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kb58

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I have a PM-935 mill on the way and thought that a power downfeed would be a fun project – not necessarily a requirement, but sometime fun to build. Reading through various threads, there are concerns about not dinging up the spindle nut, in addition to ensuring proper engagement, as well as the problem of the tool either not releasing, or dropping onto the work. Some people say that they switched to an ER32/R8 collet holder as a solution, and on this I need clarification.

I believe that the ER32 holder is intended for CNC use, but some people use them on manual mills to avoid having to mess with the drawbar. I'm guessing that using a spanner wrench on the collar as opposed to reaching up to the spindle nut is the reason why. Since this is my first mill, I don't have any tooling yet, so it makes no difference whether I buy R8 or ER32 collets.

Keep in mind I know just enough to be really dangerous, so please correct any of my thinking.
 

kb58

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I Googled "ER-32" and see that there are quiet a few ER-series holders. The ER-50 is supposed to grip down 2mm instead of 1mm (like the -32 does), but I suspect it probably costs a lot more.
 

JimDawson

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Mitch Alsup

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If the spindle is R8, there is no disadvantage in doing ER40 instead of ER32.

If nose height is ever a problem then direct use of R8 collets is ideal.
Direct R8 collets have 1 less ways to create runout.
 

kb58

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No downside to going with ER40 at all? If there is no downside, I'll certainly look into it, thanks.
 

ttabbal

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The downside is that the adapter takes Z space and can introduce runout. I use the Shars ER40 adapter on my Bridgeport and the added runout is small, meeting the spec they give.

Get some good collets, I use Techniks, but there are a few known good brands.

I prefer working with the ER40 over the R8 with the drawbar and that ER40 are self extracting. I also use them on the lathe and already had them for that use. I also have a small selection of R8 if I need the space, but that hasn't been an issue for me.
 

kb58

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Very well, sir, I will look into both. I assume that with this, the whole drawbar thing is avoided since the attachment method is in the adapter. Thanks!
 

kb58

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A couple more questions. What do you do use to chuck drill bits, an ER40 collet, or a drill chuck? If a drill chuck, did you find one compatible with the ER40 adaptor, or do you remove the ER40 adaptor and install an R8 drill chuck only for drilling?
 

kb58

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I may have answered my own questions; I'm not finding any drill chuck that fits an ER32 or 40.
 
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JimDawson

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I may have answered my own questions; I'm not finding any drill chuck that fits an ER32 or 40.
You would just use a chuck with a straight shank and insert it into a collet.
 

P. Waller

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I believe that the ER32 holder is intended for CNC use,
This does not mean that a tool holder "intended for cnc use" can not be used in a manual machine with the same spindle.
ER is a tool holding system independent of the machine spindle, do not confuse a tool holding system with a spindle taper.

Many do and this leads to much confusion, as Jim Dawson noted your machine will have an R8 spindle taper, this will require an R8 to ER collet tool holder.

Put simply you will place an R8 taper ER tool holder in the spindle then place the tools in the ER holder, simple as mud really.
If you require typical hobbyist .0001" accuracy this will not be ideal.

A typical cat spindle machine uses tool holders with a feature that allows them to be changed automatically, R8 does not support this.

If indeed you would like a good deal of accuracy and tool holding ability buy a machine from PM with an HSK spindle.
 

ttabbal

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Yes, straight shank drill chuck, held in a collet. ER or R8, both work fine. My drill chuck has a 5/8" shank, so I just use a 5/8" collet to hold it.

The big differences are the way you tighten / loosen them, and if you want to use the collets for other stuff. Collet blocks are common for ER, haven't seen them for R8.

There is no "best" collet system. Just a bunch that have various tradeoffs.
 

killswitch505

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Kb58, I would really look at the ER 40 if you have a lathe. I’ve heard really good things about the Shars zero set collet chuck. you could use one set of collets between the two machines. I think will be my next two purchases just seems handy to me
 

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Using a drill chuck in an ER collet does add to the length from the spindle. I'm not familiar with the 935 - round column or dovetail? I find that the ER40 collet chuck (or equivalent British format) is similar stick-out to my drill chuck, so I don't often have to change the head height in the middle of a project. Changing chucks isn't much of a problem with a cordless impact driver to handle the drawbar.
 

ttabbal

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935 is a knee mill like a Bridgeport. About 15" of Z according to the specs.

It does add to the stick out. I go the other way and use a battery drill on the knee with a 3D printed adapter.
 

kb58

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One last question about ER tool holders. Looking through various threads, there are comments regarding the amount of force necessary to lock the cutter in place, that it takes so much force that a few people have broken parts in their quill. Is this a "thing", or rare outliers? I realize there can't be a black-and-white answer since some people don't post what machine they're having the problem on.
 

