Exploded a GTN3 holder

[jaek]

MRR = cutting speed x feed rate x depth of cut, right?

Which of those change when facing or parting on a manual lathe with power feed?

 

[Parlo]

MRR = cutting speed x feed rate x depth of cut, right?

Which of those change when facing or parting on a manual lathe with power feed?

MRR refers to a volume per unit of time. Feed rate x depth of cut only gives an area. Turning a diameter on a lathe needs the area of the cross section x the feed rate to give the volume per rev. ( Like a stack of washers with each one the thickness of the feed per rev ). When facing, the cross section is continually reducing.
Hope this helps.

 

[jwmelvin]

MRR = cutting speed x feed rate x depth of cut, right?

Which of those change when facing or parting on a manual lathe with power feed?

Cutting speed, in this context, is RPM * circumference, and the circumference changes when facing or parting.

 

[mikey]

Okay, one last time.

There is a significant difference between cutting oil and coolant, especially in this instance. Cutting oil was manually applied, not flood coolant as I suggested. The insert had cut one previous part without flood coolant. The cutting conditions did develop / deteriorate as the cut was made, due to the lack of coolant.

Okay, instead of some nebulous contentions about MMR that you were proposing before, now you seem to be stuck on the idea that coolant alone would have prevented any breakage issues that occurred. You have a tool that is being forced into a cut that it cannot make so it breaks. That is clear for all to see. I tried to explain it but you continued to insist that some force that I am too stupid to understand is responsible. Until today. Today, its not that force; its coolant, but only if its flooded. Really?

You seem rather vexed if your opinion is challenged. A forum is for all to exchange views, not a competition.

Let me be crystal clear. I am "vexed" because of your veiled insults, Parlo.

Don't even try to put me in a position where I seem to be the inflexible authoritarian. Not only is that totally inaccurate, it makes you out to be the poor wronged martyr and absolves you of having any part of this - I'm not having it. If anything, we are here because of you. I have been a member of HM almost since the day it was created and my record of exchanging views is there for all to see.

So is yours.

 

[Jim F]

MRR refers to a volume per unit of time. Feed rate x depth of cut only gives an area. Turning a diameter on a lathe needs the area of the cross section x the feed rate to give the volume per rev. ( Like a stack of washers with each one the thickness of the feed per rev ). When facing, the cross section is continually reducing.
Hope this helps.

Same as parting.............

 

[jaek]

MRR refers to a volume per unit of time. Feed rate x depth of cut only gives an area. Turning a diameter on a lathe needs the area of the cross section x the feed rate to give the volume per rev. ( Like a stack of washers with each one the thickness of the feed per rev ). When facing, the cross section is continually reducing.
Hope this helps.

If we have an area and we need volume per time, don't we need to multiply by a speed (distance per time) instead of a cross section (area)?

 

[Parlo]

Same as parting.............

Yes, facing and parting are the same when referring to varying stock removal rates.

 

[Parlo]

If we have an area and we need volume per time, don't we need to multiply by a speed (distance per time) instead of a cross section (area)?

Yes, my comment #52 split the speed into its two components - distance and time. I used the distance to multiply the area to give the volume. The distance i.e. the circumference, reduces as the cut proceeds towards the centre and therefore the volume decreases.

 

[Parlo]

Okay, one last time.


Okay, instead of some nebulous contentions about MMR that you were proposing before, now you seem to be stuck on the idea that coolant alone would have prevented any breakage issues that occurred. You have a tool that is being forced into a cut that it cannot make so it breaks. That is clear for all to see. I tried to explain it but you continued to insist that some force that I am too stupid to understand is responsible. Until today. Today, its not that force; its coolant, but only if its flooded. Really?


Let me be crystal clear. I am "vexed" because of your veiled insults, Parlo.

Don't even try to put me in a position where I seem to be the inflexible authoritarian. Not only is that totally inaccurate, it makes you out to be the poor wronged martyr and absolves you of having any part of this - I'm not having it. If anything, we are here because of you. I have been a member of HM almost since the day it was created and my record of exchanging views is there for all to see.

So is yours.

My post #22 first mentioned plenty of coolant and again in post #27.
My post #44 states that lack of coolant was a large factor, not " coolant alone would have prevented any breakage issues ".
I think I have been fairly consistent on this.

I innocently added that other varying forces are applied to a tool that also affect its loading and never denied the existence of the surface speed forces. This seemed to unleash some anger and references were posted that I debunked as they did not consider varying loads. Thats when the nasty comments started...

I fully outlined my findings in post #48, I hope someone finds them interesting.
The link to research posted by Ken226 in post #32 - here - https://core.ac.uk/download/pdf/82734159.pdf shows on page 4 (160) section 4 item 2 confirms in its conclusions that MMR has a greater significance in tool load than surface speed.

 

[Parlo]

From the article Mikey posted. Specifically, the article is talking about parting:

"If the machine tool’s spindle speed remains constant as the parting tool moves to the center of the workpiece, the cutting speed will gradually decrease until it reaches zero at the center. A decrease in cutting speed is disadvantageous for the tool and can severely stress the cutting edge. As the edge approaches the center, pressure increases as the tool is fed at the decreasing cutting speed."

Author​

Scott Lewis
Scott Lewis is with Sandvik Coromant Co.



So, if the spindle speed and the feedrate are constant, then it stands to reason that the material removal rate and surface speed are reduced as well, as the tool plunges deeper.
Yet still, it says that In that scenario, the pressure would increase as the tool moves toward center.

He was only referring to cutting speed.