Even if you buy ready made tools they will rapidly need to be sharpened so
you would still need a grindstone and learn how to use it. One might as well
go the whole hog and grind your own from the start.
Cliff Coggin.
If you want to get straight to turning then, buy HSS tools ground to the
conventional shapes. Learn to keep them sharp to begin and in the
background, practice grinding your own.
I like Spareys book "The Amateurs Lathe". Some of it is out of date, I
find the the tool profiles work and I now only ever use carbide indexable
tip (not brazed tip) for cast iron and HSS for everything else. I don't use
any exotic materials in my projects (yet!).
So long story short, stick with HSS and learn to use the grinder. The
trickiest ones are the round nosed tools, but it's just patience and
practice in the end.
And a golden rule, if you haven't got the right profile tool, start with a
new blank, don't modify an existing one otherwise you end up never having
the right profile!!!
Steve
Personally I prefer replaceable tip tools, and would have them anytime over
basic HSS blanks.
Nice to learn how to sharpen tools etc etc., but in practice I prefere to have a
new tip at the twist of an Allen key.
Peter
--
Peter A Forbes
Prepair Ltd, Rushden, UK
snipped-for-privacy@prepair.co.uk
http://www.prepair.co.uk
http://www.prepair.eu
I started out with HSS blanks and grinding my own, bought a set of
indexable tips and now use HSS home ground again, leaving the carbide tips
for roughing cast iron. It's a hobby for me and the grinding I find a great
de-stresser! (not distressing). I find it easier to get a good finish with
sharp HSS rather than carbide.
Steve
I might suggest you're not using the right carbide inserts then. To repeat,
yet again, something I've posted many times over the years. Most carbide
tips are designed for high powered machines and high volume work. For use on
steel they have slightly rounded edges to create sturdiness and resistance
to chipping and they rely on machine rigidity, horsepower and rpm to push
them through the material being machined. What you need for small lathes and
hobby use, regardless of the work material, is razor sharp edges which
you'll only find on uncoated (usually) non-ferrous carbide inserts. Edges
very similar to what you'd grind on HSS anyway. They will generally be
bright silver or perhaps carbide grey. If the tips you are using are gold,
black or any other dark colour they won't cut worth a damn on a small lathe
on most materials. They'll just push off the work and tear it to shreds.
What you have to appreciate is that what the carbide insert manuals and
guidelines mean by finishing cuts on a CNC lathe are still probably deeper
cuts than the roughing cuts most of us use on manual lathes.
If you stick with inserts designed for aluminium you'll get perfect results
on steel, cast iron, brass, bronze and just about anything else you want to
tickle away at a few thou at a time on a small lathe and the inserts will
last almost indefinitely if you don't abuse them. HSS might get the same
finish but it'll blunt every five minutes. If you want to take 4mm deep cuts
in EN40B then sure you need 10 hp and an insert designed for roughing steel.
I use a single carbide insert turning and facing tool with non ferrous tips
for 95% of the work I do on my Student. HSS has its uses when you need to
grind a special shape or make a very small boring tool for a one off job but
for most turning and facing I'd say get the largest shanked tool your lathe
can accept, some sharp non ferrous inserts to fit it and you can forget
buggering about on bench grinders every five minutes for the rest of your
life.
My mate's £50,000 CNC lathes can use a steel specific, rounded edge insert
and still get a mirror finish on hard materials like EN52B and 21/4N valve
steels. If I try to use the same insert on my Student it just buggers
everything it touches. My 40 year old machine has 50 times the backlash his
new ones do though, half the rpm, one tenth of the hp and no coolant. It's
just a matter of horses for courses.
If you want to spend your life learning how to sharpen tools rather than
actually cut metal then HSS is the very thing. You'll just die very
accomplished rather than having ever made anything.
I completely agree.
Whilst you can get a better finish with HSS on a small lathe, the only
thing I use HSS for on my ML7 is screwcutting.
Everything else I use carbide insert tips.
