Easiest/cheapest source of R8 socket

[JasonB]

On JasonB Said:

I wonder if anyone sending their holders back to Haas as being not fit for purpose has got a refund? They are hardly likely to sell unfit goods and are not really aimed at the hobby user

ER16 & ER32. […]

A very fair point, Jason !

It does however leave me wondering which part of the R8 is taking the high torque that’s recommended for closing ER32 collets in ‘non hobby user’ situations.

i.e.  100 ft-lbs or 140 Nm

Does Haas specify  some clever protocol ?

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

On JasonB Said:

I wonder if anyone sending their holders back to Haas as being not fit for purpose has got a refund? They are hardly likely to sell unfit goods and are not really aimed at the hobby user

ER16 & ER32. […]

A very fair point, Jason !

It does however leave me wondering which part of the R8 is taking the high torque that’s recommended for closing ER32 collets in ‘non hobby user’ situations.

i.e.  100 ft-lbs or 140 Nm

Does Haas specify  some clever protocol ?

MichaelG.

That’s exactly what the post originator was asking 8 days ago? And additionally from personal experience industrial suppliers peddle far eastern crap all the time.

Tony

[Bill PhinnParticipant @billphinn90025]

Jason points out Haas ER collet chucks (including the R8 shank variety) are sold without flats.

The videos I’ve seen put out by Haas on ER collet use skip rather inconveniently over methods for tightening the nut, but the videos I have seen* show, and seem to assume the use of, a collet chuck tightening jig, in other words all tightening and loosening is done with the chuck out of the machine spindle.

This may be fine for those with such a jig** and/or those who do relatively infrequent tool changes, but less fine for those without such a jig or for jobs where the worker needs to do many tool changes. It may also be less of an inconvenience to remove the chuck every time you want to do a tool change if your machine has a powered draw bar of some kind, which not many hobby machines do.

*e.g. https://www.youtube.com/watch?v=WKikm6cQKh0

** a bench vice works, I suppose, but isn’t the ideal jig.

[GordonHParticipant @gordonh]

Hi,

I have an Arc “flatless” R8 ER40 collet chuck which i used for several years on a Bridgeport.  To change collets, the chuck spindle brake was held on and the collet spanner was used to fit or remove the collet wihout any problem.  The brake held the spindle and friction at the spindle / collet chuck interface held the chuck against the torque from the collet spanner.

My new milling machine does not have a spindle brake but the spindle has a hole for a locking bar at the chuck end and also spanner flats ar the drawbar end. I do not forsee any problem using the chuck on my mill, once I find the “safe” place I put it!

Gordon

[Tony Pratt 1]

On Tony Pratt 1 Said:

On Michael Gilligan Said:

[…]

It does however leave me wondering which part of the R8 is taking the high torque that’s recommended for closing ER32 collets in “non hobby user” situations.

i.e.  100 ft-lbs or 140 Nm

[…]

That’s exactly what the post originator was asking 8 days ago?

[…]

 

Now that this discussion has re-started, Tony … May I just say ‘No’

My rhetorical question was intended to make people think … about where all that torque actually ends up !

MichaelG.

[noel shelleyParticipant @noelshelley55608]

Surely if all that is needed is spanner flats then a few mins with a grinder will do a good enough job no matter how hard ? Noel.

[Bill PhinnParticipant @billphinn90025]

Noel, what sort of grinder do you have in mind there? Could you explain/illustrate the set-up?

[JasonBModerator @jasonb]

I expect a hand held 112mm angle grinder is what Noel had in mind with suitable grinding disk. Hold part horizontally in bench vice, grind a flat. flip it over and grind another.

[noel shelleyParticipant @noelshelley55608]

Thank you Jason ! and nobody saw my lips move ! As Jason has said, it all depends on how nice you want it to look. For a narrow flat take the bulk out with an ordinary grinding disc, 6mm thick, then finish each end with a 1 or 1.5 mm cutting disc. Mark out and cut to the line. seems simple to me ? Noel.

[SillyOldDufferModerator @sillyoldduffer]

Umm, are spanner flats needed?

