After reading the responses to my request for tooling advice for m
Myford ML7, I decided to perhaps have a go at the Glanze ones Keit
(sorry, don't know surname) suggested. Chronos have sets vailable
which I quite like the look of:
"Set of 10mm Glanze Mini Indexable Turning Tools(Reference #SCIND02)".
Presumably, it is indeed the 10mm ones I need for the ML7? I got
couple of tools with the lathe, which measure about 9.5mm square, bu
not quite 10mm.
Also regarding tooling. I had a play around last week with the lathe
and I couldn't get a good surface finish, even with the slowes
possible feed. Presumably, because the tool had a point, it was jus
creating a fine spiral cut, hence the rubbish finish. I replaced thi
tool with a half round one, and the surface finish obviousl
dramatically improved. Is the half circle tool defined as a 'finishin
tool' or a 'form' tool? In the Glanze sets I can only see the rhombu
type inserts, which will presumably return me to the poor surfac
finish scenario. Whats the score there?
Also, oil guns, mine is crap. What are the best ones to go for fot th
Thanks a lot for any advice. I apologise again for the stupidl
elementary questions, but I figure that is what forums are fo
Size of tool is governed by the distance from where the bottom of the
tool rests on the toolholder and the center height of the lathe, its
easier to pack up a tool than try to make it lower. Your existing
tools are probably 3/8" and with grinding the cutting edge is
probably a little less than this. I don't have a Myford so can't give
you the max tool size but it may vary depending on your tool holder.
The indexable bits all have a very small radius on the corners which
will help with your finish and the "rhombus" shape will typically give
5degree of clearance which will also be better than a pointed tool.
Personally I prefer brazed carbide tools for a fine finish as the
insert type are designed for higher stock removal rates and lots more
cutting fluid than a hobby turner is likely to use. For the price of a
couple of insert tools you could get a large selection of carbide
tools, grinder and green grit wheel, you will always need to frind
specials for particular jobs anyway. They are handy for getting
through the skin of castings and I like the boring bars especially the
6mm shank one that gets into small holes.
One thing you must get right is the type of insert. Most carbide inserts are
designed for high volume production on sturdy machines. They can power
inserts with rounded cutting edges into steel with brute force and rigidity
and still achieve a good finish. For home shop lathes you want non-ferrous
inserts even for machining steel because they have razor sharp cutting edges
which cut without the application of lots of force. Such edges wouldn't
remove stock for long on a 5 ton CNC lathe taking 4mm deep cuts with 15 bhp
but they're ideal for tickling a few thou off on a Student or Myford.
Usually such inserts will be uncoated and silver or gray in colour. The
black and gold coated ferrous inserts will have much less sharp edges and
are only useful for roughing work which we don't tend to do.
Also, by 'rounded cutting edges' I don't mean the tip radius which is a
separate factor. I mean the sharpness of the cutting lip. The tip radius on
most of my turning inserts is 0.8mm which is quite large but of minor
significance compared to how sharp the cutting lip is.
So always ask for inserts for machining aluminium even if you want to turn
steel. A salesman will start off by asking you the material and then try and
sell you an insert totally unsuitable for your use. An insert 'designed' for
high volume steel turning on a sturdy lathe will just skate over the work on
a Myford and leave a finish like a ploughed field. With a new sharp
non-ferrous insert I can take dust cuts on the stringiest steel on my
shagged out old Student and still get a finish you can see your face in.
Start off by measuring the height from the centreline of your lathe to the
bottom of the tool holder register. Then buy the largest tool which will fit
that and not ride above centre height. Obviously adjustable tool holders
make life much easier than fixed ones where you have to shim the tool up.
Then look at the cost of inserts which varies hugely and go for a holder
which takes cheaper inserts in preference to one which costs less to start
with but requires expensive inserts. Square and triangular inserts tend to
be good value because they give you 8 or 6 corners per insert. Diamond and
rhomboid inserts only give you 4.
When facing off material never go beyond the centreline of the bar. You'll
crack the edge off your insert every time as the cutting action changes from
down to up. If necessary stop a bit short and leave a pip and then file that
off rather than screw an insert.
I think that's it for my stock of pearls of wisdom for one day.
In article , Dave Baker
I have used lots of inserts (mostly Stellram) for cutting steel with
very good results.
