Centec 2B Vertical Head Tool Options

[Graham Horne 2Participant @grahamhorne2]

I thought I should start a new thread for this question. I think I have a Centec 2B that’s in relatively good condition. I won’t go into all the detail in this thread. I have a large quantity of horizontal mill cutters and shafts but as good as no vertical mill tooling. The head takes MT2 tooling and I have rebuilt the captive drawbar for M10. Sorry I am a republic and metric advocate. It’s a matter of science and logic. I it the most profoundly stupid idea that Brexit were pushed also for imperial. In Australia we adopted the metric system when we left the pound in 1966 which was the same time as the UK or near enough to so I grew up with both. I do get that in engineering 1,000th’s works but beyond that the fact it is base 12 numbering is nuts. I have had a life of base 2, 8 and 16 but that had a logical basis (sort of). So I am 100% metric just so you know. It’s an M10 drawbar on the vertical head and 3/8” for the existing horizontal tooling.

I have to decide what tool holding to choose for end mills, face mills and the like. I know this is probably opening up a can of worms but I like to be controversial. On YouTube everyone seems to have a different religion for cutter holding. A bit like birthdays, everyone has one and they think theirs is special. I bought some ER20 MT2 M10 collet holders and looked and the sent them back. Not because the quality was bad but the maximum tool holding for ER20 is 13mm. The best wisdom I could find on YouTube was to choose a collet chuck that the tooling only used 75% of the maximum tool holding capacity. So I am leaning towards buying ER25 MT2 M10 holders. My view is to keep the commonly used cutters dedicated into ET25 collet holders and change cutters by changing the complete cutter and collet holder. Is this a reasonable approach. I am thinking in order or maybe 10 collet holders, looks like bearing collet nuts and maybe some reasonable quality collets so runout is minimised. Ideas? Different opinions? I am not an experienced engineer and more of a woodworker.

[peak4Participant @peak4]

Like you, I have little formal metalwork training either, but have had a Centec 2B for a number of years.
My work tends to be in imperial, but that’s not too important in my choice of cutters.
I made two vertical drawbars, one 3/8″BSW and one M10, so I can use both types of tooling.
Much modern stuff is M10, so my insert tip face cutter is on an M10 threaded arbor for instance.
I do have an ER25 collet chuck on an MT2 arbor, which I use for plain shanked cutters, such as solid carbide slot drills & milling cutters.
My own preference though is to use a Clarkson collet chuck, in my case an older C type, with threaded cutters up to 16mm & 5/8″.
I find this far more rigid than the simple MT2 arbor cutters and holders.
The main reason, is that it has a second “snugging” ring at the top of the chuck, on a fine left hand thread.
Essentially fit the collet chuck as normal, gently nipping up the drawbar, and then hand tighten the ring upwards.
This provides further support for the comparatively slim MT2 arbor.
This photo is from my flickr account, which shows a wide variety of milling collet chucks

I also have an S type with a similar ring, as seen here; have a scroll through the album

N.B. don’t tighten the drawbar too much, and consider slackening off/removing the chuck whilst everything is still warm after using it.
If you over tighten, and particularly if you do so when the spindle is warm, it becomes very hard to free off the tooling later when it cools down.

Bill

[Tony Pratt 1Participant @tonypratt1]

 

Deleted

[Graham Horne 2Participant @grahamhorne2]

Never offended as long as you not either. Not afraid to be controversial as I said. Partly it is to get a reaction. Achieved. Ha

[BazyleParticipant @bazyle]

The point of a collet holder is that you can keep changing the cutter. If you are going to interchange effectively at the MT2 level you could hold at least the smaller ones by getting/making blank MT arbors drilled for the size with a grub screw or two and use non threaded (cheaper) cutters.
Dedicated arbors can be shorter making them more rigid and more headroom.

[Graham Horne 2Participant @grahamhorne2]

Must say not seen a Clarkson auto chuck before. It seems it’s an older tool that you buy perhaps on eBay or the like.  I could not find much info on it. Probably worth a bomb new even if can acquire them. Is that about right.