When a chuck is pulled into the spindle by the drawbar it’s firmly wedged by the taper.  The wedge multiplies the frictional force, resulting in a considerable grip, strong enough to resist heavy cutting and vibration.  Assuming the male and female tapers are both in good condition, is this not strong enough to hold the chuck whilst it’s being undone by a weedy human?    Maybe not enough if dirt or wear have reduced the grip, or the drawbar (or equivalent) isn’t tight enough.

My feeling is chuck flats are belt and braces, not essential.  Needing them might even be a clue that the spindle is damaged and the taper needs TLC.

One of my books goes into taper theory.  Depending on the angle, fittings can be near permanent, requiring huge force to break the joint, or so slack they just fall out.  Tool-holding is in the middle: taper angles strong enough the grip firmly whilst cutting, but loose enough to detach when the drawbar is slackened.  Without hitting it with a big hammer!

My chucks all have flats and I use them.  But only because I assumed they are necessary.   Must try using a chuck without using the flats.

Dave

[SillyOldDuffer]

On SillyOldDuffer Said:

Umm, are spanner flats needed?

When a chuck is pulled into the spindle by the drawbar it’s firmly wedged by the taper.  The wedge multiplies the frictional force, resulting in a considerable grip, strong enough to resist heavy cutting and vibration.  Assuming the male and female tapers are both in good condition, is this not strong enough […]

Ah But … R8 is a non-locking taper

My question [and similar concerns expressed by others] remains !

MichaelG.

[SillyOldDuffer]

On SillyOldDuffer Said:

Umm, are spanner flats needed?

When a chuck is pulled into the spindle by the drawbar it’s firmly wedged by the taper.

But you need to stop the chuck/spindle rotating as you tighten the drawbar or the collet nut.

If the mill as no means to lock the spindle then you need flats or a good grip.

[JasonB]

On JasonB Said:

On SillyOldDuffer Said:

Umm, are spanner flats needed?

When a chuck is pulled into the spindle by the drawbar it’s firmly wedged by the taper.

But you need to stop the chuck/spindle rotating as you tighten the drawbar or the collet nut.

If the mill as no means to lock the spindle then you need flats or a good grip.

Finally the correct answer!

Tony

[Michael GilliganParticipant @michaelgilligan61133]

Maybe worth watching:

.

.

That’s where all that torque potentially  ends-up ^^^

 

MichaelG.

[JasonBModerator @jasonb]

Not if like some you have removed the pin😉

[Michael GilliganParticipant @michaelgilligan61133]

Of course, Jason … that’s why I used the word ‘potentially’

If it’s not present then the torque just gets carried elsewhere.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

[ postscript ]

The dynamics of fitting  conventional R8 collets into  a Bridgeport spindle seem to work … it’s the relatively high torque needed to firmly close anER25 or bigger that concerns me.

MichaelG

[NealebParticipant @nealeb]

While R8 might not be “locking” in the sense that a morse taper locks – and can be a devil to remove – I’m pretty sure that it’s the R8 taper in my Warco VMC that takes the load because the pin that engages with the R8 shank slot is pretty weeny and I wouldn’t like that to take any appreciable load. Except, of course, the load initially applied when you tighten the drawbar which is quickly going to engage the taper which will take full tightening load. And ditto for releasing, of course. One hand holds the spindle pulley and one hand works a spanner on the drawbar.

My Wabeco mill with its BT30 taper works the same way and doesn’t even have a keyway in it. Hand-holding is sufficient, although the spindle nose does have tommy-bar holes for final drawbar tightening – and note that it’s the taper locking the chuck at that point. The Wabeco with its fancy self-ejecting drawbar is a bit more complicated but the basic “taper locks it all tight” is still true.

Never needed a spanner on the chucks on either machine, and not even sure if they have any spanner flats. Holding the spindle still (by holding the spindle pulley in one case and tommy-bar in spindle nose hole in t’other) has always been adequate for tightening or loosening ER32 collets – although I do always use ball-bearing collet closer nuts. R8/BT30 tapers seem to hold well enough.

