Drilling "Caldie" - Need help - Or S7...

[Matt_Maguire]

I think I’d go back to the instability you mentioned in your first post Jashley. The proof would be if an M10, 33 or 36 cobalt HSS could run 5D at the proper speed with a 130-135° crankshaft grind. I have a feeling that a high speed machine with a part weight limit like that Mori is not going to work well with the variable load and inserted drill would drive into it. A box way machine would likely knock down instability a lot.

There isn’t anything that jumps at me about the chemistry. Looks like it’s not sure if it’s hot work (that gets a little harder) or an air hard (that won’t get as hard)… The recipes running 100-125sfpm are pretty much the safe zone for the D types or A7, it should run near 50% faster if it really is annealed. The closest matches I could find in ASM was AISI-SAE 6H2 with .55C, .40Mn, 1.10Si, 5.00Cr & 1.50Mo (absolutely nothing about what it was used for or machinability in the index though).

Slightly jacked up with similar moly would be Crucible Versasteel with 1.00C, .30Mn, 2.00Si, 4.25Cr, 1.15V, 2.5Mo & .30W (machines somewhat easier than annealed HSS per their docs). The stuff is useful for different things at from 58 to 65Rc.

Good luck,
Matt

 

[Jashley73]

I have a feeling this is tool/spindle stability related as well. It's quite strange, but the NVX is a box-way machine, but with a 15k spindle...? So it makes me think the bearings are smaller/lighter, and maybe that's where everything is going wrong.

 

[cameraman]

I have a feeling this is tool/spindle stability related as well. It's quite strange, but the NVX is a box-way machine, but with a 15k spindle...? So it makes me think the bearings are smaller/lighter, and maybe that's where everything is going wrong.

NVX series – Vertical Machining Centres by DMG MORI

lol.

"Highlights NVX 5100
Slideways are used for all axes
The new spindle achieves speeds of up to 15,000 min-1 (standard)
23% higher rigidity achieved by the use of a spindle with a large-diameter bearing
Environmental thermal displacement control device(option)
The DDRT rotary table is available (option)
20% reduction in total power consumption."

What are you playing at young jashley ?

Because the machine is box way it may not be as nimble as one would like for complex 3d contouring.

It's not an ecoline machine and its pedigree IS mori Seiki not the "Germans".

I thought you like Mori-Seiki stuff very much?

@Jashley what you playing at "sunny-jim" :-)?

Experiment in marketing?

[I get the feeling I must be on "block" lol].

______________________________________________________________________________________________________________________

DMG Mori would rather folks order that machine as a 50 taper ... OR order a CMX 1100V but they seem reluctant to support the idea of a 40 taper on the NVX? Maybe you have a better idea or explanation for that/as to why that would be?

_____________________________________________________________________________________________________________________


I'm guessing the folks that bought the nice shiny new machine may be "Newbs" and maybe are just plunging/feed rate too high in a completely inappropriate way/"Pilot error". Did you not mention that one of the tools "Mushroomed" (heat) and also you mentioned that some stock may be hardened and some may not (random material handling) ?

Too many variable without you being on site YKWIM?

Maybe you can face time/skype with them so you could be "telepresent" and see what the "Heck" is really going on ?

 

[Jashley73]

Cameraman - I'm not trying to pick on their machine at all. I'm quite biased to love Japanese machines. I'm just hypothesizing, that being a 15k spindle, it probably has smaller/lighter, maybe even hybrid/full-ceramic bearings, and they probably aren't extremely rigid. But man - what a spindle. The thing is whisper quiet at speed...

----------

With regards to the issue at hand - their trouble drilling 22mm holes 5-7xD - I don't think it's entirely material related. The customer swears this stuff is most troublesome to drill, and maybe it's more difficult. But looking up the chemical composition, nothing seemed outrageous - Hence, why I polled the PM crowd. I also don't believe, at this point at least, that work-hardening is the issue.

---------- ---------- ----------

Side note/Tangent - And this is not directed at anyone specific here on PM. - I'm also quite un-satisfied with "work-hardening" being discussed so freely among machinists. The reason being, is that with maybe one or two exceptions in my entire career, no one can tell me WHY "X" material, or any material for that matter is susceptible to work-hardening - again, more accurately called "strain hardening". And at the same time, no one seems to have an understanding of WHAT strain hardening is, and what actually causes it.

