A very helpful from our friends at NTK Cutting Tools.
When you hear the word “ceramic”, the first thing people may think of is the “white” material used for plates and sanitary ware (toilets).
But that type of ceramic is just one of a number of ceramics. There are as many as ﬁve ceramics used for cutting tools.In this article, we will introduce the 5 types of ceramic used in cutting tools.
What is ceramic in the ﬁrst place?
IIn a broad sense, ceramics are a blend of metal or nonmetal with oxygen (O), nitrogen (N), carbon (C), etc., and this baked material is used as a cutting tool.
The ceramic used in cutting tools is roughly available in two types of “Alumina ceramic” (Al2O3) and “silicon nitride (Si3N4) ceramic” made by blending various additives with the main ingredients to develop specific characteristics.
It is further subdivided by the addition of various additives to the main ingredients.
Al2O3 : Alumina-based ceramics
1. White Ceramic
Alumina (Al2O3) is the main component of ceramic, and is called white ceramic because of its color. In fact, the same ingredients are in jems like rubies and sapphires (Al2O3)
The main difference is that ruby and sapphire are single crystals (particles of one large mass), while alumina is polycrystalline (a collection of multiple particles). Alumina is hard and chemically stable. Taking advantage of its properties, it is used in high-speed finishing of cast iron.
2. Black Ceramic
Titanium carbide (TiC) is added to alumina, and this is called black ceramic because of its color.
The addition of titanium carbide results in higher hardness, than white ceramic, and suppresses deformation of the cutting edge due to heat; even at high temperatures.
Taking advantage of its properties, it is used in high-speed finishing of hardened materials up to about HRC65.
It is a ceramic in which silicon carbide (SiC) is added to alumina. Do you know why it’s called whisker ?
Silicon carbide has a needle-like shape similar to a “animal beard”, so it is now called whisker (ceramic).
By intertwining silicon carbide with each other, the progression of cracks due to impacts during cutting is suppressed, and cracks are prevented. In addition, it has a resistance against sudden temperature changes. Taking advantage of these properties, it is widely used for heat-resistant alloy processing.
Silicon nitride, Si3N4
5. Silicon Nitride
Silicon nitride (Si3N4) is the main component, and a special feature is that the particles are needle-like, different from the alumina compound.
By intertwining needle-like particles, the progression of cracks due to impact during cutting can be greatly suppressed, preventing cracks.
Taking advantage of these properties, it is used in high-speed roughing of cast iron.
Silicon nitride (Si3N4), Aluminum (Al), and oxygen (O)are blended to form SiAlON, which is an initial of its component elements.
Sialons, like silicon nitride, have needle-like particles. Needle-like particles intertwine to withstand impact during cutting.
In addition, the effect of the added alumina component improves heat resistance over silicon nitride, and has excellent high temperature resistance characteristics.
Taking advantage of these properties, it is used in high-speed processing of heat-resistant alloys.
The table below shows typical machining application examples of ceramic cutting tools.
We hope this column gave you a better understanding of the types, differences, and features of ceramic materials.
Ceramic cutting tools must be used according to the material to be machined, but they can be processed up to 20 times faster than carbide tools. Increase productivity with ceramic cutting tools for your material applications.
Here are some simple quick tips when you are machining machining hard materials.
NTK CeramiX HX5 replaces CBN
NTK developed this latest game changing ceramic material NTK CeramiX HX5 to replace CBN. As a ceramic cutting tool specialist, NTK has been researching new advancements for ceramics in the industry for decades.
They recently introduced a new grade that matches CBN on performance.
The new CeramiX "HX5" grade provides a cost saving solution for hard turning applications. It's designed for Hard Turning with continuous cut in the Hardness range of 55 to 66HRc
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.
A trend that we are seeing develop in many industries, especially in the medical implant device manufacturing sector, is a rise in the number of parts being manufactured from plastics such as Peek. Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family. It was originally introduced by Victrex PLC, then Imperial Chemical Industries in the early 1980s.
Its important to note that PEEK is a thermoplastic. This polymer is capable of being repeatedly softened by an increase in temperature. Increasing the temperature leads to a physical change. That's why cutting tool pressure and heat will impact surface finish and tool life.
The medical industry has found medical-grade PEEK offers excellent strength, wear resistance and biocompatibility for components such as the dental healing caps, spiked washers and spinal implants.
PEEK polymer is available in two basic grades: industrial and medical:
"Industrial-grade PEEK is a strong thermoplastic that retains its mechanical properties even at elevated temperatures. The flame-retardant material is abrasion resistant, has high impact strength and a low coefficient of friction. Industrial-grade PEEK components are used in the aerospace, automotive, chemical, electronics, petroleum, and food and beverage industries.
