Spindle speed

[mikey]

Thanks fellas for replying. My mill uses R8 collets currently. I would not use a drill chick to hold the cutter. So what you guys are saying is the standard R8 collet isn’t really sufficient enough for my mill and I should step up to the ER cutter? Or is the ER collets just needed for long reach applications?

The key reason I suggested an ER system for your application is because ER chuck/collets dampen vibration better than most other available systems. When using longish cutters, this matters. They also dampen shorter end mills and other tooling so its a good system. The collets are available in increments of 1/32" so just about any tool you are likely to use can be held accurately. These collets can compress down about 0.040" and still hold solidly, albeit with a bit less accuracy so small variations in tool shank size won't bother an ER collet.

Consider also that a high quality collet, like a standard model Rego-Fix, has a run out of 10 microns or less. Their precision collets have 3 microns of run out. I don't know what an R8 collet runs out at but I'm pretty sure it isn't in a comparable range.

There are many reasons why ER collets/chucks are the commonest tool holding system in the world - fast and easy to use for a wide range of tooling, accurate, damps vibration well, and is probably the most accurate chucking system design out there. You can get collets in both Imperial and Metric sizes so just about any cutting tool you are likely to use can be held securely and accurately.

Is the ER system perfect? No, it's not. If you're doing a lot of heavy cuts that generate a lot of vibration then it isn't the best choice; heat shrink holders would be better. However, for almost any work that a hobby guy is likely to do it is a very good option.

You can use an R8 collet. It won't hold an end mill as securely as an ER collet, will not be as accurate, will not damp as well so accuracy and tool life will be reduced. For a hobby guy making a cut in aluminum, an R8 collet may be just fine so I am not saying you should not or cannot use it; I am saying that if I were using an end mill with a 2"+ flute length and needed it to cut accurately, I would use an ER collet to hold it.

 

[Geerbangr]

I’ll pick up a ER collet system Mikey. You’ve more than explained why it’s a better system than the typical R8 collets. I went to Tormach website and found a 6 collet pack but no chuck for R8 spindle. I’ll have to call them Tuesday for they are out for the holiday.

 

[mikey]

I’ll pick up a ER collet system Mikey. You’ve more than explained why it’s a better system than the typical R8 collets. I went to Tormach website and found a 6 collet pack but no chuck for R8 spindle. I’ll have to call them Tuesday for they are out for the holiday.

Let me back you up a little here to explain the TTS system. It uses a 3/4" R8 collet with the nose flattened. This allows all their tool holders, which have 3/4" shanks, to fit into this special collet and are drawn up solidly and repeatably in it. You can buy adapters for drill chucks, boring heads, fly cutters and so on. They also have end mill holders and ER chucks that fit into that 3/4" collet. The key attraction of the system is repeatability and speed. To change tools, you simply loosen the drawbar and pull out the tool, then insert the next tool and tighten the drawbar. You do not need to change collets or bang things loose. In addition, when the tooling is set to a specific projection or stick out, it will maintain that projection from the tool holder when you switch tool holders. Very nice system. Their tools and adapters are Chinese, with Chinese levels of accuracy, but they are actually pretty good. Just as important, they cost what Chinese tooling usually costs and that is a big plus.

Now, with that said, there are better ER chucks out there that have an integral R8 shank. My most accurate ER chuck is an ETM chuck from Israel. When used with high quality collets it is nearly as accurate as my spindle is. My spindle has less than 0.0001" of run out and a ground pin held in this chuck/collet system will hold that ten thousandths run out. So, the chuck and collet are accurate but so is the ETM collet nut.

You will discover that accuracy with these collets depends on good quality collets and good collet nuts, all else being equal. Makers of good nuts are Rego-Fix, ETM and Techniks. There are also ball bearing nuts but I don't have experience with good one; just the Chinese kind and I am not that impressed with them.

One chuck that I want to try someday is the Glacern line of ER chucks. Their advertised accuracy is very good and the guys here on HM that have them seem to be very favorably impressed. If I'm not mistaken, Glacern has the rough castings done abroad but does the final machining here, in the US. Their cost is very competitive and I've been meaning to buy one just to find out for myself.

So, my suggestion is to NOT rush into this decision. You might want to ask the HM membership about which ER chuck they recommend and why. Collets are just as important, as are the nuts used on the chuck. I have my opinions on all of this but it is important to hear from the guys.

Just one more thing. ER collets are often used on the lathe for work holding and do an adequate job of it. However, run out on the lathe is not nearly as critical and you can get away with an import collet set. On the mill, accuracy counts and there I recommend you suck it up and buy a decent set of collets. It will cost you but you will recover the cost over time because your tooling will be more accurate and will last longer.

Do more homework, talk to the guys and then decide on what to buy. You will often find some awesome deals on ebay and that is where I would search first.

 

[Geerbangr]

Ok I’m getting a little confused now. If I buy a R8 ER32 chuck and a set of collets from 1/16”-3/4” I could use my existing different size cutting bits, correct?

Or are you suggesting a R8 ER32 chuck that only accepts 3/4” shanks?

 

[Aukai]

Happy new year too....

 

[Boswell]

My understanding is that the R8 defines the interface between the tool holder and the machine. Specifically a Taper and possibly a keyway location. the ER refers to the way the tool holder holds the actual tool. So for instance I have a PM45M-CNC mill that accepts R8 tool holders. I have a number of R8 ER-16 tool holders and the appropriate ER-16 collets for the various diameter cutters that I have.

