Why carbide? Unless you have the rigidity and the need it might not be
worth it. A set-up in carbide that lacks the rigidity will be
disappointing. Explore and master HSS, grind 200 or so different
applications, learn empathy. There isn't much that you can't do with HSS.
On the other hand, carbide tooling in a good quick-change with enough HP is
sweet, especially for semi production and exotic or harder steel.
What you were told by Tom was excellent advice. If you short-cut the
basics, which you will do if you become reliant on carbide, you'll always
struggle with machining. It is of uppermost importance that you learn and
understand cutter geometry, which would be virtually impossible by using
carbide. Do yourself a favor and follow the advice. You'll never
Harold (Who has been grinding HSS since the early 50's)
Over the years, what with garage sales, close-outs and lucky finds, I have
acquired about 150 carbide bits (new) in all the standard shapes, and about
400 HSS bits and blanks -- all in various sizes from 1/4" to 1/2;" a good
stock of carbide insert holders in various configurations and types with
more than enough inserts to go along with them; a quick-change tool post
and adequate horsepower on my 12" Clausing. Finally, I have two bench
grinders .. one for HSS and the other for carbides.
My point here is not to boast about my set-up but to explain why,
despite having the option to use carbides, I find myself using the HSS bits
more and more and the carbides less and less. There are several reasons
for this, that "ignoramus31514" should consider.
1. I work a lot of brass, aluminum, plastic, and wood. Carbides are no
real advantages there .. in fact, a distinct disadvantage.
2. Carbides must operate under considerable cutting pressure or else the
finish is not good. It means you have to take bigger cuts and feeds and
therefore, it is more difficult to "sneak-up" on a finished dimension. In
the hands of an experienced pro (not me) who does it all in two or three
passes, carbides are great. For those of us who have to sneak in twice as
many passes, carbides are trickier.
3. If you're lucky (as I have been) you might pick up a whole bunch of
pre-shaped bits, created by master machinists. These are almost always
HSS. Good to know how to use these and modify them.
4. It is easier to create form bits and special bits from HSS than from
5. Honing a HSS bit to an ultra-keen edge as required for most plastics and
wood, is a lot easier than honing a carbide to an equivalent edge. No using
arkansas stones on carbides.. it's diamond.
6. Carbides break and chip and it isn't always obvious. I find that HSS
bits can take more abuse from ham-handed hobbyists like myself than can
7. You rarely find decent carbide bits or inserts at flea-markets and
garage sales. I have usually had to pay real money for carbide inserts: by
contrast, my big stock of various HSS tool blanks was acquired at 2
cents/dollar or free. A used carbide insert or bit may not look worn and
it rarely pays to sharpen carbide inserts. Sharpening a used HSS bit is
8. I only use carbide cut-off tools.
9. Carbides are definitely the way to go with stainless steel and
especially, cast iron. The latter is very abrasive and dulls HSS bits very
10. For production work, of course, there's no contest.. carbides almost
always take the lead. But then the speeds and feeds are much higher, lots
of coolants, and carefully worked-out procedures. Almost the exact opposite
of the hobbyist's typical use.
I completely concur with Tom's advice. Learn and master HSS. I also
used a lot of carbides earlier on.. and wasted a lot of time and metal doing
so. Learning something about shaping, sharpening, and honing HSS bits has
been a good investment that I should have tried earlier.
The bottom line: both have their place, but the hobbyist will probably
get a better return on investment and time with HSS.
Boris Beizer Ph.D. Seminars and Consulting
Not to disagree with Boris's advice, I find that I prefer HSS for
stainless. Seems like it's tougher and holds up just fine for
the slower sfpm that I run on stainless.
Carbide does come in mighty handy for turning hard items.
I just got done trimming up the end of a puller that I just
purchased at a garage sale. It was harder than the proverbial
billy goat's dick so HSS was right out. The carbide inserts
did just fine though.
please reply to:
Feel free to disagree .. especially if I can learn from it. I've not done
much machining of stainless and very hard steels. I had trouble with
stainless using HSS so I switched to carbide and it went just fine. I admit
that I didn't pay attention to the bit's design, cutting speed and feed,
and didn't use coolant.. and those could explain all the problems I had with
HSS on stainless. Next time I do stainless I'll pay attention to the bit
design and cutting parameters and give HSS a shot.
But I'll stick to carbides for cast iron .. at least as long as my
big cache of carbide bits lasts.
Your choice for cast iron is right on the mark, assuming you're using a C2
grade (Carboloy 883, for example).. C5 tends to show premature wear, much
like HSS would.
Stainless. HSS is an excellent choice, depending on the material and
operation, but carbide, in production, tends to outwork it. The secret to
success when machining stainless with HSS is to use generous positive rake
and light feeds. Stainless (300 series) isn't hard, it's tough. If you
can peel it off instead of push it off, it generally responds favorably.