[Graham Horne 2Participant @grahamhorne2]

The idea of dedicated holders makes sense for sure. Maybe it was over kill to consider ER25’s as static tool holders. The only reason was I saw a YouTube (sorry it was my way learning stuff) from a reputable channel that the grub screw introduced run out. Maybe they introduced enough play to get the tool in (and air out) and maybe an air bleed hole and a  tighter tolerance was needed. Am I over thinking this all?

[Graham Horne 2Participant @grahamhorne2]

Is the idea of changing tools at the MT2 arbor over kill? Remember I am not experienced at engineering. Maybe it is just overkill on my part?

[John HaineParticipant @johnhaine32865]

One good reason for changing the whole toolholder is if you have a vertical DRO, in which case you may be able to store vertical offsets for each tool.  So for example, you machine a surface flat with a tool, change to a slotting tool and tell the DRO the tool number and the new tool will have the same zero.  But the argument against is that every time you want to change a tool you have to wind the spindle up far enough for the MT2 taper to come out – that can be a real pain!  Unless you have a DRO and you really want to get into measuring and applying tool offsets I suggest you just get yourself an ER25 collet chuck which stays in the spindle and change collets and tools as you need.

[Dave HalfordParticipant @davehalford22513]

Vertex still do the Osburne Titanic version . However these all use threaded shaft cutters that are getting rare today even in the UK.

As Peak (Bill) says gently nip up the drawbar with a short spanner, though the cutter nut will need significant torque to hold and you will get trouble changing the whole ER chuck with a warm vertical head.

There are only 4 generic cutter shaft sizes that fit MT2 / your size of mill and they stop at 16mm so you just need 4 ER collets sizes.

[peak4Participant @peak4]

Out of curiosity, I’ve just been having a quick play with the Centec and a Clarkson C Type, with and without snugging ring.
This was the setup; not ideal, but just to give a rough idea.

Spring balance on the right, with tension applied by the table movement.
In order to get a 1 thou deflection on the clock, I needed 15-16 lb pull on the balance without the ring snugged up to the spindle nose.
With the ring lightly tightened with a spanner, that increased to about 20lb to get the same 1 thou, so not a huge difference, but it does indicate slightly more rigid; it might help to reduce chatter as well.
With a 20lb load, I then carefully released the ring, upon which the DTI showed a further 0.0003″ deflection, which went away after re-tightening.
The first 7-8 lb load seemed to be taking up spindle play, rather than anything actually bending slightly.

Photo not shown, or taken, but I tried a similar setup with a longer test bar with both this chuck and an ER25 MT2 arbor. Deflection was about the same with a disengaged snugging ring on the Clarkson, but improved a bit on tightening. I did take care to ensure the same overall projection from the spindle nose to the loading and indicating points

Bill

[BazyleParticipant @bazyle]

Titanic are as old a Clarkson and use the threaded tools. Newer versions are the Posilock and a few more far eastern versions sold by Warco etc, still for threaded cutters.
One of the key features of the threaded style are that the back end has a centre hole to locate on a point at the back of the chuck. It is therefore possible to put in a new cutter (new from Clarkson of course) and it will be at exactly the same vertical position as the last one, or a bigger one with a known offset. Essential for professional work so you can just keep going.
In second hand chucks the centre is often damaged by some pea brain not cleaning before use. They are in theory replaceable being on an 0MT taper pressed in with about ten thousand lb force.

Interesting test Bill.

[Bazyle]

On Bazyle Said:

Titanic are as old a Clarkson and use the threaded tools. Newer versions are the Posilock and a few more far eastern versions sold by Warco etc, still for threaded cutters.
One of the key features of the threaded style are that the back end has a centre hole to locate on a point at the back of the chuck. It is therefore possible to put in a new cutter (new from Clarkson of course) and it will be at exactly the same vertical position as the last one, or a bigger one with a known offset. Essential for professional work so you can just keep going.
In second hand chucks the centre is often damaged by some pea brain not cleaning before use. They are in theory replaceable being on an 0MT taper pressed in with about ten thousand lb force.

Interesting test Bill.

