I am a home shop machinist. I have a SB 9" lathe. I am interested in
using carbide inserts and making my own tool holders. I know that HSS
is easier to work with but I still want to experiment with carbide. I
have been doing my homework but have a few questions and need some
clarification on a few points.

1. Any insert with a "N" in the second position is a negative insert.
Any insert with any letter other than an N in the second position is
a positive insert.

2. I am assuming that the positive and negative are refering to back
rake.

3. Negative inserts if kept horizontal, really have no back rake on
their own and also no end clearance or side rake. Positive rake
inserts if kept horizontal, really have no back rake on their own just
end and side rake.

3.5 Negative inserts are more economical because both sides can be
used.

4. Tilting down a negative rake insert gives end clerance and
negative back rake. This is why they are called negative inserts when
really they have no back rake on their own.

5. Tilting up a positive rake insert *should* give end clerance and
some positive back rake would seem to be the ideal situation for a
small lathe. However this creates an interesting paradox, all of the
sources that I could find, seem to want to operate a positive rake
insert perfectly horizontal. This would make it a zero back rake tool
(neither positive or negative). Why does everyone want zero back rake?

6. I found a source suggesting using a TNMP insert. The chip breaker
goes clear out to the edge of the insert. Tipping this insert down 5
degrees gives you 5 gegrees end relief and 5 degrees positive back
rake. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.

Any help would be greatly appreciated. Thank You

You can forget using negative inserts on a SB 9" unless you just
love chatter. Those inserts require three things: rigidity, power,
and speed.

I admit I use carbide some on my SB 9" but it often doesn't work
that well. I'm always better off grinding the appropriate HSS bit
and using that - better finish, less chatter, etc. Mostly now I
only use carbide for cutoff, and on those I use the GT?-2 which
are .087" wide (GTN-2, GTR-2 ..).

You're correct on tip radius.

Grant Erwin
Kirkland, Washington

John Albers wrote:
I am a home shop machinist. I have a SB 9" lathe. I am interested in
using carbide inserts and making my own tool holders. I know that HSS
is easier to work with but I still want to experiment with carbide. I
have been doing my homework but have a few questions and need some
clarification on a few points.

1. Any insert with a "N" in the second position is a negative insert.
Any insert with any letter other than an N in the second position is
a positive insert.

2. I am assuming that the positive and negative are refering to back
rake.

3. Negative inserts if kept horizontal, really have no back rake on
their own and also no end clearance or side rake. Positive rake
inserts if kept horizontal, really have no back rake on their own just
end and side rake.

3.5 Negative inserts are more economical because both sides can be
used.

4. Tilting down a negative rake insert gives end clerance and
negative back rake. This is why they are called negative inserts when
really they have no back rake on their own.

5. Tilting up a positive rake insert *should* give end clerance and
some positive back rake would seem to be the ideal situation for a
small lathe. However this creates an interesting paradox, all of the
sources that I could find, seem to want to operate a positive rake
insert perfectly horizontal. This would make it a zero back rake tool
(neither positive or negative). Why does everyone want zero back rake?

6. I found a source suggesting using a TNMP insert. The chip breaker
goes clear out to the edge of the insert. Tipping this insert down 5
degrees gives you 5 gegrees end relief and 5 degrees positive back
rake. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.

Any help would be greatly appreciated. Thank You



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In article , John Albers says...

6. I found a source suggesting using a TNMP insert. The chip breaker
goes clear out to the edge of the insert. Tipping this insert down 5
degrees gives you 5 gegrees end relief and 5 degrees positive back
rake. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?

Yes. I think it was Ted Edwards (apolgies if this is
wrong) who makes his own holders for these inserts. He
likes that setup a lot. If I did not already have
a set of tpg221 holders from valenite, that's the
way I would go.

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.

Yes. Also coated inserts invariabley have a "honed" edge
to retain the coating at the cutting point. Because of
this they are not dead sharp and don't cut on smaller machines
quite as well.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

2. I am assuming that the positive and negative are refering to back
rake.
--------Yes, except as the rake is modified by grooves and such on the
top face.

3...., 3.5..., 4....
--------Typically true.

5. Why does everyone want zero back rake?
----------For edge strength.

6. I found a source suggesting using a TNMP insert. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?
----------You can use TNMPs on both sides. I like TNMGs better than
TNMPs, but I have a stout lathe. I find it hard to get chips to break
with TNMPs.

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.
-----------Big tip radius is bad for a lathe like yours. You'll get
chatter and pushback from the work.
Any help would be greatly appreciated. Thank You

--------I suggest trying some of the Rouse or Borite screw-down sets
that MSC, ENCO & others sell. These use TCMM, TT221, or TPMT or
similar inserts. The trick is to get good quality, name-brand inserts
like Kennametal, Carboloy, Iscar, Valenite, Sumitomo, etc. Another
approach is to get one of Circle Machine Co's square shank holders
that lets you use their boring inserts for outside turning. Their
stuff is pricey but can be found on ebay. The edges are typically
very sharp, nose radii are small, and they sell carbide grades
specifically for low surface speeds. Carbide likes to run at 250
ft/min surface speed and higher, but you will have a very tough time
doing this with your lathe.

The three rules of carbide:
1. RIGIDITY
2. RIGIDITY
3. RIGIDITY

Any slop or flex in ANYTHING and you won't enjoy it!


"John Albers" wrote in message
m...
I am a home shop machinist. I have a SB 9" lathe. I am interested in
using carbide inserts and making my own tool holders. I know that HSS
is easier to work with but I still want to experiment with carbide. I
have been doing my homework but have a few questions and need some
clarification on a few points.

