# ER collets vs. R8



## Pcmaker (Sep 25, 2018)

I have PM-25MV mill and it uses an R8 collet. I remember before buying the mill, some posters recommended going with ER collets. 

I don't know too much about ER collets, as I see way too many of them ER numbers. ER32, ER8, ER11...

What's the difference between those?

right now, i have 1 `12 piece R8 collet set

Is it easier to swap tooling with ER? Which ER number is the one to get? Is it compatible with R8?


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## T Bredehoft (Sep 25, 2018)

Stay with the R8 collets. While an ER collet system can be used with your R8s, it would be a duplication of effort and would subtract at least an inch from the collet to table distance. All collets are for holding round things, the cutters you will be using in your mill all have round shanks, that are standard sizes. An ER32 collet (size wise) would duplicate the R8 collets you already have.  
Swapping tooling. you will have to put a wrench on the top of the draw bar to release the tool and another on the collet holdelr for either set up. 
The only advantage I can see is that the ER collets are about 1/3 the length of the R8 collets and would be somewhat easier to  change.


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## dtsh (Sep 25, 2018)

In general, ER collets have a larger clamping range, approx 1mm, in comparison to many other collet systems, which I think is why many prefer them. There are other benefits as well, such as having a through hole so that you can work on stock which is significantly longer than the collet - you can't do that in an R8 collet.

As for the various ER sizes, it depends on the general size of work you do which would be preferable; I prefer ER40, as the largest collet size is close to the hole through my lathe's spindle. If I chose a smaller size I would limit myself on max diameter and chosing larger I'm not really gaining much....for what I do.

I also have r8 on the mill and I use them quite a bit, but due to needing a drawbar, no through hole, etc, I don't see them as especially useful elsewhere. I don't tend to use my ER collets on the mill mostly because an ER chuck takes up height, I just go with the R8 there. For any given range, I need more R8 collets to hold the same range of sizes, but *for me*, I tend to use only a very limited number of R8 collets, though I use them very often.

IMO, each has advantages and disadvantages and serve differing functions in my shop. I don't often do much workholding in the R8 collets, instead it's toll holding which doesn't need the through hole. I often hold long stock in my lathe chuck, so the length limitation of R8 would be a problem. My collet blocks are ER40 to take advantage of the through hole and to take advantage of the collets I already have.


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## RJSakowski (Sep 25, 2018)

Here is what I said in another thread earlier today.

I use the Tormach TTS system on both my Tormach machine and my old mill drill.  In my mind, a quick change system has the ability to change tooling quickly and without losing tool height registration.  The TTS system uses the R8 collet to hold the 3/4" TTS shank and to draw the flange of the TTS holder tight to the face of the spindle.  Upon releasing the drawbar tension, a light tap on the drawbar will release the TTS tooling.The relatively short length (1-3/8") of the shank means minimal clearance is required for a tool change. 

I use the ER20 collets but holders are available for ER16 and ER32.   I also have a boring head set up for the TTS system and rnd mill holders for Weldon tooling.  When I need to use larger tooling, I can fall back to my R8 collets.  I use a digital dial indicator to set my tool height.  It is permanently set up in one of my TTS holders.  I set my zero height reference on my work and zero out my off side height gage with it.  Tool height settings are then done off side which means I can change end mills, drills, etc. without disrupting work in progress.

To effectively use the system, multiple collets and tool holders are required. Minimally, one should have enough holders to accommodate the tools needed to complete a job.  I have 16 collet holders, 6 end mill holders, and 6 drill chucks in various sizes.  Four are dedicated to an edge finder, the dial indicator, a laser centering device, and a simple point for rough x-y positioning.

As to disadvantages of the TTS system, the main one is that adding to the drive chain will necessarily increase runout. I suspect that rigidity is lost as well.  There is a cost factor because of the TTS tooling holders but ER collets are cheap compared to other collets.  I have multiple collets for the common end mill shank sizes as well as a full metric set for use with drills.


