Pros and Cons of the ER collet system

[Mark CParticipant @markc]

John,

The original mention of aerospace came with the implication that this was the state of the art for machining operations. I would not argue that it is a very demanding arena but it is not focused on maximum metal removal which is what the post alluded to – maximum gripping force, not maximum accuracy or repeatability/accuracy.

It would be very easy to wander off and start confusing the metrics we are using here. Aerospace (and automotive for that matter) is generally concerned with quality, repeatability and process capability – things that are outside of the requirements for most model workshops.

Mark

[Mark CParticipant @markc]

By the way, I like my Autolock, its just a bit of PIA compared to the ER chuck (Indian I hope/think) so gathers a bit more dust than I anticipated when it was "won"on that auction site… It does hold threadded cutters well be to be fair but I do not have the power to push either to buttock clenching extremes…

Mark

[AjohnwParticipant @ajohnw51620]

I don't know why aerospace is cropping up. High end machining centres have been used for even moderate mass production for a very long time. They will turn, mill and do all sort of things and even take stuff by the pallet load and re pallet them when done. Work can be done to very high accuracy and with a very high quality finish. They cost rather a lot of money but economics are such that it can be cheaper to machine from solid rather than precision casting followed by some or no machining. A company I saw working like this started doing it about 25 years ago and they were very probably late comers. They mostly machined castings all over but some lower volume items were made from solid. Later more were as it gave a shorter time to market and changes were more easily made. Also some product might finish leaving a rather expensive machine idle. That can mean that at that point in time machining from solid makes a lot of sense.

Even over this period actual tool setting is done by the machine right down to the final cut. They can even machine out machine misalignments. The only thing a setter needs worry about is the actual tool type and also speeds and feeds. Not much different to turning really as that is where the part can put limitation on all the factors.

Massive thread this for something that has a grip length problem compared with others and for high end use on cutters in particular I doubt if anyone makes any real use of the collapsible aspect. Clearly the people who came up with traditional work holding collets were nuts and at least partially out of their minds – or were they? ER collapsable is considerably cheaper and as such are bound to be popular for something that they were never really intended to be used for.

John

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Edited By Ajohnw on 23/09/2016 23:15:35

[Mark CParticipant @markc]

John,

You need to read ALL of the posts to understand this thread before you jump in.

Mark

[Raymond AndersonParticipant @raymondanderson34407]

John S , Lets just start at the beginning, The ER is not the best workholding system even Rego fix has said so. Now Im not knocking them why would I? as I use them myself for workholding and am happy with them, although I am not blind to their shortcomings when used for workholding.

Secondly, I said they are not even the best toolholding system Now I admit I should have specified in what areas ie, HPC. They ARE the best endmill holding system for our needs thats a no brainer, we would never need the rigidity of a true milling chuck. . So I should have specified what area I meant.

Thirdly, I answered a fellow posters reply where he stated CORRECTLY that the er was originally designed for drilling / reaming he was met with the reply "utter tosh " well he didn't post utter tosh, as again Rego fix confirmed.

This is not about me, you,or somebody else winning "browinie points " This thread has moved into insults and personal attacks of which I myself am guilty of [ although only in response to some others including yourself. ] and there is no need for it. I enjoy [ed ] this thread because I'm interested in why the findings occur. as are a few others but it has been twisted out of shape by misquotes and a lack of clarity [on my part ] . I have no intention or ever had of dissing the er. I simply like to know why it is not suited to large radial forces.[ which it has been proven that it isn't ] and that comes not just from Albrecht ,Shunk and others, but from Rego fix themselves. Just let people get on with what interests them and there is no need for insults from ANYONE me included.

cheers

It would be a waste of time using a hat for my avatar as I never wear a hat.

[Raymond AndersonParticipant @raymondanderson34407]

Almost forgot, Any new posters to this thread please follow Mark C's sensible advise and read ALL the posts from the beginning. Don't just jump in, as that leads to more misquotes / confusion.

cheers

[Raymond AndersonParticipant @raymondanderson34407]

Mark C, at least you have taken note of what I said originally [when mentioning Radial rigidity ] I never alluded to er's being unsuited to milling, only that they are not suited to Heavy radial forces found in HPC. Just half an hour or so ago I phoned the brother and asked what the e's were used for on the WFL Millturn. and he said he very rarely uses them on the WFL. The Inconel part [ as an example ] in my album "various heavy stuff " was done completely on the WFL and no er's were used in the milling operations, it was was all Albrecht chucks on HSK T 63 and HSK T 100 fittings. The millers using the DMG Mori's use the er's for milling quite often for "normal " milling but also use Albrechts or Shunks for high feed milling. as the er's would struggle with that. So really I should have specified that scenario in my original post, therefore I am guilty of not being clear on what I meant.. Of course that is a world away from us hobbyists, but I still like to find out why things happen

cheers

Edited for a missing word.

