I assume you're thinking principally about vertical mode.
Well, a friend and I both have 2Bs - he uses 2MT collets and I use ER32.
The main advantage of the 2MT collets is that the tool ends up closer to
the quill and so gives less overhang and more headroom: both good
things. The main advantage of the ER system is versatility: both metric
and Imperial sizes can be handled with the same set of ER collets. My
friend built his 2MT set over time as he needed them, I purchased my
complete ER32 set from RDG Tools - they had the keenest price and were
made by Vertex. All in all I prefer the ER system.
There are more drawbacks and advantages worth thinking about:
- Isn't that stable as MT collets
- very long tools (drills) can't be pushed in far enough sometimes (when
you are going out of headroom).
- not as precise as MT. There is an extra place for tolerance (ER in the
ER holder) and the area of contact is smaller).
+ Takes less space to change the mill. There are situations where you
don't want to move the table (or can't).
+ Cheaper collets
+ Often can be used on the lathe or rotary table
So what is better? Both! I'd first buy ER and then buy MT when a setup
requires it. YMMV.
I would certainly add my vote for starting with the ER system. I bought
a Vertex ER32 system for my small mill several years ago and have never
felt the need to buy any direct MT3 colletts. While the Vertex system
is superb I have purchased several additional colletts from ArcEuro
Trade, RDG, JL and Chronos. While most of these have no manufacturers
name they have all been fine. The flexibility is a tremendous asset and
I have experienced no problem whatsoever with their accuracy.
In a word: Clarkson.
They brought the threaded endmill and holders to market a looooong time ago, so
most end mills are threaded to suit their holders. Many copies out there, all
pretty much equal.
Note that there are imperial and metric body/thread sizes and matching collets
to hold them.
Peter A Forbes
Prepair Ltd, Luton, UK
Yes and no. They fit into collets without problem.
But if you are roughcutting, mills get pulled out of the collet and that
is why some do have a flat or a thread. ER-collets can't clamp there, so
you have to step back a bit and not make to hard a cut.
As Peter and Nick have said the threaded cutters were designed to stop
any possibility of the cutter pulling out during a heavy cut. This was
a particular problem as colletts became worn and cutting loads
increased with better cutter materials. The ER design collett has more
"splits" than the older designs which allows the internal part of
collet to contract with parallel faces and it generates higher holding
pressure on the cutter. While I know that it is possible to have a
cutter pull out of a ER collett it is not a common occurance and rare
in the home shop with normal HSS cutters. The ER system will hold,
threaded, flat and plain cutters of both imperial and metric sizes,
that's one of the major benefits of the system. The ER system is widely
used in industry and known for long life and reliable holding.
The main problem that the OP has got is the 2MT spindle mounting. This
severely limits the stiffness of any collet system that is mounted on it.
I would seriously suggest using 2MT collets if you are going to use 1/2" or
12mm cutters. This is based on my experience with a 2MT Vertex Pozilock collet
chuck on a Myford ML7. The deflection was visible when pushing any cutter
bigger than 1/4". I cured the problem by making a new collet chuck that
screwed onto the lathe mandrel. This was _much_ stiffer than the original 2MT
arbour and had less overhang. I don't think the Centec would have this option
(could be wrong :-)
Of course, a 2MT head is probably going to struggle with a 5/8" or larger
cutter, but a 5/8" roughing mill will chomp away on cast iron quite happily.
Mark Rand (this advice is worth what you paid for it :-)
Mark, excellent point I had missed the fact that it was 2MT. My
experience is based on my 3MT Vertex chuck and like you on the lathes I
use home made direct mounting chucks. I do remember when using Centecs
years ago they needed to be treated fairly lightly, then again they
might have been clapped out. Pity because the ER system is very
flexible and my drill chucks are rarely used these days. Good job
someone is awake.
But this only helps, if you clamp something smaller than the nominal
size of the collet. But then, ERs are really much better.
I have ruined quite some pieces when the rough-cutting mill was pulled
out some mm. I use "softcut" mills. They cut so smooth and silent! The
more feed, the more silent they get. You can really go to the limit of
the mill. Diameter of mill 20mm, 20mm deep full cut. That's how they get
pulled out. :-)
They more and more use shrink collets or hydro collets. Especially for
HSC milling. Nothing else keeps the required tolerances.
But that is out of reach for HSMs.