8 corners??? To do this, a square insert must presumably be able to work
upside down; never sen any like that, maybe I'm using the wrong sort
Been using them for years, never been careful to stop at the centreline,
and never had a tip break under those circumstances (broken plenty in
other ways, usually by being careless and digging in). Perhaps this is
because I tend to take light facing cuts, rarely more than 20 thou. I
can see that the tool cutting edge would be weaker if it was working
backwards (just like reamers, which should never be turned backwards).
However, if the tool is accurately set to centre height, there is
nothing there to press the cutting edge backwards once you pass the
Are you a member of a club, if so have a talk to some of the members. If not
join a club, most members have a lot of experience.
This is not a dig at you. I wish when asking for help about operating
machine's they would give some idea were the are in the country. I have
always said if a new model engineer needed a bit of help and it is not to
far from North Lincs I would willingly give them a morning or afternoon in
the workshop. FREE. A cup of coffee would be acceptable. I have spent 40
years working in machine shops and turned or milled most things.
Never worry about asking what you call elementary questions we all
started there and were given the help we needed, although as an
apprentice it invariably came with a very large helping of ribbing.
The problem is when you have been turning for some time it becomes
"second nature" and you can forget to mention some of the gems learnt
early on. Communication can be difficult and it's easy to see why
those who can communicate effectively with the written word are held
in high regard. As David mentioned on another post George Thomas with
his book The Model Engineers Workshop Manual is well worth reading. I
also agree with Bill a couple of hours "face to face" over a coffee
with the lathe in use is worth many pages of reading.
It becomes difficult when explaining a comment or piece of advice to
know how far to go to explain "why". As advised you can indeed get 8
cutting edges on a square insert and each with large radius nose but,
(you knew that was coming), on some the edge's of the tip are square
to the top and bottom surfaces and the tool, to get cutting clearance
is presented to the work with a negative rake angle. I have seen
others which are "wasted" in the thickness to produce cutting
clearance but they are (were?) relatively thick to avoid rubbing and
were only really suitable for small diameter work, again to avoid the
lower upside down edge from rubbing. To be honest I only saw these
inserts when a tooling rep was trying to sell them and for us they
were not successful so I don't know if they were ever in general use.
Negative rake cutting has advantages and works fine when you have a
large very rigid machine with lots of horse power. With our
lightweight machines a positive rake cutting edge is essential. The
same power/rigidity issue exists with the nose radius; the larger that
is the greater the contact area between tool and work and the more
rigid the machine needs to be to avoid chatter.
Here it gets confusing again as with HSS you can get the tool very
sharp and reduce the speed so that a HSS tool with large nose radius
(or a form tool) can cut well on our machines. Inserts only work well
at relatively high speed and when working hard with a minimum depth of
cut of say .004", so reducing the speed and depth of cut to avoid
chatter takes the insert well outside its operating range. Keeping
speed up can induce chatter which instantly chips the tip and renders
it useless. Therefore we need to find the right compromise for
successful cutting in our situation. You have mentioned taking a cut
of .001" off a bar and that is not an ideal way for an insert tool to
work well, in fact most inserts when they have been used for a while
will not cut at all with only .001" cut they will merely rub. One
other strange thing about most inserts is that they produce a better
finish when they have been used, with new edges producing a slightly
ragged finish. This is to do with the "sharpness" of the cutting edge
where a (minutely) blunt edge will burnish the material and produce a
better finish. Don't be under any false illusion, on our machines
tipped tooling when used correctly can produce superb finishes but it
is a different technique from that used with HSS.
The set you have identified is fine, Glanze are good mid-range tools
and will last well. My only concern is if you really want to start
with a set that expensive before you have confirmed that you are happy
with insert tooling. I have several sets, Warco do one that is a fair
bit cheaper (=A345 ish) although it uses a variety of tips rather than
the one CCMT type that the Chronos set uses. Some of the tools
included with these sets never see the light of day. I have always
recommended that a good start is to buy a SCLCR Right Hand tool in
10mm square for a Myford. This =A315 will let you try to see if the
indexible system is right for you. The tips are CCMT and have a small
tip radius and are capable of providing a good finish when either
turning or facing. As I mentioned above they work best with a fairly
high speed and with a reasonable feed/DOC. One of these is in the set
you mention and this is the one you will use the most. I tend to use
uncoated CCMT-06-02-04 tips from Widea (RDG currently) and they are a
good compromise for steel between metal removal/finish/life on my
Myford S7. The coated type (gold coloured) do not work quite so well
for me and I use them more for heavier work. As I metioned before I
have had excellent results from the TPUN type as well.
