Bridgeport J head collet question

FlyinChip · Jul 27, 2018

Hi All, just a quick question, just purchased a Bridgeport with J Head, and it came with a bunch of R8 collets. Is that the only size these are made to accept, or are there other spindles that were optioned like on my SB heavy 10.

If so, is R8 considered the "good" size?

Thanks

Rob F. · Jul 27, 2018

If by good you mean common and easy to get then yes it is the good one. At some point they had other spindles.

FlyinChip · Jul 27, 2018

I did just find this discussion, which describes the R8 as common but a weakness is that it's tool holding is only at the base and the grip is not as good on larger tools. Just wondering how this falls in context, how really important or not is the weakness of R8.

LINK:
https://www.practicalmachinist.com/vb/bridgeport-and-hardinge-mills-and-lathes/r8-vs-others-339203/

thermite · Jul 27, 2018

FlyinChip said:
..how really important or not is the weakness of R8.

Since you have already BOUGHT a BeePee WITH R8?

The only thing "important" NOW is getting comfortable with its limitations [1] so you don't have avoidable problems. About sebenty-leben-brazilian folk have had to do this already. You can do it, too.

You cannot CHANGE this as easily on a BeePee as putting better wheels, tires, or brakes on a motor vehicle.

Learn to live with it.

Or trade it for a mill with a better spindle taper.

40-taper is a "sweet spot" for a balance between affordable tooling and proper grip and power transfer. 30-taper is not as common, goods often cost MORE than 40-taper as there is less out there in the used-but-good market, and fewer "economy" makers of new.

All that's for "next time"... when you do your research BEFORE you make the purchase, yah?

[1] Basically, it's a piece of s**t, but a cheap and common POS everybody just USES without much discussion. Sorta like toilet-paper in public washrooms. Most ANYTHING is better than an empty roll, yah?

FlyinChip · Jul 28, 2018

I learned on a BP and I'm sure I'll be happy with it. That being said, need to learn about the machine and this is part of it.

How much of an end mill can I use on steel and depth of cut? For example, at school, on bigger BP's I used 2.5" shell mills and cant recall but took pretty substantial cuts.

I read on here that with an R8 setup, I should be thinking about 3/4" end mill as a max, which sounds kind of small.

So for anybody reading this, in realistic terms, if this is an average condition BP J-head with the R8 setup, milling steel, how big of an end mill and how deep of a cut would be the maximum, approximately?

thermite · Jul 28, 2018

FlyinChip said:
I learned on a BP and I'm sure I'll be happy with it. That being said, need to learn about the machine and this is part of it.

How much of an end mill can I use on steel and depth of cut? For example, at school, on bigger BP's I used 2.5" shell mills and cant recall but took pretty substantial cuts.

I read on here that with an R8 setup, I should be thinking about 3/4" end mill as a max, which sounds kind of small.

So for anybody reading this, in realistic terms, if this is an average condition BP J-head with the R8 setup, milling steel, how big of an end mill and how deep of a cut would be the maximum, approximately?

I thot it was 3/8", not 3/4"? My smallest are B&S #9, about double an R-8's limits. I don't have to push even that above a 3" shell or face mill, nor a 1" endmill. The 40-taper is there for heavier work.

The idea, of course, when YOU OWN a mill, is to preserve the mill by respecting its limits so you can use it on the next task, not trash it pushing beyond its limits. I don't mean fear it or baby it. Just use the maker's published limits, not what Bubba "got way with.."

"School" mill or "company mill" you don't have to pay for or live with, the idea is to get to the end, even if you DO trash the mill.

There are TONS of things an R-8 can do all-day, every-day for YEARS.

Smaller diameter cutter can make just as big a cavity. It's a mill, after all. Not a drillpress or a grommet-punch. It has infrastructure. Traverse. Rotabs, even.

That takes more passes, usually more time - sometimes not. But all of it at lower stress.

FlyinChip · Jul 28, 2018

so.... how big an end mill can turn on steel with R8 typically?

thermite · Jul 28, 2018

FlyinChip said:
so.... how big an end mill can turn on steel with R8 typically?

As big as you can find room to swing with the dovetail-ram clear out without hitting the column ways. Want's a reduced shank, mind.

Now.. would you care to actually REMOVE any of that steel? "Take a cut". "mill it".

You ain't out of the woods, yet Pilgrim.

I can put a very basic one-inch thick by four-inch square slab of the most ordinary LOOKING steel you've ever seen into your hands, watch you clamp it in the vise, tool up and ...

... stand aside, watch...and laugh my ass off because.. you wont be able to mill it AT ALL.

Steel. Not Osmium.

Mind... it might have a bit of Manganese in it, but y'know.. alloy, schamalloy.. still mostly ignorant Iron, why would the small shit matter?

I don't think you PLAN to "troll", but to a mill hand, the question put only as "how big" means we cannot communicate.

There isn't enough information in the question to look for an answer.

What yah should do is get a job with Durex as a condom sales rep to 7-Eleven and Circle-K.