I do have a Titanic II as well, but my MT2 version lacks the additional ring for the added rigidity with the thin arbor.
The MT3 one feels more rigid, as do the Clarkson & Titanic Int30 ones I have.
Unfortunately I don’t have an MT3 or Int taper mill to take advantage of this.
My second mill is a Dore Westbury, but since that features a Myford nose thread, I use a direct screw-on 2 piece ER25 chuck for milling cutters normally.

I guess R8 would be more rigid than MT2, but don’t have one of those, or a spindle to fit it in.

Bill

[DiogenesParticipant @diogenes]

I’d buy an ER collet holder and change the collets – I keep a couple of eregular tools pre-loaded in their collets – just to save knocking the morse taper out of it’s hole every tool change.

If you buy a ‘threaded shank tool’ holder you’re stuck with buying threaded shank tools to go in it.

[Graham Horne 2Participant @grahamhorne2]

The ability to swap tools directly at the MT2, was for both setting up tools in the DRO with tools indexed and having known offsets as you mentioned and to some extent good tooling setup in the holder to minimise runout and improve more predictable.  I do this on my lathe and have all my tooling in about 12 quick change tool holders (bison) on the Boxford Dickson QCTP. As a matter fact I will remove the compound slide and replace it with a solid raiser block which I think is best so the QCTP never moves. I must say I didn’t think about the clearance needed above the workpiece for the holder to slide out of the taper and admit that changes things a bit.

Initially my thinking was to buy a stack of cheaper ER25 tool holders, improve their tapers perhaps and use good quality collets and collet nuts for low runout. Someone asked “why not just put them directly into purpose made MT2 taper blank” and that made sense but now I see what you mentioned as an issue in having to possibly drop the knee some distance to change cutters. On the lathe QCTP that is easy and I suppose I was following that pattern of work.

I must say I was also considering using a small butterfly air driven impact driver on a drop down mechanism to engage the drawbar nut thus making it a simple quick tool changer. The Centec 2B has a captive draw bar and it seems pretty easy to create a frame to hold the impact driver and create a forward reverse lever, have the driver drop onto the drawbar nut. Hit reverse and drop the tool and holder out of the spindle, put in a new tool holder, engage the impact driver and hit forward. I watch many built and thought it would work on the Centec. Because of thinking of that the idea of changing at the MT2 appealed. Most of those videos were Bridgeports and they were using the quill movement but the Centec only has 50mm of movement.

that’s was a good point. Thank you for you input.

[peak4Participant @peak4]

Rather than a butterfly, maybe try something like this style of spanner; it sits and stays nicely on the top of the drawbar, and spins easily around with just a finger after the bar is loosened.
Very quick and easy releasing of the arbor, with little chance of dropping a fiddly spanner.

The other gizmo engages with the retaining nut at the top of the drawbar, which forms the self eject collar, above the spring. It’s far easier than playing with a peg spanner.
The hex is machined to M17 as that’s the size I use for most of my clamping kit’s M8 flange nuts; again a short M17 combination spanner’s ring end sits there nicely with little chance of dropping anything.
It makes changing the drawbar from 3/8″ to M10 a breeze.

Bill

[not done it yetParticipant @notdoneityet]

I’ve amassed a few different options.

Some finger collets that allow far less stick-out, so less chatter potential.  I’ve not used any of those for years.

ER32 seemed to be the largest size for general work, so that is what I bought (lathe spindle will accept 25mm).  Since then I have purchased a through-collet chuck for use on the lathe.  Useful because other sizes than the few standard shank-size collets that get used with the mill.

I bought a set of ER16 for finer work – particularly on the Raglan.

I needed a larger diameter holder for a particular job so bought an ER40 and just two collets.  Been used twice.

A Clarkson came with the lathe and gets used occasionally – but not often.  Useful when both machines were set up.  Most of my cutters have plain shanks.

I have no Sheldon-type holders and cutters.

One day I might rationalise the whole lot and sell the others.  The ER system would be retained.

I have both square and hexagonal Stephenson’s ER32 collet holders.  Useful, when needed, but not used often.

I don’t make models.  Most of what I do is for old machinery restoration/repair.

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