What's the deal with R8's?

[EmGo]

It has its uses..........

If length is a big problem, you can get an extended bed and use a steady rest to locate the outer end ...

 

[CarbideBob]

Maybe park the little kid comments and do the math on how it works,

 

[EmGo]

Maybe park the little kid comments and do the math on how it works,

Or even better, forget the entire thread because it is retarded, suitable only for Home Shop Machinist

The only reason R8 exists is because Bridgeport uses it. Period.

 

[eKretz]

Man, don't forget the smileys, it can really get you in trouble around here...

For rigidity of the tooling I think the cross-sectional area at the point of interface of the toolholder with the spindle is more important than the length after a certain point (enough to ensure good registration) is reached.

 

[Peter from Holland]

One of the nice things about R8 collets is they give you maximum space under the spindle. I find that pretty useful at times, and my mill has a 4"? riser block as well. For example using a dividing head with its spindle vertical. Not just milling cutters, you can hold say a stub drill in a collet when it's tight for space.

This also puts the cutter as close to the spindle bearings as possible.

I would guess both of the above are useful on a mini-mill (not sure what a mini mill is, but they sound even more floppy than a BP).

That would be true too if you use NT30 collets

Peter

 

[Peter from Holland]

I recently noticed the taper on R8 is the same as on a 30 taper
So what if a put a collar on the extented end of a Iso 30 taper and change the drawbar ??
Would that work ??

Peter

 

[Turbowerks]

I suppose you could stick a cat 30 in a r-8 but the tapers are not an exact match and only about 1/2 of the 30 taper would be engaged in the r8.
It would be the half closest to the flange but the taper would be the no go in my mind. Maybe to repair a damaged r8 if you ground it and had a bunch of 30 taper tooling could work.

R8 transposed over a cat 30


When I find it I don’t need it
When I need it I can’t find it!

 

[guythatbrews]

I'm happy with the R8 system and glad we use it here.

In a way many types of systems are popularized by availability. Like boats. What is considered the best in one region may not even be available in the another. You can argue which boat is best but at the end of the day the choice may be what is at hand. If R8 is unknown and hard to get in your area use what is in general being used and available.

As often happens, Bridgeport filled a niche and made something popular. And popular for a long time so tons of stuff available. And cheap compared to other systems. And many real mill hands have had a very productive career on R8 machines.

Not all machines need a 40 or 50 taper and not all endmills need to be held in an endmill holder, nor should they be. Whether you like it or not the R8 is ubiquitous in the class of mills for which it is intended. And works well for what it is intended. And a Bridgeport type mill is very versatile and works well. Again for what it intended.

Unless you have a very nice, new, endmill holder, an endmill in a collet enjoys less runout, lasts longer, finishes better. And does not suffer the inherent spindle bearing overhang due to stickout. In a R8 collet you can't hog out stuff like you can with a big roughing endmill retained with a Weldon shank in a 40 or 50 holder. But no shame for the little R8 because it never was intended to fill that role.

As regards the ALIGNMENT key, I would not recommend removing it from an R8 spindle. It's not there to drive, it's there to hold the collet while it is installed and removed. For crying out loud it's just a 10-32 screw with a smaller square head. The collet taper connection provides the drive, just as the collet drives the endmill with no key. Again for the duty range it is intended. If the tool assembly slips due to a wreck or misuse or being too large for the R8 system don't blame it on the key.

If your main need is heavy milling by all means gat a heavy mill with heavy duty tool holding. I've run them and was glad to have them for the work at the time. Also ran R8 mills at the time and was glad to have them, not the least because tool holding was quick, adequate, and weighed a ton less tha 50 taper holders.

One thing for sure. Definately would not have a mill with Morse or jarno taper. Especially jarno you can't beat a holder out with a sledge. And finding rotating tool tooling? Not much selection.

At the end of the day, each tool holding system and machine type has its place, and each performs better than the other when used as intended. And rember part of the performance is price point and availabilty.

 

[guythatbrews]

OT No drive torque on keys?

It holds the collet while you tighten the draw bar until the taper starts holding. No drive torque on keys: motor shaft, drive axles, or collets is a general rule. Keys align, not drive.

I've got to say I agree with you on an R8 key but not all keys in general.

Short of a shrink fit or a keyless friction coupling, both of which are better than a key but not always feasible, how do you propose to transmit torque? And splines don't count since often they are too expensive for the application.

 

[memphisjed]

I've got to say I agree with you on an R8 key but not all keys in general.

Short of a shrink fit or a keyless friction coupling, both of which are better than a key but not always feasible, how do you propose to transmit torque? And splines don't count since often they are too expensive for the application.

friction. A tight bolt clamps the wheel (or whatever shape) and holds it. Ideally you thread left or right so the wheel is self tightening most of the time.

 

[EPAIII]

Well, Bridgeport may have started it, but that is not the whole story. I do not know if Bridgeport designed the R8 but they most likely choose it for reasons of economy. Someone then made a BP clone or some other mill that tried to compete with them. And, the R8 collet was already around so they copied. Then another, and another, and another.