1. Any insert with a "N" in the second position is a negative insert.
Any insert with any letter other than an N in the second position is
a positive insert.

2. I am assuming that the positive and negative are refering to back
rake.

3. Negative inserts if kept horizontal, really have no back rake on
their own and also no end clearance or side rake. Positive rake
inserts if kept horizontal, really have no back rake on their own just
end and side rake.

3.5 Negative inserts are more economical because both sides can be
used.

4. Tilting down a negative rake insert gives end clerance and
negative back rake. This is why they are called negative inserts when
really they have no back rake on their own.

5. Tilting up a positive rake insert *should* give end clerance and
some positive back rake would seem to be the ideal situation for a
small lathe. However this creates an interesting paradox, all of the
sources that I could find, seem to want to operate a positive rake
insert perfectly horizontal. This would make it a zero back rake tool
(neither positive or negative). Why does everyone want zero back rake?

6. I found a source suggesting using a TNMP insert. The chip breaker
goes clear out to the edge of the insert. Tipping this insert down 5
degrees gives you 5 gegrees end relief and 5 degrees positive back
rake. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.

Any help would be greatly appreciated. Thank You

In article , Tom Gardner says...

The three rules of carbide:
1. RIGIDITY
2. RIGIDITY
3. RIGIDITY

I don't understand how that's any
different than using HSS tooling.
Those rules still apply.
Rigid, more rigid, and even more rigid
than that!

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

(John Albers) wrote in message om...
I am a home shop machinist. I have a SB 9" lathe. I am interested in
using carbide inserts and making my own tool holders. I know that HSS
is easier to work with but I still want to experiment with carbide. I
have been doing my homework but have a few questions and need some
clarification on a few points.

1. Any insert with a "N" in the second position is a negative insert.
Any insert with any letter other than an N in the second position is
a positive insert.

2. I am assuming that the positive and negative are refering to back
rake.

3. Negative inserts if kept horizontal, really have no back rake on
their own and also no end clearance or side rake. Positive rake
inserts if kept horizontal, really have no back rake on their own just
end and side rake.

3.5 Negative inserts are more economical because both sides can be
used.

4. Tilting down a negative rake insert gives end clerance and
negative back rake. This is why they are called negative inserts when
really they have no back rake on their own.

5. Tilting up a positive rake insert *should* give end clerance and
some positive back rake would seem to be the ideal situation for a
small lathe. However this creates an interesting paradox, all of the
sources that I could find, seem to want to operate a positive rake
insert perfectly horizontal. This would make it a zero back rake tool
(neither positive or negative). Why does everyone want zero back rake?

6. I found a source suggesting using a TNMP insert. The chip breaker
goes clear out to the edge of the insert. Tipping this insert down 5
degrees gives you 5 gegrees end relief and 5 degrees positive back
rake. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.

Any help would be greatly appreciated. Thank You

Hi John,

I've been a CNC programmer for the past twenty three years, and can
offer a few general comments about carbide inserts.

Always use negative G style inserts when you can - they're cheaper and
stronger than positive P style - which aren't true positive inserts,
but normally cut cleaner and break chips better than the G's - they
just won't take high depths of cut/high feedrates as well.

Negatives usually work fine for turning on rigid machines and with
rigid workpieces. The most widely-used rough turning insert in
industry is undoubtedly the CNMG series, which is an 80 degree
diamond. It's very useful on CNC machines because it's quite strong
and can turn or face equally well in the same toolholder. They're
double-sided, so you get four corners. SNMG (squares) are stronger but
less versatile, TNMG (triangles) are weaker but can get into odd
places or close to a tailstock center.

The previously mentioned geometries also come in an M style, which is
single-sided. They're designed for heavy roughing - the 100% contact
on the bottom gives better support than the G style has.

The P styles are economical for light roughing (especially where chip
control is a problem) or finishing. They are double-sided and have
four corners.

Positives generally cut cleaner than negatives, but negatives almost
always work well enough. Negative inserts often don't work well at
all for milling.

Recognize that there are lots of sub-categories. Insert salesmen will
gladly sell you ten slightly different configurations of chip breaker
if you let them. Most of them can be ignored.

Larger radii theoretically give a better finish at the same feedrate,
but in practice the reverse sometimes happens, particularly when
machining a thin-walled or otherwise unstable workpiece where the
extra tool pressure from the large radius is detrimental. Most shops
have standardized on a 1/32 radius for finishing, but 3/64 and 1/16
are around too. Sometimes the blueprint will force you (maximum
inside corner radius callout) to go to 1/64 or even smaller.
Generally, tool life suffers as the radius size decreases.

That's my five minutes worth. Most of it's pretty standard stuff,
some might be debatable.

Mike

(John Albers) wrote in message om...
I am a home shop machinist. I have a SB 9" lathe. I am interested in
using carbide inserts and making my own tool holders. I know that HSS
is easier to work with but I still want to experiment with carbide. I
have been doing my homework but have a few questions and need some
clarification on a few points.

1. Any insert with a "N" in the second position is a negative insert.
Any insert with any letter other than an N in the second position is
a positive insert.

2. I am assuming that the positive and negative are refering to back
rake.

3. Negative inserts if kept horizontal, really have no back rake on
their own and also no end clearance or side rake. Positive rake
inserts if kept horizontal, really have no back rake on their own just
end and side rake.

3.5 Negative inserts are more economical because both sides can be
used.

4. Tilting down a negative rake insert gives end clerance and
negative back rake. This is why they are called negative inserts when
really they have no back rake on their own.