Armed with that information, one should move away from 0 or negative rake.
Needless to say, slower spindle speeds are in order, and coolant helps
prevent tip burning.
My experience is, keep the sfpm below what one would use
for carbon steel, and be sure to keep the feed rates up
to prevent work hardening the material while turning it.
I tend to use a lot of kerosene/lard oil mix for this,
but I've also seen folks use water-based cutting fluid
like soluble oil.
I think the key is to recognize the material a) work hardens,
and b) has a very low thermal conductivity. The second means
you need to turn slower than you would think to keep the
tool tip from degrading.
please reply to:
I can't help but think we're accomplishing the same mission, but through
different avenues. When you use extreme positive rake and light feeds,
there's little pressure at the cut, so there's not much work hardening going
on. Quite the contrary, and at first glance you get the impression the
setup won't work. The metal cuts off in thin, smooth chips, assuming you've
ground your tool properly. It is best to use flood coolant, due to the
thin cutting edge, although I have run that type setup with an acid brush
instead. I don't, and won't, run soluble oil in machines. Don't like
it, and never have. I like to be able to let go of machines when I choose
to. Soluble oil makes that difficult. I do use chemical additives,
however, which perform exceedingly well.
My positive rake tools generally are generous chip breaker types, a deep
groove that gently winds the thin chip. Needless to say, this type of
setup is not very good for heavy feed stock removal. The thin edge won't
tolerate the load, nor the heat.
One place it really shines is if you're rounding up a plate on a lathe, one
that has had the corners clipped and is an interrupted cut, driven by
tailstock pressure. By using a tool wide enough to plunge on the edge of
the plate, you can bring it round with no strain. Carbide falls right on
its ass in such a setup.
I've noticed that. Carbide just doesn't like an interrupted cut. It
looked to me that when you got the tool pressure high enough to get a good
finish, the interrupted cut chipped the edge of tool in no time. Perhaps
its because my 12" clausing just isn't stiff enough for that kind of work
with carbides and/or my entire toolpost etc. setup has too much spring in
Boris Beizer Ph.D. Seminars and Consulting
It's (carbide) far better than it used to be, but it still isn't the
greatest choice for interrupted cuts, especially with heavy feeds.
While your lathe isn't known as a heavy weight, you'd not have much better
luck with a heavy machine, including an EE Monarch, which likely outweighs
your machine by far more than 200%. I think if you could see down at a
microscopic level, you'd likely see that a spindle does a slight stop and
start motion as an interrupted cut occurs, especially under heavy load. The
slight hesitation tends to pull the edge off the tool.
I can remember carbide that was so fragile that the slightest backwards
motion pulled long slivers off (brazed tooling, long before a wide variety
of inserts were available). Carbide of today is far more forgiving.
Still, in the scheme of things, having HSS at one's disposal for certain
jobs, and the skill to grind proper tools, makes all the difference in the
world. Even better is to have some Stellite. You're not likely to
encounter much of that, though.
The quickest test is with a magnet. Unlike HSS, Stellite is *not* magnetic.
All Stellite I've seen has been well marked by electro-etch, but it's
possible you could find some that has had the marking removed, possibly from
using the same end as the markings. Should you find any, don't pass it up.
It's as close to carbide as you can get and not be there. It is ground with
aluminum oxide wheels with no difficulty. It's wonderful stuff, but was
replaced by carbide, which has a slight edge in some ways. Very
I had the good fortune to buy a small lot off ebay about two years ago.
Unfortunately, what was sold was remnants that had been cut off from 1/2"
squares, and were 1/2" shorter than the 3" represented. Fortunately, the
markings are intact, so I know what they are. They aren't as long as I
would have liked, but they are long enough to use. One of my goals was to
grind a couple parting tools for deep cuts, but that isn't possible because
of the short length. Sigh! Haynes Stellite is reputed to be tougher at
red heat than at room temperature. Good stuff, Maynard.
Thank you for the well thought out points on HSS versus carbide. I am very
new to all of this and found it very informational. I for one plan on taking
the advise to use HSS and learn to grind my own cutters.
Just got a mini lathe and mini mill last week. Have never used either tool
before this weekend. I am really enjoying it. I bought a QC tool post for my
lathe and it arrived friday only to be missing the bolt and sleeve to mount
it. Since I did not want to wait a week to use it I made the part myself. It
was a great first project and it only took two tries to get a working part.
I think I am already hooked as I spent most of the weekend cutting metal,
what fun to learn a new trade.
Thanks again for your advice to the group.
I'm sooo jealous! There is still the thrill of dominating a piece of metal
but I usually make a piece because I have to and I have to do it under the
gun in order to get some machine repaired and running. Enjoy the process,
there's NOTHING like the feeling!
The downside of training people over the years is that they are making chips
and I'm on the phone, or "No, I don't need your help...go away!" They may
not do something exactly like I would but...
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