Where "size matters".

calvin b · Jul 28, 2018

Flyin Chip, Sir
R8 is "common" because it works. With that said.. 'R8' is a style of collet and a way to designate said stye of collet. There are literally hundreds of different tools made that 'fit' a r8 spindle. Do yourself a favor and look up r8 weldon tool holders.. no 'slippage' there... I think you are to ignorant of milling/machining to know what your really trying to ask. ( This is not a slam, just an observation)
Go forth and edumacate your self on speeds and feeds and such.. such knowledge will be applicable to all other machining problems/needs you may come across. (K.H.Moltrecht's tome "machine shop practice vol 2 would be a great start along with a copy of the machinery handbook )
What I believe you are trying to ask is "how much metal can I remove with a tool in one pass with a BP ?" and the answer is "it depends".. Lots of variables as Thermite eludes to in his own way... Really it all boils down to the eternal quest of man for horsepower and the more the better.. So go forth and educate yourself on speeds and feeds and HP calculations and you will find your answers.. Also trial and error can be a good guide also..
Hope you find this helpful
Stay safe
Calvin B
PS Just in case it helps in any way I do most of my milling on my little knee mill will a 1/2 inch end mill held by a r8 weldon style tool holder

batw · Jul 28, 2018

FlyinChip said:
so.... how big an end mill can turn on steel with R8 typically?

Chip your missing the whole point, your working on a piece an emergency the line is down, there breathing down your neck WERE LOOSING MONEY,WERE LOOSING MONEY.
so your I'll just speed up the feed good ol BP cuts right into it cuts to good and when you take the piece out sob the damn cut is 200 thou to deep because of the DAMN collet wouldn't hold the bit is ok the BP would spin but the DAMN collet would not hold... both my mills have bxs 7 and bxs 9 never had that problem again

thermite · Jul 28, 2018

batw said:
Chip your missing the whole point, your working on a piece an emergency the line is down, there breathing down your neck WERE LOOSING MONEY,WERE LOOSING MONEY.
so your I'll just speed up the feed good ol BP cuts right into it cuts to good and when you take the piece out sob the damn cut is 200 thou to deep because of the DAMN collet wouldn't hold the bit is ok the BP would spin but the DAMN collet would not hold... both my mills have bxs 7 and bxs 9 never had that problem again

To be fair, he didn't say R-8 COLLET.

Even so.. a Weldon side-lock in MT or B&S taper has a long precision-ground "in bearing" fit to transfer power AND resist side-force.

A side-lock holder in an R-8 has only the shorter closing taper at its nose in "bearing" contact for transfer of driving force. The long tail doesn't much help with EITHER driving force or resistance to side force - it's a slip fit, not a ground "bearing" fit.

The R8 may suit the need if not abused. It will still wear faster than the long tapers.

Take three equally old, equally hard-done-by mills? The MT and B&S will need de-burred. They will have been used seldom with collets, and their collets bear longer against the spindle taper even with relieved center of span and an internal grip a good deal shorter on the tooling.

The R8 will need REGROUND. It will have seen "too many" collets, had to deal with slip and side-to-side rocking, may even see some "lobed" effect, same as hard-worked 5C and such. All the wear, all possible sources, is concentrated into a much smaller area.

The only genuine plus is that an R-8 is far, far, less likely to get "stuck" in a hot spindle than a B&S taper.

MT doesn't belong on a mill to begin with, but that war was over and done with more than a hundred years back, so mostly, it ain't.

Newman109 · Jul 28, 2018

It's possible to swap spindles on your BP to something like a 40 taper. However, to take full advantage of that size, you would need more horsepower than the typical BP.

Used within its limits, the R8 is perfectly fine for a typical BP.

thermite · Jul 28, 2018

Newman109 said:
It's possible to swap spindles on your BP to something like a 40 taper. However, to take full advantage of that size, you would need more horsepower than the typical BP.

..and rather a lot of other changes, few, if any, that are practical or even CLOSE to "economic". As with s**t, the stresses "flow down hill" to the next point yah just over-stressed.

South Asia, motor-scooters grew into 3-wheeled banana-haulers and taxi-buses. While they had no better options. See also "Iron water buffalo":

Thailand's Iron Buffalo in action, Its rice planting season. - YouTube

Mostly, we DO have better options than "tuk-tuk"ing of lightweight milling-machines.

So - if one actually NEEDS such? Don't abuse the R8 BirdPort. Leave it undamaged for he who can live with that.

Go find a stronger-EVERYWHERE mill for those greater challenges - even if only a later, stouter, BP.

FlyinChip · Jul 28, 2018

OK thank you. I think I get it although one post suggests not using a tool holder for an end mill, other post does. I have a bunch of R8 collets that came with the machine. Before I started asking questions I would simply have used on for holding an end mill and going to work. And I still will, but I'd like to get a consensus on using a tool holder and how that works vs just holding the tool in a collet...