5. Tilting up a positive rake insert *should* give end clerance and
some positive back rake would seem to be the ideal situation for a
small lathe. However this creates an interesting paradox, all of the
sources that I could find, seem to want to operate a positive rake
insert perfectly horizontal. This would make it a zero back rake tool
(neither positive or negative). Why does everyone want zero back rake?

6. I found a source suggesting using a TNMP insert. The chip breaker
goes clear out to the edge of the insert. Tipping this insert down 5
degrees gives you 5 gegrees end relief and 5 degrees positive back
rake. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.

Any help would be greatly appreciated. Thank You

Yup, the TNMP is double-sided and cuts well if tilted at the right
angle. I used to make all my own toolholders years ago, though not
with the fancy cams and so on; just a socket-head capscrew with the
underside of the head turned at a taper to set the head lower in the
insert so it doesn't interfere with chip removal.
Larger tip radius gives better finish, but unless the radius is
large (like a small, round insert) the power increase needed is
marginal. Chatter will be more of a problem if the radius is large and
the lathe is light or worn. A larger radius runs cooler, too, which is
important in carbide, as it suffers thermal shock easily. For the same
reason, either use no coolant at all, or flood it. Intermittent
splashing will cause thermal shock and cracking.
Get TiN coated inserts, and they'll last longer.

Dan

"jim rozen" wrote in message
...

I don't understand how that's any
different than using HSS tooling.
Those rules still apply.
Rigid, more rigid, and even more rigid
than that!

I'd say HSS is significantly more lenient in regards to a lack of ideal
cutting conditions.

Generally, anything slower than *too fast* is fine with HSS. I've run a HSS
cutter such that it (3/8" square) was hanging out a good 1" from the
toolpost and flexing about 1/8" down each time the work piece hit the cutter
(interrupted cut on O1, massive feed and DOC, very low surface speed).

A carbide insert or brazed cutter would have snapped on the first hit. In
that situation, carbide would have been a slow method of material removal
because of the interrupted cut.

Of course, I'm not saying one can throw rigidity out the window with HSS,
but when you're running carbide so hard that the spindle is close to
stalling (not usually possible with HSS), rigidity becomes a big issue.

Regards,

Robin

On 15 Oct 2003 14:49:56 -0700, jim rozen
wrote:

In article , Tom Gardner says...

The three rules of carbide:
1. RIGIDITY
2. RIGIDITY
3. RIGIDITY

I don't understand how that's any
different than using HSS tooling.
Those rules still apply.
Rigid, more rigid, and even more rigid
than that!

Jim

Because the crux of the matter is, Jim, HSS properly done, is heads
and hands sharper than carbide.

I tend to use a lot of HSS with my lathes and shapers, and have a
decent Baldor grinder with a set of diamond wheels. Ive played with
both, and the HSS wins 90% of the time under normal turning,
particulary if you can flood cool with oil. This is only true if you
keep your tools sharp, which is labor intensive. Which is one of the
reasons production shops use a Lot of carbide, because they have rigid
machines and labor is a significant part of production costs.

A goodly number of the tool makers I know, still use a ****load of
HSS, rather than carbide in MOST one off applications as they can do
more, with the HSS, than with carbide.

Gunner

"You cannot invade the mainland United States. There would be a rifle
behind each blade of grass." --Japanese Admiral Isoroku Yamamoto

I totally agree with Gunner's comments. You can really tell the
difference between guys who actually have small machines and have
tried carbide, and the ones for whom this is merely a "thought
experiment".

Really, 9" SB lathes are all about HSS. You can certainly use some
carbide some of the time, but negative inserts? forget it. - GWE

Gunner wrote:

On 15 Oct 2003 14:49:56 -0700, jim rozen
wrote:


In article , Tom Gardner says...

The three rules of carbide:
1. RIGIDITY
2. RIGIDITY
3. RIGIDITY

I don't understand how that's any
different than using HSS tooling.
Those rules still apply.
Rigid, more rigid, and even more rigid
than that!

Jim


Because the crux of the matter is, Jim, HSS properly done, is heads
and hands sharper than carbide.

I tend to use a lot of HSS with my lathes and shapers, and have a
decent Baldor grinder with a set of diamond wheels. Ive played with
both, and the HSS wins 90% of the time under normal turning,
particulary if you can flood cool with oil. This is only true if you
keep your tools sharp, which is labor intensive. Which is one of the
reasons production shops use a Lot of carbide, because they have rigid
machines and labor is a significant part of production costs.

A goodly number of the tool makers I know, still use a ****load of
HSS, rather than carbide in MOST one off applications as they can do
more, with the HSS, than with carbide.

Gunner

"You cannot invade the mainland United States. There would be a rifle
behind each blade of grass." --Japanese Admiral Isoroku Yamamoto



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"Gunner" wrote in message
...
On 15 Oct 2003 14:49:56 -0700, jim rozen
wrote:

I tend to use a lot of HSS with my lathes and shapers, and have a
decent Baldor grinder with a set of diamond wheels. Ive played with
both, and the HSS wins 90% of the time under normal turning,
particulary if you can flood cool with oil.

What's normal turning? I would think facing and turning as opposed to
grooving and forming. In this case, why does HSS *win*? With what little
experience I've had in toolmaking, radius tools are constantly used along
with other form tools. In this case, carbide is a loser. However, I don't
see why anyone would use anything _but_ carbide for turning/facing.
Esspecially with high carbon, high alloy tool steels and machine steels
(like 41freakin'40).

This is only true if you
keep your tools sharp, which is labor intensive. Which is one of the
reasons production shops use a Lot of carbide, because they have rigid
machines and labor is a significant part of production costs.

