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View Full Version : ER Collet for lathe use on short parts?



KEJR
06-08-2010, 09:23 PM
Hello,

I've dived into using an ER40 collet set on my home lathe to hold parts (logan 210). It works very well for pieces that are long enough to go into the collet a fair ways, but short pieces don't really work.

In alot of ways I'm kicking myself for not spending that money on a 5C collet chuck, but I digress....

Basically I've run into the problem where you try to hold a part feature that is short and the collet doesn't tighten up right. I've put plugs inside the back of the collet that match my work piece but unless you have plugs for every size you plan to machine I don't think this is even a good approach. I don't want to buy $800 worth of gage pins for every size from 0.120"-1.000" just to justify my $150 ER40 collet set!

Does anyone know of an adjustable plug that you can make fit your part (maybe a short expanding arbor or something?). Any other tricks to using these collets?

Thank you,
KEJR

Jim Shaper
06-08-2010, 09:33 PM
You could start by not abusing the collet set you bought and try something intended for work holding. :eek:

Andrew_D
06-08-2010, 09:36 PM
Can't say as I have run into this problem....I make sure that there is enough stock sticking into the collet to reach past the gripping area.

I can see where it would be a problem though for second-op work where the stick-out on the piece is short...the ER collet doesn't clamp evenly. Unfortunately, the only way to get it to clamp evenly is by introducing a spacer at the back of the clamping surface...just as you are doing.

Just had a thought...
If your collet chuck attaches to your spindle without a drawbar, maybe you can measure the distance from the left-end of your spindle to the back of the collet. Now cut a length of stock turned to the desired diameter and 1/2" longer than the measurement. Insert it from the left-end of the spindle into the collet. That should make it easier to handle than trying to deal with a small plug that might (will??) fall out of the collet each time you loosen the nut. Of course, you will still have to make a new piece every time you are dealing with a new diameter. Not sure how you would get around that one....

Andrew

oldtiffie
06-08-2010, 11:33 PM
Hello,

I've dived into using an ER40 collet set on my home lathe to hold parts (logan 210). It works very well for pieces that are long enough to go into the collet a fair ways, but short pieces don't really work.

In alot of ways I'm kicking myself for not spending that money on a 5C collet chuck, but I digress....

Basically I've run into the problem where you try to hold a part feature that is short and the collet doesn't tighten up right. I've put plugs inside the back of the collet that match my work piece but unless you have plugs for every size you plan to machine I don't think this is even a good approach. I don't want to buy $800 worth of gage pins for every size from 0.120"-1.000" just to justify my $150 ER40 collet set!

Does anyone know of an adjustable plug that you can make fit your part (maybe a short expanding arbor or something?). Any other tricks to using these collets?

Thank you,
KEJR

Too or very short stuff is potentially a problem for any collet - and any chuck.

The best solution is soft jaws on a 3-jaw chuck.

Black_Moons
06-08-2010, 11:39 PM
Simple solution: just cut another 1/2" of stock off after turning to the diamiter of your work. make plugs as needed.

jugs
06-09-2010, 03:07 AM
Simple solution: just cut another 1/2" of stock off after turning to the diamiter of your work. make plugs as needed.

Thats what I do, but make it like a top hat & use blu tac to stop it dropping out.
store them in a block of polystyrene (write the size on).
john
:)

MuellerNick
06-09-2010, 03:22 AM
A ER collet isn't intended for that kind of abuse. ;)
They work perfect as long as the material sticking inside is at least as long as the collet.
Collets that are only half slit (only from one side) work better.
But for short parts, collets like these (http://schmuckwerkzeug.de/F-Lorch-Stufenfutter-Stufenspannzangen-10-St-8mm-Schaft) were invented. Maybe you call them stepped collets, I don't know. They are not so easy to get.


HTH,
Nick

oldtiffie
06-09-2010, 06:02 AM
Thanks Nick.

Here is the Google translation German >English of that link:
http://translate.google.com/translate?js=y&prev=_t&hl=en&ie=UTF-8&layout=1&eotf=1&u=http%3A%2F%2Fschmuckwerkzeug.de%2FF-Lorch-Stufenfutter-Stufenspannzangen-10-St-8mm-Schaft&sl=de&tl=en

So far as I am aware, those collets are available from Hardinge and "Royal" (Sp?) and would be for R8 or C5 perhqaps - and MT? I don't recall seeing them in ER collets.

DR
06-09-2010, 07:42 AM
As has been mentioned, get a work holding collet.

The 5C is the most common, although the Logan spindle probably is not large enough to have the collet inside the spindle like it should.

The ER collet as a work holder is mostly a "hobby" thing. I don't recall ever seeing them used this way until recent years. And, never in production shops.

jugs
06-09-2010, 08:20 AM
A ER collet isn't intended for that kind of abuse. ;)
They work perfect as long as the material sticking inside is at least as long as the collet.
Collets that are only half slit (only from one side) work better.
But for short parts, collets like these (http://schmuckwerkzeug.de/F-Lorch-Stufenfutter-Stufenspannzangen-10-St-8mm-Schaft) were invented. Maybe you call them stepped collets, I don't know. They are not so easy to get.


