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Dunc
05-25-2008, 11:52 AM
Had a look at the LMS comparison chart of mini mills. Seem to be a choice of MT3 or R8. R8 (according to Wikipedia) is a Bridgeport design specifically for milling vs the MT which seems to be a "universal" taper.

That said, practically, is one better suited than the other for a milling machine? Is more tooling available "out there" for one vs the other? Any appreciable difference in costs of MT3 vs R8?

Any other thoughts you wish to pass along are welcome.

Thanks for

Benta
05-25-2008, 12:05 PM
The R8 will hold cutters directly.
The MT3 you need a collet holder, which means you have more overhang.

Benta.

JCHannum
05-25-2008, 12:11 PM
MT#3 collets are available, but MT collets in general do not grip as well as R8, and R8 is more of a standard than MT for milling machines. Given the choice, R8 is the better of the two.

rantbot
05-25-2008, 12:41 PM
but MT collets in general do not grip as well as R8,
Huh? R8 isn't even a locking taper, and is a relatively feeble way to hold anything.

pcarpenter
05-25-2008, 12:57 PM
Huh? R8 isn't even a locking taper, and is a relatively feeble way to hold anything.


Feeble....yeah...compared to the NTMB (and CAT etc) tapers, perhaps. However, the morse tapers hold no competitive advantage over the R8. Morse tapers are *not* self holding in a milling machine where it sees side loads. There's far more tooling out there in r8 and R8 collets are capable of holding larger end mill shanks than you can fit in an MT3.

I think the folks who find the R8 inadequate are the same folks who are more often than not stretching the limits of the mills whose spindles are ground for an R8. Its also important to separate out the holding ability of collets vs. end mill holders from the issue of the taper of the same collets and end mill holders.

I have the HF mini-mill with the R8 spindle. I am glad I went that route. I now own a Bridgeport knee mill and the tooling is interchangable.

Do not let the fact that Bridgeport may have invented the taper many decades ago lead you to believe that its in any way proprietary....far from it. Browse any tool catalog and you will find plenty of things with an R-8 shank that are not available in another taper. If you have one of the other tapers, you have to buy the item with a straight shank and put it in an end mill holder....extending the length, flexibility, and force on the spindle bearings as well as reducing precious work envelope (especially on such a tiny mill).

Paul

rantbot
05-25-2008, 01:00 PM
R8 (according to Wikipedia) is a Bridgeport design specifically for milling vs the MT which seems to be a "universal" taper.
The usage has, historically, evolved somewhat, so the "universality" of one taper now has little practical use. Locking tapers were originally standardized as a way to mount tools directly to spindles. So drill bits and similar tools were made with tapers on one end. This worked well enough if the application involved an axial force which kept the taper locked in place. Not too bad for drilling, but not so good for vertical mills. So collets with drawbars appeared, originally to fit in these older locking tapers. The self-locking geometry was no longer very important, as the drawbar did most of the work, so soon other (non-locking) tapers appeared for use with collets and drawbars - not for self-locking applications.

A spindle with a Morse taper isn't "universal" in any practical sense, since you can't just bang in tools with Morse tapers on the ends (like, say, drill bits, or lathe centers). The drawbar is in the way and those tools won't fit. Your tools need the appropriate taper and a threaded hole for the drawbar, OR they need to be a shape (usually a cylinder) which a collet for that taper can grab onto. For special applications you could remove the drawbar and use a solid Morse socket in a Morse spindle, but generally that's not too useful. I've done it maybe once, ever.

In the US, for mill use R8 tools and collets are far more common than Morse.

rantbot
05-25-2008, 01:09 PM
Feeble....yeah...compared to the NTMB (and CAT etc) tapers, perhaps. However, the morse tapers hold no competitive advantage over the R8. Morse tapers are *not* self holding in a milling machine where it sees side loads.Quite right, a Morse taper without a drawbar is not adequate for milling machine use. I only mentioned the locking property of the taper because I found the above claim that Morse tapers don't grip as well as R8 to be, basically, incredible. And the reason why is simple geometry - which happens to be the same geometry which makes some tapers locking, and some not.