I'm not trying to condemn anyone here on PM. But rather, I am suspect when people begin talking about "work-hardening" and then can offer no explanation or understanding, as to what/why/how it's caused. Yes, even the magazine article that came in the mail this week...

Perhaps this is just my personal frustration - One of those, "If you don't understand it, and can't explain it, then don't expect me to take you, your advice and experience seriously" type things... Again - Not directed to anyone here on PM...

It just begins to sound like a generic, lazy, cop-out excuse that people turn to, when things don't go as planned, and they don't care to investigate why. If someone can truly explain it to me, I'll listen, and I'll buy in if it makes sense. Until then, I'll remain extremely skeptical...

---------- ---------- ----------

Getting back to their issue.... Again, most of the problems seem to be mechanical damage related. Not wear+chipping --- straight up chipping/fracturing/cracking/breaking.

I've got enough education & experience with tool-wear analysis, to know that sometimes it's a chicken-and-egg game. Meaning, did the chipping cause the rapid wear, or did the rapid wear cause the chipping? Seldom do you see only one failure exclusively. Most of the time, the failure will show evidence of at least two, maybe three failures simultaneously, meaning they're most often time cause & effect of each other.

At this point however, all the failure modes seem to be mechanical failure exclusively. Which leads me to believe it's a stability issue, and/or extreme mis-application of feed. I plan to visit them next week, break out their indicator, and start pushing on things.


----------


And since you asked/inquired/pondered earlier. MY GOAL through all of this, is simply to fix their problem, and help my customer make more money. That's really it.

I don't have access to any machinery, beyond what they are using in their shop, to run their jobs. Would I love a tech-center machine for testing? You bet, but ain't gonna' happen with my current job.

 

[Monarchist]

I also don't believe, at this point at least, that work-hardening is the issue.

I'm also quite un-satisfied with "work-hardening" being discussed so freely among machinists. The reason being, is that with maybe one or two exceptions in my entire career, no one can tell me WHY "X" material, or any material for that matter is susceptible to work-hardening - again, more accurately called "strain hardening". And at the same time, no one seems to have an understanding of WHAT strain hardening is, and what actually causes it.

I'm not trying to condemn anyone here on PM. But rather, I am suspect when people begin talking about "work-hardening" and then can offer no explanation or understanding, as to what/why/how it's caused. Yes, even the magazine article that came in the mail this week...

Perhaps this is just my personal frustration - One of those, "If you don't understand it, and can't explain it, then don't expect me to take you, your advice and experience seriously" type things...

Cleary that is your personal "blind spot" then.

You never worked the Bronzes? Most exhibit work-hardening. The Aluminium and Nickel-Aluminium Bronzes are effing notorious for it.

How about a seriously high-Manganese alloy? Ten percent or more?

Hadfield alloy as used in the rail industry was a ball-buster on planer, lathe, and drillpress fifty and more years ago. HSS and HSS Cobalt, razor sharp, one could find a way. Neg-rake carbides were all we had back then, and those were outright suicide.

"Modern" alloys, stainless and such, include many that exhibit work-hardening. INCO could near-as-dammit make it part of their name, and share Hadfield's license to distribute pain and suffering amongst machinists.

I cannot understand how you have avoided the exposure at the tool-tip, whether you ever read even one metallurgical explanation or not, agreed with it or not, or believed they actually understood the mechanism of it or not.

I don't know that they DO. But I wasn't given the luxury of PONDERING over it.

Jobs had to get out the door.

"Understood" or not, it very much does exist in the real world and in real metals and machining conditions.

Page two:

I am even MORE puzzled as to why you think a high-RPM spindle on ceramic bearings would be LESS "stiff" than a lower-speed one?

Tons of money and research had to be spent to get to where they've gotten to, because the buggers would self-destruct in VERY short order were they NOT easily as precise and stable as they are fast.

"More fragile"? Less tolerant of abuse? Those, they could be. But wobbly or limp noodles, NOT. Quite the reverse.

 

[Jashley73]

Cleary that is your personal "blind spot" then.

You never worked the Bronzes? Most exhibit work-hardening. The Aluminium and Nickel-Aluminium Bronzes are effing notorious for it.

How about a seriously high-Manganese alloy? Ten percent or more?

Hadfield alloy as used in the rail industry was a ball-buster on planer, lathe, and drillpress fifty and more years ago. HSS and HSS Cobalt, razor sharp, one could find a way. Neg-rake carbides were all we had back then, and those were outright suicide.