Garth I'll leave it there as the post is getting very long but you can
see cutting tools are a "science" in themselves and we could go on and
get more and more confusing. When I've exhausted my little bit of
knowledge no doubt someone else will come in with more scientifically
based answers that get further and further away from the actual
cutting experience. Garth I suspect that this will ask as many
questions as it provides answers but there is much to consider and the
best way to learn is to "play" a little and see what works for you. In
my experience there is no "ideal" set of cutting tools of any type
currently on the market. Most people using small lathes seem to end up
using a mixture of HSS and tipped tooling. I agree with Bill, if you
let us know what part of the country you are in, someone may be
willing to spend a couple of hours with you for the price of a couple
of cups of coffee or in my case tea as I can't stand the stuff.
I think that whilst Keith is probably right on the ball, it is time to
simplify the reply to say to Garth, 'Look Chum, you bought a design
which came out in 1948' As such hundreds of thousands of users have
used HSS and carbon steel tools on them in those years- and will
continue to do so. You may have a problem, Garth, but had you taken on
board the comments of Charles Ping and later, my own self, you would
have read up the works of Sparey, who drew out formats for lathe
tools, you would have read up Ian Bradley who wrote up on three of the
Myfords and as an encore, wrote up a complete book on merely doing
lathe and shaper tools. OK, Bradley did touch on carbide but not on
'inserts'. Thomas, who was one of the most expert workers on Myford
lathes- and whom I recommended- criticised the need for carbides as
being unnecessary save for ropey castings which should have gone back!
Thomas went on to describe the use of 'hardened nails and having had
Myfords for yonks, carbide is not a substitute for the inability to
correctly sharpen a lathe tool and to set one up correctly to cut to
The information is there but if you wish to have a time breaking
expensive carbide tips in your learning pattern, press on- regardless.
The suggested books are by no means the sole information but I would
suggest that you go to Chronos or wherever, and buy distilled wisdom-
which will outlast your present ideas.
No charge for my tips, sharp though they may be.
Thanks for the comments - always appreciated.
Far from not heeding your advice, I am simply trying to analyse all th
differing bits of wisdom I am getting, in order to get some toolin
which will a) be fairly inexpensive and b) actually give me some tim
on the lathe in order that at some point I can make my own decisions.
The fact is that I have three of the suggested amateur lathe an
machining books on order from Amazon which have not arrived yet. Thi
is part of the reason that I am asking for advice here, which - as yo
say - will almost certainly be contained within the books. I can't ge
them here any quicker unfortunately, and they have been on order fo
two weeks now. I am just keen to make a start.
I do read all responses to my questions. I also appreciate the dept
and quality of the experience of those who have taken the time t
respond. Remember though, that at some time in the distant past, eve
you were once a 'beginner' ! So please be patient.
ps. I haven't actually bought any tooling whatsoever yet, just use
what was with the machine when I bought it
In article ,
I think you should lighten up a bit, Norman. We were all beginners once,
everyone benefits from a bit of sound advice when starting out; I don't
think there is any reason to get tetchy.
As someone who was in your position once, i.e. absolute beginner, no
metalwork teaching at school, etc. etc. I know how it feels. The
following is my opinion, based on my experience of 25 years of home
engineering with no tuition or professional experience, using a Myford
S7 and a modest size milling machine (FB2).
Norman refers to several books by highly respected authors. However,
many of them were written 50 years or more ago, and some things have
moved on since then; also, there is often room for different views, even
among contemporary commentators.
I started out with a miscellaneous collection of HSS tools, some new and
quite good, some decidedly dodgy, a bench grinder with only a plain tool
rest, and some sharpening stones. I learned to grind fairly simple
knife, facing and threading tools, and to hone them, but frankly it was
all hard work and a bit hit-and-miss for me. When I discovered
replaceable tip tools it was like my enjoyment of the hobby was doubled.
Sure, the tools and tips are not cheap, but (a) I've mostly been in the
position that my time was in shorter supply than the modest amounts of
cash involved, (b) top quality HSS tool blanks are not cheap themselves,
and (c) I concluded that the only way for a home user to get good
results every time is to buy or make a proper tool grinder, the cost of
which will buy a *lot* of replaceable tips. Time-served master craftsmen
can probably do this sort of thing freehand, but the hobbyist will have
a lot more trouble.
