In the shop I work in, and as often as not, have to train apprentices in, we do a lot of work that does not need the production rates as much as we need the precision.
We often have jobs where there are no practical carbide inserts available (or they are silly money!) where HSS tools are quite capable of being used.
As a result, we still teach a lot of grinding, as a basic skil, so that they will be able to, if they get to a job that can be done no other way.
I'm going to see about ordering in a package or two of those CCGT inserts for or boring bars, though, and perhaps a few lathe tool holders to suit.
As someone else said, horses for courses!
I beleive that a beginner is better served to learn to turn with a tool that does not readily chip, and is relatively inexpensive, anf forgiving to use. HSS suits what I need it to do at home on my S-7, for most things, though I have a few carbide tools around that I can use.
As to being at the grinder every few minutes. Not so much. I am finding that tools will last sometimes for several hours use, now that I do not do as many beginners mistakes. Regrinding a tool, is a good time to contemplate what happened, and how to not have it happen again. :-)
Now, learning to TIG weld! There is a way to teach yourself tolerance! And electrode grinding!
They sell for less, when they are wholsaled out to the sellers of said sets.
Probably cuts way down on the number of phone calls the sellers of kits get from the new guys, asking why they were given inserts for aluminum, rather than for the steel they want to cut, too.
Peter, it's no secret really, but I buy mine from e-bay, you just have to keep an eye out for them. I e-mailed Keith rather than posting here at first as there are some up for sale on there now.
About 2 years ago I bought a pack of Walter (brand) CCGT's from e-bay. These are 09's, so need a 12mm shank holder, but these things are mirror polished with a coppery coating, and are sharper than the point on a demons tail. Talk about a lucky find, as I hadn't heard of Walter before, but they will shave the hair off a gnats b***s without breaking the skin. They weren't dear either, and I've since bought another 2 packs at around £12-£15 to keep for the future, as the Walters don't seem to come up that often. Mine supposedly have a 0.4 nose rad, but it feels like a much sharper one than that. There are some sandvik CCGT's on at the moment, listing here:
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here
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both for £14.95 at 'buy-it-now', but both also have 0.8 nose rad, so I don't know how they will compare to the Walters. Even though they are meant for aluminium they work brilliantly with mild steel and alloy steel like EN19 and 316 stainless for a finishing cut.
When I bought my first lathe (an old ML7) in 1982 it came with a giant box of HSS bits, literally hundreds of them, and I have been using them ever since. As has been said, regrinding them freehand on an offhand grinder is relativly easy, they are cheap and you can also make odd shapes as well. Having built a Worden grinder from the Hemmingway kit I can now grind the tool angles very accuratly and repeatably as well. A few years ago however on a whim I bought a couple of Arrand indexable turning tools and these are superb. The tips last for ages, give a good finish and are hard enough to easily deal with things like chilled areas on cast iron castings. If I was starting from scratch (and had the money) I would invest in a set of quality indexable tools such as Arrand or the ones available from Greenwood Tools and leave the HSS for the special jobs.
They're also handy for sharpening drills and centre punches and taking the burrs off cold chisels and generally removing relatively small quantities of hard-ish material. Many of the typical small trade books like Zeus and the Dormer Drill book that turn up a boot sales etc for a quid or two have diagrams of what you're aiming for in terms of tool shape. Hand sharpening drills can be a bit tricky, especially in small sizes, but again it's a skill well worth learning even if only to recover broken ones to start with.
On or around Fri, 23 May 2008 13:01:25 GMT, Trevor Jones enlightened us thusly:
anyone care to point to a decent place to get tips on this, ideally online? Or if there isn't such an online resource, does anyone fancy having a go at producing one? While I mostly make tools that work, it sometimes takes more than one "go" and I daresay mine could be better if I knew a bit more about it - I expect most of us end up with a tool that does the job adequately rather than well, quite often.
I have one indexed tool, for general turning and one indexed boring bar. I like the carbide tool for the fact that it stays sharp, it's difficult to bugger up by cutting too fast or inadequate coolant, and it's dead quick and easy to get a really sharp edge, you just change the insert, or turn it round to get a new cutting edge.
Downsides, as others have said: it's an expensive way of doing it: a single half-inch square HSS tool will last for ages, and costs little (although, to be complete, you should factor the grinding wheels and the electricity the grinder uses into the cost).
Carbide tips also last quite a while but they're difficult to say the least to sharpen credibly, they break if you're careless and they cost quite a lot to replace. The general turning tool I use has a CCMT09 insert and they cost several pounds each for decent ones, as much as a whole half-inch HSS tool, which will last much longer unless you do something really stupid with it.
Now, I've just given the impression that I only use 2 tools, both indexed. That's not really true. Okay, a lot of the time I do use just the one tool, but then a lot of the time that's a good tool for the job. In fact, if you come and look at my lathe, chances are the normal indexed 75° tool is on one side of the toolpost and the parting-off tool is on the opposite side. But that just reflects that these are the tools I use most often.
I have quite a few other HSS tools, some of which came with the previous lathe, and some of which I bought. I also have a parting tool with an HSS blade. I use the HSS tools primarily for anything that needs a non-standard shape or angle. The most recent one was a funny pointy tool to turn the reverse chamfer I mentioned in the post about the pipe bulging tool I made. This requires an odd set of angles on the tool which you'd not get on an indexed tool anyway - technically, it could be done with triangular insert but the small diameter would mean there wouldn't be enough clearance below the cutting face. On the HSS tool, that just meant a bit more grinding.
