Worked with my lathe today

It was rather pleasant. It does work as advertised, although there were some things that I did not like, which I wil mention later. Madea
piede that enabled me to make a toy elevator for my son (he is crazy about elevators). I will soon buy carbide bits.
i
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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.
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Well, I dug up a couple of carbide bits from the tooling that came from the lathe, today, and tried them. Much more fun than HSS. I bought a set of carbide bits this morning, on ebay.
i
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HSS.
is
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 regret it.
Harold (Who has been grinding HSS since the early 50's)
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wrote:

Thanks, I will follow your advice.
i
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is
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 carbides.
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 carbides.
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 easy.
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 quickly.
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
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Boris Beizer Ph.D. Seminars and Consulting
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says...

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.
Jim
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Boris Beizer

very
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.
Boris
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Boris

admit
with
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.
Harold
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says...

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.
Jim
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Boris Beizer

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.
Harold
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Boris

one
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 it.
Boris
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Boris Beizer Ph.D. Seminars and Consulting
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Boris

of
on
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.
Harold
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A few years ago I purchased a handfull of HSS TPG inserts that fit my tooling for those "special" jobs.
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Last year I managed to find a one Stellite toolbit in the used toolbit collections of various vendors at NAMES. This year, nothing. cs
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What does Stellite look like? Distinguishing labels, appearance, names, etc. How can I tell if any of those old tool bits I passed up are Stellite?
Boris
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The one I found said Stellite on the side.
I did manage to find MoMax and its good stuff. MoMax cobalt is excellent stuff.
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Stellite?
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 unfortunate.
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.
Harold
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Boris 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. Larry

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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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