JohnEvans · Jul 28, 2018

If you are afraid of end mills pulling out of the R-8 collet get a few [ie 1.2-5/8-3/4] Weldon side locking end mill holders. Use these where you are taking the biggest cuts the old BP can handle,normal usage use the R-8s and don't lose sleep over the holding abilities of the R-8. Over thinking this for the most part I think!!

thermite · Jul 28, 2018

FlyinChip said:
OK thank you. I think I get it although one post suggests not using a tool holder for an end mill, other post does. I have a bunch of R8 collets that came with the machine. Before I started asking questions I would simply have used on for holding an end mill and going to work. And I still will, but I'd like to get a consensus on using a tool holder and how that works vs just holding the tool in a collet...

B&S #9, as said, has roughly DOUBLE the grip and HP transfer of R8.

For two mills with B&S 9 spindles, I have one full set of brand-new B&S 9 collets. But only because B&S has gone scarce. They've never left their wrappers. They will probably ALL still be in their wrappers when I die.

I have side-locks. Lots of them. My PDQ-Marlin VS and S are also side-locks.

IF.. I had a 5K, 10K or 20K RPM CNC spindle to tool? THEN I'd want a milling chuck or shrink holder because.. only up at those challenging speeds does the very minor clamping offset of a Weldon side-lock's screw actually matter to a mill. Needless to say, it would not be R8, either. Capto, probably.

Down in the "manual" world, a mill doesn't ordinarily mount a no-flutes item like diamond wheel. Cutters have teeth or flutes. Each one is already a form of "interrupted cut" as it is rotated into the cut on material that is also moving, relative to its axis.

Low/no TIR does bring better tool life. But really.. its a mill. Not a balance staff in a fine Swiss watch. You can't make all the other movements go away and still do useful work, anyhow. There WILL BE imbalanced side-forces at work. Or it is not a mill, it's an "only direction is DOWN!" drill press.

Eschewing side-locks is just not helpful. Those should become your go-to for routine milling, especially if you could "only have one".

Better to HAVE both "available", of course. I do have ER and TG and Gorton collets -even "native" 40-taper collets for the mills.

2CW

thermite · Jul 29, 2018

car2 said:
I respectfully disagree, that on an R-8 spindle, that if one wants the best tolerances and finish without more haranguing, that extra 1+ inch projection required for side-lock holders makes a noticeable difference in rigidity in the flexy R-8 system and bearings. (notwithstanding more runout and extra clearance needed). Of course, this is with a good-condition r-8 quality collet and good-condition spindle bore and bearings comparison.

You are simply blaming BOTH the side-lock AND the R8 for circumstances beyond the control of either one.

The degrees of freedom and flexibility a BeePee delivers come at the price of .. too MUCH "flexibility" when it is NOT wanted.

Your reduced stick-out just shortens the lever-arm that was over-stressing that limited rigidity. A machine-specific "band aid", if you will.

Even a mere R8 is not restricted to a BeePee. Heavier mills have offered R8 as optional. Many are not as flexible, and routinely manage not only close-coupled side-locks, but also extended "hang out" side-locks, so as to get down inside places where that is needed.

And "of course" extra finesse is required with greater stick-out. Any mill. Any spindle system.

thermite · Jul 29, 2018

car2 said:
(one reason folks seem to use toolholders is that they have had tools slip, or think they will.

"One reason".. they can slip. They do slip. Who needs that?

My MAIN reason though, is that a collection of commonly used cutters can be left mounted, each to its own inexpensive side-lock.

And those are the "ordinary" ones.

With PDQ-Marlin, they take less daylight to swap as well as being faster:

Quick Change Tooling

Collets? In the boxes.

Next owner may like a "virgin" set.

Great items to have for lathes, though..

texasgeartrain · Jul 29, 2018

I think a J head and R8's are fine, as it kind of matches the power of machine. It's 1hp typically, with a belt for the different speed selection on step pullys, like a drill press, which will probably slip on the pulleys if you are trying to hog off too much material, also like a drill press. Lots of R8 tooling out there at reasonable prices.

It can be a nice machine, but like the others said, you need to run it and learn its limitations. Might have to run more passes or slower feeds than a more powerful machine, but you can still do quite a bit with it.

Not sure how much shop space you have, or budget, but generally speaking mills themselves can be had at fairly reasonable prices. Getting a vertical or horizontal with a little more ass to go with the bp is not a terrible idea.

FlyinChip · Jul 29, 2018

Reading all the posts, basically it seems that a tool holder will help prevent slippage and the tool such as an end mill from slowly pulling out and ruining the z axis, but, at the expense of more leverage to cause lateral movement. I think the extent of that depends on the condition of the spindle and machine.

That being said, this is a personal use machine and I can always try tool holding vs loading the cutter into a collet and compare how they run for me on this particular machine.

As of now, this machine is on two pallets in three pieces outside my shed workshop. Once I find a way to get it in place and running, these collet posts will be helpful. If nothing else, I will keep a watch for slippage from the R8 collet.

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