I think the folks who find the R8 inadequate are the same folks who are more often than not stretching the limits of the mills whose spindles are ground for an R8.As for that, I can't say. All I can say is that I have occasionally had cutting tools move axially when held in R8 collets, and don't happen to have had the same problem when using collets with more gradual tapers. While hardly proof of anything, those experiences inspire some skepticism when I see claims about the mystical properties of the R8 taper.

Its also important to separate out the holding ability of collets vs. end mill holders from the issue of the taper of the same collets and end mill holders.Yes, separate issues entirely.

tattoomike68
05-25-2008, 01:17 PM
First off I would go with the R8, its cheap and very common.

You can get MT endmill holders, they are rock solid.

One little warning with MT is never over tighten the draw bar , They will get stuck so damn tight its not one damn bit funny. R8 is far less prone to getting stuck.

You can get away with a tight draw bar with an R8 but you do that with a MT you will be sorry you did. ;)

JCHannum
05-25-2008, 01:24 PM
Self releasing vs self holding has little to do with the gripping power of the collet. DA, TG and ER collets are all self releasing. The R8 has better holding power than MT collets coupled with the fact that once sufficient force has been applied to hold the tool, it can be removed without destroying the spindle bearings.

Bridgeport initially used MT collets on their early heads. Recognizing the need for improvement, they developed the R8. It has been an industry standard since, replacing the MT and B&S collets in most cases. While it might not be the best, it represents significant improvement over MT collets.

Forrest Addy
05-25-2008, 01:35 PM
Here's the real issue. R-8 holders are in plentiful supply, generally cheaper, and considerably stiffer since they are 1 1/4 dia on the big end Vs 0.938 for the #3 Morse.

If you have a choice of either, lunge for the R-8.

If you have a chance at a #40 MMT machine for nearly the same price go for it provided the spimdle properly supported by bearings and not merely a #40 grafted on an R8 spindle.

rantbot
05-25-2008, 03:35 PM
once sufficient force has been applied to hold the tool, it can be removed without destroying the spindle bearings.
Another very strange assertion.

rantbot
05-25-2008, 03:43 PM
Bridgeport initially used MT collets on their early heads. Recognizing the need for improvement, they developed the R8.The early Bridgeport heads also were available in B3 tapers. B3 looks just like R8 but smaller capacity. It was standard in the C head, optional in the M. It didn't sell well. I've never seen one - I don't suppose it gripped any better than R8. 2M and 7B&S were the big sellers.

Chipslinger
05-25-2008, 04:13 PM
Rant bot, What do you have against Jim?

You are arguing over silly preferences.

JCHannum
05-25-2008, 04:28 PM
MT taper collets, not being self releasing must be driven out to release them. Once you have used a mill so equipped, and experience the force needed to drive one out, you will understand. Bridgeport and some others did make an arrangement to jack the collet out, but not every manufacturer did. Beating on a spindle with precision bearings does not contribute to the longevity of the bearings. Tattoomike68 seems to agree with this.

A quick inspection of collet styles will reveal the vast majority are of the self releasing taper style. If it is indeed inferior, one must wonder why it is so universally accepted.

Regardless, as Forrest states, it is much more common and economical, and is the better choice of the two.

rantbot
05-25-2008, 06:17 PM
Rant bot, What do you have against Jim?

You are arguing over silly preferences.
How so? I'm arguing the technical merits of a claim made in the thread. What's silly about that?

rantbot
05-25-2008, 06:21 PM
MT taper collets, not being self releasing must be driven out to release them. Once you have used a mill so equipped, and experience the force needed to drive one out, you will understand. Bridgeport and some others did make an arrangement to jack the collet out, but not every manufacturer did. Beating on a spindle with precision bearings does not contribute to the longevity of the bearings. Tattoomike68 seems to agree with this.
I use such a mill every day. The spindle has held up just fine so far. It is over fifty years old, and still excellent.

I won't claim that any collet system isn't vulnerable to abuse.

tattoomike68
05-25-2008, 06:45 PM
I use such a mill every day. The spindle has held up just fine so far. It is over fifty years old, and still excellent.

I won't claim that any collet system isn't vulnerable to abuse.