With each new machine that used R8, it became harder and harder for a new machine to try to buck the inexpensive trend so they continued to choose R8. At this point it is more a matter of history and what the purchaser of an inexpensive milling machine expects.

Disadvantages of R8:
Not a positive drive so it can slip
Low power handling capability
Limited grip range (~7/8" maximum)
Can shear the locating pin off

Advantages of R8:
Very common and easy to find
Easily available for a variety of shank types (round, square, hex, and more)
Low price: A set of CAT30s can cost twice the price of a mini-mill. US made R8s are about 1/4 their cost.
They do work - at least with smaller cutters and less aggressive cuts
Almost zero lost head room under the quill
More versatile: used on many machines AND accessories, like indexing blocks and dividing heads so one set serves several purposes
Requires less storage space

I can not draw on experience, but I see no reason why an R8 collet would be no more or less accurate than any other type.

As for the rather steep taper of the R8 as compared to something like a MT, it has both advantages and disadvantages. The R8 is less likely to lock in the spindle and easier to remove. But the R8 will slip more easily than the MT. It can be noted that the MTs usually do not use a locating pin for tightening and removing as the R8s do. The R8s need this feature more than the MTs, which grip the spindle better.

Overall, it is a combination of an engineering decision (as in better, cheaper, faster - pick any two) and a sales decision. And deciding to use a feature that will actually sell is not retarded. It is SMART if you want to be in business tomorrow.

Or even better, forget the entire thread because it is retarded, suitable only for Home Shop Machinist

The only reason R8 exists is because Bridgeport uses it. Period.

 

[taiwanluthiers]

As for cost, this is why they have Aliexpress.

Tooling from them cost the same whether it's NT30, R8, or MT3.

The cost you are quoting above is assuming American made tooling...

 

[taiwanluthiers]

CAT30 doesn't need much engagement, it has positive drive blocks so the taper engagement isn't really critical.

Keep this in mind if you think of sticking CAT30 tools into a R8 spindle...

 

[winger]

The Z collets on my Tree mill holds better than R8 due to the design that collapses straight in like an ER collet. Much nicer than R8 with a manual drawbar.
But with a power drawbar the R8 is much faster. In my maintenance job I would have hated using much heavier 40 tapers for a lot of changes. the big mill I ran used a 40 and was great for hogging, but no quill, so the Bridgeport won out a lot.
The speed and availability is probably why they continue to be used.

The TTS system my cnc mill uses, repeats z lengths but again it is still based on an R8 holder. So I try not to use larger ems than 1/2".

Dave

 

[guythatbrews]

The Z collets on my Tree mill holds better than R8 due to the design that collapses straight in like an ER collet.

Dave

No doubt double angle collets hold better than R8 spring collets.

I'd like to see a pic of your spindle nose setup. What is the capacity?

 

[CarbideBob]

Drawing above would be a bit more accurate with the tapers aligned and a endmill sticking out of both the same.
Then a look at moment arm and radial deflection and alignment as loaded.
Plus to most 30 taper VMCs are bigger and so way stiffer bearings. That is huge.

First thing I have always done to all my R-8 machines is remove that frigging pin even when brand new.
Have neither the time or effort to deal with it if I need a tool change every minute or two.
It is just a problem child that gets in the way and pucks with runout. Your mileage may vary.

 

[Scottl]

What's the deal with R8's?

Basically the same as 5C collets for lathes. Very common, relatively inexpensive, and easy to find new or used.

Are there better for both? Absolutely, but R8s are very common in mills and 5Cs besides being common in lathes are found in collet blocks, spin indexes and of course the Hardinge mills.

 

[52 Ford]

R8's are great. I like the older ones with the V10. The newer ones all have V8s... Sort of detracts from it, for me, anyway. Still AWD, though. 2022 Audi R8 performance Coupe | Performance Sport Coupe | Audi USA

 

[Peter S]

R8's are great. I like the older ones with the V10. The newer ones all have V8s... Sort of detracts from it, for me, anyway. Still AWD, though. 2022 Audi R8 performance Coupe | Performance Sport Coupe | Audi USA

'52,

It was the older R8 models which had the V8 and the one that visited a neighbour a few years back might have had an aftermarket exhaust, because it sounded good. I mean a loud, very pleasant V8 sound.

The only V10 I recall hearing was in a BMW and it sounded like a sewing machine.

 

[52 Ford]

'52,

It was the older R8 models which had the V8 and the one that visited a neighbour a few years back might have had an aftermarket exhaust, because it sounded good. I mean a loud, very pleasant V8 sound.

The only V10 I recall hearing was in a BMW and it sounded like a sewing machine.

I just looked it up. Apparently the V10 is an option. 4.2L V8 vs 5.2L V10. HP isn't THAT different (50 more on the V10), but I imagine the power curve is pretty different looking.

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