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## ttabbal (Sep 25, 2018)

If you already have a decent R8 set, there's no reason not to use them. I have an ER40 chuck installed in the Bridgeport as I have a larger selection of good quality ER40 and the chuck was a similar cost compared to filling in the gaps in my R8s with quality collets. I have some end mills that I lack R8 in the correct size for, so I usually leave the chuck in there and use the ER40s. I also already have the ER40s and a chuck for the lathe, which gets a lot of use. My collet blocks also use ER40 for the through hole capability as another post already mentioned. 

Rather than using the drawbar, you can change collets using a spanner on the ER chuck. Some people like this better, it's about even in my mind. I'm about 6'4", so the drawbar nut on the top of the machine isn't a big deal to reach up for. That could be a bigger issue for the more vertically challenged. A down side is you need more torque on an ER collet than you do with the R8. 

While the chuck does add some runout, it's a couple tenths in my case. That is acceptable for the work I do. If it ever isn't, I won't hesitate to get more R8s as needed. 

I don't notice any difference in rigidity, though I suspect it's there. I may just have not pushed things hard enough to notice. More stickout almost has to drop some rigidity. 

You do lose some space in Z as well, a couple inches. This isn't an issue for me, but I have a fairly large Z travel. It might or might not matter for you. 

If you were to use the ER collets, you would need to purchase ER collects AND an ER to R8 adapter chuck. In your case, I would say not to spend the money unless you were already buying the ER collets for another reason, such as the lathe or collet blocks. At that point, it might be worthwhile to have another option for tool holding in the spindle.


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## P. Waller (Sep 25, 2018)

R8 is a spindle taper, if your machine has an R8 spindle you have no choice outside of replacing the spindle itself.
You cannot directly place an ER collet in the spindle only a collet chuck with a taper that matches the spindle.
A better question would be What Is The Best Spindle Taper for a machine this size but I suspect that there is no choice.


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## Mitch Alsup (Sep 25, 2018)

Pcmaker said:


> I have PM-25MV mill and it uses an R8 collet. I remember before buying the mill, some posters recommended going with ER collets.
> 
> I don't know too much about ER collets, as I see way too many of them ER numbers. ER32, ER8, ER11...
> 
> What's the difference between those?



If you consider exactly 1 machine, you get collets to fit that exact machine.
If you have a variety of machines, and fixtures, then you may (MAY) have other options.

For milling with an R8 head, R8 collets give you the most nose space on the mill. {nose = maximum height between quill and table} The smaller the mill the more this parameter maters.

You are not going to find an R8 square or hex collet blocks, you get to choose MT3 or ERxx (typically ER40). You use these to mill square or hex heads on turned screws and bolts.

Nor are you going to find R8 on your lathe--they are almost invariably MT-based. 

However you can find MT3-ER40 lathe adaptor, and you can find R8-ER40 mill adaptor, and use ER40 collet blocks in all of them. So, it is possible to standardize on one kind of collet and use adaptors for the various machines. If you do this, you typically lose 0.000,5" in concentricity (minimum) over using the R8 collet in the R8 milling head or MT3 collet in the lathe.

It is your money, invest wisely.


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## ddickey (Sep 25, 2018)

Looks like the R8-ER32 holders are much smaller. Largest size in ER32 is 7/8". Probably the biggest you'll ever need on the mill.
If I decide to go this was ER32 is what I will get.


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## Cooter Brown (Sep 26, 2018)

I love my ER40 collet chucks.....


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## Pcmaker (Sep 26, 2018)

I guess that's a no then. 

I'll just have to get more R8 collets for in-between endmill sizes.


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## mickri (Sep 26, 2018)

I went with ER32 collets.  I have an r8 to er32 adapter for the mill/drill and mt2 to er32 adapter for the lathe.  I plan to either make or buy an er32 collet chuck for the spindle on the lathe.  I went with the er32 metric collets because the spindle bore on my lath is 7/8 which is just under the maximum size of er32 collets and unlike imperial er32 collets there are no gaps in coverage with the metric er32 collets.