Edited By Raymond Anderson on 24/09/2016 07:32:50

[AjohnwParticipant @ajohnw51620]

Posted by Mark C on 23/09/2016 23:17:40:

John,

You need to read ALL of the posts to understand this thread before you jump in.

Mark

i have read most of them Mark. Posted more because I am amazed that this thread collects more and more posts.

I did mention get real previously and why.

John

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[Neil WyattModerator @neilwyatt]

I have read all the posts in this thread.

It strikes me that the problem is there are two debates going on at once.

One is an essentially academic discussion of the technical aspects of ER collets. A discussion marred, I think, by a failure to explain how and if workholding and toolholding loads vary and simplifying the loads to just radial and axial while essentially ignoring torque and the impact of cyclic loads, both of which are particularly important in this context.

The second debate is a practical one, where the conclusion has to be that whatever the theoretical shortcomings of the ER system, they remain the most practical and cost-effective solution to accurate tool and workholding for most people.

Neil

[John Stevenson 1Participant @johnstevenson1]

Bingo ! ! !
Give that man a prize off the top shelf.

Neil, you have said in one post what everyone else has tried to say in 300 pages

[AjohnwParticipant @ajohnw51620]

There is an outfit called Niken that make a style of milling chuck for high radial loads. I would say that it is only of academic interest to people on here. The one they do that isn't is also pretty good but again only really of academic interest. I have seen similar systems in use. As I see it of little interest really unless some one has rather a lot of HP.

**LINK**

John

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[Chris TriceParticipant @christrice43267]

Posted by John Stevenson on 18/09/2016 18:59:04:

Oh I'm pleased that has come up on this thread.
I'm 99.9% sure that's me.

But for the record I stated that Myfords are over rated and are living on a name. A point of view I still hold. A Boxford for example is a far better lathe and can be bought for half the price.

That would be a valid opinion no Myford owner should take offence at but…

"Chances are though that the new owner would have ripped everything off as it wasn't genuine Myford, filled all the holes in and painted it back to colour me standard.

All the while muttering about bodgers and heretics and why could he not have left it standard as Myford's MUST have known what they were doing [ if so it was a first ]"

That offends all Myford owners. There are more examples but I have neither the will or time to search out other swipes. This is why I don't come here anymore or buy from Arc Euro Trade.

[HopperParticipant @hopper]

I think this might sum it up reasonably well:

Where "Allowed Region" refers to the size of the head of the pin, I believe. But I may be wrong.

[CirclipParticipant @circlip]

Hope after twenty days and twelve pages someone can reach a reasoned choice? It wouldn't have lasted two years in PMs day.

Not as good as an Autolock but better than a drill chuck and far better than a three jaw and quicker than a four jaw.

Regards Ian

[AjohnwParticipant @ajohnw51620]

The only real problems with Myford 7's is that they do not wear well Chris. In original condition they are excellent lathes in a number of areas. Very precisely made like all of their kit. It comes at a cost though and restoring to original condition is not a trivial task for the vast majority of people. Once they have signs of wear it's a matter of degree.

Boxfords were more expensive until the ME10 cropped up. That seemed to happen when they changed the design of their main machine and used them to use up old parts stock. However I have a feeling that a brand new spanking ME10 was still a bit dearer than some Myford 7's but probably cheaper when all singing and dancing versions were compared.

The Boxford's do wear pretty well down to the design of the lathe bed – vertical prismatic V's like the majority of lathes. These wear as well and given enough use the bed wear will cause the lathe to turn a taper but unlike Myfords unless it's incredibly bad no other user problems. A big plus is headstock bearings that can be fairly easy to replace. Neither of the Myford 7 arrangements are so simple and the super 7 is worse than the plain bearing ML7 in that respect. The catch with a Boxford is adjusting them but that's not too bad but there are better arrangements. Unusually Boxfords also follow the better precision lathe design in terms of the saddle guides. Not in the area of headstock bearings though.