HTH,
Nick

Agreed BUT In a jobbing shop, where you may be doing only 1 or 10 off, if you havent got a 5c that size but an ER that fits..... Collets should be treated as disposable items & replaced when worn.
:)

DR
06-09-2010, 01:16 PM
Agreed BUT In a jobbing shop, where you may be doing only 1 or 10 off, if you havent got a 5c that size but an ER that fits..... Collets should be treated as disposable items & replaced when worn.
:)

The way I do it is using 5C emergency collets bored to size. We are a job shop.

Over the years I've accumulated probably a hundred or more soft collets. When an odd size or short part comes in we bore the collet to fit.

Start with small parts on a new collet. As other jobs come in over time we keep boring it larger and larger until it's used up. For the fairly expensive Hardinge soft step chuck collets (2" and up in size) I've been known to weld in inserts to reuse the collet.

Thomas Staubo
06-09-2010, 05:09 PM
Here is the Google translation German >English of that link:
http://translate.google.com/translate?js=y&prev=_t&hl=en&ie=UTF-8&layout=1&eotf=1&u=http%3A%2F%2Fschmuckwerkzeug.de%2FF-Lorch-Stufenfutter-Stufenspannzangen-10-St-8mm-Schaft&sl=de&tl=en Sometimes (most of the time with technical language) Google translate is NOT your friend :D.

Stufenspannzangen = stage riser clamps? I think not!

I believe these (http://schmuckwerkzeug.de/bilder/produkte/gross/1539_F-Lorch-Stufenfutter-Stufenspannzangen-10-St-8mm-Schaft.jpg) are called pot chucks in English. Yes?


.

oldtiffie
06-09-2010, 05:50 PM
Thanks Thomas - points noted.

But as I don't have a clue about any language other than English any usable translation is better than none - mostly - as I can usually work it out from the context once I 've got a usable start.

I can even make a lot of sense from "Chingalish" - at last - but it took a lot of time, effort, frustration and heart-ache.

After that effort "Google" translation looks pretty handy to me.

oldtiffie
06-09-2010, 05:57 PM
All or any of these "pot chucks" (thanks Thomas) are OK if and only if you have the adaptor for them on your lathe.

I can't see why soft-jaws on a 3-jaw chuck are not considered as a good solution. If you have a 3-jaw chuck that can take soft jaws you have all that you need. Making or buying the soft jaws is quite feasible and very practical.

Further, you can leave the job in the soft jaws and remove the chuck from the lathe to the mill and back again if needs be. Most "pot" collets don't have that portability.

GadgetBuilder
06-09-2010, 10:05 PM
Like KEJR, I got an ER collet set but in my case it is used for long items where the stock protrudes into the spindle. The answers in this thread indicate using ER's for short items may not be the easiest approach.

To hold short items I make pot chucks to fit into my 3 jaw chuck, basically split sleeves with a shoulder on the outer end for alignment. If marked so their orientation vs the jaws can be repeated they typically have about 1 thou runout. It takes a little time to make them but I am slowly building a small collection so I do get to re-use them occasionally.

See: http://www.gadgetbuilder.com/MiniMods.html#PotChuck
The examples shown are for very short items but I now have some for longer items with smaller diameter - works well for them too although there is a lower limit dictated by the thickness of the slitting saw.

John

MuellerNick
06-10-2010, 02:36 AM
I didn't expect anybody to understand the German description. But a picture is worth a thousand words. ;)
And, there is absolutely nothing wrong with soft jaws!
And for a quick job, you can always turn something that looks a bit like a collet and goes into your chuck. You do have a lathe and I bet a saw too to slit that collet.


Nick

derekm
06-10-2010, 07:22 AM
The gripping length on an ER40 is long. if the diameter is less than the ER40 capacity try a smaller ER chuck... e.g. ER16. You can hold a straight shank ER16 chuck in the ER40.

Er16 holds up to 10mm dia.
You can get an ER16 and collets for circa 50$.

S_J_H
06-10-2010, 08:58 AM
I honestly have not run into any issues using short stock with my ER collets.
I use them for tooling on my mill and work holding on my lathes.
I also find they grip tighter than R8 collets on the mill. While I have had solid carbide end mills pullout with R8's I have not had that happen with the ER's.

I have not run into any issues holding short stock on the lathe. Stock of 1/4" or so in length is not any trouble. The ER collets grip tight without marring or distorting the stock.
All of these mini brass gears were held in the lathe with my ER32 collets-
http://i109.photobucket.com/albums/n48/S_J_H/misc/pmrlatheprogress003.jpg

I will usually use a rod through the left end of the headstock to help position the stock when it is very short. If the stock is near the limit of the collets closing range I will then turn up a plug for the end of the collet out of some scrap. But typically I don't find the need to do that.

I have ETM brand of ER collets which are very good quality.
For real tiny part or tool holding I use ER11 collets with a 1/2" diameter straight shaft chuck.
http://i109.photobucket.com/albums/n48/S_J_H/er11spindle005.jpg

Steve

Paul Alciatore
06-10-2010, 12:21 PM
Hello,

.........

