production rate.
Alternately beveled teeth keep chips from sticking in the cut and in the tooth gullets.
And Remember that there should be at least 2 teeth engaged in the cut at all times.
Rake Angles and Side Clearance Angles
Just as in an end mill or a band saw blade, a rake angle is the term used to describe the direction of the blade’s teeth, as referenced from the rotation and central axis of a saw blade. If you imagine a line going from the exact center of the blade to each tooth, having the front of the tooth directly on that line would be a zero degree rake angle. The rake angle of the blade is described in comparison to that imaginary line.
A positive rake angle meana that the teeth are angled more towards the angle of rotation, while a negative rake angle would mean that they are angled backwards, away from the direction of rotation. Generally speaking, the preferred rake angle is:
SIDE CLEARANCE (Tangential Clearance Angle)
This is also known as dish or hollow grind. You measure down the side of the tip and the difference it is the difference between front and back. As you cut, material it gets compressed and springs back after the cutting edge passes.
A steep side clearance angle gives plenty of room for the material to expand and prevents thermal expansion of the base material. Keep in mint that a very flat side clearance angle can provide a smoother cut in some materials. For stainless steel and tenacious metals such as copper, zinc, tin or lead an increase in the side clearance is desirable as these materials tend to "spring back" (thermal expansion) on the blade.
Why do Circular Saw Blades Break?
It's commonly known that when saw thickness is less than 0.125″, keyways can cause stress risers and cracks. That is why washers are often used. However, Breakage, Wobble and Rubbing problems are often caused by how the washers are mounted on either side of saw.
Remember, washers drive the saw in the absence of a drive key. They must always be clean, flat and bur-free. A speck of dirt will let saws wobble and cut oversize.
If a saw breaks, it may score the washers. Always check for scoring marks around saw hole for dirt, chips or grit. Shiny spots, as small as a pinpoint, indicate that chips where imbedded under washers.
Circular skid marks indicate the nut was not tight.
Saw Blade Teeth most often break as a result of:
NOTE: HSS saws will turn colors as they heat during cutting. A straw color is the limit. The saw will lose its temper when it starts turning blue.
DEPTH OF CUT COLUMN
by Jack Burley, President and COO at BIG KAISER Precision Tooling Inc.
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 Forces
This 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.
A Cautionary Tale
If 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 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 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?
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.
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
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
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.
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 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.
Here are some simple quick tips when you are machining machining hard materials.
Alpha Granite & Tile in Austin, TX, has grown steadily since its opening in 2003, adding and diversifying machinery, materials and service offerings along the way, eventually earning the title “Accredited Natural Stone Company” from the Natural Stone Institute. They’ve expanded to deliver a range of custom residential and commercial stone surfaces, from wall cladding to kitchen countertops, in more than 150 colors of granite, marble, onyx, quartz, quartzite and ultra-compact sintered surfaces.
To keep up, Alpha Granite has invested in several advanced CNC machines, diminishing or altogether eliminating many of the laborious and time-consuming processes. Despite the technological advances, there was still a bottleneck that frustrated owners Denis and Sonia Phocas.
“Measuring tools in the stone industry was always a very laborious process,” explained Denis Phocas. “It’s archaic. You get wet, dirty and it takes a really long time. In reality, the process destroys tools because employees know the time and effort involved, so they tend to skip the necessary measuring intervals [ultimately cutting tool life roughly in half].
Dressing of the tools is also skipped, as this process needs to be done after a set amount of linear feet of work. In essence, the tools need to be measured and sharpened at set intervals to increase life.”
The traditional measuring process is manual. Measuring height and diameter to set up and inspect tools requires handheld instruments like calipers. Phocas explains how important accurate and sharp tools are to cutting stone profiles.
Since each profile requires several passes by six or seven different tools, each dependent on the accuracy, and more delicate than the one before. In other words, if the first tool isn’t dialed in right, the profile shape will be deformed, tools wear faster and the hours spent preparing them are wasted.
“Finding the center of one tool is hard enough,” he said. “Finding the center in relation to six others is very difficult.”
Phocas had heard about tool presetters, essentially a powerful microscope with a high-resolution monitor and basic computing power. It allows for precise inspection and measurement of tool edges. The process is relatively new to the stone industry and mostly limited to larger fabricators. As he explored further, Phocas began to understand why — only the big guys could afford them.
The presetters he saw from his distributers were big, expensive and, frankly, had more bells and whistles than a family-owned independent shop like Alpha Granite would need. Phocas recalled thinking, “It was such a major expense. Who needs to spend $60,000 on something you don’t need fully automated? There had to be a smaller solution.”
Phocas approached suppliers about entry-level options, but they continued pushing more expensive options. He got creative and found a metalworking supplier, Big Kaiser Precision Tooling in Hoffman Estates, IL, that might be able to help. The Speroni STP Essentia they offered featured a compact bench-top design, could work with any brand of router tools and handle the more complex tool profiles in stone cutting with ease. Most importantly, it was much less expensive than the other options he had found.
After working closely with a representative from Big Kaiser, even trying out an Essentia in his shop, Phocas was convinced and decided to purchase one. While there are significantly fewer types of tools used for profile cutting, this new capability and process would be an adjustment at first, starting with installation.
“I had never worked with one of these,” said Phocas. “It’s a precision tool. I wouldn’t call it daunting, but the process was interesting. We installed it in the workshop manager’s office because we wanted to keep it in a clean environment and because it’s got a computer hooked up to it. In the end, the installation process was pretty straightforward.”
To shrink the learning curve for his team, Phocas worked with Big Kaiser to develop a simple calibration manual. In just 18 pages, they were able to include step-by-step instructions for using the touchscreen system and measuring their 11 most common tools, from simple drillers to ogees.
“Once we got used to it, it was very easy,” said Phocas. “Our employees simply love the Essentia and now depend on it.”
The results have been undeniable. “The Essentia quickly tells you if a tool is out of shape,” explained Phocas. “I can prepare a set of tools in about 10 minutes, put them on the machine and start running. Whereas, with the old system it would take me anywhere between two to three hours, re-measuring and re-dressing while machines sat idle. We think our tool life has improved by 35 to 45 percent as well. It’s just phenomenal.”
Alpha Granite isn’t stopping there. In the near future, they’ll install software on their CNC routers that will precisely monitor the amount of linear feet each tool is working. This data will make tool recalibration even more streamlined. As things stand now, they have scheduled days for using the Essentia to recalibrate tools. With the new software, they’ll be able to recalibrate on-demand, so to speak, right when a tool has reached its manufacturer-recommended linear feet.
The addition of the Essentia has sparked dramatic process improvements. While presetters aren’t foreign to stonework, they aren’t all that common at fabrication shops like Alpha Granite. But if the results are any indication, other independent fabricators may want to get creative in their exploration of tool management options too.
The full story about Alpha Granite & Tile can be found in the April 2018 issue of Stone World or online at: www.stoneworld.com.
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
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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