I agree with most of your points when taken in a wider industrial
context, however we are discussing the use on a Centec 2B in the home
shop with as Mark rightly pointed out a 2MT spindle. I had also assumed
that they would be used within their recommended range, silly I suppose
as I should have remembered from my industrial experience that is never
You are right to point out the dangers of the newer generation of
milling cutters as they will eventually find their way onto our
machines and this gives us an insight into just how far they can be
pushed. I should have also mentioned the possibility when taking deep
cuts in the more ductile materials. In my defence, I still cannot see a
Centec 2B taking 20mm cuts with a 20mm cutter, however silent it is.
I also agree that industry is in the process of moving on with regard
to tool holding but they always are. It's also true to say that much of
smaller scale industry haven't even got as far as ER yet and I doubt
very much they will make the jump to shrink or hydro colletts let alone
to High Speed milling. As you rightly say I can't see machines with
absolute minimum spindle speeds of 10,000rpm fitted with the best
possible spindles that manage at most 4,000 hour lives, being widely
adopted in the HSM. Then again with smaller cutters and more
sympathetic feed rates just think how many pieces of scrap I could turn
out in the hour.
I find this type of development very interesting and indicative of the
increasingly inevitable demise of the remnants of British production
industry. I suppose you could argue that by being slow to pick up these
developments our industry will be able to "cherry pick" the best and
miss those expensive "dead end" developments, a bit like telling the
poor b*****s at Agincourt we'll skip the longbow and go straight for
Anyway, I digress, Nick thanks for your post as I think it's important
to take us outside of our old machines and little sheds once in a
while. Problem is it makes me depressed when I consider what I can do
against what is possible. Just getting old I guess.
Nick M=FCller wrote:]
None taken Nick, I do think it is good to see what real industry is
doing with some of this kit that we play with.
Yes good, I don't think you should hold your breath though, I can't see
a real commercial need particularly as they must easily outperform the
holding potential of the MT taper in an old spindle?
I have one 9mm slot drill that I have mounted in a 2MT blank arbour by boring
the arbour to a good fit, then removing another 0.002" in the middle part of
the hole, then holding the cutter in with loctite 603. This is not quite as
good as a shrink collet, but it's not far off. When the cutter is worn out,
I'll heat the arbour up to 150 degrees or so and pull the cutter out.
One of my projects, once I've got the Beaver mill recommissioned, is to make
some genuine shrink fit INT30 holders for some of the larger cutters that I
have acquired. I can either use the shrink fit induction heater at work, or
make my own for fitting and removing cutters.
... or I could go back to using the shaper
Mark, given that blank 2MT arbours are cheaper than colletts that's a
brilliant idea. Once fitted the cutters could be ground complete with
arbour. The assembly would also increase available height table to
cutter a real benefit on smaller machines. I suppose that I might worry
if the cutter was too large so that the arbour rotated in the spindle
rather than the cutter rotating in the work. What sort of
interference/temperature rise do you think we would be talking about
with a 1/2" cutter. Inspiring idea though.
I do that (without removing material in the middle) when I need long
drills (small sized, about 2mm). Locktite centers the drill very well,
so I just bore some rod with the drill that I want to glue in.
Pun intended? ;-)
Some of the Clarkson milling chucks had a screwed ring over the body
that once the chuck was tighten in the taper the screwed ring was
wound back to dear on the ends of the spindle to increase rigidity.
Not that I know anything about rigidity at my age
Visit the new Model Engineering adverts page at:-
Out of my depth here John but if we cut a thread on the outside of the
blank arbour and made a matching sleeve nut, then when the arbour is
tightened up we could load the sleeve nut against the spindle? Would
that reduce the flexibility of the fairly small 2MT arbour that Nick
was talking about before? Would it not reduce the holding pressue on
the taper though, as I said I'm out of my depth.
Yes - mine's like that. Advantage of the Clarkson over plain collet is
that cutters don't pull out - ever. Disadvantage, on my 2A, is that
the space between cutter and bed is reduced, so I can't get big items
For big items I fisit a friend, who has gone over to ER collets on his
3MT mill almost exclusively. He occasionally gets the cutter moving a
bit, but usually when he's not tightened it enough. Really big
advantage for him is that the ER system will also hold drills. So you
don't need to keep swapping the Clarkson for the Jacobs.