Hello Conrad Hoffman
I'm mot sure about all the tech. info that you, Carbide Bob & others talk about, but one thing I do know for sure. For the conditions that Blake In Spokane was asking about I would recommend Stellram's WNMG 432A-4T NL 92 (I'm sure there are others, just going with what has been working for me). That kind of shaft is practically all that I ever turn around here. It's a real treat to chuck up a new piece of steel. Not a production shop here, just doing job/repair work. But still I've done a fair bit of it & I'm still on my first insert, believe it or not. They are practically indestructible. The only time I had to flip to a new edge is when I started to burn off an inner bearing race on a shaft & instead of maybe damaging the shaft, I figured, what the heck, I'll turn it off on the lathe. When it hit that partially cut race it chipped off the edge.Darn, had to burn it off anyway.
C grades Classifications – 1940’s
These are carbide classifications developed by the United States Army and by Buick during World War II. The idea being that production would tell a Buick buyer what they were going to do and Buick could tell a supplier what grade they needed. The supplier would then give Buick whatever carbide they thought would work. This is all the designation there was. A C-1, C-2, C-3, and so on, has absolutely nothing to do with hardness, toughness, cobalt percentage, grain size or anything else.
The supplier gives the customer whatever the supplier thinks will work. If different suppliers have different opinions then it makes it very difficult to switch suppliers.
C-1 to C-4 are general grades for cast iron, non-ferrous and non-metallic materials
C-2 General Purpose
Steel and steel alloys – these grades resist pitting and deformation
C-6 General Purpose
C-9 No shock
C-10 Light shock
C-11 Heavy shock
C-15 Light cut, hot flash weld removal
C-15A Heavy cut, hot flash weld removal
C-16 Rock bits
C-17 Cold header dies
C-18 Wear at elevated temperatures and/or resistance to chemical reactions
C-19 Radioactive shielding, counter balances and kinetic applications
Carbide grades 2011 | Carbide Processors Blog
Straight Titanium Carbide and Titanium Carbonitride parts can be made and used. There are actually titanium carbide or titanium carbonitride grains cemented together with a binder that is usually something like a nickel cobalt.
The Forintek research paper, at the following address, shows some of the results on research we did in cooperation with Forintek. Forintek Research Paper on Ceramic Saw Tips
Forintek is a consortium of the Canadian government, the University of British Columbia and several dozen timber companies.
FPInnovations - Forintek Division - Canada's Wood Products Research
These straight titanium carbide or titanium carbonitride grades do not have the fracture toughness of tungsten carbide with a cobalt binder. In the most popular grades commercially available you'll have titanium carbide or titanium carbonitride with tungsten carbide for toughness.
Traditionally a higher Cobalt percentage meant toughness and a lower Cobalt percentage meant longer wear but it would break more readily.
With the development of submicron grains you now have grades that are both extremely tough and extremely long wearing. Ceratizit has an MG 18 grade with a 20% cobalt binder and a submicron grain structure that is both tougher and longer wearing.
There is a lot more to carbide wear than just straightforward wear. I find it most helpful, when doing failure analysis, to use a check list of 17 items which is available at the following link.
The Different Factors that Affect the Wearing of Tungsten Carbide
You can get tungsten carbide razor sharp, I guess. The term ‘razor sharp’ is not used much in the scientific world. Technically edge sharpness is measured as a radius.
Here are typical values as of about 10 years ago. I don't think they've changed much.
Cermets (titanium carbide or titanium carbonitride) 3 -4 micron radius
PCD – Poly Crystalline Diamonds 4 -6 micron radius
Micro grain carbide or Stellite® 8 -12 micron radius
Sharpened carbide sawmill sawblade 10 – 18 micron radius
You can get tungsten carbide as sharp as you want to because you can actually sharpen to the level of individual grains. Down at this level it's very tricky and not beneficial.
You can get carbide with smaller grains a lot sharper, much more easily than you can carbide with larger grains. See the following article, please:
Making Cermet Two Material for Cutting Tools.
Stellite© is a registered trademark of Stoody Deloro Stellite and they protect it very carefully.
Stellite© can take a pretty sharp edge but you run into problems with burring on the edges. If you're going to sharpen it is recommended that your final pass the in the opposite direction of the original passes and that the wheel rotate in a direction counter to the original rotation. O
As you get tungsten carbide or cermets sharper, you run a greater risk of chipping or spalling. See the following article for pictures of chipping at the microscopic level.