My favourite tool is one of these:
http://www.greenwood-tools.co.uk/ishop/728/shopscr16.html with a
Sandvik GC4025 insert with a 0.2 radius tip. This grade is designed
for stainless but works pretty much perfectly for just about anything.
And if I need a *really* fine finish or half a thou' or so taken off,
then I use an SCLCR holder with a CCGT insert made for aluminium, like
this:
http://www.cnccookbook.com/img/OthersProjects/Tools/CCGPInsert.jpg
works fine, even on stainless. (ignore the mispelt 'CCGP' in the
link).
Life's too short and time in workshop too limited to spend all your
time grinding HSS, albeit this is defintely a usefull skill to have.
However, if you get the HSS grind wrong - which beginners always do-
then you'll be constantly frustrated with the poor cutting ability and
lousy finish until you get it just right.
Peter
Peter Hi, a friend of mine by way of a gift of a couple, introduced me
to the CCGT (aluminium) inserts a while ago when I still had time to
go into the workshop. In planning a return to work :-), I haven't yet
found an economic source (ie less than £5 each), have you - or is it
one of those instances that the bullet just has to be bitten?
Regards
Keith (short of both time and money)
On Sat, 24 May 2008 03:25:20 +0100, Peter Fairbrother
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:
http://cgi.ebay.co.uk/10-Sandvik-Carbide-Turning-Inserts-CCGT-09T308-UR_W0QQitemZ380008837407QQihZ025QQcategoryZ112399QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
and here
http://cgi.ebay.co.uk/10-Sandvik-Carbide-Turning-Inserts-CCGT-120408-UR_W0QQitemZ380008837355QQihZ025QQcategoryZ112399QQrdZ1QQssPageNameZWD1VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247
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.
Peter
After reading all the posts on lathe tools and grinding HSS I think on our
club stand at Harrogate next year I should take a grinder and some HSS
blanks and show people how to grind tools by hand. No jigs, no gauges. It
would only take a few minutes per person to get them started. Once you know
what you are after doing that's the hardest part done. Of course we would
not have to tell the people selling tips. If not a grinder on the stand we
could be available to talk to people and have a few sketches and tools we
had ground. It might help someone. I might start taking some tools to the
steam rallies I go to so people can see how it is done.
Bill
While at the Dutch engine rally in Nuenen a week or so ago, we picked up a small
boring bar and a new box of DCMT tips for a reasonable price.
We already have an external tool holder that takes the same tips, so we are now
more or less set up for our workshop Raglan Littlejohn lathe.
We also have a selection of standard Jones & Shipman boring bars which we mangle
the tools for occasionally.
Peter
--
Peter A Forbes
Prepair Ltd, Rushden, UK
snipped-for-privacy@prepair.co.uk
http://www.prepair.co.uk
http://www.prepair.eu
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.
Bill, I think that is a wonderful idea.
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.
Cheers
Trevor Jones
Good idea - someone showed me, took about ten minutes, and it then took
me a couple of hours of solo practice before I was grinding good working
tools, every time, by eye.
Might take me a couple of tries now to get new type of tool cutting
right, especially if I've never seen it in the flesh.
But that's all it takes.
-- Peter Fairbrother
On another thread ('I'm sure this has been asked before') is a link to a
site (shopswarf). This has the lathe cutting angles for HSS.
http://shopswarf.orconhosting.net.nz/turntool.html
Best regards,
Dave Colliver.
http://www.AshfieldFOCUS.com
~~
http://www.FOCUSPortals.com - Local franchises available
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!
Thanks!
Cheers
Trevor Jones
It depends what I'm doing. If I'm trying for a precise fit on something, I
use coolant to stop the job heating up and therefore expanding. In the
past, I've cut things that got fairly hot to an exact size (this is for
something that's a tightish push fit) and then, when it's got cold, it's not
the fit I wanted.
generally, though, I only use coolant if it seems like it needs it. Tend to
use it for parting things.
--
Austin Shackles. www.ddol-las.net my opinions are just that
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