Basically I've run into the problem where you try to hold a part feature that is short and the collet doesn't tighten up right. I've put plugs inside the back of the collet that match my work piece but unless you have plugs for every size you plan to machine I don't think this is even a good approach. I don't want to buy $800 worth of gage pins for every size from 0.120"-1.000" just to justify my $150 ER40 collet set!

Does anyone know of an adjustable plug that you can make fit your part (maybe a short expanding arbor or something?). Any other tricks to using these collets?

Thank you,
KEJR

Just a thought as I have never tried it, but ET collets will grip a range of diameters. It seems reasonable that the two ends would actually grip slightly different diameters. Instead of a full range of plugs, perhaps you would only need plugs at 0.004" to 0.008" steps. That would greatly reduce the number of plugs you would need to keep for situations like this.

I have yet to get a set of larger collets for my lathe. I have a SB-9 and it's collets only go up to 1/2". I have been debating between 5Cs and ERs. I hadn't considered this drawback of the ER collets.

KEJR
06-11-2010, 12:49 PM
Thanks all for the comments (although I really don't think I'm abusing my collet set since I haven't cranked down on any short parts yet...)

I do now wish I spring for the 5C collets and the 5C chuck for my lathe. I've even been looking to see if I can upgrade to a larger spindle. I've used 5C collets on Hardinge HLV lathes and it is a beautiful thing.

I don't want to use a 3 jaw unless it was a run tru type since if you machine something and then flip it around you have largely mismatched TIRs on your features unless you start marking the parts and going through all that trouble.

Most of my work is 1" and under, so I thought the ER collets would be good. I hadn't considered the short work holding aspect, which does work very well with 5C collets. BTW, I'm talking about "reasonable" short lenghts, like 1/16" to 0.25". I've gotten away with this in the past with 5Cs, but I guess I cheaped out too much on the ER collets. I can still use them in my tailstock and my bridgeport.

I've thought of making plugs in the common sizes in steps of 0.005" or so. Its not ideal, but it might work for most applications. If you think about it, its similar to how a 5C collet works if you plug the back end. You can even picture a single piece with 0.005" increments stored with each collet (assuming you are using a collet chuck and you have enough room behind the collet).

Thanks!
KEJR

MuellerNick
06-11-2010, 04:16 PM
But you know, that the 5C-types only work good at their nominal diameter. The part is not held as good (or better perfect) as in a ER when you are off of the nominal diameter. ERs clamp 1mm below their nominal size.


Nick

John Stevenson
06-11-2010, 05:03 PM
The way I do it is using 5C emergency collets bored to size. We are a job shop.

Over the years I've accumulated probably a hundred or more soft collets. When an odd size or short part comes in we bore the collet to fit.



What money is tied up in these hundred or so. ?

What's wrong with soft jaws, they last far longer and ore more versatile and you can weld them back or weld / bolt new faces to them.

Paul Alciatore
06-11-2010, 06:38 PM
But you know, that the 5C-types only work good at their nominal diameter. The part is not held as good (or better perfect) as in a ER when you are off of the nominal diameter. ERs clamp 1mm below their nominal size.

Nick

Yes, the ERs will grip well over a 1mm range. But even so, they will grip better at the nominal size. When a smaller size is gripped, the area of contact is reduced because each of the fingers of the collet has an inner diameter of the nominal size but the work has a smaller diameter. So contact is increasingly concentrated at the center of the collet finger's center. Less area of contact equals less grip.

And even a 5C will grip a few thousanths under size. Of course, you will have the same problem I mentioned in the paragraph above. And in a 5C it will be worse due to fewer fingers in the collet.

Nothing's perfect.

KEJR
06-12-2010, 08:20 AM
But you know, that the 5C-types only work good at their nominal diameter. The part is not held as good (or better perfect) as in a ER when you are off of the nominal diameter. ERs clamp 1mm below their nominal size.


Nick

I appreciate all of your comments.

Maybe I've been lucky or am abusing the 5C collets at the shop, but I've been able to grip just about anything I tried with a 5C collet set in 1/64ths. I've not done a ton of work that needed super gripping capacity, and probably would make a special fixture, soft collet, soft jaw setup if I had a production job I needed to do. The problem is that for "one off" hobby work it can double your job time to make all this tooling.

I've also seen this of exerienced toolmakers that I know aren't gripping nominal diameters and they don't make special collets, just the 5C.

Neither of these collet types is perfect and will grip ideally on the diameter it was ground to originally. That doesn't mean you can't use it on something for a light grip to clean up a back face of a cutoff part, add a chamfer, etc.

I think with all of your help and reading my own typing I've convinced myself that even the import 5C 1/64th set is a better use of my time and money than trying to get the ER 40 to work for all cases.

I also am thinking of buying a 6 jaw "set tru" chuck for other oddball parts. They are more convenient than 4 jaws and hold thin wall parts better due to the three extra jaws.

I'll save the ER40 set for holding oddball tooling in my mill and tailstock where I need decent concentricity (reamers, odd size end mills, etc).

Thanks guys!

~Ken