"Modern" alloys, stainless and such, include many that exhibit work-hardening. INCO could near-as-dammit make it part of their name, and share Hadfield's license to distribute pain and suffering amongst machinists.

I cannot understand how you have avoided the exposure at the tool-tip, whether you ever read even one metallurgical explanation or not, agreed with it or not, or believed they actually understood the mechanism of it or not.

I don't know that they DO. But I wasn't given the luxury of PONDERING over it.

Jobs had to get out the door.

"Understood" or not, it very much does exist in the real world and in real metals and machining conditions.

Thank you for that wonderful explanation. Exactly what I was talking about in my rant...

I don't know if it's fair to call a "blind spot" when I freely admit that I don't fully understand the topic, and have researched & sought understanding... Clearly, I haven't reached that level of personal, satisfied understanding. I would love to learn more, put it to use, and pass it on...

Yes, I have worked with bronzes, including aluminum bronze in the flavor of Ampco 18, 21 & 25. Turning, milling, drilling, grinding if you're curious. And tool-steels of many varieties - soft & hard, in bar and forged-blank styles. And some 300 & 400 series stainless alloys, and a few PH grades too.

No, I have not worked with high-manganese steels, although I am familiar with rail-way parts that you describe. Nor high-nickel super-alloys either, although I have run into several since being on the sales side...



I know it's difficult to believe, but somehow I managed to feed myself and keep a roof over my head for 10 years cutting metal. Yes, I understand "parts must get out the door."

My customer is in a "parts must get out the door" situation. Yes, everyone here on PM understands that academic knowledge & theory take a back seat to invoicing...






Now, can you offer any explanation of what actually causes strain-hardening, and the effects it has on the material? Or how to work with the specific material in question?

I apologize for sounding like a dickhead, but that is exactly the kind of non-helpful advice that is given way too often on the subject...

 

[Monarchist]

Now, can you offer any explanation of what actually causes strain-hardening, and the effects it has on the material? Or how to work with the specific material in question?

Probably. But I will not. Better men who ACTUALLY work "Caldie" (I never have) HAVE ALREADY DONE SO.

And you've closed your ears?

I am not AT that "tool tip".

Neither are YOU.

If you've worked those Bronzes, you should KNOW that you need to go and watch, listen, touch, feel, smell lay eyes-on before you can do them any good.

You can't FIX this shit with a laptop keyboard from a distance. You cannot even analyze it accurately from a distance.

You HAVE NOT - so far - really even given the PM community much real "meat" to chew on.

The view you want, and the keyboard you want is at the machine-tool working the metal. Get on your horse.

Better yet, as you are but going 'round in CIRCLES?

Ask your customer to pay macds (re-read his post) to get on HIS horse, parachute in, and "JFDI" rather than argue it to death over terms, semantics, and what should be explained or understood.

 

[Jashley73]

Probably. But I will not.

Well, thanks for your help...



I couldn't be any closer to the tool tip unless I stuck my head in it's path. All that talk about their failure modes - did you think I was making that up?

Two things have surfaced as being common themes and areas to observe. Stability in the setup, and possibility of work-hardening. Disregard my dis-satisfaction with the work-hardening theories... There is no evidence of any kind of excess heat in the chips, or heat-related tool failures. The failure modes have all been mechanical failure related, and lead to some kind of instability. Supported by the fact that they're using carbide, at an extremely slow cutting speed.


Before starting this thread, I really wasn't sure what was going on. It now looks to be pretty obvious. And thus, like I've posted a couple times already --- I'll be visiting them again early next week, to inspect the machine, and look for deflection that might cause instability. Then onto the toolholder, drill body etc...

Thank you for your input, but if you have nothing helpful to add, please stop.

 

[Monarchist]

..if you have nothing helpful to add, please stop.

*yawn* I'm not the one going in circles due to his own pre-conceived notions. You've been reading LOTS of useful advice, then ignoring it, so neither am I lonely.

But here.. Cle-Forge. HSS Cobalt. Parabolic grind. Shave-with sharp.
1950's vintage AB5/S. Low. Slow. And as lubricious as a nibbled-on hot date. Watch the chip and the PRESSURE more than the heat.

The machine in-use, its speeds and feeds may simply not be the right one for this material. Accept that as a possibility, if nothing else, and try another way.

THEN you can try to "port" what the experiment turns up back to it...

Or not. First comes "good". THEN comes "fast".