JS is I suspect talking used machines and it's a fact that if some one is seeking perfection both need checking over rather carefully. Both types can see a lot of use even ME10's. What JS means I think is that people have been prepared to pay too much for Myfords that are in a dubious condition and Boxfords may be too but are less likely to cause owners user problems such as parting off or heavier turning etc. In fact if the headstock bearings are in decent knick and the rest of the lathe adjusted correctly they will give a pretty decent finish but not up to the same standards as a perfect super 7 – if one can be found and can also be adjusted perfectly when it's actually being used.

John

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[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Stevenson on 24/09/2016 10:55:36:
Bingo ! ! !
Give that man a prize off the top shelf.

Neil, you have said in one post what everyone else has tried to say in 300 pages

.

I agree entirely [except that 300 should read 12]… and therefore can we please recognise that Neil's 'second debate' is closed; Q.E.D.

Neil's 'first debate' however, remains of interest to some of us … So could we please continue that without the 'noise' of "but they work for me" etc. etc.

We know that they work 'well enough' for most jobs; but a few of us are interested in how & why they might behave at the limits.

MichaelG.

.

P.S. The title of this thread is "Pros and Cons of the ER collet system" … The Pros are widely accepted, the Cons remain of interest.

[Raymond AndersonParticipant @raymondanderson34407]

Hopper Not being funny but what is an "angel " or is it just a slight typo. I don't pretend to understand it, but i'm sure some will [understand it }

John S and Neil, Now at least we are getting a bit clearer and just to finally take away any grey areas that are left.

I use the er's for workholding and they are fine, but as I said earlier to John I find it a pain in the backside to have to turn a "plug " every time I want to hold a short part . Which is why I am going to upgrade to one of the "C " types or [ once I have done a bit more research] possibly to one of the "multi bore " types. I like to be able to pick up a collet of the size needed and insert the part and go, not farting around doing another operation just to get the part held correctly. Now that might just be me that feels that way ,I don't know. So to that end there are better suited systems as even Rego Fix say.

Point 2 [ now I feel this is where we are going off in a tangent ] I have said it before and I will say it again the er system is perfect for our needs. and I use it a lot,it's great, no argument there. But when I say it;s not the best system at HEAVY Radial loads of course i.m not meaning at our levels, because I had already said it's perfect for our needs. I was [ am ] merely, pointing out a fact . and has been verified by various makers including Rego Fix themselves. and,according to Rego Fix and the others the radial situation at Heavy feeds is directly related to the torque that the cutter is gripped by . I have presented the makers data including from Rego Fix. What more do people need ? This radial situation does not affect us but it was interesting to discover what causes it

Talking to some of the millers using the 2 DMG Mori DMU 600's [ amongst other types ] and they all say the same they never use er's for HPC / HPM simply because they are not designed to handle that type of loading. Of course they use them for lighter loads It is also a fact the Albrecht is so rigid and precise that there is no need to switch to an er for finishing.

The thread has been pulled twisted and twirled around that it is becoming a problem to understand and "yes " I am guilty of not being more specific. although Mark C and a few others managed to see what I was trying to say.

I will try and be more specific in future to try and avoid this debacle [although it is still an interesting thread for me and a few fellow curios types ] So thats my points cleared up because I am at a loss as to HOW make them any clearer.

cheers

[Raymond AndersonParticipant @raymondanderson34407]

Just noticed you're post Michael re the cons The biggest one and really the only one [ for me ] is this turning a plug every time I want to hold a short part . I just don't like it, in fact detest would be a better word, and am switching to a true workholding type [ after some research, and brain picking ] I dont have a problem with them in any other aspect.

cheers

[Michael GilliganParticipant @michaelgilligan61133]

My summary of where I think we've got to, in the 'first debate':

• The 'high-end' manufacturers all agree that ER is best suited to axial loads, like drilling.
• ER is, however, in fairly wide use for milling operations which generate side-loads at the cutter.
• Such use is considered sub-optimal by those 'high-end' manufacturers.
• We are trying to understand why.
• Practical tests have demonstrated that there are two regions of 'grip" [i.e. front and rear of the collet], with a 'no-grip' region between them.
• There is some debate about whether these regions qualify as points or lines, but that may depend upon the clamping pressure.
• Finite Element Analysis is, by definition, an approximation; but Mark has provided an excellent model to which we can refer.
• There has been some confusion of terminology, notably in the matter of 'radial' loads.

