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ER Collets

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Enough!09/01/2011 22:50:42
1719 forum posts
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I read that ER collets have a grip range of about .03".
 
Does this mean:
 
nominal diameter +/- .015" ((e.g. a 1/2" collet would go from ..485 - .515")
or nominal +.03" (e.g. a 1/2" collet would go from .500 - .530")
or nominal  -.03" (e.g. a 1/2" collet would go from  .470 - .500")
 
 
Keith Long09/01/2011 23:04:35
865 forum posts
11 photos

According to the data in the MSC/J&L catalogue the collets can collapse by (normally) 1mm or 40 thou. The small sizes can only collapse by half that, while ER50 collets can manage twice that. So it's nominal size - minus.

Keith


Enough!10/01/2011 00:44:50
1719 forum posts
1 photos
Thanks, Keith. I thought it would probably be nominal - minus.
 
So it sounds like .03" would be about right for ER25.
 
I only have a metric set and it helps to know what size to use for inch sized tools or material.
John Olsen10/01/2011 02:58:31
1197 forum posts
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If you have the full set with no gaps, just find the smallest collet that the piece will slide into with no force, eg an easy sliding fit. This is done before mounting the collet in the chuck. You only need to be concerned if you haven't got the next size down, in which case you should check that the piece is not too small for the one you do have.
 
In effect, I am saying use the collets themselves as gauges.  They must not be sprung outwards, but will spring in to meet the maximum of the next one down.
 
regards
John
Chris Banninger10/01/2011 11:51:00
12 forum posts
The today most common "double taper double slit" ER25 collets with 12 slits, 6 from the front and 6 from the rear, have a COLLAPSING range of 1mm for all sizen down to 2mm. Sizes below 2mm nominal diameter have a collapsing range of 0.5mm. Early style ER collets of some 30+ years ago had less slits and only 0.5mm range. You can instantly ruin an ER collet by forcing it to clamp oversize: for example, a 10mm collet can clamp anything between 10 and 9mm, but is damaged if made to clamp 10.1mm.

ERcollets were invented by the Swiss Rego-Fix. Originally for toolholding, but they are also suitable for workholding, albeit not for uses that require "dead length" repetability. Meaning that the lathe workpiece moves axially during clamping.

As a Swiss invention, ER collets are metric. And most ER collets available today are metric, even the popular cheap Chinese made ones with engraved imperial dimensions. Since you ask about in "Inches", I thought you should be aware of the disadvantages of using metric ER collets to clamp imperial tools or workpieces. For example: a 6mm shaft will fit perfectly into a 6mm ER collet, less than half a revolution of the closer nut will clamp or release the shaft, and contact area will be maximal (=maximal torque transmission and minimal runout). But clamping a 1/4" shaft (=6.4mm) into a metric series collet of 7mm diameter will require about 1.5 turns of the closer nut to clamp or release, and contact area will be much reduced.
If most you do want to clamp is imperial stuff, you really should get yourself some true imperial colletsts, not metric ER collets. There are true imperial ER collets made in the US, but these are rare and expensive and you need a larger number of them to cover gaplessly the whole claming range, because the most used fractional Inch diameters do not fit exactly the designed 1mm collapsing clamping range (there is some overlap). What I mean to say, if most you do is imperial, better choose an imperial design collet like c5 or the like. Yust a point to be aware of....
Chris  
 
Chris Trice10/01/2011 12:16:04
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Actually, you can get genuine imperial ER collets from the usual suppliers in the UK as well as metric ones. Arc Euro Trade springs to mind but there are others.
Chris Trice10/01/2011 12:18:49
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Edited By David Clark 1 on 10/01/2011 12:26:53

Terryd10/01/2011 12:41:42
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1936 forum posts
179 photos
hi There,
 
I have no experience of ER collets for holding milling cutters having always used Clarkson types previously, plus 5C collets for workholding on the lathe.  As I am re equipping my workshop I would like some advice on this matter.  Will ER collets hold milling cutters properly without the positive locking of the Clarkson type of holder? And can I use the same collet set for workholding?
 