Sure, there are debates about whether a replaceable tip of some
particular design is "ideal" for our purposes on a fairly light lathe
with modest cuts. All I can say is that after using them for 20 years I
have found them fine, I can take a few tenths off FCMS with no trouble
and get good finishes. Maybe I could get an even better finish with a
polishes HSS tool (and I do have many of those) but frankly a couple of
minutes work with a No 6 cut Grobet Swiss file well soaked in cutting
oil puts both to shame if finish is what you are after (and when you see
the price of those, you will think carbide tips are dirt cheap).
I do plan to buy (or make) a fairly high performance tool cutter
sometime soon; however this is not to turn out plain vanilla turning
tools, but to sharpen milling cutters and the like (of which I have a
drawerful requiring attention) and to make cutters I cannot buy.
However, that is one strand of opinion, you have heard others here, and
some from people who have lots of experience and knowledge. It maybe
that some replaceable tip tools are better for our purposes than others,
it may be that the others' experience is too much oriented at heavy
production-level cuts, it may be that I have been doing second rate work
or have more money than sense. As usual with usenet, you will have to
read all the answers, pick the ones that you think suit *your* case the
best, and do some trials of those chosen paths to see if they suit you.
.....and I think you'll have to go a long way to find better advice than
that offered by Keith, Norman and Bill. I endorse everything they say - do
take their advice and then you can at least come back for more without the
risk of pissing people off.
Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"
Sadly I am now too old to be included in 'the Grumpy Old Men'.
I mentioned 1948 conscious of the possible backlash. Then, young men
were given all of 6 weeks to master the skills of keeping aeroplanes
in the air.Oh, yes, keeping the Boss man's favourite Griffon Spitfire
in the air fell to a young man who unashamedly admitted that he had
not the education from those uncertain days of bombed out London.
The years moved on and 'Johnnie' got his pension for the terrible
injuries which he sustained from those days. He asked me why I had
The answer was a simple one. Johnnie had also strapped me in the back
seat of other aircraft and with only a fragmentary training had
ensured that I came back each time. Of course, the Boss's old Spit is
still airworthy though in San Diego. Somebody flogged the other old
girl which had gravitated to being the hack of the Battle of Britain
Memorial Flight and she took off from 'John Lennon' after another
Two more of the old girls are at RAF Cosford keeping company with two
of our Antarctic Austers.
Naturally, I always drew the short straw- I never even got the 6 weeks
His Easter greeting card rests on my mantlepiece as a sort of thank
you for 'insuring the last bit of his old age.
Blame Johnnie, if you must.One can learn a lot from a sprog engine
But you have to listen!
When I discovered
There seems to be a body of opinion among certain model makers that HSS is
the "proper" way to do things and that carbide is cheating or maybe
replacing tool sharpening skills that took a long time to acquire. All I can
say is that anyone who makes a living from their machines doesn't bugger
about with HSS anymore and hasn't done so for many years. A non-ferrous
carbide insert is as sharp as you need to machine anything I've ever come
across. Maybe you can get an even keener edge on steel, a razor edge so to
speak, but that's not what you need for machining metal anyway. Wood
perhaps, or if you want a shave between jobs but an edge like that is only
going to last seconds on metal anyway.
As can I. The idea that carbide inserts only work when taking cuts of
several thou as mentioned in a previous post is pure nonsense. Even the pros
have to creep up on a size a few tenths at a time sometimes and if you could
only take cuts of a certain minimum depth with carbide you'd be stuffed when
you got any closer to target than that.
As I said in my original post, the trick is having the right inserts and for
our occasional and light machine use that means as sharp an edge as possible
so either non-ferrous inserts or finishing inserts for steel but I still
don't find those as good. The only time I'll use a ferrous insert is when
I'm hogging a lot of metal off steel and don't want to risk damaging the
edge on a nice new sharp non-ferrous insert until I have to.
I've tried brazed tip tooling, as have we all no doubt, and I still use it
occasionally, for parting off mainly, but out of choice I'll always use a
carbide insert when I can. I'd also say that you can't beat having a diamond
wheel if you need to sharpen brazed tips. Green grit wheels are a dismal
second best and one of the best things I ever bought was a cheap Chinese
diamond cup wheel from Cronos which I mounted on an arbour and use on my
mill. It's taken many mm off dozens of milling inserts I use for valve seat
cutting and hasn't worn at all.
Anyway, each to their own I guess but if I need to mill 2mm off a cast iron
engine block or a big flywheel the last thing I need is an HSS tool which
will need resharpening half a dozen times during the job. I want to stick a
tool with a carbide insert on the job which will take most of the metal off
in one pass, the rest in a finishing cut and still be sharp enough to do
another 5 similar jobs before it needs replacing.