HSS can be run as efficiently as carbide if kept sharp?

Regards,

Robin

In article ,
John Albers wrote:
I am a home shop machinist. I have a SB 9" lathe. I am interested in
using carbide inserts and making my own tool holders. I know that HSS
is easier to work with but I still want to experiment with carbide. I
have been doing my homework but have a few questions and need some
clarification on a few points.

1. Any insert with a "N" in the second position is a negative insert.
Any insert with any letter other than an N in the second position is
a positive insert.

Yep. At least for lathe tool inserts. Not too sure about those
for milling cutters and such. And, of course, there are things like the
threading inserts (There are two styles, one is the "laydown" which have
the triangular inserts mounted more or less flat (there are solid
carbide anvils with various angles to allow you to tune the angle of the
insert to match the lead of the thread, since you can't just grind more
relief on the typical insert.)

The other style of threading insert is also triangular, but is
mounted on edge. I know of no way to tune this for the needed clearance
angles.

2. I am assuming that the positive and negative are refering to back
rake.

Basically.

3. Negative inserts if kept horizontal, really have no back rake on
their own and also no end clearance or side rake. Positive rake
inserts if kept horizontal, really have no back rake on their own just
end and side rake.

End and side clearance -- not rake.

The positive ones have whatever back rake may be contributed by
any chipbreaker which they may have -- if it comes close enough to the
edge.

3.5 Negative inserts are more economical because both sides can be
used.

They also are stronger, because there is more meat behind the
edge. The edges on positive inserts are more fragile.

4. Tilting down a negative rake insert gives end clerance and
negative back rake. This is why they are called negative inserts when
really they have no back rake on their own.

Right.

5. Tilting up a positive rake insert *should* give end clerance and
some positive back rake would seem to be the ideal situation for a
small lathe. However this creates an interesting paradox, all of the
sources that I could find, seem to want to operate a positive rake
insert perfectly horizontal. This would make it a zero back rake tool
(neither positive or negative). Why does everyone want zero back rake?

They don't -- except for turning things like brass. But they
depend on the chipbreaker to generate the effect of rake.

And if you tilt a positive insert, you actually *reduce* the tip
and side clearance -- which might not be too bad, depending on the feed
rate.

The tip clearance on a positive insert is formed by the
combination of the clearance angles on the two sides which join to make
the tip -- and it is affected by the angle at which they join. There
are *lots* of shapes. On my 12x24" Clausing, I use the triangular form,
while on my little Compact-5/CNC, I use the 55 degree diamond. The
choice for the Compact-5/CNC was made for be by the tooling which came
with it.

The triangular ones on the Clausing are the TNMP, and usually
uncoated, which gives a sharper edge. These give a total of six corners
which can be used (assuming that the wear to a given corner is not
sufficient to destroy the use of the flip side one).

The diamond shaped ones on the Compact-5/CNC are positive rake
ones, and the diamond only allows two of the four corners (the sharper
two) so there is a 3:1 ratio in favor of the triangular ones on the
Clausing. Most of my inserts for the Compact-5/CNC are also uncoated,
though I have a certain percentage of TiN coated ones.

The diamond shaped ones have three formats (in the collection
which I have). In one (the first ones I had were all of this type), the
chipbreaker ran around the full diamond shape. The other two either
have the chipbreaker only on the left edges (for right-hand-side turning
tools), or on the right edges (for left-hand side turning tools and for
boring bars). The corners are a bit stronger on the ones which have
only the half chipbreaker. I presume that there are also diamond-shaped
inserts with *no* chipbreaker (good for brass), but I don't have any of
them. I have a large collection of the other styles, thanks to an offer
from someone else in this newsgroup a few years ago. He was willing to
send a few samples free to anyone in the list, and as I was the only one
(at the time) who could use them, he wound up offering to sell me the
rest (several thousand, I think) for what I considered a reasonable
price -- which I gladly accepted.

6. I found a source suggesting using a TNMP insert. The chip breaker
goes clear out to the edge of the insert. Tipping this insert down 5
degrees gives you 5 gegrees end relief and 5 degrees positive back
rake. I think that this insert has chip breakers on both sides so it
could be turned over and used again. DOes anyone know for sure? I
think that this is the best way to go. Has anyone tried this?

Yes -- the chipbreakers are on both sides in the TNMP inserts.
These are what I use in the Clausing -- both in normal holders held in
Aloris style quick-change holders, and (lately) in the special holders
made by Aloris which directly accept two inserts -- one on each end for
the turning and facing operations. This makes for a more rigid setup,
and reduces chatter. There are two forms of this -- one for the positive
inserts (16P), and one for the negative inserts (16N). I have the
latter only. I won a couple of lots on eBay which had 100 of the TNMP
inserts and a straight holder (I later got the left and right holders
via MSC to go with the inserts which I already had. All of these are
uncoated, and seem to work well for what I normally do -- though for
certain materials, the TiN coating could improve wear life and friction,
while reducing the sharpness of the available edge (which isn't that
sharp on a TNMP anyway. :-)

Note, however, that most of my threading inserts *are* TiN
coated.

7. What effect does the tip radius have. I beleive that the larger
the raduis the smoother the surface finish on turned work. However,
the larger the radius the more power required.

And -- the more likely you will get chatter, because of the
higher forces.