Saw Blade Wear Cutting Gypsum
Figure that a tool that is as sharp as you can get it has a value of 1 and a tool that is too dull use has a value of 10. A light and charming to create a land or chamfer takes the sharpness from a 1 to 1.5. However, the tool that is completely sharp will hit the 10 level and be too dull to use while the tool with a honed edge will probably be somewhere around the 2 to 3 level.
Carbide grain size is extremely hard to determine. Tungsten powder, carbon powder and cobalt powder are mixed together and then centered. The tungsten carbide grains grow during the sintering process. If you've ever grown sugar grains on a string in grade school or done something similar you'll realize that you grow some grains that are much larger than others.
The techniques for making submicron grains seem to be pretty well known and I would think that you could get them from any major supplier.
We used to do a lot of work with the Kennametal on experimental grades before they change their direction and decided to grow by buying other companies. As they bought other companies they consolidated plans and lumped grades together or just eliminated grades they thought were duplicates. We haven't been able to use them for research in years.
There is much more on our website at the following address.
Carbide Parts | Tungsten Carbide and Advanced Grades | LongLife Saw Blades
I have a great deal more information based on research we've done over the last 30 years that I haven't put up yet. I'll get to it eventually, I suppose. If you contact me directly, I’ll do the best I can answer your questions.
Excellent info Tom.
The only things I'd remark on is that Straight Titanium Carbide and Titanium Carbonitride parts using nickel cobalt are usually called cermets. From what I've seen very different processing and not made in the same plants as traditional tungsten carbide.
I'm told MG18 is a 10% cobalt product (I use a lot of it).
You can't just mix Tungsten powder, carbon powder and cobalt powder together and throw it in the oven. I'm sure you know that it's a bit more complicated than that.
Grain growth and grain growth inhibitors are a whole subject of their own. The only easy thing to say is that it is always bad.
As Tom's website and references provide tons of good technical info I'll bow out now.
Last edited by CarbideBob; 06-03-2011 at 07:02 PM.
Although CarbideBob made a few good point, he did not tell all the truth. First, sub-micrograin carbides are only possible with large cobalt content. It literally kills the tool i machining of automotive aluminum alloys at high speeds (not as many automakers use today - I mean HIGH as for example GM TTO uses). This is because aluminum Sticks to COBALT not to carbide ceramic particles. The greater cobalt content, the greater adhesion (sticking in shop language), the greater adhesion wear of the tool. Second point about the scale. It is true that grain size of submicrograin carbides is approx. 0.5 microns (at best), but the surface finish required to get "good" finish is 0,08 microns (with 1600 grit wheel). So, whatever you do, the cutting edge WILL BE SERRATED as this edge is A LINE of intersection of the rake and flank surfaces. Edge preparation can help to smooth the serrations on the cutting edge, and thus decrease adhesion. Third, the surface finish of ground carbide depends not only on grit size of the wheel, but it a system property, i.e. a rigid grinding setup is needed to achieve good surface finish. With 95% of semi- and fully automated tool sharpening machines is virtually impossible particularly for drills, reamers and other axial end tools.Any last (though not least) - the cost of the wheel and time required for tool sharpening with fine-grit wheel. Forth, I would appreciate Bjb's explanation of coating on a razor-sharp cutting edge and its pealing in first few minuted of machining. To finish, I'd like to mention tat I HAVE NOT SEEN THAT FAR a properly sharpened tool for high-speed machining, not to mentioned proper design, proper tool material, coolant supply means, etc. As they say - men can only hope.
Saw Blade Wear Cutting Gypsum
First time I've ever seen someone cutting drywall(what we call it in these parts) with a circular saw. Around here the drywallers score the paper with a utility knife, give it a hit, the board breaks, bend it over & then cut the paper on the back side, The only saw they use is a little drywall saw(I think it might be called a pocket saw) to cut out for the electrical boxes after they put the board up.
Another question(or point, whatever) about 20 some years ago I was running a portable sawmill. It had a Simmonds 44" circular blade with plain steel teeth(I assume mild steel as I sharpened them with a file) I took the blade & my edger blades to A.M. Ludwig Saw Shop in Thunder Bay Ontario to get them hammered & inquired about carbide teeth as I was tired of filing the others every 2 hours or so. He asked me if I had a lot of knots in my logs. Yes. Then he recommended HSS teeth instead because the carbide teeth would chip in the knotty logs. I had to buy an expensive Jockey grinder to sharpen the HSS teeth but could saw all day between sharpening.