[Michael GilliganParticipant @michaelgilligan61133]

I am honestly delighted to hear that it works for you Neal … but the recommended torques for the larger ER sizes still seem too high to achieve like that.

Perhaps I am just being  ‘over-sensitive’

See about 16:20 in the Haas Video that Bill Phinn kindly linked.

… the use of high torques is justified earlier in the video.

MichaelG.

[NealebParticipant @nealeb]

…and if my machines could achieve the same material removal rates as a Haas machine, I might worry about tightening torques as well! For various reasons I was looking up the manufacturer’s recommendation for depth and speed of cut for an 8mm 3-flute carbide cutter. They reckoned it was good for an 8mm depth of cut in cast iron at something like 450mm/min and 2400rpm. Not in either of my machines, I think.

We do have to accept that we are using very much scaled-down versions of industrial machines and adjust our behaviour accordingly. I use ER32 because that seems in keeping with the scale of my machine and I seldom use cutters much bigger than 10mm; I have a 50mm face mill but that goes on a BT30 or R8 shank directly and works well like that. But even then, I tighten its securing bolt relying on the machine taper to hold the body still while I have the spindle locked.

Be aware of the guidelines, accept that they are not immutable rules, and see what works for you? YMMV, as they say elsewhere. I can’t say what that stands for as I believe that Trump has put a tariff on its use…

[JasonBModerator @jasonb]

You need to bear in mind that those 8mm depth cuts (1D) are generally combined with a small stepover typically 0.1D or 0.8mm.

As for small machines I was profiling some cast iron flanges a couple of days ago on the CNC. 6mm dia 3-flute carbide in a R8 ER16. 7.5mm depth of cut and 0.6mm stepover. Running at 4500rpm and a feed of 500mm/min. all on a benchtop hobby machine

Even the smaller 2.7 can move at a fair lick.

[Michael GilliganParticipant @michaelgilligan61133]

Very happy to concede the point, Neal … my wondering explicitly occupies a different part of the Venn diagram to your practical usage.

MichaelG.

.

Ref. https://www.model-engineer.co.uk/forums/topic/easiest-cheapest-source-of-r8-socket/page/2/#post-808043

[Michael GilliganParticipant @michaelgilligan61133]

A very impressive demonstration, Jason

MichaelG.

[PeteParticipant @pete41194]

Consider the taper angles between any Morse Taper and an R8. Quite obviously Morse Tapers self center and retain themselves within the spindle taper extremely well. Because of the fine taper angle, there known as a self holding taper and why there used with the addition of that draw bar thread when milling. But without some type of method of forcing the tool or collet tapers to release as the draw bar is loosened, they hold a bit too well just getting them to move enough to allow that release. And no amount of hard hammering on a draw bar is considered at all good for spindle bearings. It even beats the hell out of your draw bar and tool threads. I own mills with MT 3 and R8 tapers, there’s no comparison between the two and getting a tool shank to release.

The steeper taper angle of the R8 is within the range and considered as a self releasing taper. In practice, mine most times still requires a light tap on the end of the draw bar. I’d guess Bridgeport designed the R8 to get around the issue that the Morse Tapers all have without some type of tool shank extractor to force them loose. Prior to inventing the R8, BP even used a MT and at least one B & S taper for there mills. Other than that one issue, MT’s are still an excellent tool taper. Probably something like a MT 4 would be even better than the R8. Even the very rigid older Schaublin and Deckel mills picked MT 4 for there spindle tapers. And there good enough almost all lathe tail stocks still come with a MT. I don’t know about the UK and western Europe, but in North America, R8 tooling is relatively cheap and easy to find. Although that seems to be slowly getting less each year for at least industrial quality tooling.

