I tend to buy the kits on special from either Enco or MSC, but this recent post by a member of the 12x36 Yahoo email group was awesome, and talks a lot more about the different aspects, so I am just copying it here on its entirety:
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FWIW, my personal experience has been with a 50(?) year Logan 11" or
12" with old belt drive and a 20+ year old Birmingham 12x36 with gear
drive. I sold the belt drive, and love the gear drive, and wouldn't go
back.
With regard to your question about HSS vs carbide, I hope nobody minds
if I submit here my posting from earlier this year in the MWHINTS
(metalworking hints) Yahoo group. As it is now, I can't remember the
last time I used a HSS bit on my lathe, and my tolerances and surface
finishes have never been better. My comments at the time addressed
comments made by others in that group regarding tungsten carbide and
the manufacturers and sales people, but I think it best to post it here
in its entirety. I probably wouldn't be happy with carbide on a belt
driven lathe like my old Logan. My comments are about tungsten carbide
INSERTS. I have thrown away all the brazed carbide tools that I once
had. Keep in mind that these are just my opinions. As the saying goes,
everybody has one! I'm going to expose you to mine. I use my lathe
primarily as a hobby, aspiring to make gasoline and hot air engines.
From Feb, 2008:
" I agree that most tungsten carbide inserts are not suitable for small
lathes. But some of them are. I'd like to contribute some of my
experience to those who DO want to use tungsten carbide inserts on
small lathes. They have become an integral tool in my workshop, but
as others have said, they are not right for everybody or for every
situation. But I didn't realize until the recent thread that my
success with tungsten carbide has not been widely shared. Allow me
to share what I have learned, and what works for me. If you are
happy with HSS, don't waste your time reading this, for changing to
carbide would be a waste of money for you. Personally, changing to
carbide made my hobby a lot more fun and productive. Your mileage
will vary. Being a jack-of-all- trades kind of guy, I'm not an expert
in any one field, and can only claim amateur abilities in my home
shop. But I do know more than most about tungsten carbide
applications. Almost my entire career involved some aspect of using
tungsten carbide. I began my career with 11 years as a product
evaluation engineer for a major manufacturer of oil field rock
drilling bits using tungsten carbide teeth, and finished it with 11
years as a tungsten carbide tooling sales rep for Iscar, Valenite,
and Mitsubishi Carbide. I sold tungsten carbide inserts to
manufacturers and machine shops in Washington, Oregon, Idaho,
Montana, Wyoming, Colorado, and Utah. The most common materials used
in these states are steel, stainless, aluminum and high temperature
alloys, but I have very little experience with cast iron. This was
the great job for a home shop machinist, for many days I couldn't
tell when the hobby stopped and the work began. I always took a
problem solving, applications approach to my customers, and most of
them appreciated that I machined for a hobby. When I faced
particularly difficult or unfamiliar materials, I commonly took scrap
samples home to learn how to machine it on my own lathe. I couldn't
duplicate what their CNC machines could do, and I do all of my
machining dry, but what I learned with my 1.5 HP lathe could often be
scaled up to their 20 HP machines. I retired about 15 months ago. I
have no ties with, and receive no retirement benefits from any of my
former employers. It puzzles me that some think that tungsten
carbide is a sham. The products of the major manufacturers are not
shams. The problems I faced were that there were so many product
choices (grades, chipformers, shape, coating, etc), but the best
combination of them could not always be made in every configuration.
And what worked well in one shop might flop in the same application
in the shop across the street due to some subtle difference in
programming, coolant, etc. As a factory rep, I always offered to "no-
charge" any test tools when the customer wasn't convinced that they
reduced his TOTAL manufacturing costs for that operation. This is
common industry practice. Just ask for a "GTO" - a "guaranteed test
order" - when you try something new. If your distributor or factory
rep won't offer this, go to someone who will. Factory reps have a
lot more authority to do this than distributors do, but good reps
with good rapport with good distributors will back them up.
Admittedly, I couldn't offer this for specially designed tooling, nor
for home shop machinists. None of my bosses ever questioned my
efforts to ensure customer satisfaction with any of our tools, even
without a GTO, or when used as a replacement tool, or when they
bought tools that weren't optimum for their needs. Mitsubishi
Carbide even offers new milling cutters for any reason - even
operator error ! Unfortunately, not all factory reps took care of
their customers, and when I changed jobs, I frequently had to
retroactively correct their negligence. In contrast to the
experience of others, mine has been that tool room lathes and Swiss-
type automatics can be good applications for indexable carbide
tooling. Mechanical screw machines are not.