Maybe getting off topic here, but any comments on why carbide teeth would chip on wooden knots yet strong enough to cut steel.
Very interesting run down on tungsten carbide and nice to find your web site. It was years ago when we got a lot of specials from Kennametal. That was at a government place in Tennessee were a lot of turning was getting done that had a hot line to Kennametal and most others for cutting tools used on unusual materials. Are you familiar with using a DeVlieg Micropoint to grind turning tools? Interested in brazed turning tools with very accurately ground radius that have polished top and conical grind clearance face. It is very easy to damage carbide in the rough grinding stage so that microscopic cracks introduced at that stage are propagated rather than being removed in the fine grinding, lapping and polishing stages. I think this is the source of the common opinion that extremely sharp edges are easily damaged and wear very quickly. Special handling at first stages can get some special results.
Did you used to run a micropoint?
I used to have 4 plus we built swing fixtures for the sgs to duplicate the action.
Lots of shops had setups like this :WitOMatic
Now most shops do this on cncs but I do have a friend who still runs a bank of DeVliegs.
A 4 axis cnc will make the conical (constant clearance) rads.
Cylindrical rads (constant size) are best done on a 5 or 6 axis if there are multiple rads/clearance angles involved.
Per your previous posts what do you consider "very close radius tolerances" and on what size rads? Generally we don't like making smaller than .004 rads as they are such a PITA to accurately check.
Radius tolerance is always interesting as each manufacture seems to have a different inspection method used to define good from bad.
We mostly stay away from 3/8 square brazed tip tooling cause it's a ..... (rhymes with doors) market.
We do some special forms on Empire style blades and make some weird brazed stuff like carbide tipped facedrivers. Most of our brazed work is PCD/CBN tips on carbide which is nicer since you don't have to deal with grinding the steel.
I think member "Man That's Sharp" does a lot of work like you are looking for.
See here: Grind Shop
A couple points I probably should have mentioned earlier.
Cermet stands for metal based ceramic. Thus tungsten carbide is technically a cermet. The way I got the story was that ‘Cermet’ came to mean titanium nitride, titanium carbonitride or similar was due to a translation error. An American asked a Japanese what the new material was called and the Japanese said that it was a cermet. Because it was a titanium based material the term cermet came to be used for titanium based materials.
The language in this industry is often very imprecise. A great many manufacturers are now and have always been extremely reluctant to share any technical data. I too have heard, as has CarbideBob, that the MG 18 grade is 10% cobalt. Lately I have heard that it is 20% cobalt.
There've been huge advances in the tungsten carbide and cutting tool tip industry in the three decades I have been in it. This is especially true in the last decade.
As part of our work on filtering coolant we got peripherally involved in plants for the manufacturing of computer chips. In these operations they measure contamination in terms of individual atoms. A single sulfur atom can ruin a transistor or similar device.
This necessity to make ultrapure materials created the technology to make ultrapure materials which has been adapted into the tungsten carbide industry.
Carbide Bob wascorrect about how the powders are mixed. Tungsten, carbon and cobalt powders are just a start. There is quite a variety of other metals that are added to control grain growth, to change the characteristics of the binder and otherwise improve the materials.
The powders are incredibly fine and hard to work with. If you've ever had to work with toner powder you'll understand. A big advancement has been spray drying which creates ultrafine powders and makes them more mixable.
Cutting steel with carbide
If you look at it from a certain standpoint you really don't cut steel. Rather you could consider it that the process of cutting steel is actually more a scraping action. This makes more sense if you consider that steel is a homogenous material and compare that to something, such as wood, which is a heterogenous material. Wood is a bundle of individual fibers that have to be actually severed.
There were some excellent discussions above about edge prep. As near as I can tell, much of what look like disagreements was actually accurate information about differing methods.
Then, again, the term carbide covers a huge range of individual grades.
Could you please be more specific and explain to simple people like me what is the difference between cutting and , as you mentioned, scraping of steel by carbide tools?