 

[nsharma]

Hi @Jashley73

I've drilled something similar, perhaps worse than the one your client has. The drill I used was from OSG, with a pre-drill of 2.5D using:
PREDRILL 61580 OSG D 8 EX-SUS-GDS
DRILL 8622880 OSG D 8x10D TDXL


The material was:


The part where the hole is lateral, the hole was 8D, it was done in one shot, with zero TSC, just feeding continuously. After 40 such holes the drill still looks like new.

 

[kenton]

Cameraman - I'm not trying to pick on their machine at all. I'm quite biased to love Japanese machines. I'm just hypothesizing, that being a 15k spindle, it probably has smaller/lighter, maybe even hybrid/full-ceramic bearings, and they probably aren't extremely rigid. But man - what a spindle. The thing is whisper quiet at speed...

----------

With regards to the issue at hand - their trouble drilling 22mm holes 5-7xD - I don't think it's entirely material related. The customer swears this stuff is most troublesome to drill, and maybe it's more difficult. But looking up the chemical composition, nothing seemed outrageous - Hence, why I polled the PM crowd. I also don't believe, at this point at least, that work-hardening is the issue.

---------- ---------- ----------

Side note/Tangent - And this is not directed at anyone specific here on PM. - I'm also quite un-satisfied with "work-hardening" being discussed so freely among machinists. The reason being, is that with maybe one or two exceptions in my entire career, no one can tell me WHY "X" material, or any material for that matter is susceptible to work-hardening - again, more accurately called "strain hardening". And at the same time, no one seems to have an understanding of WHAT strain hardening is, and what actually causes it.

I'm not trying to condemn anyone here on PM. But rather, I am suspect when people begin talking about "work-hardening" and then can offer no explanation or understanding, as to what/why/how it's caused. Yes, even the magazine article that came in the mail this week...

Perhaps this is just my personal frustration - One of those, "If you don't understand it, and can't explain it, then don't expect me to take you, your advice and experience seriously" type things... Again - Not directed to anyone here on PM...

It just begins to sound like a generic, lazy, cop-out excuse that people turn to, when things don't go as planned, and they don't care to investigate why. If someone can truly explain it to me, I'll listen, and I'll buy in if it makes sense. Until then, I'll remain extremely skeptical...

---------- ---------- ----------

Getting back to their issue.... Again, most of the problems seem to be mechanical damage related. Not wear+chipping --- straight up chipping/fracturing/cracking/breaking.

I've got enough education & experience with tool-wear analysis, to know that sometimes it's a chicken-and-egg game. Meaning, did the chipping cause the rapid wear, or did the rapid wear cause the chipping? Seldom do you see only one failure exclusively. Most of the time, the failure will show evidence of at least two, maybe three failures simultaneously, meaning they're most often time cause & effect of each other.

At this point however, all the failure modes seem to be mechanical failure exclusively. Which leads me to believe it's a stability issue, and/or extreme mis-application of feed. I plan to visit them next week, break out their indicator, and start pushing on things.


----------


And since you asked/inquired/pondered earlier. MY GOAL through all of this, is simply to fix their problem, and help my customer make more money. That's really it.

I don't have access to any machinery, beyond what they are using in their shop, to run their jobs. Would I love a tech-center machine for testing? You bet, but ain't gonna' happen with my current job.

I'm not anything close to an expert but I was always under the impression that work hardening was caused by basically cold working the material instead of cutting it. I don't understand the why of the process but I have seen the results of cold working resulting in hardening many time. This notion may not be correct but it has worked well enough to steer me to a solution in almost every case.

 

[nsharma]

I'm not anything close to an expert but I was always under the impression that work hardening was caused by basically cold working the material instead of cutting it. I don't understand the why of the process but I have seen the results of cold working resulting in hardening many time. This notion may not be correct but it has worked well enough to steer me to a solution in almost every case.

Metal cutting is actually a high rate of deformation followed by shearing of chips. This process is basically called cold working of the material and this is what does the work hardening. Suppose you do a finishing cut on stainless or titanium or high tensile strength Al alloy such as 7075, you'll have a thin layer, something between 0.5-10 thou thick depending on the material you're cutting that will be at full hardness of a material that is prone to work-hardening. So if you're cutting one of the work hardenable materials, your finish passes least depth should be more than the work hardened layer, or else you'll need to start stamping your own carbide inserts. That's one of the reasons to take at least 0.2mm or greater of finishing pass in Ti6Al4V. The other is that you need to have a chipload per tooth of at least 2.5D of the tip radius of the tools cutting edge, or else this cold working will not happen and the chip will not get formed and you'll rub the tool against the part and just heat it up and it will collapse.