First, my experience with HSS. My exposure to sharpening and using
HSS bits is far from professional level, but probably more than most
of today's hobbyists. My grandfather was a tool room machinist, and
I have inherited hundreds of HSS bit that he had ground to a wide
assortment of configurations. My dad taught me to run a lathe and to
sharpen HSS bits. And, believe it or not, sharpening and using HSS
bits was a requirement for my BS Mechanical Engineering degree at Cal
Poly, San Luis Obispo, CA, whose motto is "Learn by Doing". However,
since I've learned to use tungsten carbide inserts, my enjoyment
level has soared while my frustration level has dropped. I now use
HSS for less than 5% of my lathe work. (I choose to use carbide
indexable inserts for about 20% of my milling work, but I have only a
one horsepower motor, and won't be discussing milling in this
posting.) Chip control is much better. Surface finishes are much
improved. Dimensions are more predictable. I don't have to use
coolant no matter what SFM I choose to run. And I no longer wrestle
when I pick up a piece of material of unknown alloy. I primarily
machine steel, stainless, aluminum, brass, wood and plastic, but I've
successfully machined on my lathe the toughest materials that my
customers encountered: cast stainlesses, titanium, nitronic, inconel,
hastelloy. Indexable carbide inserts are my first choice for
turning, facing, boring, grooving, threading and partoff in all of
these materials - even plastic.
Some thoughts on using tungsten carbide in a home shop- (I refer to
the products of Iscar, Valenite, and Mitsubishi due to my familiarity
with them - most of the other major manufacturers offer comparable
products. Ask them for details.)
- Lathe Horsepower, Drive, and Rigidity
If you have less than 1 HP, you are in unfamiliar waters for me.
You'd probably be better off with HSS, or positive, single-sided
insert holders. I agree with most of what is said in the website
http://www.thegallo s.com/carbide. htm referred to by another group
member. But I prefer not to use the TiN coatings or utility grade
inserts on a small lathe because they don't have what I feel is a
sharp enough edge. I have a Taiwanese 12" gear-driven Birmingham
lathe that I inherited from my dad. It replaced an old belt-driven
12" Logan. I couldn't recommend carbide tool for the Logan since it
was worn and sloppy, and I don't think the belt would have
transmitted the required power. The Taiwanese lathe came with a
motor rating of 1.5 HP, but the starting windings burned out one day
as I made repeated partoffs with a carbide insert partoff tool. The
replacement US-made motor also has a rating of 1.5 HP, but appears to
have twice the power of the original, so my experiences are based
upon this new motor, and this is probably a good lower horsepower
limit to my recommendations here. [[ It will repeatedly partoff with
a 3mm (.118") wide partoff insert. I've thrown away all of my HSS
partoff blades after learning how to use Iscar's tools, but this is
tricky for any manual lathe, and if you overlook any parameter,
they'll break. (A common industry term is "grenade".) So I don't
suggest these to most amateurs.]] I commonly limit my maximum DOC
to .040" , but if I recall correctly, I've pushed it to .070" DOC in
steel without a problem. Carbide doesn't like flexible setups, or
chatter, so if your machine is old and sloppy, you might as well stop
reading this. And, as a rule of thumb, if your lathe is too small to
hold at least 3/4" shank tooling, stick with HSS or single-sided
inserts. The sharp carbide I'm recommending doesn't tolerate
chatter, or dragging backwards out of the cut.
- Brazed Carbide
My comments here relate to indexable tungsten carbide inserts.
Brazed tungsten carbide stick tools have their place, but they don't
have any place in my shop. Inserts offer repeatablity, accurate
indexability, positive geometries, chip control, coating options,
accurate corner radii, no grinding, and they are not subjected to
the heat from brazing - features I've never enjoyed from brazed
carbide. If you want to use brazed carbide, maybe someone else here
can give some pointers.
- Costs
I use 3/4" and 1" shank OD turning tools. A holder will cost about
$80. The insert styles I prefer cost about $14 to $18 apiece when
bought in boxes of ten. Most distributors don't sell partial boxes
of inserts, but some do, so ask. MSC sells single inserts at a
higher individual cost. You'll have to evaluate for yourself if you
can justify the expense. In my case, if I feel that if can't afford
the inserts, I can't afford the lathe. I'd avoid the no-name carbide
sold by the lower echelon suppliers mentioned in other postings .