I can't easily reach the draw bar on the mill/drill.  So tooling changes that require loosening the draw bar are a PITA.  I have found that changing er32 collets is a breeze.  No big deal.  Everybody seems to mention how tight er32 collets need to be and that they are hard to tighten.  I have not found this to be a problem.  But then I have a very large wrench that fits on the collet chucks.  There is something to be said for leverage.

The biggest advantage to using er32 collets is on the mill/drill.  I have found that I rarely have to raise the head to change tooling.  Unscrewing the collet nut provides more than enough room to change tooling.  I am thinking about buying more collets nuts so that the collets I use the most will have their own collet nut.

ER32 collets have worked very well for me.


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## P. Waller (Sep 27, 2018)

I used a Bridgeport mill today that employed a system that uses a retention knob on the end of the tool holders, it was fast.

It does not use R8 collets only R8 tool holders but I imagine that ER collet holders with the modified R8 taper drawbar system are easily purchased.
Someone above has mentioned this, I do not know what it is called.
The tool holders look like this



The key way is not used, I suspect that the tool holders and mechanism to hold them will cost a good deal more then many hobbyists would like to spend, it is a slick system for light milling however.


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## mikey (Sep 28, 2018)

Pcmaker said:


> I have PM-25MV mill and it uses an R8 collet. I remember before buying the mill, some posters recommended going with ER collets.
> 
> I don't know too much about ER collets, as I see way too many of them ER numbers. ER32, ER8, ER11...
> 
> ...





Pcmaker said:


> *I guess that's a no then.*
> 
> I'll just have to get more R8 collets for in-between endmill sizes.



I think you need to re-read the responses and then learn about the difference between the R8 and ER systems before making a choice. There are advantages and disadvantages to both. 

The R8 system is great if minimizing loss of Z-space is your main concern. It is also very easy to change tooling - just loosen the drawbar, give it a whack to disengage the tool, change the tool, re-tighten the drawbar and you're off. Run out with R8 collets varies with the maker and at the hobbyist level it should be just fine. Truthfully, you really only need the common collet sizes to fit your tooling. I would imagine that the largest tool your lathe can handle is maybe 1/2"; a 3/4" end mill would be pushing the limits of what your mill can handle, I think. So, if you had 1/8", 3/16", 1/4", 3/8" and 1/2" R8 collets then you could probably handle almost any end mill you're likely to use. You do NOT need every possible size collet.

Go and look up info on the ER system; don't just ask here. The different ER systems vary in their clamping ranges, primarily. So, why even consider an ER system if all you do is give up headspace due to the chuck hanging out there? Well, ER collets have the potential to be very accurate; they are the commonest tool holding option in the industry for a reason. They also damp vibration better than any other system in widespread use and that affects finishes, tool wear, tool life and accuracy. While an ER collet can clamp down on a range of tool shank sizes and has a range much broader than an R8 collet, the ER collet is intended to clamp most accurately on shanks very close to the stated size of the collet. That is, if your tool shank is 1/2" then a 1/2" ER collet will hold it very accurately. You can hold smaller shanks but run out will increase when you do. 

The key advantages of an ER system, again, are accuracy and vibration dampening. This has a direct bearing on tool performance, tool life, accuracy and finishes. For cutting tool holding, it is a better system. For holding other tools like drill chucks or fly cutters, the R8 system is fine. I have and use both systems and I use them exactly this way. In reality, the choice of systems is not an "either/or"; it is a "both/and" but as always, it is your choice.


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## ddickey (Sep 28, 2018)

One thing about drill bits is unless you use a common size you won't be able to hold in an R8 collet. Same goes for a tap, shank sizes are not common.
That's an advantage I can see for an ER system.


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