The world has moved on since the books mentioned previously were written. I
don't use an open fire and a skewer for cooking my evening meal, I stick it
in a microwave oven for a few minutes, I don't cut the lawn with a scythe, I
push a petrol engined mower around for half the time and it collects the
clippings while it's working. I don't use HSS steel for machining if I can
avoid it, I use carbide inserts which last ten times as long and remove
metal five times as fast. Maybe 'proper' engineers can sharpen an HSS tool
to the ideal edge on a grinding wheel or reface a drill bit to exactly 118
degrees by eye. I can't do either of those things but I can fit a new drill
bit which only cost a quid anyway in a fraction of the time and get back on
with the job.
I think it boils down to this. Do you want to become highly skilled at
refurbishing shagged out bits of HSS or do you actually want to spend your
time cutting metal? If the latter then buy some carbide insert tooling and
enjoy your hobby.
I can also forsee this debate moving on in 20 years to the 'old timers' who
think carbide inserts are the only 'proper' way to machine anything and
newcomers who use PCD (polycrystalline diamond) and CBN (cubic boron
nitride) to do things five times as fast again.
OK, so I will now once again forget the HSS tools (as I had don
previous to reading Norman's recent advice), and return, somewha
wearily, to my 10mm Glanze Mini Indexable Turning Tools. Simpl
question - are the inserts supplied with these suitable for the kind o
speeds and depths of cut that the ML7 is capable of?
Did no one 'do' history at school? Since 1948, things
have changed but never quite repeating itself.
As far as Garth is concerned, he can now have the choice of lathe and
other tooling at what is give away prices because with a bit of
lateral thinking what cost many thousands of pounds then, is available
for perhaps a =A3100 now. It translates into a couple of tanks of fuel
for the motor car.Moving off further, this works out at less and
perhaps only a third of the price of the materials to make up a home
tool and cutter grinder for which there is the long term need to
actually construct. I've done it on a Quorn and and I have done it on
a Stent and I nearly did another Quorn and hastily flogged the plans
and castings etc for a locally available Clarkson Mark one which
probably came out of the Ark but resided in a barn.The pedestal was
too heavy to remove but the rest of it is OK. My luck doesn't take in
all the bells and whistles but these came later. It is surprising just
how effective B&Q 50mm PAR timber makes tool holders if fastened down
with Wilkinsons best bolts!
Of course this is for HSS stuff- well? Today, rising to the
challenges, diamond wheels and CBN things fit which is more than I can
say about my incontinence pads!
So are we finished? Nah, let's go for double top! Today, or was it
yesterday,? I got a set of 10 diamond pastes of bewildering grades for
a modest =A320 note.
True, I haven't really been able to get my head around low speed
pulleys to hone- err, carbide tooling on the beast.
Now where did I put my Zimmer frame? Bugger, fell over it as usual.
Pity about the 6 week course but I did get the offer of a scale
Tornado Bomber 14 foot long- for free. So has anyone got a helicopter
which was originally used to do drop tests? It was the Royal Air
Force who offered it!
In article , DR_G
You will still need to use HSS tools when you want to make something you
can't buy, but probably quite rarely.
I have never used the Glanze tools, but all the accounts of others
suggest they will be fine. I have used Stellram tools for many years
with considerable satisfaction, and recently acquired a couple from
Greenwood (which IIRC originate from Sandvik).
Your best course is to suck it and see.
(Snipped lots of good stuff)
(snipped lot more good stuff)
And surprisingly as the author of some of the "previous nonsense", so
can I, and I do as a matter of course day to day. The advice was not
meant for someone who has years of experience and has gained the
confidence to select an appropriate tip type, wear state, speed, feed,
coolant (if any); whilst putting the tool in the required position
within a couple of tenths by fully understanding how their machine
works and where it is worn and even with some of the old crap I've
used where to lean at the appropriate time. The advice was to help a
guy working on his own with an old lightweight lathe, not looking to
earn his living, and with no previous experience. I stand by the
original comment that in this context HSS is easier to use particulary
for steel finishing. Of course you can use carbide to remove minute
amounts of material but it is not just a case of fitting one of the
easily available "general purpose" steel cutting tips and winding the
cross slide dial until it reads two tenths more than before, risking a
higher speed of 350 rpm and pouring oil all over it. I don't mind
being rubbished it is a way of learning but if you are going to do so
at least keep the context similar.