This is sometimes reground material, unpredictable, and unlikely to
come with the top-face geometries and sharp cutting edges that a
small lathe needs.
- Carbide Grades
Wow - how to summarize such a broad topic in few words. In general
terms, carbide grades are a compromise between toughness and
heat/wear resistance. Most inserts are optimized for use in high
production CNC environments, where cost savings are often found in
higher feeds and speeds, which result in higher temperature. Like
most materials, tungsten carbide is sensitive to high temperatures,
so most industry research is in the direction of increasing heat
resistance. That's not a factor for most hobbyists. When my face
is 18 inches or less from a spinning chuck, I tend to keep the feeds
and speeds down. I'm looking for toughness in an insert because my
manual lathe doesn't have the rigidity of a CNC, and my boneheaded
handle-cranking is by no means repeatable, or predictable. I prefer
to have an insert wear rather than chip. The demands of industry
have led to grades specific to certain materials, but where I may be
turning steel, stainless and brass all on the same day, or same hour,
I want a general purpose grade. A C2 grade is a good compromise
for most metals, or a C5 if you turn mostly steels. Coatings help
primarily by protecting the inserts from the heat of cutting , but by
nature the act of applying the coatings in hot furnaces degrades the
toughness of the base carbide. In many cases the home shop machinist
would be better off with an uncoated insert in order to optimize
toughness and edge sharpness, and you also save a couple of bucks per
insert. I'd change to a coated grade if I were experiencing built-up
edge (where the material adheres to the insert), or if I did a lot of
stainless steel. If I were to suggest a coating for general home
use, it would be one that uses a PVD, rather than a CVD, process, due
to the lower furnace temperatures, and the typically thinner, more
lubricious coatings. The PVD process can also coat up to a sharp
edge, where the CVD process requires a rounded honed edge. My
favorite coating materials are TiCN (titanium carbo-nitride) , and
TiAlN (titanium aluminum nitride). Counter-intuitively , TiAlN is a
wonderfully temperature resistant coating initially designed for use
without coolant, but it also offers a high lubricity factor, which
helps prevent built-up edge. To the best of my knowledge, the
toughest coated insert in the industry is Iscar's IC3028 (IC328 for
milling). I can't verify it, but I have been told that it's
toughness, while not equal to HSS, is at least comparable to HSS.
This has a PVD TiCN coating. The TiAlN coating version is called
IC9028. The uncoated version of this is IC28 grade. This is
classified as a non-ferrous grade, and is not optimized for steel but
will work in steel, too. All major manufacturers offer something
competitive with this, and what they have on their conversion chart
that's equivalent to Iscar's grades are what you want. ( Grade
numbers are added and deleted constantly. I left Iscar 7 years ago,
so specifics may have changed since then, but IC 28/IC328/IC3028 have
been benchmark grades for them.) Unfortunately, the toughest
grades generally aren't available with the chipformers designed for
light depths of cut. Even though I call it roughing on my
lathe, .040" DOC is generally considered a finishing application, so
these inserts tend to come with wear resistant grades to handle the
higher SFM's commonly used in industry. So when I choose a finishing
chipformer, I have to compromise and select the toughest grade
available in that configuration.
- Insert Shape
The most commonly used insert shape and size is the double-sided 80
degree diamond, such as the CNMG432. With its 80 degree included
angle, it can cut up to a 90 shoulder. It's popularity ensures that
it is available in the most configurations and grades that are of
interest to me, and at the most competitive costs. EVERYBODY makes
CNMG's. There is valid ground to argue for a narrower angle, like
a DNMG , if needed, but these will cost more, and offer fewer
choices. There is also a very valid argument for using single-
side "positive " inserts. They are freer cutting, and if you need
the freest cut, they are the way to go. But the cost per edge is
higher than a double sided insert with the same features, and there
are fewer options available if you need to address a specific
application problem in the future. I can't remember any instance
where the "upsharp" double-sided/ "negative" inserts didn't provide a
free enough cut, but cutting a long, slender shaft might be more of a
challenge. Since I'm an amateur and more likely to chip an insert
than wear it away, the double-sided, four-cornered CNMG-style is my
choice if I could only have one. The third letter of the ANSI/ISO
nomenclature (M in this case) denotes the tolerance class. The two
most common options are "M" and "G". A home shop machinist needs to
equate the "M" with "as molded", and the "G" with "as ground". As an
insert comes out of its molding process, the cutting edge has
a "hone" of .005" or more. This is well illustrated in Mitsubishi's
product bulletin #B036A
(
http://www.mitsubis hicarbide. com/mmus/ catalog/pdf/ b/b036a_fj_ mj_gj_ms
_01-04.pdf), where their photos distinguish between a "M class"
and "G class" insert. This is advantageous in most applications in
order to keep the cutting edge from chipping. To get an "up sharp"
edge or tighter tolerance, the insert must be peripherally ground.