As for different grades of carbides - they do exist because the users do not ask proper questions. When one buys a steel to be used in making a machine part, he ask for the so-called mechanical properties (the UTS, for example, or elongation at fracture) - these properties are used in engineering calculations of stresses, required cross-sections, allowable deformations and so on. When one buys a carbide, a long list of properties are available starting for example with the compression strength to TRS...However, NOBODY ever asks a simple equations - how these properties correlate with the performance of this carbide as a tool material. Besides very general speculations, nobody gives you a direct answer so the "let's try and see what happens" approach dominates in the "intelligent" selection of a particular carbide grade, its geometry including edge preparation, coating, etc.
He's not trying to describe a difference between cutting and scraping of steel, he is saying that unlike substances that are being cleaved in two, during which process the material splits in half with no waste, machining is more like scraping off the excess material. For instance when a saw cuts through a shaft, it has to sort of scoop or scrape away at the surface as it cuts in, rather than cutting through like a knife blade or an axe.
As an aside, great discussion. Keep going, by all means. We might have another thread for the greatest hits section or whatever it's called.
I would not agree with you. Knife DOES NOT CUT as well as a hatchet - they SLIT material. That is why I asked a question. The proper answer to this question is of high importance to understand what DOES IT MEAN CUTTING and METAL CUTTING. I will explain the difference later if someone wants to understand.
I have a Micropoint. The tools I am interested in would have a radius around 0.032" with about of 120 degrees of useable edge with a 4-6 deg. positive rake up to 30 deg. positive rake. Conical grind with good relief and a polished radius and top to give the sharpest possible edge. I think the tool grinder guys that made the tools I found most useful started with a special micro grain insert and went really slow on the early stage shaping to avoid introducing micro cracks. The tops and radius were lapped and then polished on the same or similar equipment we were using for diamond tools. The roundness of the edge contour was about 10 micro inches and the inspection of the radius was was done with an LVDT on an air bearing spindle with the tip of the indicator just below the edge to avoid chipping. Same inspection as used on single crystal diamond tools. The contour on the project at hand doesn't use a lot of radius except for tool setting so the roundness isn't as important. Waida, Ewag and Coburn are some other good tool grinders.
An interesting book for people who want to argue about cutting versus scraping is "Tribology in Metalworking, Friction, Lubrication and Wear"- Schey. It isn't really about cutting tools but lots of information about working fluids which is pretty important and less understood than carbide compositions. Theory of chip formation work of M.C. Shaw is out there, a lot of it can be found on Google. Libraries full of information on machinability, tool materials etc.
An interesting book for people who want to argue about cutting versus scraping is "Tribology in Metalworking, Friction, Lubrication and Wear"- Schey. - not a word in this book on the subject
It isn't really about cutting tools but lots of information about working fluids which is pretty important and less understood than carbide compositions. - the level of understanding if the same - next to nothing. Nobody really understand the relevant properties a carbide as the tool material. Nobody but very few, understands why the coolant works in metal cutting and what it actually does. As a result, a lot of 'bed time stories" about MQL (near dry machining) still attract attention of metalworking specialists.
Theory of chip formation work of M.C. Shaw is out there, a lot of it can be found on Google. Libraries full of information on machinability, tool materials etc. - there is no such a thing as the Shaw theory of metal cutting or chip formation. Qualitative description "I write what I see" does not constitute a theory. Nowadays, they found how to trick metalworking specialist with colorful interfaces of FEM - looks so attractive though nobody understands what they are looking at.
Libraries full of information on machinability it is true...but nobody actually knows what is that. Machinability does not have units to be measured, thus everybody understands it in his/her own way.
Astvik, if you are going to bad-mouth every person who replies you are going to kill this thread. If you wish to refute something that's fine, but have some proof or relevant publications or links to back up your words. Why are you qualified to say the 2 guys replying to this thread who are certainly pros in their field (carbide manufacturing and grinding) are wrong or "not telling the truth?" What is your background? What do you do for a living?
I am presently most inclined to ignore you and listen to/believe the guys who have shown through past threads and experience that they know what they are talking about.
P.S. Are you a non-native English speaker? Some of your replies are hard to understand because the sentence structure doesn't make sense. I can't tell what you are trying to say sometimes.
I can't agree with that statement. There very definitely are quantifiable measures of machinability. The most fundamental one is specific energy in inch-pounds per cubic inch (joules per cubic millimeter in the metric world), which corresponds directly to metal removal rate in cubic inches per horsepower (cubic millimeters per kilowatt in the metric world). Any decent textbook on machining (e.g., Moltrecht's Machine Shop Practice) covers this.