Any help would be greatly appreciated. Thank You

One consideration for true negative rake inserts (not the TNMP)
is that it takes a more rigid machine to hold them without chatter. And
chatter can destroy an insert where a HSS tool would not have problems,
because the carbide is more brittle. I'm not really sure whether the 9"
South Bend is rigid enough (and has enough power) for true negative rake
insets, but it is probably sufficient for the Positive/negative ones
which we are discussing. The true negative rake ones take *lots* of
power, and are better for cutting really hard materials, where the
clearance for the positive inserts weakens the edge too much, as does (to
a lesser extent) the chipbreaker groove that turns a negative insert
into a positive/negative one.

I hope that this helps. Now off to read your other responses,
to see how many agree or disagree with me -- or offer other things that
I didn't think of.

Good Luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
Grant Erwin wrote:
I totally agree with Gunner's comments. You can really tell the
difference between guys who actually have small machines and have
tried carbide, and the ones for whom this is merely a "thought
experiment".

Hmm ... does a 5" swing machine, used almost entirely with
carbide count? It is my Compact-5/CNC, and I have some *very* sharp
(uncoated) carbide inserts for it. They are a win in part because it
*is* CNC, and the ability to turn or replace an insert and to not have
to change the offsets throughout the program (at least at every tool
change -- since that machine is too old to have a single place to
insert the offsets for a given tool once and for all.)

Really, 9" SB lathes are all about HSS. You can certainly use some
carbide some of the time, but negative inserts? forget it. - GWE

The ones with the chipbreaker designed to give a positive rake
with an otherwise negative insert may work for him. They work for me,
in the 12x24" Clausing -- but admittedly, that is a more rigid and more
powerful machine than a 9" SB. Maybe the heavy 10 (10l) might be closer
to sufficient.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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"Robin S." wrote in message ...

What's normal turning? I would think facing and turning as opposed to
grooving and forming. In this case, why does HSS *win*? With what little
experience I've had in toolmaking, radius tools are constantly used along
with other form tools. In this case, carbide is a loser. However, I don't
see why anyone would use anything _but_ carbide for turning/facing.
Esspecially with high carbon, high alloy tool steels and machine steels
(like 41freakin'40).

Normal turning is anything you would do on a lathe, including
grooving, forming and threading. Carbides can be very "hungry", but
unless you've got lots of power and rigidity, it comes second to a
good high speed tool. A solid 14 or 16 inch lathe would be about the
minimum I'd even look at a carbide for, the smaller ones just don't
have what it takes. Most of us have smaller machines or imports, and
carbide is the way to ruin both your budget and your machine. Very
few of the bench machines are heavy enough to run carbide without
either shortening it's life, or making your life miserable. But,
(Giggle, snort), I don't use carbide, and I'd rather work 4140 or
4140HT than the gummy soft stuff. May take me a while longer, but
normally I get a good finish, hold size easily, and if I want to
polish it, nothing else comes up as nice.

HSS can be run as efficiently as carbide if kept sharp?

Ummmm, yes. If a job has something, like an interrupted cut, it can
raise hell with inserts, and I've seen it pull the brazed tools apart.
However, the only time I ever stopped the spindle on the 7A J&L was
with a 1/2 inch radius on a 1 inch square piece of Congo. However,
one of the common things that I've seen is people wasting time trying
to make a carbide work, because "High speed would take too long."
Usually, by the time they give up and use the HSS, they've already
wasted more time than it would have taken them to use the HSS the
first time. Carbide can remove a lot of metal in a hurry, but power
and rigidity have to be there or you're wasting time.

On Wed, 15 Oct 2003 22:07:57 -0400, "Robin S."
wrote:


"Gunner" wrote in message
.. .
On 15 Oct 2003 14:49:56 -0700, jim rozen
wrote:

I tend to use a lot of HSS with my lathes and shapers, and have a
decent Baldor grinder with a set of diamond wheels. Ive played with
both, and the HSS wins 90% of the time under normal turning,
particulary if you can flood cool with oil.

What's normal turning? I would think facing and turning as opposed to
grooving and forming. In this case, why does HSS *win*? With what little
experience I've had in toolmaking, radius tools are constantly used along
with other form tools. In this case, carbide is a loser. However, I don't
see why anyone would use anything _but_ carbide for turning/facing.
Esspecially with high carbon, high alloy tool steels and machine steels
(like 41freakin'40).


I turn a lot of O1, 4140 etc with HSS. Its quite true that it dulls
MUCH faster than a proper grade of carbide, but then, carbide dulls
much faster than a proper grade of ceramic, which dulls faster than
diamond. G

It all goes back to having a rigid machine, able to force the carbide
into the workpiece.

I liken it to this: You can cut hardwood, easily with a very sharp
chisel, or you can hammer it in with a dull one. Carbide is in its
element, when you are making hard contact and are cranking out hot
blue chips. This is simply not possible with many/most small flexible
HSM lathes. Something of interest for you to try.... get a hard turn
going, nice blue chip load, good sounding cut with carbide, and turn
off the lights. You will note that in most cases..the cutting
interface is glowing red. That red heat is caused by friction of the
workpiece being forced by the duller carbide tool. Make the same doc,
same feed with a properly sharpened HSS bit, and it will likely not be
glowing, and the chips will likely not be blue.

Again carbide comes into its own, when the workpiece is hard. When you
are approaching the hardness of HSS, yes..carbide wins hands down, for
same doc/sfm.

