ER collets

[phantomcow2]

I see often people using ER type collets for their mills. Why is this?
I currently use regular r8 collets for my X3 mill, they work fine. But I see these ER40 collets that would fit my machine, but they are pretty expensive. What is the advantage to this collet system over the traditional collet?

[lakeside]

with er collect sizes have a range when made with r-8 co;;est it that size by 1/16

[big_mak]

R8 Collets fit R8 Spindles - ER Collets fit R8 adapters CT BT NMTB HSK KM and a myriad of other Adapters, so a set of collets could cover a few machines in a shop, provided each had the corresponding adapters.

We pretty much use ER Collets exclusively because of the accuracy. These Collets collapse ER 16 range of compresion is 1mm for sizes larger that 1mm. I've found that the holders for ER collets are more compact that that of say TG collets.

[dertsap]

er are the most accurate out of any holders that ive ever used including shink fit and hydraulic which are hieghly over rated and over priced

[Geof]

I see often people using ER type collets for their mills. Why is this?
I currently use regular r8 collets for my X3 mill, they work fine. But I see these ER40 collets that would fit my machine, but they are pretty expensive. What is the advantage to this collet system over the traditional collet?

One advantage to ER over R8 is that there is a stop screw inside the body of the ER holder (or there is in all the holders I have). This means you can always insert the cutter to the same position each time which is not the case with R8. Also the ER collets have a gripping range of 1 mm (0.03937") so you can get by with fewer collets (sometimes) and you can grip sizes that are not even sixteenths which is the case with R8.

A disadvantage that I see with using an ER holder in an R8 spindle is that the end of the tool is much further out from the end of the spindle. When you are using larger tool sizes, above 1/2" for instance, and taking aggressive cuts this could mean you do not have enough rigidity.

[GBeaman]

We use the ER 16 collets on our cnc machines for sizes up to 3/8" and 1 inch series acura flex collets after that. We still use R8 Collets in all of our manual mills. I think most of the ER collets are being used in CNCs rather then manual type mills. The ER collets are nice for putting drills and reamers that don't have nominal shank sizes, they grip well and run very true even when collapsed 40 thou. They do make larger sized ERs but we just fell into what someone else had already decided on. Hope this helps.
-Greg

[phantomcow2]

So what makes the ER collets more accurate? Is it just typically higher quality collets?
I would need the ability to hold from a 1/8" shank to a 1" shank ideally. A problem I had when I tried the 1" r8 collet is that it only holds onto about 1" of the shank, the shank is 2" long. Plus the gripping is not indside of the collet, so it does not grip it well. The cutting action is something like 6" below the spindle. All of this made for pretty lousy performance at .025" depth of cut in aluminum. I've used this same end mill with an endmill holder with good performance. How does the ER compare?

[dertsap]

tg holders would probably be your better bet if you are wanting to hold larger tools , the collet is longer so you will gain more contact around the shank ,along with the lesser angle of the collet things should be more rigid