Hope this gives you an idea. If you need more, go to your favourite tool suppliers technical manual and read about the cutting process, it will be fairly illuminating.

Naresh

 

[gregormarwick]

Side note/Tangent - And this is not directed at anyone specific here on PM. - I'm also quite un-satisfied with "work-hardening" being discussed so freely among machinists. The reason being, is that with maybe one or two exceptions in my entire career, no one can tell me WHY "X" material, or any material for that matter is susceptible to work-hardening - again, more accurately called "strain hardening". And at the same time, no one seems to have an understanding of WHAT strain hardening is, and what actually causes it.

Work hardening is not black magic. Your lack of knowledge on the subject is not evidence that everyone else is tossing the term around in ignorance.

The processes are understood and well documented if you care to look.

 

[Monarchist]

Work hardening is not black magic. Your lack of knowledge on the subject is not evidence that everyone else is tossing the term around in ignorance.

The processes are understood and well documented if you care to look.

I see an huge opportunity here, though.

We, collectively, need to get our man Jashley73 to teach the rest of us how refusal to recognize and accept can be applied to make TAXES - or even paperwork in general - (even bitchy bed-partners?) .. just not exist.

 

[litlerob1]

I see an huge opportunity here, though.

We, collectively, need to get our man Jashley73 to teach the rest of us how refusal to recognize and accept can be applied to make TAXES - or even paperwork in general - (even bitchy bed-partners?) .. just not exist.

 

[litlerob1]

Metal cutting is actually a high rate of deformation followed by shearing of chips. This process is basically called cold working of the material and this is what does the work hardening. Suppose you do a finishing cut on stainless or titanium or high tensile strength Al alloy such as 7075, you'll have a thin layer, something between 0.5-10 thou thick depending on the material you're cutting that will be at full hardness of a material that is prone to work-hardening. So if you're cutting one of the work hardenable materials, your finish passes least depth should be more than the work hardened layer, or else you'll need to start stamping your own carbide inserts. That's one of the reasons to take at least 0.2mm or greater of finishing pass in Ti6Al4V. The other is that you need to have a chipload per tooth of at least 2.5D of the tip radius of the tools cutting edge, or else this cold working will not happen and the chip will not get formed and you'll rub the tool against the part and just heat it up and it will collapse.

Hope this gives you an idea. If you need more, go to your favourite tool suppliers technical manual and read about the cutting process, it will be fairly illuminating.

Naresh

I agree with everything you said, just unclear about what you mean in Blue. If I am Turning and using 432 insert, are you saying I should feed it .078" per revolution?

R

 

[cameraman]

New style of machine argument

Cameraman - I'm not trying to pick on their machine at all. I'm quite biased to love Japanese machines. I'm just hypothesizing, that being a 15k spindle, it probably has smaller/lighter, maybe even hybrid/full-ceramic bearings, and they probably aren't extremely rigid. But man - what a spindle. The thing is whisper quiet at speed...

----------

With regards to the issue at hand - their trouble drilling 22mm holes 5-7xD - I don't think it's entirely material related. The customer swears this stuff is most troublesome to drill, and maybe it's more difficult. But looking up the chemical composition, nothing seemed outrageous - Hence, why I polled the PM crowd. I also don't believe, at this point at least, that work-hardening is the issue.

---------- ---------- ----------

Side note/Tangent - And this is not directed at anyone specific here on PM. - I'm also quite un-satisfied with "work-hardening" being discussed so freely among machinists. The reason being, is that with maybe one or two exceptions in my entire career, no one can tell me WHY "X" material, or any material for that matter is susceptible to work-hardening - again, more accurately called "strain hardening". And at the same time, no one seems to have an understanding of WHAT strain hardening is, and what actually causes it.

I'm not trying to condemn anyone here on PM. But rather, I am suspect when people begin talking about "work-hardening" and then can offer no explanation or understanding, as to what/why/how it's caused. Yes, even the magazine article that came in the mail this week...

Perhaps this is just my personal frustration - One of those, "If you don't understand it, and can't explain it, then don't expect me to take you, your advice and experience seriously" type things... Again - Not directed to anyone here on PM...