Some materials simply will not "shear", but must be softened then
ripped off the parent body. Inconel is one such. You MUST have a hard
contact, lots of force, or the heat of the contact will work harden
the material. You MUST be ahead of the heat treating zone when digging
in or it turns to **** on you. Ive cut inconel with HSS. It cuts ok,
if you find that magic angle/doc/sfm, but it wears out HSS quickly.
Let it heat treat itself, get behind the cutting curve and it
instantly gets nearly as hard as the HSS tool itself. Even Carbide has
a hell of a time cutting it at this point. You have to dig in deep
enough to get under that heat treated zone.
This is only true if you
keep your tools sharp, which is labor intensive. Which is one of the
reasons production shops use a Lot of carbide, because they have rigid
machines and labor is a significant part of production costs.

HSS can be run as efficiently as carbide if kept sharp?

Define efficently. Can the cheaper HSS do the same cut as carbide in
most common materials? Yes, indeed. It will do it (Sometimes slower
and shallower), and with less cutting force needed. Other times, it
actually does it faster than carbide.

Carbide is much more brittle than HSS. Interuppted cuts kills carbide
in the blink of an eye, as does chatter. I have both carbide and HSS
cutoff tooling. If cutting off something..I get some sudden chatter, I
will immediately pull out the carbide tool and look at the edge for
damage. With HSS, I simply dig in a bit harder.

When cutting some materials, such as plastics..a very very sharp
positive rake on a HSS tool, cuts that plastic like it was air, even
in huge DOC. Carbide on the other hand, tends to melt it, smear it and
make a huge mess.

I have a good number of plastics houses that cut almost exclusivly
with hand sharpened HSS in their CNC machines for this reason. They
only go to carbide for phenolics, G10 composits etc because the
material itself is abrasive as hell, and they are needing longer tool
life that only carbide or diamond/ceramics gives them. And they are
willing to pay the price for less downtime in sharpening costs and a
worse surface finish.

I also service machines in Swiss screw machine houses. They use a
mixture of HSS and carbide, depending on the material, how many
hundreds of thousands of parts to be cut and the detailed features. In
many of those shops, HSS is cut under a microscope for form tooling,
where a groove may be .005 x .1 deep for example. Carbide (some
grades are better than others) tends to bust like crackers when
subjected to this kind of loading. Shrug.

Efficency is a big variable and you will have to narrow your
parameters a bit for a better answer.

Just keep in mind..that we are discussing here, HSM usages, rather
than production quantities of thousands, and when one can grind a HSS
tool to the proper angles and degrees, its often a hell of a lot
cheaper and quicker than ordering out a $20 insert . Simply put..it
can be more efficient than carbide in many applications. And Id dare
say, in MOST HSM applications..it IS more efficient than carbide,
given price alone.

Gunner


Regards,

Robin


"You cannot invade the mainland United States. There would be a rifle
behind each blade of grass." --Japanese Admiral Isoroku Yamamoto

On 15 Oct 2003 23:35:11 -0400, (DoN. Nichols)
wrote:

I'm not really sure whether the 9"
South Bend is rigid enough (and has enough power) for true negative rake
insets

From past experience..a Logan 10" in good condition, is barely rigid
enough for a negative rake insert, at any DOC. My 13x36 Clausing gear
head, eats it up like it was made for it. Ones 250lbs..the other is
2000 lbs G

Gunner

"You cannot invade the mainland United States. There would be a rifle
behind each blade of grass." --Japanese Admiral Isoroku Yamamoto

On 15 Oct 2003 22:27:57 -0700, (Lennie the
Lurker) wrote:

"Robin S." wrote in message ...

What's normal turning? I would think facing and turning as opposed to
grooving and forming. In this case, why does HSS *win*? With what little
experience I've had in toolmaking, radius tools are constantly used along
with other form tools. In this case, carbide is a loser. However, I don't
see why anyone would use anything _but_ carbide for turning/facing.
Esspecially with high carbon, high alloy tool steels and machine steels
(like 41freakin'40).

Normal turning is anything you would do on a lathe, including
grooving, forming and threading. Carbides can be very "hungry", but
unless you've got lots of power and rigidity, it comes second to a
good high speed tool. A solid 14 or 16 inch lathe would be about the
minimum I'd even look at a carbide for, the smaller ones just don't
have what it takes. Most of us have smaller machines or imports, and
carbide is the way to ruin both your budget and your machine. Very
few of the bench machines are heavy enough to run carbide without
either shortening it's life, or making your life miserable. But,
(Giggle, snort), I don't use carbide, and I'd rather work 4140 or
4140HT than the gummy soft stuff. May take me a while longer, but
normally I get a good finish, hold size easily, and if I want to
polish it, nothing else comes up as nice.

HSS can be run as efficiently as carbide if kept sharp?

Ummmm, yes. If a job has something, like an interrupted cut, it can
raise hell with inserts, and I've seen it pull the brazed tools apart.
However, the only time I ever stopped the spindle on the 7A J&L was
with a 1/2 inch radius on a 1 inch square piece of Congo. However,
one of the common things that I've seen is people wasting time trying
to make a carbide work, because "High speed would take too long."
Usually, by the time they give up and use the HSS, they've already
wasted more time than it would have taken them to use the HSS the
first time. Carbide can remove a lot of metal in a hurry, but power
and rigidity have to be there or you're wasting time.


Damn..something else Lennie and I can agree on. There is a (insert
Diety of your choice) afterall!

Gunner

"You cannot invade the mainland United States. There would be a rifle
behind each blade of grass." --Japanese Admiral Isoroku Yamamoto

In article , Robin S. says...

A carbide insert or brazed cutter would have snapped on the first hit.

Things carbide does not do well under *any* circumstances:
interrupted cuts.

Things that carbide does well, under any circumstances:
turning hardened items.

I use carbide instead of HSS on smaller machines, when
having to turn something that cannot be annealed.