Originally Posted by astvik
Those long tables of how "machinable" a given material at a given hardness is compared to the reference material in its class are summarizations of these specific measurable quantities.
Last edited by sfriedberg; 06-06-2011 at 02:16 PM.
Reason: Corrected units for specific energy
Astvik, if you are going to bad-mouth every person who replies you are going to kill this thread. If you wish to refute something that's fine, but have some proof or relevant publications or links to back up your words. Why are you qualified to say the 2 guys replying to this thread who are certainly pros in their field (carbide manufacturing and grinding) are wrong or "not telling the truth?" What is your background? What do you do for a living? - I have no intent to bad-mouth anybody - sorry if I offend anybody. I just want to show that many people are dreaming about carbide grades, for example. I can bring relevant publications and other proofs to what I said. My intent is to ignite discussion on the matter in order to improve the current practice in the cutting tool industry on one hand, and among the users of the cutting tools on the other.
I am presently most inclined to ignore you and listen to/believe the guys who have shown through past threads and experience that they know what they are talking about. - I do have sufficient background and experience in metal cutting and tool design both theoretical and very practical, as every day I have my fight with various cutting tool manufacturers. It is another story - I can tell it if you want to know why I am fighting why other people "simply buy" cutting tools.
P.S. Are you a non-native English speaker? Some of your replies are hard to understand because the sentence structure doesn't make sense. I can't tell what you are trying to say sometimes. - Yes, I am non-native speaker - sorry if some of my sentences are not up to your standard.
I can't agree with that statement. There very definitely are quantifiable measures of machinability. The most fundamental one is specific energy in inch-pounds per cubic inch (joules per cubic millimeter in the metric world), which corresponds directly to metal removal rate in cubic inches per horsepower (cubic millimeters per kilowatt in the metric world). Any decent textbook on machining (e.g., Moltrecht's Machine Shop Practice) covers this. - unfortunately, it is not so. This energy IS NOT A CONSTANT for a given work material. In reality, this energy is a system characteristic which depends on the overwhelming number of parameters of a particular machining system (Astakhov V.P., Geometry of Single-Point Tools and Drills, Springer, 2010). Simplest is the tool geometry as, for example, the rake angle affects the cutting force, and thus the cutting power to a great expend (the the tool cutting edge angle, the inclination angle - the basis of ISKAR tools) - see Astakhov V.P. Metal Cutting Mechanics, CRC Press, 1999. Then tool material and coating that affect the friction condition at the tool/chip interface. Then the coolant can have a great effect on the cutting power. On so on. Moreover, the feed and cutting speed also affect the cutting power - the higher the cutting feed, the lower the plastic deformation of the chip (constitutes up to 70% of the energy required for metal cutting); the higher the speed, the lower the cutting force). This is the idea of the optimizing of the cutting process for giving conditions - achieve the smallest possible power for a given cutting conditions (if, as you've mentioned, this power is a constant (property of the work material) then why even try to optimize the cutting process). This objective is not just save on the electrical bill (this saving is insignificant) but rather to increase tools life which is A DIRECT FUNCTION OF THIS POWER and to improve the surface integrity of the machining surface. This sweet spot - the minimum energy required to separate the layer been removed from the rest of the workpiece - is achieved when the cutting temperature is equal to the so-called OPTIMAL CUTTING TEMPERATURE (the Fist Metal Cutting Law) - Astakhov V.P., Tribology of Metal Cutting, Elsevier, 2006.
Those long tables of how "machinable" a given material at a given hardness is compared to the reference material in its class are summarizations of these specific measurable quantities. - unfortunately, hardens of the work material is not relevant parameters in metal cutting although it is stated so every book and the so-called Merchant metal cutting theory. Simple practical example "kills' this daydream - the hardness of a stainless 303 steel is much lover that that of cast iron. However, "machinability" (properly considered not as in the known literature sources) of cast iron is a way greater than that of the stainless steel - lower forces, temperatures, often no coolant is needed (if one does not afraid of the dust ).
astvik, I'm not going to quibble with you. We agree that machinability is not a matter of a single parameter. I completely disagree with your statement
In fact, I can't believe that you really agree with that statement, considering practically everything you just wrote in response can be quantified, measured, and explicitly taken into consideration.
Machinability does not have units to be measured