Medical-grade PEEK possesses those same physical properties in addition to biocompatibility, high chemical resistance and compatibility with several different sterilization methods. It is also naturally radiotranslucent when viewed using X-ray, MRI or computer tomography (CT). Medical-grade PEEK provides doctors with an unobstructed view of tissue and bone growth around the PEEK implant during the healing process. Some implantable-grade PEEK polymers have a bone-like stiffness and can remain in contact with blood or tissue indefinitely."
There is also a glass and carbon-fiber-reinforced PEEK, which offer high wear resistance for components such as articulating joints and tends to wear out inserts rather quickly.
Peek parts are generally very small, ranging from 0.039" to 0.250" in diameter, which adds to the complexity of machining the non-ferrous materials.
Because of the thermoplastic properties, too much heat at the cutting edge results in Built Up Edge (BUE) and tool pressure affects part tolerance.
That where NTK's KM1 grade insert work great. The inserts are extreｍely up-sharp edge and the mirror insert surface creates excellent surface finishes.
Things to Remember when Cutting Peek
Keys to Succesfull Machining of Peek
1. Limiting Heat Build-up – The softening or melting temperatures of engineering plastics are roughly 1/10th those of metals.
2. Melting or Scorching– The thermal conductivity of plastics is low relative to metals. Most of the heat generated by machining will stay at the surface. Temperatures at the surface can rinse unexpectedly high.
3. Loss of Tolerance – If the overall temperature of the stock changes during or after machining, expansion or contraction can cause the part to fall out of tolerance. Softening of the stock can allow it to deflect at the surface under the pressure of the cutting tool. When the pressure is removed, the stock will recover and fall out of tolerance. This can frequently be managed by using lubricants and changing tooling or speed.
4. Controlling Deflection – Plastics inherently vary in their stiffness (modulus) and are more elastic at higher temperatures. The entire stock can deflect under the pressure of cutting. Proper tooling and support remains important and particular attention should be given to adequately supporting the work.
NTK Cutting Tools USA launched its first Webinar on 30th January, 2018. The featured presenter is Steve Easterday, NTK's Swiss Product Manager.
The topic focuses on chips created during Swiss machining operations and the mainstream concept which is that breaking the chip is important. But is this accurate? NTK has a different concept of Chip Control.
The topics covered in the video below include:
How do you break a chip?
There are a few different ways to break a chip. Many people tend to think that the best methods of breaking chips in swiss machines are through the use of chip breakers on the inserts, slowing down the speed, increasing the feed, taking a bigger depth of cut and through the use of high pressure coolant. Each one of these, or some combination of them is certainly what is commonly used to gain chip control.
Typically the solution is to reduce the SFM, increase the Feed Rate and increase the Depth of Cut.... but that can lead to workpiece deflection and lower production rates.
NTK believes that CONTROLLING the Chips is more important than BREAKING the chips. NTK does this by doing two things:
NTK creates a "softer" chip because there is much less heat transferred to the workpiece AND the chips. The translates into better part quality, longer tool life and much more stable machining.
Check out the video below for all the details on chip breakers and their toolholder solutions.
NTK's industry leading line of ceramic cutting tools recently expanded with new solid CERAMIC end mills! You can see our product announcement here: NTK now offers SX9 Ceramic End Mills for Cutting Exotic Alloys which contains the various features. Below is the technical info on how to run the NTK Ceramic End mills and a troubleshooting guide.
NTK's SX9 cermaic end mill grade can run at speeds of 2000 SFM. The line-up includes 4 and 6 flutes in inch and metric versions. Again, you can learn more about on our Blog Post.
Solid ceramic end mills are made with SX9 SiAlON grade substrate which features a balance of toughness and wear resistance. It's suitable for even the most demanding applications.
First Step Machining Procedures
Gernarel Recomendations for machining heat resistant alloys & PH stainless steel
As with any other techncial questions please get in touch with us on our CONTACTS page and we can provide both over-the-phone troubleshooting or schedule at time for on-site techncial training.
This article originally appeared in decomagazine March 2013 entitled "Real Thread Whirling" Edited September 30, 2020 by Bernard Martin to add new video and additional content.
“Thread Whirling” has become a popular process for Swiss machines, especially among bone screw manufacturers. Although most Swiss machine engineers agree that thread whirling delivers outstanding productivity with the highest efficiency vs conventional single point threading, not all engineers know the “Real Thread Whirling” process.