I dont like milling with collets anyway myself. (endmill holders rock)

My little smithy here at home has a MT2 endmill holder and I snug the draw bar with 1 finger on the mill wrench. any more than that and I have to beat on my mill and its not the best to start with so I sure dont want to hit it with a BFH.

I have been stuck on a mill at work for months on end and tend to horse the living dog piss out of it and make it work hard. Every 6 months I like to pull the spindle and grease it up and set the preload. Im not nice to mills I work the hell out of them because I hate milling, its a job for a mexican if you ask me. I take good care of a machine and try not to use a hammer on the spindle even if I do like to run them real hard.

ERBenoit
05-26-2008, 06:41 PM
Im not nice to mills I work the hell out of them because I hate milling, its a job for a mexican if you ask me.

As much as you hate milling, you'd probably rather be milling than unemployed. Probably pays better too. Even if part of your job sucks, it must be better than losing your and/or your co-workers jobs to that/those "mexican(s)".

Sorry, this has nothing to do with the topic.

Chipslinger
05-26-2008, 07:30 PM
I didn't read he was Quiting a mill job, but IF he left His Job may be replaced by a Hispanic Laborer for Just over Minimum wage, and Half of that money will go back to err , Umm, the Hispanic republic.

toastydeath
05-26-2008, 07:36 PM
An interesting obersvation:

One sees MT tapers on big mills (50-100 hp) with power drawbars to kick the tool out. I've noticed through virtue of looking around reseller websites that large boring mills, with 8" spindles and above, very often have MT7 or MT8 spindles.

However, since an MT-7 is bigger than the entire spindle assembly from a bridgeport, I don't think it holds much bearing here. I don't know why they don't use an equivalent sized NMTB taper or even if one exists; anyone ever heard of a NMTB-60 or NMTB-70?

oldtiffie
05-26-2008, 09:26 PM
.................................
................................
However, since an MT-7 is bigger than the entire spindle assembly from a bridgeport, I don't think it holds much bearing here. I don't know why they don't use an equivalent sized NMTB taper or even if one exists; anyone ever heard of a NMTB-60 or NMTB-70?

Good one TD.

I have an MT3 on my HF-45 mill and have no problem at all with driving an 80mm (mean) diameter indexable facing cutter nor in removing the tapers. Sure, the tapers get tight but using a phosphor-bronze "dolly" on the draw-bar and hitting it with a largish engineers hammer (so that it does not "bounce" (acts as a "dead hammer") works fine. This cutter has a 45 degree lead angle and about 10 degree positive rake - both of which increase the cutting capacity as well as decreasing the load and "chatter".
http://i200.photobucket.com/albums/aa294/oldtiffie/TC_end-cutter1.jpg
http://i200.photobucket.com/albums/aa294/oldtiffie/TC_End-cutter2.jpg
http://i200.photobucket.com/albums/aa294/oldtiffie/Brake-disc2-1.jpg
http://i200.photobucket.com/albums/aa294/oldtiffie/Brake-disc3-1.jpg

The largest NMTB taper I could find the details of quickly was a 50. 60 or 70 may well exist - but I didn't look too far:
http://i200.photobucket.com/albums/aa294/oldtiffie/machine_tapers/Machine-taper5.jpg

http://en.wikipedia.org/wiki/National_Machine_Tool_Builders_Association

http://en.wikipedia.org/wiki/Machine_taper

http://www.parlec.com/pages/nmtb_taper_specifications

http://www.timgoldstein.com/cad_cam/tapers.htm

wierdscience
05-26-2008, 09:46 PM
R-8 has replaced MT3 and B&S#7,it is cheaper and many times more plentiful.

It also does everything the MT3 will and adds the benifit of quick release,R-8 is king of the mountain at least here in the states.


The big mills some of them are proprietary.Devlieg was one such mfg IIRC so was Ingersol.

toastydeath
05-26-2008, 11:36 PM
tiffie -

I work with 50 taper machines at work - they're big. Much, much bigger than 40. But I'd say they're only a little bigger than MT5, which is long and skinny compared to the squat and fat CAT-50 holders. My only thought that was maybe, pound for pound, there was some advantage to a huge Morse taper that you didn't get in bigger size ranges with NMTB since they make Morse tapers into obscene sizes and NMTB stops at 50.