It just begins to sound like a generic, lazy, cop-out excuse that people turn to, when things don't go as planned, and they don't care to investigate why. If someone can truly explain it to me, I'll listen, and I'll buy in if it makes sense. Until then, I'll remain extremely skeptical...

---------- ---------- ----------

Getting back to their issue.... Again, most of the problems seem to be mechanical damage related. Not wear+chipping --- straight up chipping/fracturing/cracking/breaking.

I've got enough education & experience with tool-wear analysis, to know that sometimes it's a chicken-and-egg game. Meaning, did the chipping cause the rapid wear, or did the rapid wear cause the chipping? Seldom do you see only one failure exclusively. Most of the time, the failure will show evidence of at least two, maybe three failures simultaneously, meaning they're most often time cause & effect of each other.

At this point however, all the failure modes seem to be mechanical failure exclusively. Which leads me to believe it's a stability issue, and/or extreme mis-application of feed. I plan to visit them next week, break out their indicator, and start pushing on things.


----------


And since you asked/inquired/pondered earlier. MY GOAL through all of this, is simply to fix their problem, and help my customer make more money. That's really it.

I don't have access to any machinery, beyond what they are using in their shop, to run their jobs. Would I love a tech-center machine for testing? You bet, but ain't gonna' happen with my current job.

Yeah no worries.

I know where you are coming from on this.

Sometimes I wish questions would be posed in a less "Paradoxical" manner lol. [Everyday I struggle to communicate more directly lol (work in progress)].

So minor "Pivot".

@Jashley and in general, your "Thesis" or "conjecture" is that a small footprint 50 taper super rigid machine IS needed for many applications that are hindered by so called "Ductile" Iron.

I remember we discussed the details of what I called a Jashley-Monozokuri-Mo'sheeeen; here on PM forum.

The idea being the machine is built like a small brick sh*t house (as we say in the U.K.), like bridge style (I call it WALL style lol) so it has a small force loop, hence massive rigidity and massive torque capability (50 taper). Emphasis on small foot print.

Side note: The tricky part of this application problem is the 6" depth... 22mm diameter (I'm not using diameter ratios as real tools do different things depending on actual size IMO). Supposing one could apply enough torque and the tool tip had the perfect coating and the tool geometry was perfect for the exact material and method... And the machine was theoretically absolutely rigid (not sure how that is accomplished 100% even on box way system)... I still find it hard to believe that the tool wouldn't just explode :-)Is this why we need "Caldie" lol.


I think "Caldie " crops up or is selected as Jashley correctly points out that Moly can have a significant "toughening" effect. So I wonder if "Caldie" is just the toughest of the toughest?


I guess also the point being is that Very difficult ductile iron can be very time consuming to cut via conventional methods... So would a small footprint ultra rigid 50 taper high torque, high load machine be off benefit?


If one was to do theoretical cutting tests beyond normal loads in a hyper rigid and high torque machine what machine would you even test that on?
____________________________________________________________________________________________________________________________

That's why I think the cryogenic stuff has a lot of useful new data that could be extrapolated to a more room temperature understanding but that's all arm chair musings.

__________________________________________________________________________________________________________________________

What do the tool manufacturer's use to test their tools to destruction?

 

[cameraman]

I tell you New Mexico is great for that! Great place if you want to disappear... Slowly coming back to civilization (Denver AND Elsewhere). In NM time stands still and you can stick your head in the sand for as long as you want. I guess that's why a lot of people retire here (in NM right now) after "smashing atoms" for the government.

 

[gregormarwick]

I agree with everything you said, just unclear about what you mean in Blue. If I am Turning and using 432 insert, are you saying I should feed it .078" per revolution?

R

He's talking about the theoretical radius of the not-actually-sharp cutting edge of the tool, and how far the cutting tool must penetrate the workpeice to make it shear, rather than just deform out of the way. Cutting vs. rubbing.

 

[nsharma]

I agree with everything you said, just unclear about what you mean in Blue. If I am Turning and using 432 insert, are you saying I should feed it .078" per revolution?

R

No, that 0.078 not the cutting edge's radius, thats the tools radius. When you look at the tools cutting edge, the rake side: the leading edge of the cutting face and the flank side, that edge, that is not actually sharp and has a radius, thats the radius I'm talking about. It will be larger for coated tools and less for uncoated. So the angle between the rake and the tool flank. Got it?

I thought that it will be helpful to make a quick sketch to show what I intended and not leave an ambiguous answer.