MichaelG.

[Raymond AndersonParticipant @raymondanderson34407]

That is well clarified Michael. Now we will mean a sideways loading for the Radial loads. Re the clamping pressure on Nick and I's tests That is why I mentioned to Nick about how do we know how much torque was applied was it correct for the Ø or over [ don't think it was under ] And if at the correct torque will the point contact increase? What would happen to the contact points if it were over torqued ? That is what I find interesting and would like to know. According to Rego Fix themselves the transferable torque has a big say in this as has been remarked at by other makers. I have to applaud Rego Fix for being so open re the Radial situation. I do know they have a new milling chuck called [I think ] POWRGRIP.

I think I am going to find out the specified torque for a 20- 21 Ø and a 19-20 Ø collet and I have access to a Stahlwille Digital torque wrench and I am going to use the test bar and a couple of new collets and OVER torque the closer to see what happens to the contact points. Will have to get a couple of new collets first.

[John Stevenson 1Participant @johnstevenson1]

Posted by Raymond Anderson on 24/09/2016 13:35:39:

John S and Neil, Now at least we are getting a bit clearer and just to finally take away any grey areas that are left.

I use the er's for workholding and they are fine, but as I said earlier to John I find it a pain in the backside to have to turn a "plug " every time I want to hold a short part . Which is why I am going to upgrade to one of the "C " types or [ once I have done a bit more research] possibly to one of the "multi bore " types. I like to be able to pick up a collet of the size needed and insert the part and go, not farting around doing another operation just to get the part held correctly. Now that might just be me that feels that way ,I don't know. So to that end there are better suited systems as even Rego Fix say.

cheers

.

So as not to muddy the waters anymore on this subject but wanting to address the above quote from Raymond I will shortly start a new thread, probably called Holding short lengths ? once I have sorted some pictures out.

[Raymond AndersonParticipant @raymondanderson34407]

Yes John that would be excellent,. as I detest turning a plug. that's my only "bugbear " with them.

cheers

[John Stevenson 1Participant @johnstevenson1]

OK, working on it but struggling for some pictures as I'm not at the workshop, bear with me.

[Raymond AndersonParticipant @raymondanderson34407]

No probs, just when you get a chance.

cheers

[AjohnwParticipant @ajohnw51620]

I suspect thing have gone astray due to some person somewhere stating that ER is not suitable for milling because of side loads. I'd be inclined to say twaddle to that. Any effect has to include metal deformation so there would be little difference on any holding system. There would be more need to be concerned about the tool bending in a typical sensibly sized chuck. Many morse taper collet chucks aren't terribly sensible. It's also an odd thing to say about a system developed from E collets and aimed at tool holding. I wonder what type of tools? Pick axes maybe ? Not drills either. Curiously drill chucks are mostly used for that.

Point contact at some degree of precision is a fact of life with any collet system tool or work holding.

I have read some where or the other that ER are ok providing circa 2/3 of their length is engaged with work or tools. More dubious on the later. Obviously ideally they need the work to pass completely through them. They are not going to bell mouth unless there are metal deformation effects. The back end isn't even going to bend unless some of that is going on at the front end as the front will stop the collet from going in further. So some reduction in grip length shouldn't cause any problems. 2/3 for work holding maybe even a bit less should be ok.

Anyway the above put me off ER40 or bigger as there were obvious problems at smaller sizes. You could say that the xx in ERxx is roughly the min grip length.

Work holding collets are likely to have a grip length of around 2 diameters, decent ones anyway for alignment purposes. I have seen set go up to pretty large sizes by 1/64" and then switch to 1/32". Then there is square and hexagonal etc. A lot of collets. To my mind a mixed set of various ER types makes more sense. I don't think that a complete set of ER40 makes any sense at all. It makes more sense to have more than one chuck. Plus on milling if head room can be a bit of a problem at times a few collets that fit directly into the millers spindle. I have ER16 and 25. If buying again I would probably make it ER16 and ER32 for sizes over what the 16 can cover. 32 because that is what can pass directly through my lathes spindle. True I might buy a complete set of 32 but wouldn't be loosing my ER16's.

As it turns out i have a multisize collet chuck as it was at the right price and it does have a reduced grip length at some smaller sizes. So ok even though JS wont use his. Some reckon that they are the most accurate of the lot. Pass but if made in the right way they could be so who knows.

John

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