Thanks in advance for any comments and advice.
 
Terry
John Stevenson10/01/2011 13:18:25
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Terry.
Yes and Yes.
I have read various forums about the gripping qualities of ER collets or lack of, in some cases but I have never come across it.
 
Just up the road from me is an Aerospace CNC machining company, they have about 30 CNC machines including some very large ones that do wing spars for Airbus and Boeing.
These start off with a slab of alloy 2 metres by one metre by 300mm which is loaded with a fork lift truck.
Eleven hours later one guy lifts this thing off on his own ! It uses about 30 tools to do this and runs unattended and also thru the night.
 
The profit margins on this job as so low they cannot afford to put an operator on it, aerospace is a very cut throat business. All the tooling is held in ER32 collets, in fact other than a bit of ER40 and the odd ER25 they have standardised on ER tooling.
 
If there was something better for the price, I'm sure they would be using it.
 
Clarkson's are good but have been pushed out of the market  by the modern chucks which are more freely available, cheaper and fit in with the tooling makers better.
 
No having to grind threads onto shanks and no wasted material making only 4 sized shanks regardless of what size cutter is needed. It's cheaper to buy say a 4mm or 5mm cutter with a 4mm or 5mm shank than one at 6mm and ground down but where are the 4mm and 5mm collets in Clarkson type ? They don't exist.
 
Industry drives prices.
 
And industry is using solid carbide and don't want to waste time or material making cutters to fit an obsolete holding system. Long - short.
 
John S.
KWIL10/01/2011 13:46:07
3422 forum posts
66 photos
Chris Banniger, may I suggest you read Rego-Fix's own data sheets as they quite clearly state that you can use the full clamping range, eg put a 12.2 in a 12-13 collet and still maintain concentricity. So there is no need to worry about putting 1/4" in a 6-7mm ER
Terryd10/01/2011 13:59:02
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1936 forum posts
179 photos
Thanks John,
 
Thanks for that advice it's just what I needed and makes up my mind for me, I'll go for the ER collets,  Probably ER32.  I do like the look of the system as such a wide range of collets are available and become economical when it can be used for both cutter and work holding enabling one to standardise.
 
Terry
JasonB10/01/2011 16:17:10
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Terry you may want to read the "Milling Chucks" thread. You will see their that I said similar to John S.
 
If you are just buying one milling chuck then an ER is the better all rounder IMHO, if you went for a clarkson you will find the need for an ER for plain shank tooling etc. You can also think about adding an ER chuck for the lathe that takes the same collets.
 
J
Terryd10/01/2011 16:45:36
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1936 forum posts
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Thanks Jason,
 
That confirms my decision,  As the milling machine and lathe I intend to purchase both have MT3 tapers I think that the ER32 range would suit my purposes best.  Your thoughts?
 
Many thanks
 
Terry

Edited By Terryd on 10/01/2011 16:48:32

John Stevenson10/01/2011 19:58:38
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Terry,
If you can see your way forward purchase two ER 32 chucks, one on a MT3 to suit your mill and a backplate mounted one for your lathe.
The reason being that although the MT3 will fit your lathe you will loose any long holding capability because of the tapered shank.
 
The backplate mounted option will allow up to 20mm thru the collets but this is also dependant on your spindle bore.
 
Another alternative is to turn an ER chuck up on your machines spindle nose to ensure it runs true.
 
John S.
JasonB10/01/2011 20:42:53
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Thats the type of chuck I was thinking of for the lathe, like john says it will allow longer items to be held which is where you need it more.
 
The only thing to consider re ER 25 vs 32 is the size of the collet nut, particularly when using small cutters you can find the nut gets close to hold down bolts or when using a 3-jaw on the rotary table mounted vertically the nut can get close to teh jaws or you need a lot of work protruding from the 3-jaw. I have ER 25 size and a few MT3 collets for larger items.
 