Happy New Year

 

[Boswell]

Ok I’m getting a little confused now. If I buy a R8 ER32 chuck and a set of collets from 1/16”-3/4” I could use my existing different size cutting bits, correct?

Or are you suggesting a R8 ER32 chuck that only accepts 3/4” shanks?

You are correct in that you can use one R8 ER32 tool holder and then the collets to swap out for the different tools you have. You must have the exact size of collet to match the cutting tool. If you find that you are using a specific cutting tool more often that others then you can purchase another R8 ER32 and the specific collet you need to hold that tool, then you can leave the cutter in the R8 ER32 all the time, making tool changes faster. I have about a dozen dedicated R8 ER32 holders dedicated to specific tools.

 

[mksj]

There is a range of clamping with ER collets, so it is often suggested to purchase a 1mm increment set, to cover both imperial and metric end mills. But in my experience, the accuracy suffers, so I recommend purchasing collets sized to the specific size shaft you want clamped. I use two ER sizes, an ER-40 1/32 set that serves as a holding system on my lathe, and on my mill an ER-32 1/16" set along with a few dedicated metric sizes that I commonly use. On the mill, most end mill shanks are standard sizes, so you probably would do just fine with a 1/8" increment set. One negative aspect of the ER system is the size of the holder/nut should you need to mill deep in a pocket. If going to dedicated end mill holders, then a R8 end mill holder system would be less expensive and have a narrower holder. Something like a Taiwanese Sowa end mill holder would be around $40 each. Some feel that the end mill holders may have slightly higher TIR then say an ER system, but insignificant at our level of work.

As Mikey outlined, ETM/Iscar, Rego-Fix, Lyndex if you can find them at a reasonable price are high quality. Some of these show up at auctions as sets, lightly used at a fraction of their normal selling price, so worth considering. I would also recommend Shar's (precision nickle plated), Galcern, Sowa, Tecknics, Bison as new mid level priced alternatives that are very well made. My ER-32 R8 chuck is Glacern, ER-40 R8 and MT3 Shar's both have almost undetectable runout. A high quality nut does make an measurable difference in both the TIR and tightening the nut to the proper torque. On ER collets, it does pay to get better quality collets, at least for the sizes you use frequently. If I were to recommend a mid priced ER set, I would go with the Tecknics high precision set. There is a significant difference in both the clamping characteristics and TIR between the inexpensive collets and higher quality versions. This has been stated repeatedly, but you must always snap the ER collet into the nut first then thread it partially onto the ER chuck, then insert you end mill and tighten. Failure to snap the collet into the retaining ring will result in collet misalignment/clamping.

 

[mikey]

Ok I’m getting a little confused now. If I buy a R8 ER32 chuck and a set of collets from 1/16”-3/4” I could use my existing different size cutting bits, correct?

Or are you suggesting a R8 ER32 chuck that only accepts 3/4” shanks?

Let me see if I can make this crystal clear.

Your spindle is an R8 spindle that accepts any R8-shaped shank. This tool is held solidly in the spindle with your drawbar. As the drawbar is tightened, it pulls the R8 shank up into the spindle and holds it solidly. If the thing you are placing in the spindle is a solid shank, like a chuck with an R8 shank, then the drawbar simply holds that thing solidly in place. If the thing is an R8 collet then as the drawbar tightens it collapses the collet around whatever you put in the collet and that holds that tool solidly. Sorry to get so basic but I hope this removes the confusion.

An ER chuck has an R8 shank on one end and an ER chuck on the other, like this one from Glacern.



The R8 part is held solidly in the spindle of the mill by the drawbar and the ER chuck part now becomes the tool holding part of this assembly. ER collets have the same outside dimensions and shape but the holes inside the collet vary in size. When a collet is inserted into the chuck and the nut is tightened, it collapses the collet to solidly clamp whatever tool you inserted into the collet. An ER32 collet set typically allows you to clamp any round tool shank from 1/16" to 3/4". That is, any tool you have with a shank that falls somewhere in this range can be clamped in one of the collets. So, one chuck, many tools.

Some guys, especially the CNC guys and in most industrial applications, will use multiple ER chucks. Rather than change the tool in the chuck, they just change chucks. He might have a rouging end mill in one chuck and a finishing end mill in another chuck. Because the end mill sticks out a precise amount and since it takes time to set this stick out, it is simpler to just leave it in the chuck and buy another chuck to hold another end mill that will have its own degree of stick out. This allows the user to go from one operation, roughing, to another operation, finishing, very quickly by just changing chucks. I believe this is what @Boswell is alluding to.

This is not the norm for most hobby guys. We have one chuck and we change tools in that chuck by using the appropriately sized collet. One chuck that holds any tool within the clamping range of the collet set, and it will hold every tool solidly and accurately.

 

[Downunder Bob]

And Happy New Year to you also. Just re-inforcing and consolidating what has already been said. Ok a 1" cutter is a bit big for your mill, 1/2" should be good , you might get away with 3/4" but I wouldn't push it any further.

Your mill has R8 pocket in quill, R8 collets are not as good as ER so get a R8 - ER 32 collet chuck will fit directly into your mill and allow you to use the best collet system around, Try to avoid the cheapest, but you don't have to buy the best either. You can get a R8 - ER 32 collet chuck with a full set of collets at quite reasonable prices.

Also if you have a lathe, it will most likely have a Morse Taper in the spindle bore, so you can also get a MT - ER 32 collet chuck to suit your lathe, thus using all your collets twice. ER collets are very good for holding small round stock in a lathe as well as mill cutters. In a lathe you can use this set up for horizontal milling. best of both worlds.