Most manufacturers call these CNGG's or CNGP's. This adds several
dollars to the cost of each insert, but this is a necessity for most
aluminums, titanium, plastics, or wood. I also use them for taking
off a few thousandths, even is steel, which normally requires a honed
insert edge. For aluminum and plastic, I prefer inserts that are
both ground and polished. The top faces of these are polished to
practically a mirror finish, which greatly helps to prevent builtup
edge from forming. When dragged by hand across the top of your
thumbnail, a proper CNGG or CNGP will easily shave off some
material. A CNMG will not. The third digit designates the cutting
tip corner radius. In this example it is "2", indicating a 1/32"
radius. A "1" indicates a 1/64" radius. CNMG's are available with
corner radii down to 1/64", but most inserts below 1/64" must be
ground, so can only be made in a CNGG or CNGP style. It isn't a hard
and fast rule, but it is generally recommended that the tip corner
radius is the minimum depth of cut for that insert, in order to
ensure that the radius is full engaged in the work. Thus, the
minimum DOC for a CNMG432 would be .031". Where I generally don't
cut more than .040" DOC due to horsepower limitation, a CNMG431 is a
much better choice for me. I won't explain the nomenclature here,
but for manual turning (and facing) TOWARD the chuck, the proper
insert holder for a CNMG or CNGP or CNGG431 is MCLNR12-4 (for 3/4"
shank tooling) or MCLNR16-4 (for 1" shank tooling). These holders
hold the insert at a 9 degree negative angle toward the work piece,
thus giving a 9 degree front relief angle.
- Chipformers
Ahhh - the blessings of chipformers! To be able to make little chips
in the shapes of "6"s and "9"s instead of a rats nest of entangled
razors! But keep in mind that if you are machining a tenacious
material like some aluminums or stainlesses, it may still be a
challenge to always break the chips. Subtle differences in
chipformer shape can make a big difference, and proper chipformer
selection was often the hardest part of selecting the right insert
for a customer. Chipformers also can give you a POSITIVE cutting
edge at the material even when the insert itself is held at a
negative angle by the MCLNR holder. Chipformers are not
standardized between manufacturers like the insert sizes and shapes
are, so every manufacturer has their own nomenclature. For the
depths of cut that I use, I need a chipformer designed for finishing
or super-finishing, even when I consider .040" DOC to be roughing.
And even the super-finishing chipformers aren't expected to control
the chips at DOC below .020". Chipformers usually have a two letter
designation, and it is common for finishing chipformers to include
the letter "F". I prefer to use what are known in the industry
as "high positive" chipformers. For DOC below about .005-.010", I
use a ground insert like a CNGG or CNGP with a finishing chipformer
like Mitsubishi's "FJ" (with a positive top rake that varies from
+12 to +20 degrees) or Valenite's "SR" (with a positive top rake of
+12 degrees). When held in a 9 degree negative holder, a 20 degree
positive top rake will enter the work with an 11 degree positive
angle. Since these inserts have an "upsharp" edge, they may chip if
used too aggressively in interrupted cuts. They are not recommended
for heavy cuts in steel, but they have worked well for me up to .040"
passes in steel, and everything I do in aluminum. Since these
inserts are commonly used for high temperature alloys like titanium,
the grade choices are limited to the higher hardness end of the
spectrum, but tend to be PVD coated or uncoated. I pick the toughest
grade available. These are designed to work at about .002" to .010"
feed, and .004"-.050" DOC. From .010"-.040" DOC roughing, I feel
more secure about not chipping the insert by using an "as molded"
insert. Examples are the Valenite CNMP 431-C5 (+12 degrees top
rake), the Mitsubishi CNMG 431-MJ (+12 to 20 degrees), and the Iscar
CNMG 431-PP (+13 degrees). The honed edges can handle steels very
well, and can even handle moderate interrupted cuts. These are
available in more grades than the CNGP or CNGG, and once again I'll
select the toughest PVD or uncoated grade.
I hope this helps."
Bob G
Salt Lake City
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If you have patience, the prices are often unbeatable.