Jim

==================================================
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==================================================

When I first started metalworking I insisted on trying carbide in spite
of what I was told. It never did work well for me on my atlas lathe.

I have a friend who has been a machinest, model maker, and tool and
die maker for years. He still grinds and uses lots of HSS. He has taught
me a lot and NOW I listen to him. One time I was making a crankshaft
out of 4140. I sort of figured I would need to use carbide because 4140
is pretty damn tough stuff. Surface finish resembled sandpaper.
I changed to HSS with cutting oil at 50FPM and it worked much better.
Just like my friend said it would!
chuck

John Albers wrote:

I am a home shop machinist. I have a SB 9" lathe. I am interested in
using carbide inserts and making my own tool holders.

If you haven't already found it, check out
http://www.metalwebnews.com/howto/to...oolholder.html

Since I wrote that, I have written some more stuff on these. Not quite
sure what to do with it.

Ted

I'm not going to waste my time plowing through *all* the used hay in
this thread such as:
"Ya have to have a really rigid machine to use carbide." I use it on
a Chinese 3-in-1 for the vast majority of my turning. I use HSS when I
want a special shape cutter.
"Carbide can't be as sharp as HSS." I use uncoated carbide TNMP-321
inserts. When I want them *really* sharp, I hone the edges on an
Easy-lap diamond hone.
"You need to turn at really high speed to use carbide." You *may* run
carbide at much higher speed than HSS but you don't *have* to. I run it
at whatever speed I feel comfortable and my machine can handle.
There's more but I suggest you try it for yourself.

Ted

I agree with you in most respects.

COMMON carbide inserts are NOT very suitable for small lathes. It's true
that negative rake carbide (or even HSS) tools do NOT work well except
in rigid machines. It's also true that small low powered machines cannot
make the BEST use of carbide.

There are, however, families of small uncoated inserts, mostly
triangular, that are VERY sharp, have considerable relief, NO rake, cut
with minimal pressure, and work well at most any speed. I use these
regularly, on a 6" Atlas, and even on my old round-way Unimat SL. While
the rake is zero (flat on top), these cut with less pressure than most
positive rake tools (which are less sharp). I can take as heavy a cut,
with as good a finish, with these carbides as I can with HSS ... even on
the Unimat!

I also use these, and a variety of more common carbide inserts on a 10"
Logan. This heavier machine is more forgiving of the commonly available
carbides inserts. It still doesn't like negative rake tools much, however.

The advantages of the carbides are that they stay sharp longer than a
HSS bit in the same service. I find this especially advantageous in
turning soft but abrasive plastics. It is also useful when one has to
turn hard materials. The inserts work reasonably well with almost all
materials, but there is no advantage when turning softer steels, brass, etc.

Disadvantages include problems with interrupted cuts, the inability
(easily) to custom grind odd shaped tools, and higher cost (considerably).

That said, I use HSS for perhaps 90% of my turning needs. The carbide is
less versatile, and more expensive. On a small lathe, carbide is NOT
the best choice for general work. But, to say it's NOT suitable at all
for use in a small lathe, even a Unimat, is just plain WRONG!

Dan Mitchell
==========

Ted Edwards wrote:

I'm not going to waste my time plowing through *all* the used hay in
this thread such as:
"Ya have to have a really rigid machine to use carbide." I use it on
a Chinese 3-in-1 for the vast majority of my turning. I use HSS when I
want a special shape cutter.
"Carbide can't be as sharp as HSS." I use uncoated carbide TNMP-321
inserts. When I want them *really* sharp, I hone the edges on an
Easy-lap diamond hone.
"You need to turn at really high speed to use carbide." You *may* run
carbide at much higher speed than HSS but you don't *have* to. I run it
at whatever speed I feel comfortable and my machine can handle.
There's more but I suggest you try it for yourself.

Ted

Ted Edwards wrote in message ...

"You need to turn at really high speed to use carbide." You *may* run
carbide at much higher speed than HSS but you don't *have* to. I run it
at whatever speed I feel comfortable and my machine can handle.
There's more but I suggest you try it for yourself.

Ummm, Ted. The only thing we used that tiny an insert on was one of
the shaft gears we used to make. 3" diameter, 670rpm, .022 feed, and
3/16" per side. I don't think any chinese 3n1 is going to come
anywhere near reaching what the insert is capable of. Oh yeah. 8620
normalized forging. Industry didn't design carbide for slow light
cuts. It's meant to rip metal off as fast as possible. Home shop
machines don't have the backbone to handle what the carbide was
intended for.

On Thu, 16 Oct 2003 01:18:39 GMT, Gunner wrote:
Because the crux of the matter is, Jim, HSS properly done, is heads
and hands sharper than carbide.

That's only true if you're using coated carbide inserts, and using them right out
of the box. On smaller machines, I only use uncoated inserts, and hand hone
them for an even keener edge. I'll put the edge I can get on those inserts up
against anything you can achieve with HSS (and maintain for more than one
second of cutting).

Carbide gets a bad name by people using *coated* inserts right out of the
box on small lathes. That doesn't work well at all. But you can put a *very*
keen edge on uncoated carbide with a diamond hone.

About the only time I don't use carbide is when doing interrupted cuts
(everything you've heard about that is true), or when I need to grind a
special form tool.

I even routinely run carbide tooling on my Taig. Lathes don't get much
smaller or underpowered than that. Of course carbide performs much
better on my larger machines, which have the rigidity and power to really
get the most out of it. But the fact that you *can* get a keen enough edge
on it to work on a Taig puts the lie to the idea that you can only get a
*sharp* tool with HSS.