Maybe the non-releasing nature of a Morse taper is an advantage in that powerband.

oldtiffie
05-27-2008, 12:21 AM
I think we need to sort out whether the OT is interested in a relatively light-use Home Shop non-commercial shop - or not.

If its "Commercial" - sure "go for it" - as hard and as big as you can go.

But if it is a "Home"/"Hobby" shop, I'd guess that "hogging" is not such an issue - if at all.

I get by very well with an MT3 ER-32 collet set (up to 20mm shank size) end mill holder. "Corn-cob"/"roughing" cutters work very well, are not too expensive, remove metal quite quickly, give a quite "passable" finish and do not over-load the machine or make it "chatter".

http://i200.photobucket.com/albums/aa294/oldtiffie/Corncob3.jpg

If you have any end milling cutters that are "blunt" on the bottom/end edges for about 1/8" or so, you can just put a 45 degree bevel on them (it works even with hand grinding on a common old pedestal grinder with an emery wheel - if you are careful). It is a small but quire surprisingly effective smaller version of this cutter:
http://i200.photobucket.com/albums/aa294/oldtiffie/TC_end-cutter1.jpg

This is the ER-32 adaptor in my lathe with a corn-cob cutter:
http://i200.photobucket.com/albums/aa294/oldtiffie/AirSmith03.jpg

This is my MT3 HF-45 vertical column mill (the white rule is 250mm (10") - for scale:
http://i200.photobucket.com/albums/aa294/oldtiffie/HF45-1.jpg
http://www.machineryhouse.com.au/Products?stockCode=M143

This is my 3-in-1 (lathe-mill-drill) that also has MT3 in the mill - that lathe head-stock spindle is MT4.

I have just taken delivery of my new Seig X3 mill - which also has an MT3 quill. I will retro-fit a CNC kit in due course. It is still all greased up as delivered. Details as per my supplier catalogue are at:
http://www.machineryhouse.com.au/Products?stockCode=M153

So, "light" works for me in my hobby shop. I am there to enjoy myself. My "hogging" and "tear-arsing" days are long gone and they are NOT coming back!!.

Light small machines and 3MT and ER-32 collets "do it" very well for me as I don't "push" them.

J Tiers
05-27-2008, 09:20 AM
If it is a light duty vertical mill, R8 is the choice.

if it is a horizontal mill, AVOID the R8 at any cost. MT will be fine, 30 or 40 taper better.

At least one maker offers a combo mill with R8 horizontal, which is beyond stupid. A horizontal with any sizable cutter will probably SPIN an R8, while a vertical with an end mill probably will never do that. And getting an arbor for R8 .... well I don't think there ever has been one except for that chinese machine.

Whoever said the MT will destroy bearings on removal is not a very creative machinist.

It is SO EASY to make a drawbar that will PUSH OUT the collets, that the argument has less than no merit.

Even HSM, the mag that sponsors this site, has had an article for one, and at least one other not printed. I know, it came out one month after I SENT them an article on making one.

You can make a spindle cap if there is any threaded spindle sticking out. If not, you can thread the ID of the spindle end and either insert a sleeve, or make a differential threaded drawbar.

JCHannum
05-27-2008, 10:49 AM
Whoever said the MT will destroy bearings on removal is not a very creative machinist.


That would be me, and I am rather creative. But lacking a threaded nub on the spindle to attach a jacking attachment, or threading a hardened spindle, the remaining method is to pound the collet out. For some reason, this appears to be the norm, and the bearings do seem to hold up, but there is a cringe factor when doing it. I merely presented it as another reason for self releasing collets.

Morse tapers and Milling machine tapers are fine for workholding. Morse taper collets are less than ideal and R-8 is a better choice when available, which is, after all, the OP's question.

J Tiers
05-30-2008, 12:30 AM
That would be me, and I am rather creative. But lacking a threaded nub on the spindle to attach a jacking attachment, or threading a hardened spindle, the remaining method is to pound the collet out. For some reason, this appears to be the norm, and the bearings do seem to hold up, but there is a cringe factor when doing it. I merely presented it as another reason for self releasing collets.