But that R8 pin screwed into the side of the spindle that protrudes inside has absolutely nothing to do with any possible amount of drive torque being transmitted to a collet or tool shank. That keeps being incorrectly thought of for the reason it’s there. It’s simply a very light weight and inherently weak method of keeping a R8 tool taper from spinning as the draw bar first starts into the threads, and it’s sized to do that job. If both the draw bar and tool threads are kept in good condition and running a tap and die through and over them once in a while, there’s no need for the pin. Once the R8 tool or collet taper does start to get pulled up and even slightly tighten inside the spindle taper, the pin isn’t needed. And that R8 taper still has the usual holding capability due to friction and a bit of wedging action much like any MT tooling would have. It’s just over a much shorter but apparently still adequate taper length. So it’s that same friction between the shank and spindle tapers that’s designed to resist the cutting tool torque and keep an R8 tool shank from any rotation inside the spindle as long as the draw bar is correctly tightened. It’s not a tool taper that was designed nor meant to use that pin to ever provide an appreciable amount of drive torque.

That R8 pin design also has a known and what can sometimes be a highly detrimental and expensive flaw that quite a few have experienced. Forget to fully tighten up a R8’s draw bar with a larger diameter cutting tool and start a decent depth of cut. If the tool shank doesn’t spin in the tool holder, that pin tip can be easily sheared off. Go back through the Practical Machinist forum posts and more than a few have had that sheared pin end get forced into and jammed between the inside of the spindle and a collet or tool shank. That usually results in completely seizing whatever is inside the spindle. One in fact about a month or two ago on the PM forums was bad enough he had to replace his spindle. For that same reason my pin has been removed for years and I’ve never missed it. If I were to ever forget to properly tighten my draw bar? At most the tool and short R8 spindle taper might get scored a bit. A simple and relatively cheap taper re-grinding would fix that. It’s not even impossible to do in a home shop with a tool post grinder or similar. https://www.youtube.com/watch?v=CFAkb93_V3M

To prove that pin isn’t meant to provide any real drive improvement, 30 taper milling spindles would be roughly comparable to most of the larger R8 spindle mills as far as having around the same HP and overall mill rigidity in most cases. Then compare the size and depth of the 2 drive dogs on the end of the spindle to that tiny 1/4 x 32 tpi R8 pin. That’s also the same reason or why those 30,40,50 tapers in commercial cnc use may or may not have any wrench flats on there ER collet chucks. There’s no real need for them as almost always ER collet chucks would have tools changed and fully tightened in them using a bench mounted fixture that also keeps the tool shank from spinning with a pair of the same sized drive dogs.

For reasons I’ve yet to figure out, the steep 30 and other sized tapers were introduced and patented around 1927. Bridgeport invented the R8 in the 1950’s as there own proprietary tool taper. Yes it’s ok and does work fine obviously. Adequate even for most of what we might be doing. But still limited in tool rigidity and how much HP it can handle. That 30 taper as well as the larger tapers are so superior there in almost universal use world wide other than minor changes to the flange design, drive lug sizes, draw bar or pull stud threads size and pitch. It’s always seem a bit strange that BP invented a whole new tool taper when that 30 taper was already well proven, and imo would be quite a bit superior to the R8. For the smaller bench top sized mills, even the rarely seen and used 20 taper would be a good choice. But very hard to find tooling would mean few would buy any mill with that spindle taper.

High volume industrial cnc milling, and absolutely with a tool changers with large tool libraries are only somewhat related to what most of us might be doing with our ER collet chucks and manual mills. For them and for each mill, they might have dozens of ER collet chucks, a few sets of the same series of ER collets, even more extra collets for the most used tool shank sizes, and dozens more collets and chucks in the various ER collet series. In general and unless the part run is changing to something different and a tool change out is needed. Then cutting tools get tightened into an ER chuck and are not removed until there tool life is used up.

It’s also simple to figure out, Haas doesn’t need to specify any special protocol at all. It would be automatically assumed the usual tool tightening fixture would be used since everyone with those tool tapers and drive dogs uses them. I’d think most of us might only own 1 or maybe 2 different sized collet chucks and collet sets. We change collet sizes and the tools held in them far more often, and probably for most, while the collet chuck is still in the mill. So a spindle brake, lock or wrench flat on the collet chuck would be desirable for us. I do have a built in spindle brake on my BP clone, but it can’t be engaged and locked like a real BP can. Trying to hold that brake applied while at the same time loosening or tightening a collet nut is far more awkward and inconvenient than just using the wrench flats, an open end wrench, and the collet nut wrench.

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