Gary

In article , Gunner says...

Because the crux of the matter is, Jim, HSS properly done, is heads
and hands sharper than carbide.

1) carbide will turn harder materials than HSS. This is
one reason for the hsm type to keep a selection of carbide
inserts handy.

2) *Coated* carbide inserts have a deliberately honed
edge. The uncoated ones (and I have used a *lot* of
these) are razor sharp and cut like it.

Jim

==================================================
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JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

In article , Daniel A. Mitchell says...

The advantages of the carbides are that they stay sharp longer than a
HSS bit in the same service. I find this especially advantageous in
turning soft but abrasive plastics. It is also useful when one has to
turn hard materials. The inserts work reasonably well with almost all
materials, but there is no advantage when turning softer steels, brass, etc.

And this niche is exactly why carbide can be used to advantage
in the home shop. Abrasive, and hard material cutting.

Jim

==================================================
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JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================

I have always been told that carbide has a certain minimum depth of cut.
If you try to cut only 1 thou the toolbit can't quite dig in and cuts
part of the time and rides on top part of the time producing a poor
finish. This seems to hold true when I used brazed carbide toolbits.

chuck

Lennie the Lurker wrote:

Ummm, Ted. The only thing we used that tiny an insert on was one of
the shaft gears we used to make.

Your point?

normalized forging. Industry didn't design carbide for slow light
cuts. It's meant to rip metal off as fast as possible. Home shop
machines don't have the backbone to handle what the carbide was
intended for.

The considerations of a production shop are kinda irrelevent in a thread
on light home shop machines. Your idea of optimum isn't the same as
mine.

Ted

Charles A. Sherwood wrote:

I have always been told that carbide has a certain minimum depth of cut.
If you try to cut only 1 thou the toolbit can't quite dig in and cuts
part of the time and rides on top part of the time producing a poor
finish.

This is true of *any* cutter that is not *really* sharp. If you use
uncoated carbide inserts that have a good edge (you can hone them
yourself with a diamond hone), they work fine. I've done this lots of
time with TNMP-321's in my tool holders.

Ted

Ted Edwards wrote in message ...
Lennie the Lurker wrote:

Your point?

The considerations of a production shop are kinda irrelevent in a thread
on light home shop machines. Your idea of optimum isn't the same as
mine.

My point: why spend extra, several times extra, for something you have
neither the need or the power and rigidity to fully utilize? Carbides
were not designed to meet the needs of the HSM, they were designed for
machines capable of providing brute force power and rigidity, of which
damn few of us have.

In article , Lennie the Lurker
says...

My point: why spend extra, several times extra, for something you have
neither the need or the power and rigidity to fully utilize?

For turning abrasive or hard items, carbide is the tool
of choice, even for the hsm-type, using a small machine.
Certainly worth spending extra under those circumstances.

Jim

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On 18 Oct 2003 19:29:43 -0700, (Lennie the
Lurker) wrote:

Ted Edwards wrote in message ...
Lennie the Lurker wrote:

Your point?

The considerations of a production shop are kinda irrelevent in a thread
on light home shop machines. Your idea of optimum isn't the same as
mine.

My point: why spend extra, several times extra, for something you have
neither the need or the power and rigidity to fully utilize? Carbides
were not designed to meet the needs of the HSM, they were designed for
machines capable of providing brute force power and rigidity, of which
damn few of us have.

Speak for your self! My lady friends have absolutely no complaints,
and always want seconds!

Gunner

"You cannot invade the mainland United States. There would be a rifle
behind each blade of grass." --Japanese Admiral Isoroku Yamamoto

Lennie the Lurker wrote:

My point: why spend extra, several times extra, for something you have
neither the need or the power and rigidity to fully utilize? Carbides
were not designed to meet the needs of the HSM, they were designed for
machines capable of providing brute force power and rigidity, of which
damn few of us have.

I bought a bunch of TNMP-321's for $3 each and that's Canadian$.
That's $0.50 per point. Not much for the use I get from them.

Ted

jim rozen wrote in message ...
In article , Lennie the Lurker
says...

My point: why spend extra, several times extra, for something you have
neither the need or the power and rigidity to fully utilize?

For turning abrasive or hard items, carbide is the tool
of choice, even for the hsm-type, using a small machine.
Certainly worth spending extra under those circumstances.

Yes, and I've said in past threads that I do keep a couple of
carbides, but brazed tools, for just such things. Normally, I find
that below RC40, the high speed will do it, but your fpm won't be
anything to write home about. 4140HT is about RC32, and I have no
problems working it with even import HSS. Depending on the alloy,
sometimes HSS will do the job on even harder stuff, but you better not
get in a hurry unless you like to grind. If I were to pick up the 20
inch Monarch that I'm not making a decision on yet, it might be a
different story, but my 12 inch Grizzly isn't a Monarch. As things
are, I'll use the carbide to cut through a case hardening, then switch
back to HSS for the rest of the machining. The half dozen carbides I
have will probably last me for as long as I'm able to move under my
own power. The only other place I make an exception, the carbide
brazed boring bits are cheaper than good HSS kits, by more than half.
other than that, the HSS is more economical for most of the HSM uses.

In article , Lennie the Lurker
says...

...The only other place I make an exception, the carbide
brazed boring bits are cheaper than good HSS kits, by more than half.
other than that, the HSS is more economical for most of the HSM uses.

Because I have not ability to sharpen carbide at home,
I stick strictly with the HSS boring bits. I've also
found that the mistakes I make when setting up a boring
tool will often trash out a carbide tool. Now *that's*
expensive.

Jim

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