Morse tapers and Milling machine tapers are fine for workholding. Morse taper collets are less than ideal and R-8 is a better choice when available, which is, after all, the OP's question.

It is NOT at all unknown for various SOLID MT devices to become well and truly stuck, at which time they benefit from a push-out. At least mine does.

And, you may note that I DID mention R-8 as better for vertical mills.......

Incidentally, if your spindle lacks a threaded end, it is unlike most I have ever seen...... It may, however, be covered by a nut which is used to set tension etc........

That nut isn't welded on, and may be replaced with a nut having "suitable enhancements"..... like threads. It can be ensured , by suitable locking and the addition of flats or the like, that the nut does not turn relative to the spindle when a "removal" is done.

JCHannum
05-30-2008, 08:44 AM
The mill, a Benchmaster is long gone, having been replaced with a Rockwell with R8. I do not recall the details of the spindle.

The statement was somewhat tongue in cheek to point out that one of the benefits of the R8 and self releasing tool holding devices is to obviate the need to resort to beating on them, make jacking devices or other means of removal.

Dunc
05-30-2008, 09:08 AM
Didn't realize when I first posted that the topic would give rise to so much discussion but the discussion is sure an education - much appreciated. Well, reality has stepped in.

After all that it seems the choice at the local "toolery" will be either MT3 or MT3 (Princess Auto or Busy Bee). We sure get the short end of the stick up here. Given that, it seems that a push out bar is the way to go. Back to checking out the spindles.

wierdscience
05-30-2008, 09:25 AM
Didn't realize when I first posted that the topic would give rise to so much discussion but the discussion is sure an education - much appreciated. Well, reality has stepped in.

After all that it seems the choice at the local "toolery" will be either MT3 or MT3 (Princess Auto or Busy Bee). We sure get the short end of the stick up here. Given that, it seems that a push out bar is the way to go. Back to checking out the spindles.

If your looking at a mini-mill like the Seig x-2

http://www.siegind.com/Products/br-x2-lathe.htm

And want the R-8 spindle,but can only get the MT3 locally your still in luck.

LMS carries the R-8 spindle as a replacement part-

http://littlemachineshop.com/products/product_view.php?ProductID=1407&category=6

gnm109
05-30-2008, 09:26 AM
I've never used anything but the R-8 as that's what my little Mill Drill is set up for. Thanks to the fact that they are so widely used, I was able to amass quite a collection of them in all of the popular sizes at quite a reasonable outlay. Most of them were bought used at a local used machinery warehouse at $2 to $5 apiece.

Harbor Freight used to carry them new at $5 apiece, even up to 1-1/2" capacity. I haven't seen one there for a long time, although they have them online. I don't need anymore anyway since they don't seem to ever wear out.

I like the end mill holders but sometimes I will use an R-8 split collet to hold a smaller end mill with the advantage of easy removabillity. They seem to grip quite well. I seldom need more than a light tap with a soft hammer to remove an R-8 adapter.

So I guess I'm an R8 booster. ;)

rantbot
05-30-2008, 03:27 PM
Didn't realize when I first posted that the topic would give rise to so much discussion but the discussion is sure an education - much appreciated. Well, reality has stepped in.

After all that it seems the choice at the local "toolery" will be either MT3 or MT3 (Princess Auto or Busy Bee). We sure get the short end of the stick up here. Given that, it seems that a push out bar is the way to go. Back to checking out the spindles.
You may not have heard quite the right lesson; there's been a lot of noise here.

(i) In the US, R8 is far more common in this spindle application, so tooling is easier to find and much cheaper.

(ii) For a given drawbar tightness, Morse taper collets grip much more tightly than R8.

(iia) A corollarly to (ii) - to hold a tool adequately, Morse collets need not be tightened nearly as much as R8 collets.

(iib) A consequence of (ii) - if Morse collets are overtightened, they can be a bit of a chore to release.

The important point is that although both collet tapers do the job, they do not behave exactly the same, and that should be taken into account by the user. If you're used to R8s, don't sock Morse collets down as tightly, and everything should be fine.

If R8 is easily available in the machine you want, get it. If it's not and you're "stuck" with the Morse spindle, don't worry about it; learn to use it. It will work fine if you do your part.