BTW the WM280VF has an MT4 spindle, you will want one of the short MT4 to MT3 sleeves that ARC sell to mount MT3 tooling.
 
Jason
John Stevenson10/01/2011 21:06:26
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Good point Jason about the nut, really down to personal choice.
 
I like those small ER11 chucks that Ketan sells for the little X0 mill
 
 
They are 16mm on the OD and will fit in a ER25 or 32 chuck.
This gives you the ability to hold small cutters and drills up to 17/64" or 7mm whilst keeping the nut away from the work.
 
They do run very true, I have a spindle speeded, 1:4 increaser on the big CNC on a 40 international taper, unfortunately it has a built in Clarkson collet chuck that can't be changed.
I use this for small drills usually 2.5mm and 3mm so I have one of the ER11 chucks with the Clarkson adaptor fitted, in fact I have about 4 or 5 to save changing cutters.
 
From the end of the spindle on the CNC to the end of a stub drill is 7" and no runout unless we start talking silly figures I can't measure,
 
Another thing to remember with ER collets is that 4 collets 7-6, 10-9, 13-12 and 16-15 will hold 8 sizes of cutter shanks, in fact all the popular sizes 1/4", 3/8", 1/2" and 5/8" plus 6mm, 10mm, 12mm and 16mm.
 
John S.
Terryd10/01/2011 22:13:01
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1936 forum posts
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Hi John and Jason,
 
Thanks for the much appreciated advice.  I had looked at the various options and now you have given me more food for thought.  Now I only have to wait until the builders get their act together and finish my workshop.  Folks who's magazine is a couple of weeks late are complaining.  I wonder how they would manage waiting for over 6 months for the insurance companies, loss adjusters and builders to get their act together.
 
Best regards,
 
Terry
John Stevenson10/01/2011 22:17:36
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Terry,
If it's not too painful what caused the fire.~?
John Olsen10/01/2011 22:38:05
1197 forum posts
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ER collets are only metric in the sense that the range they are specified to work over is metic, eg 6 to 7 mm for example. They neither know nor care if you think the piece of material is 1/4 inch or 6.35 mm. In my experience they will clamp well right down to the lower limit.I would not risk anything above or below that limit, they are too expensive to replace.
 
For work piece holding in the lathe, it should be possible with a backplate style of holder to make up a stop that goes inside the spindle and is adjustable. You do normally want the job to be the full depth of the collet holding area, so would need to make sure you did not set the stop so far out as to interfere with that. I have been thinking of this since I got my first set of ER16 collets, nearly 30 years ago, but so far have not done it, but it seems like a good idea....  It should also be possible to have a fixed depth stop inside  a taper mount for the milling cutter to butt up against, giving a consistent depth for each cutter. Again this would have to be clear of the deepest position a collet can get to.
 
My earlier collets don't have the self extracting feature, and these are not compatible with the later closing nuts which  do, so I bought myself a spare nut for that chuck. One has had the self extracting bit removed from it, the other has not. It is handy to use the self extracting when you can, as the only other reasonably nice way to get them out is to poke from the back with a bit of brass rod, which means taking the chuck off if it is a taper mounted one.
 
Locally one of the importers does sell sets of  ER25 or 32 with a chuck and the four common milling cutter sizes. It seems like quite a good deal pricewise. I guess some of the UK dealers may do the same thing.
 
regards
John
Terryd10/01/2011 22:43:33
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1936 forum posts
179 photos
Hi John,
 
Apparently it was an electrical fault in a fluorescent light unit according to the chief firefighter.   Most of my tool collection and models from my apprentice days onwards were lost. Together with a couple of Triumph Stags.   But it was one hell of a good way to cure woodworm.
 
Best regards
 
Terry
 
P.S. there are a couple of pictures in my albums if you dare look.  If Ketan from Arc reads this there is a picture of the remains of the Sieg C1 I bought from you just a week or so earlier among the photos.
 
T

Edited By Terryd on 10/01/2011 22:51:50

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