Other things I've got HSS tools for are machining circlip grooves (a very very thin cutting edge, only cuts about 1mm deep and on the end of a 1/2" tool - took a bit of grinding, that one, but invaluable once done, also tools with large radii on the end, tools that leftwards instead of right-wards, one that cuts a semicircular 2mm groove, and so on. All of these had a special use at the time, and some are still in use. Or they get re-ground to a different shape for the next special job. For this sort of turning, you can't beat HSS unless the material to be worked is simply too hard.
On or around Fri, 23 May 2008 21:09:53 +0100, "AC" enlightened us thusly:
If you grind the tool wrong, it will do one of 2 things, either not cut at all, or snag in the work and break something.
Or it may cut poorly, leaving a poor finish and generating much heat, resulting in going blunt quickly.
Oh fer fexache, get off your high horse.
Even if it did come over a bit patronising, he's right.
No-one said you can't buy tools, most of us do. But you also do need to learn how to make them, if you're going to do anything more adventurous than straight turning or facing or boring.
as for patronising: it's like offending people. You can only take offence, you can't give it. I could be as offensive as I like, but if you decline to be offended, then I'm wasting my time.
On or around Fri, 23 May 2008 13:25:31 +0100, Peter A Forbes enlightened us thusly:
I agree: but then again, that's not a good reason for not learning about grinding tools. There's inevitably a day when you chip your last decent insert, or it's blunt, and you need to turn something.
And yes, I do use an insert tool as mentioned elsewhere for general turning and facing, but that's mostly 'cos I'm lazy.
Several hundred pages, mostly devoted to very small lathe and milling machine work.
There are a couple pages of info on tool grinding there, that are worth a look.
If you are not on a dial-up account, search around and find a copy of the South Bend Lathe book, How to Run a Lathe. Tool shapes are covered there pretty well.
A copy of this book in hard copy form, can usually be found for under $20 on this side of the ocean (Lee Valley Tools sels a older version for $10) and I am pretty certain it is available from the booksellers in the UK. Same book, is the Boxford manual, titled, IIRC, Know your Lathe.
I usually steer beginners towards 3 UK published books to start off.
The two Tee Publications books (or whomever has taken over that line) Workholding in the Lathe, and Milling operations in the Lathe, by Tubal Cain, and The Amateur's Lathe by Sparey. Between them, they cover a LOT of ground, and show that many things are possible with limited tooling.
An awful lot of us that have some experience, have forgotten how daunting it all looks from the outside, as it were.
As I butchered a quote earlier, a decent demo is worth a thousand questions.
One of the very first tools I get the apprentices to make, is a simple grind of 5 degrees back from the point, on the end, the cutting side (either towards or away fron the headstock) and with a compound grind on the top face, with 5 degrees top and back rake. I have then us a protractor, and a Sharpie marker to lay it out.
Not really optimal for any one material, but it provides a sharp edge that is easy for them to get their heads around.
Typically, I have them stome a .010" radius on the tip, too.
I have the benefit of an optical comparator for them to see the lines and angles with, and to measure the radius, but I show them how to do as well using a loupe and a Micrometer to get as close as they can to a size.
I agree with the sherline pages, I learnt to grind tools following this:
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One thing I disagree with however is the recommendation to have a cup of water to dip the blank in if it gets to hot (pretty sure it was this article). Dipping hot HSS into water can cause micro cracking of the steel. The water cooling is a throwback to Carbon steel tools HSS should be ground hard and quickly, faffing about taking light passes wastes time, and heats the blank excessively. My top tip: clamp the tool blank in a pair of mole grips and have at it, you wont burn your hands, and its virtually impossible to draw the temper on a good HSS blank. grind it hard and fast to approximatly the correct shape and then tune it up on the other wheel, and finally (if you need a good finish) a diamond 'stone' Dont worry to much about the angles, they are to aim for, not gospel. The correct shape is one where the first and only bit that contacts is the cutting edge.
I show the guys the mole grip/ vice-grip technique.
From what I read, the microfracturing of the surface tends to come about from dropping the red hot tool bit into the water. I tell folks to consider that HSS will hold a cutting edge at red heat, and that for the most part, they cannot hurt the tool blank enough to affect the way it cuts, by anything they do with a grinding wheel.
A dip tank is nice, for when you have ground away the most of the tool, and you have to get down to the fine bits of work, and you want to be able to hold the tool bit by hand.
It's amazing, how heavy those little bits can be, when they have been in contact with the wheel for a few seconds! :-)
I mostly use insert tools on the ML7. I'm lazy and I like to be able to replace/rotate inserts to get repeatable results without removing the tool from the toolpost. Much of what I've been doing over the last year has been with pre-hardened EN24 and it's hard to get a decent metal removal rate with HSS. Carbide allows me to run at 250sfpm with .040" cuts where HSS would be limited to about 70sfpm with the same conditions. Ironically, if the ML7 were more rigid, I could run at lower speeds, deeper cuts and still remove the metal.
I do use HSS for threading, form tools and fine finishing. I do tend to cheat here as well though. Whilst freehand grinding a tool on the bench grinder might be a simple job for an 8 year old, I'm 50. I find I get vastly more accurate results with a vice, angle blocks and a surface grinder... Hey, you use the tools you've got, don't you :-)
On the shaper, I only use HSS and CS tools. Carbide just doesn't cope well with the intermittent cuts and dragging on the reverse stroke.
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