NTK first released thread whirling tools with (9) inserts back in 2008. NTK engineers never perceived thread whirling as a complicated process.
The complication was not with regards to machining difficulty but in producing the perfect thread form described on the print itself.
The so called “Bone Screw” is a major part produced by the thread whirling process. It is quite unique, compared with the other industrial screws, since there are no female threads to mate.
Bone screws are attached directly into human or animal bones for medical repair applications. The screw is not expected to be loosened at all once it is fixed in place. The characteristics of bone screws are: larger pitch size and larger screw depth and length as their key function is to be tightened into bones rigidly and as quick as possible.
As a result of this uniqueness, inspection of screw forms has become extremely difficult. Due to the larger helix angle to make a high pitch thread form, you cannot visually see the cross section at all with a common optical comparator. What you can check with an optical comparator is only the peripheral or bottom diameter of the thread.
The only way to measure the real thread form of a bone screw is to inspect it with a (CMM) Coordinate Measuring Machine. However, there are not many manufactures which use CMM type of measurement machine for the inspection after machining. Most of them focus on visual inspection of thread form and surface roughness and use an optical comparator for the final inspection.
Another surprise for NTK engineers, is the fact that even in manufacturers that have the very latest machines, well experienced and highly educated staffs, the engineers make small adjustment on a helix angle or pitch size when they cannot get the ideal thread form.
As you may understand, if you change the helix angle or pitch size, thread form itself could be totally out of print specifications.
Why does this happen? One factor comes from the uniqueness of bone screw: There is no female thread. That is, if the thread form is made close enough to the print, the screw can perform its function to be tightened rigidly to a bone since there is no mating surface (female thread). The other comes from difficulty in designing thread whirling inserts due to complexity of thread form itself.
Having a visual image of thread whirling process in your mind is extremely difficult. Thread whirling inserts are set on the round cutter body and the cut- ter is attached to the spindle which is tilted with a helix angle. The spindle revolves at a higher rotation (like 3000 rpm) while the bar stock revolves in the same direction but at a much slower rate like 10-30 rpm.
During this rotating process, each thread whirling insert machines the bar stock while they rotate much faster than the bar stock. The spindle and the inserts tilt to make thread form and the inserts shave or cut bar stock not only at the center of the bar stock but also the upper or the lower side of the bar stock.
Conventional, single point threading inserts are designed with exactly the same thread form as the thread itself because it always machines with regards to the center of the bar stock.
On the other hand, thread whirling inserts cannot be designed with the same concept because the actual machining point always varies on the upper or lower side of the bar stock. However, there are some competitor’s thread whirling inserts designed with the identical methodology as single point threading.
With this incorrectly designed thread whirling inserts, bone screw manufactures are frequently required to re-make the inserts, in some cases, not one time but several times. Or, they are forced to make inappropriate manual adjustment on the helix angle or pitch size to obtain the thread form which looks closer to the prints specification.
NTK thread whirling does not require such guesswork process manipulation. Thanks to the design capability of our inserts we can obtain perfect threads right from the start. This process designing technology is now patented.
Recently, to reduce surgery hours, bone screws with double lead threads are becoming more popular. This industry trend is creating another challenge for most bone screw manufacturers. Producing double lead bone screws require longer machining times than single lead screws. Most manufacturers machine the 1st lead within the guide bushing length and then machine the same length with the 2nd lead while the guide bushing is still holding on to the bar stock.
As a result, they need multiple passes to achieve a double lead thread form bone screw. If the bone screw is very long then this process has to be repeated the full length of the bone screw which is a more time consuming process.
As you can imagine, single pass machining of the double lead bone screw is the best solution to improve productivity. To enable single pass machining of double lead screw, both inserts must have a different geometry ground on 1st and 2nd threads. This is simply because thread whirling machining is calculated with regards to the upper and lower point of the screw’s centerline. This process generates the double lead bone screw in a single pass cutting both the 1st and the 2nd leads at the same time.
NTK thread whirling designing technology and highly accurate insert grinding ability can produce the per- fect thread whirling inserts the first time. This feature enables double lead bone screw manufactures to achieve single pass machining. We believe that you will appreciate NTK’s highly advanced thread whirl- ing system technology once you use NTK’s double or triple thread whirling tools.
When your machine is equipped with the correct helix angle setting, correct tool setting and a NTK thread whirling system, you will experience “real Thread Whirling” which can produce perfect thread form screws. NTK is looking forward to your inquiries from those who eager to have perfect thread form from the beginnings, of course with no incorrect manual adjustment, or to improve your double, triple lead screws productivity.
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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