JimDawson

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One last question about ER tool holders. Looking through various threads, there are comments regarding the amount of force necessary to lock the cutter in place, that it takes so much force that a few people have broken parts in their quill. Is this a "thing", or rare outliers? I realize there can't be a black-and-white answer since some people don't post what machine they're having the problem on.
Never heard of that happening. I normally use 2 wrenches on ER collets
 

kb58

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Oh yeah... duh. Good point about using two wrenches (I've never seen an ER setup but instantly realized what you mean). Okay then, an non problem!
 

kb58

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I went and talked to the machinists at our company. After explaining my situation, and them explaining all the options, they did point out that, unless I'm doing frequent cutter changes, sticking with a simple R8 collet set isn't such a bad thing. Some decisions to be made.

(First-world problems)
 

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For the first 45 years of my chip making life I never used anything but R8 collets/tool holders in a mill. It has just been in the last 5 years or so that I have had machines that used other collet systems.
 

ttabbal

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For hobby stuff, I find myself swapping tools often enough to make it nice. That said, I don't really mind R8. I usually use ER40 as I have a larger selection of them so I don't see any reason not to.

If I were to buy only one set, it would be ER40. The biggest reason is that I use them on the lathe and with collet blocks in addition to tool holding on the mill. Being able to pass long round stock through the collet and holder is very handy.
 

kb58

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Hmm, thanks for that note. On the list is to someday upgrade my old Grizzly mill so I'll keep it in mind.
 

jbolt

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I'll add another option here. Not saying it is the best or appropriate for the OP's situation but just another available option.

I have a Tormach Tooling System (TTS) on my CNC mill that has a pneumatic drawbar. The system uses a 3/4" R8 collet in the spindle to hold the tool holders that have a 3/4" shank and flange that indexes off the nose of the spindle. Tormach has a large variety of tool holders and drill chucks that are reasonably priced.

On my manual mill, 90% of the time, I just keep a 3/4" R8 collet in the spindle and manually change the tool holders/chucks which is simply loosening and tightening the drawbar nut. I have a block of hardwood strapped to the wrench body for tapping on the drawbar if needed.

FYI tool drop can happen with any collet system, even the ER collets. It's just a matter of supporting the tool when releasing from the collet.
 

mikey

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There are pros and cons to every tool holding system, most of which have been discussed here. What hasn't really been addressed is the accuracy of the tool holding system itself.

The ER system is the most widely used tool holding system in the industry for good reasons. It allows rapid tool changes while still providing maximum precision. The chucks tend to be quite compact and are available for almost any spindle configuration. In fact, the norm (not in a hobby shop, of course) is to leave a tool in a chuck and change chucks as needed. The ER system provides the best vibration damping of the available systems a hobby guy is likely to encounter, although if you can heat shrink your tools into a holder then that might top it for tools that vibrate a lot as they cut; most hobby guys don't heat shrink their tools. It also allows you to pass longer tools through the collet; this is a big deal when you have a double-ended cutter that is big and long.

The good ER chucks boast run out in the low tenths, as do collets. In comparison, to get the accuracy of a good ER collet in an equivalent R8 collet, you're looking at Hardinge R8 collets. Those things have 0.0002"TIR but only if you run it in a precision Hardinge spindle. Most R8 collets do not get anywhere close to that precision, just as most hobby milling spindles don't get close to a Hardinge spindle. Moreover, most Chinese R8 collets won't hold tight tolerances even if you run it in an accurate spindle.

The main reason to look at the accuracy of the system is that run out impacts on tool life, tool accuracy and finishes. Techniks estimates that for every 0.0001" of run out, you see a 10% reduction in tool life. This is because only one flute on an end mill is cutting the most and that flute will wear faster. You might think this is not a concern in a hobby shop but consider that if the spindle has 0.0002" TIR all by itself and the tool holding system introduces another 0.0002" TIR then you're looking at a theoretical 40% reduction in tool life. Looked at this way, it isn't such a bad idea to consider how accurate your tool holding system is. I also suspect this is why the ER system is so prevalent in industry.

I'm not saying that you shouldn't go with R8 but there is a whole lot more to this than how fast or easy it is to change tool holders. Compared to the time we spend actually working, the time it takes to change tool holders is minor. What really counts is how accurately that tool holder will hold that cutter.

Personally, I use the Tormach TTS system to hold ER-32 chucks, drill chucks and so on. It is nowhere near the top of the line tool holding systems but it is pretty damned accurate for what it is. Many guys who use this system change ER chucks instead of changing end mills in those chucks. The chucks are low cost but pretty accurate for what they are; if you use good collets and nuts with them they are quite sufficient for hobby level work. It is also very fast to use; loosen the drawbar, give it a tap and the tool drops out. You might take a look at it.

Bottom line for me: I would highly recommend the ER system instead of R8.
 

kb58

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That you for all of the replies, everyone.
 
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