Pros and Cons of the ER collet system

Edited By John Stevenson on 05/09/2016 17:07:38

If I had a BT40 fitting I would. I can't modify my DW to take one.

The problem with ER for work holding is simply the grip length as it is with the Bernard multi size actually. Jacobs rubber are a touch better as they do shorten it on some of them.

The answer on ER is simple really. Have more than one size and use small for small and bigger where it's needed. Ok that means more than one collet chuck but given what many buy cost difference is unlikely to be that much. A full high precision set of ER40's is rather a lot of collets as well. Many probably wont get used and some will be used at larger sizes where a mm or so change of diameter wont make much difference to what ever is being made providing things are adjusted to suite.

While ancient milling cutter chucks may seem rather twee they do have a bit of an advantage. Easy to get cutters in and out, relatively little loss of headroom and good ones also run true. There is also the morse and R8 collet solution if the fitting is suitable.

Frankly I can't see how milling cutters can avoid being subject to both radial and axial heavy loads. ER still function with drills and slot drills in them.

John

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Edited By John Stevenson on 05/09/2016 17:45:53

First off John, Not being a designer I could'nt tell you how the Er's are at their best Axially and less so radially. I just know that is the case. You would need an "egghead " to give the calculations. And if the lad from Guhring mentioned it there must be something in it. Maybe all will be revealed once I hear back from Regofix. As far as the collet system goes I have already explained why I think there are better than ER's

I am going to try find the info I got a while back from Albrecht as regards milling chucks. In it they conducted tests using a ground 20mm Ø high tensile pin with a 18mm thread on the end. They then marked each pin with a scribe line and inserted them into each of the chucks Albrecht milling chuck , shrink fit and the ER. They then proceeded to apply a torque with a Stahlwille Digital torque wrench The ER let go at such and such newton mts The shrink fit and the Albrecht exceeded the torque of the ER and went past it until the nut sheared off and the witness marks had never moved. I have it on a brochure from Albrecht I will rummage about and try to put it up on here. Failing that I will see if Albrecht can give me some more info. Like I said I wouldn't profess to understand the calculations, some folks on here might certainly not me,. but there has to be something in it.

cheers.

I would have taken a few from you for the K & T but alas they are ISO 50. what a bummer. Yes that I think would count as Production.

Hi Raymond

Glad you like a debate.

The middle picture in the **LINK**

States for tools or materials, what ever that might be. We need M.G. to dig out the patent application that would stipulate what the original intention was.

Happy debating, must get my tea and get into the garage and make or mend something!

Cheers michael

Ajohnw, No one said the ER's didn't function.

So until someone does I for one am ignoring all the chaff

Michael Who is M G? And with respect there is no need for sarcasm!! if you want to join in the discussion fine feel free, or if not then do as you said, go and make or mend something. I have already seen that brochure and it does not tell me anything I didnt already know.

cheers

As a slight aside:

In a previous thread, Raymond linked to the ISO standard ... from which I quote:

________________________________________

INTERNATIONAL STANDARD ISO 15488:2003(E)

© ISO 2003 — All rights reserved 1

Collets with 8° setting angle for tool shanks — Collets, nuts and fitting dimensions

1 Scope

This International Standard specifies the dimensions, materials and manufacturing requirements, and designation of collets (of form A or of form B) for tools with cylindrical shanks and their corresponding holders and nuts. For non-standardized clamping devices, such as clamping devices specified in drawings, these holders can be agreed upon between customer and supplier.

Form A applies to milling and any other application where a hard collet bore is required, provided that the clamping range of h10 be sufficient.

Form B applies for general purposes where an extended clamping range is required.

__________________________________________

.

With all the interest in ER collets, it is surprising how little interest has been expressed in the difference between the two forms.

MichaelG.

[just stirring the pot]

Edited By Michael Gilligan on 05/09/2016 18:57:36

Ahh, So Mr Guhring and Mr Albrecht are only talking chaff Well in the words of Johnny Nash "I can see clearly now" . and here's me thinking they surely must know what they are talking about. well well, we live and learn .

cheers.

.

I'm guessing that I would be M.G. ...

In which case; what you actually need is to learn how to 'dig things out' for yourself.

MichaelG.

Hi Michael, I clean forgot about that Document.. Thanks,. maybe folks never realised there were 2 types.. I certainly didn't until I read the document.. The pot is going "still " now

cheers

May be of interest, seems the hydralic chucks slip first, the SX single taper is better and there BC best, no ER in that test

This one is the same guy testing a ER40 which outperforms the hydralic ones in teh video above

Jason, thats an interesting video. It was tests similar to those that Albrecht did, although I got it in a brochure not on a video. I am going to try find the brochure and also more about the SCHUNK Sino R Milling chuck.. both of which outperform the ER's, although us hobbyists will never use them. or need them. It is interesting.

cheers

The makers of those chucks here

Some good looking gear there. I have never heard of that make.. Another query, why do most manufacturers that put videos up on you tube nearly always show their Vmc's / Hmc's using milling chucks of various types but very little using ER. I wonder how that can be. just wondering.

cheers.

I would imagine the ER collets are just about as rigid as most other systems when used at their largest holding capacity. However, with the collet pulled further into its holder, as when gripping smaller tools or workpieces, the collets will have only line contact with the collet holder and the item being held,

The first picture is of a simplified holder/collet/tool setup and the second picture is my attempt to show where the gaps would be between the holder, collet and tool.

How much this affects accuracy or rigidity I don't know.

Martin.

Martin

As you show, when the tool (or work) is smaller than the nominal size of the collet it will only make line (hopefully broad lines) contact with whatever it is gripping. The OD of the collet though should still make full contact as it is a cone within a cone.

Ian

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The breadth of the lines will be determined by the compressibility of the materials

... If both collet and 'whatever' are very stiff materials, then contact will closely approximate a true line.

MichaelG.