I fully agree that once you have gained some confidence and a working
knowledge of the machine you are using most people with a Myford will
be comfortable with modern positive rake tipped tooling. Unless you
deal regularly with people who are starting out from scratch it can be
difficult to understand why they are at all reluctant to ignore all
the "manufacturers tables and previously published charts" of
appropriate tool tips and use a non ferrous one, but they are. Dave,
whilst I have sufficient experience to see the merit in your advice, a
surprising number of people in this position are looking to reduce the
risk of their own mistakes and feel they must stick rigidly to the
"recommended" techniques. With confidence and experience it soon
becomes obvious that there are many ways of "skinning the cat" and
most work reasonably well, the trick is to keep experimenting while
retaining the solid known base of what works to fall back on if the
change is not totally successful. I suppose this is the reason I have
a couple of boxes full of tips and holders that might one day see the
light of day but equally might see E-bay, no doubt they will work for
The one other issue is that for someone embarking on a hopefully long
and enjoyable "hobby" they will at some time need to use a form tool
of one sort or another. Here HSS is almost essential as it can be
easily shaped and sharpened. Also, sadly in these days of obvious
oppulence in some quarters, in later years not everyone is able to
replace a =A31 drill everytime it just needs to be sharpened. For many
of us in later life, time becomes cheaper and tools more expensive. If
you are going to meet HSS at some time you might just as well make it
part of the learning experience at the start.
Sorry for still taking the opposite view in the context of the OP
question, but there we are one of the advantages of these forum is
that many differing views are available. As has been said before read
it, consider it, remember what it cost and .............. try it. The
most effective learning method in my experience is to stick a piece of
metal in the chuck, stick some sort of tool in the toolpost and switch
on the machine and make chips.
Best regards, hope you have all had a better day than I have, took
someones advice on a chain saw - now why on earth did I do that?
I have a set and am happy with the results I get in my 15 year old
CCMT tips are easily available from a number of suppliers.
Personally if using the standard toolpost I go for 12mm shanks for
rigidity, but I find the tips of some 10mm tools are a bit high for a
quick change toolpost.
Yes they are, the one issue I might see is that for very small
diameter work, if that is on the agenda, the top speed of the ML7
could be a little low for them to work at their best. These tools work
fine for me on my S7 using FCMS.
Good original question Garth, you have managed to get some discussion
going when it looked like the forum had gone to sleep a bit.
I'd definitely recommend starting with HSS tools and a cheap £10 grinder.
If you are set on carbide, get a few brazed tools and try them (or as
someone else said, get a good RH indexable tipped carbide tool and four or
more inserts - I normally say to get two of things that might break, just in
case, but these _will_ break - and you will find it useful sometimes even if
you don't end up using carbide by preference).
You need to get someone to show you how to grind HSS tools, preferably an
old ex-apprentice - I don't think it's something you can learn from books,
at least for the basics, though books may help later. That way you can
quickly learn how to grind tools by hand - it took me about four days to get
the hang of it, six months to get good at it - so I can grind tools which
last - and it will take forever to get perfect :)
You'll begin to see how the cutting action works, without breaking expensive
carbide tips. That's what it's all about, cutting metal with metal (or
carbide, or..), and it just isn't obvious to the beginner, which I was three
or so years ago. I had the idea then that you just moved the handwheels to
the right numbers and the workpiece became the shape you wanted - but it
doesn't work like that.
If the HSS breaks (it won't, but it might well get blunt quickly) you can
just regrind. And please get some good quality HSS - you should be able to
get half a dozen good 3/8 or 10 mm HSS blanks for something like £30. Sorry,
but the Chinese/Indian HSS tool blanks just aren't good enough unless you
are only swarfing aluminium.
Brazed carbide is not for me, but it is cheap and will give you an
introduction to carbide, see if you like it - I wouldn't bother with green
grit wheels though, use diamond - even the very cheap 20 mm dia diamond
wheels in a Dremeloid are better than green grit.
Indexable carbide tipped tools (which are not really indexable if you want
to change a tip and use the settings for the previous tip to eg turn to the
same diameter with hundredth accuracy) have three great advantages, first
you never have to sharpen them, second they cut faster when employed right
and third you never have to sharpen them. They have two great disadvantages,
first the tips are fragile, and second, you can't sharpen them.
Remember, cutting metal with metal (or..) is what it's _all_ about. If the
cutting edge does what you want, that's all you need.
(I do a fair bit of work on hard-to-machine metals with CBN and diamond