"High speed hard turning"- some questions

[George]

Hi,

I am looking for info about "High Speed Hard Turning" and i find it very
general. Is the term "high speed turning" spesific for each material ? For
example Inconel 718 has its own maximum turning speed to be cut? From which
factors this speed depends?
When we say "High speed turning" we mean higher speeds and higher feeds
together?
What do we mean by talking about "high speed turning with cbn or pcbn
tools"? Can we turn a hard material (like AISI 1552 steel) using a cbn or
pcbn tool in conditions: lighter cuts with higher speeds and feeds ?
I would be gratefull for answering any from the above qwestions or for any
help.

[Smitty Two]

Post by George
Hi,
I am looking for info about "High Speed Hard Turning" and i find it very
general. Is the term "high speed turning" spesific for each material ? For
example Inconel 718 has its own maximum turning speed to be cut? From which
factors this speed depends?
When we say "High speed turning" we mean higher speeds and higher feeds
together?
What do we mean by talking about "high speed turning with cbn or pcbn
tools"? Can we turn a hard material (like AISI 1552 steel) using a cbn or
pcbn tool in conditions: lighter cuts with higher speeds and feeds ?
I would be gratefull for answering any from the above qwestions or for any
help.

I'm far from an expert, but my understanding of high speed turning is
that it means higher speeds, which also means higher feeds, because the
two are inextricably linked. Higher speeds and feeds mean enclosed
turning centers are required, because the tool and part need to be
flooded with coolant/lubricant. Of course, a manual lathe isn't designed
to run at high speeds, anyway. Just as in "low-speed" machining, every
material and type of cut has it's own optimum speed. A machining center
(think mill) is programmed to slow down at corners, for example.

[Anthony]

Post by Smitty Two

Post by George
Hi,
I am looking for info about "High Speed Hard Turning" and i find it
very general. Is the term "high speed turning" spesific for each
material ? For example Inconel 718 has its own maximum turning speed
to be cut? From which factors this speed depends?
When we say "High speed turning" we mean higher speeds and higher
feeds together?
What do we mean by talking about "high speed turning with cbn or pcbn
tools"? Can we turn a hard material (like AISI 1552 steel) using a
cbn or pcbn tool in conditions: lighter cuts with higher speeds and
feeds ? I would be gratefull for answering any from the above
qwestions or for any help.

I'm far from an expert, but my understanding of high speed turning is
that it means higher speeds, which also means higher feeds, because
the two are inextricably linked. Higher speeds and feeds mean enclosed
turning centers are required, because the tool and part need to be
flooded with coolant/lubricant. Of course, a manual lathe isn't
designed to run at high speeds, anyway. Just as in "low-speed"
machining, every material and type of cut has it's own optimum speed.
A machining center (think mill) is programmed to slow down at corners,
for example.

There are several types of inserts out there that specifically forbid
coolant while hard turning, as the thermal stress will crack the insert,
specifically, ceramics. Chips come off those babies like tracers off a 50
Cal.
We do quite a bit of hard turning, because it is MUCH cheaper than
grinding.

[Cliff]

On Mon, 09 Jan 2006 09:19:35 -0800, Smitty Two

Post by Smitty Two
because the tool and part need to be
flooded with coolant/lubricant.

Umm ... Ceramic tooling ..... thermal shock ....

[m***@gmail.com]

Materials need a minimum hardness, and other features of machining are
usually readily obtained thru insert supplier catalogs, in thier
reference sections. memory says 56 Rc. and higher, and the cbn/pcbn
cutting tip will not tolerate bieng buried into the material at inside
corners. High speed is retoric, and feed rates may be dependent on
surface finish requirements. D2 steels at 62Rc , .006" depth of cut,
machine nicely, with very little paste polishing for 8uf. (but this is
a factor of wiping action along the trailing edge of the tool also).
greater depths of cuts are usually done with ceramics. 2 Types of
these, and again look in manufactures catalog reference sect.
softer hardness materials may be machined with carbides at 1/10 of
normal SFM and 1/5 DOC
It has been over ten years since doing these/ so question the accuracy
...

[Dixon]

Post by George
Hi,
I am looking for info about "High Speed Hard Turning" and i find it very
general. Is the term "high speed turning" spesific for each material ? For
example Inconel 718 has its own maximum turning speed to be cut? From which
factors this speed depends?
When we say "High speed turning" we mean higher speeds and higher feeds
together?
What do we mean by talking about "high speed turning with cbn or pcbn
tools"? Can we turn a hard material (like AISI 1552 steel) using a cbn or
pcbn tool in conditions: lighter cuts with higher speeds and feeds ?
I would be gratefull for answering any from the above qwestions or for any
help.

High speed turning creates enough heat just ahead of the tool to form red
hot chips that are very soft. If you are trying to turn inconel 718 I think
you are in trouble. Without doing research on 718 and very high speed, I
believe slow is the only answer. Extremly slow speed and very ridgid set-ups
are the only way it has ever worked for me.
Dixon

[D Murphy]

Post by Dixon
High speed turning creates enough heat just ahead of the tool to form
red hot chips that are very soft. If you are trying to turn inconel
718 I think you are in trouble. Without doing research on 718 and very
high speed, I believe slow is the only answer. Extremly slow speed and
very ridgid set-ups are the only way it has ever worked for me.

For Inconel you can do "high speed" turning with whisker reinforced ceramic
inserts. The last time I saw it done was quite a while ago so maybe things
have changed. We used inserts from Greenleaf. You need lots of horsepower
and rigidity.

[SurfsUp]

Post by D Murphy

Post by Dixon
High speed turning creates enough heat just ahead of the tool to form
red hot chips that are very soft. If you are trying to turn inconel
718 I think you are in trouble. Without doing research on 718 and very
high speed, I believe slow is the only answer. Extremly slow speed and
very ridgid set-ups are the only way it has ever worked for me.

For Inconel you can do "high speed" turning with whisker reinforced ceramic
inserts. The last time I saw it done was quite a while ago so maybe things
have changed. We used inserts from Greenleaf. You need lots of horsepower
and rigidity.
--
Dan

[SurfsUp]

I agree with Dan, I had Inconel 718 as a Project several years ago and
Greenleaf whisker reinforced ceramics are the way to go. There is a lot
more to it however, a lot mmore prepping of material and longer
programming times duu to the need of "ramping" cycles, but the results
are worth it, I went from 20M/min to 200 M/min. For this to work speeds
and feeds must be strictly adhered to however as its the temperature at
the tip which does the work. Oh! one more thing, strictly no coolant!!!
John

[john smith]

high speed machining or turning is to maximise the cutting tool and material
within it's limits , you need a machine or good software which can make hsm
happen , hsm doesn't make speeds or feeds that more faster , it maximises
liniure moves , slows sharp corners ,
I have not had much sucess with lathes so when going fron center (6000 rpm )
to 6." (1000 rpm) I find it nesasory to put in a dwell , g4 u2000' it makes
the insert live longer .
thanks for putting up with a drunks babble .
alan

Post by George
Hi,
I am looking for info about "High Speed Hard Turning" and i find it very
general. Is the term "high speed turning" spesific for each material ? For
example Inconel 718 has its own maximum turning speed to be cut? From which
factors this speed depends?
When we say "High speed turning" we mean higher speeds and higher feeds
together?
What do we mean by talking about "high speed turning with cbn or pcbn
tools"? Can we turn a hard material (like AISI 1552 steel) using a cbn or
pcbn tool in conditions: lighter cuts with higher speeds and feeds ?
I would be gratefull for answering any from the above qwestions or for any
help.