R8 - Wimpy or Wonderful

[JRouche]

Hi,

Ain't nobody here running their Bridgeport/clone hard enough to have a real concern over what type of spindle you should get.

Pretty much true. The only reason I use kwik-switch is it was on my boss5 bridgeport and I didnt want to use both r8 and KS, too many tools. Keep it all in one family. JR

[Bob La Londe]

At one time we had a Bridgeport with a spring loaded retention knob system that did not work terribly well, these are solid holders.
There were also modified R8 collets with a nut clamping device on the end like an ER. Do not recall the name of the system but it made for fast tool changes but not robust tool holding.

Mach 1 Systems. I had that system briefly on my RF45. I gave it away for free to another RF45 user. He never thanked me. As much as I had against using a master holder hanging out of it for kwik switch stuff it was a step up over Mach 1 IMO.

I was excited at first. I figured I could just make the knobs, but nope. Its was set up so you had to cut down the tool or tool holder. Don't know if I ever decided if that was necessary to clear the claw or if it was a choice to drive sales of their own line of modified tools.

[eKretz]

It isn't a 'drive key'. Its just there to hold the collet while you tighten the drawbar, and to provide repeat indexing for the collets. So many people pull the key, but if you have a collet with a little chip or dirt in the drawbar thread its better to have the key in there.

You can call it whatever you want, it acts as a drive key if the holder tries to move. And if that happens, you can kiss it goodbye as well as usually get some damage to the inside of the spindle from the mangled parts. They are a weak point. Most shops I've worked in remove them the first time they fail because of that. Leaving the key out prevents the key related destruction but a spin in the taper can potentially be even worse.

The guys bellyaching about not pushing a Bridgeport or similar mill to high horsepower levels are way off base. Lots of guys try to drill and/or bore fairly large holes and also flycut at pretty good sized diameters. One accidental heavy cut or a bang into a shoulder or a drill grabbing during breakthrough is enough to load the spindle with enough torque to cause damage. Horsepower has nothing to do with it.

The other nice thing about NMTB or CAT tapers is that they have repeatable Z locations - that's nice when doing multiple parts, especially if you have readouts.

[J Tiers]

.................................

The other nice thing about NMTB or CAT tapers is that they have repeatable Z locations - that's nice when doing multiple parts, especially if you have readouts.

Yes, that puzzled me about the TTS, because the collet pulls in, so it is not too well defined in Z. Kinda OK, but clearly not to thou. Seems like there should be an external surface to register on, like the spindle face. In fact, I thought that was a feature of it.

But earlier folks were talking about grinding the collet flat.

[oxford]

You can call it whatever you want, it acts as a drive key if the holder tries to move. And if that happens, you can kiss it goodbye as well as usually get some damage to the inside of the spindle from the mangled parts. They are a weak point. Most shops I've worked in remove them the first time they fail because of that. Leaving the key out prevents the key related destruction but a spin in the taper can potentially be even worse.

The guys bellyaching about not pushing a Bridgeport or similar mill to high horsepower levels are way off base. Lots of guys try to drill and/or bore fairly large holes and also flycut at pretty good sized diameters. One accidental heavy cut or a bang into a shoulder or a drill grabbing during breakthrough is enough to load the spindle with enough torque to cause damage. Horsepower has nothing to do with it.

The other nice thing about NMTB or CAT tapers is that they have repeatable Z locations - that's nice when doing multiple parts, especially if you have readouts.

All this is correct. I wiped out the pin on the r8 mill at work boring a large diameter interrupted cut. I was no where using any amount of high horsepower. Boring head shank got pretty messed up but still usable. It was a heck of a time getting it out of the spindle.

New pin did NOT go back in.

With all the talk of 3-5hp knee mills, I am going to say it has more to do with variable speeds using a vfd than anything else.


Unless you have a bunch of r8 collets and tooling I don’t really see any advantage on getting a new mill with a r8 over 40 taper.

[Bob La Londe]

Yes, that puzzled me about the TTS, because the collet pulls in, so it is not too well defined in Z. Kinda OK, but clearly not to thou. Seems like there should be an external surface to register on, like the spindle face. In fact, I thought that was a feature of it.

But earlier folks were talking about grinding the collet flat.

The TTS collet is ground flat on the face so it does not stick out of the spindle when tightened. This allows the collar on the TTS tool to register on the spindle face. The collar is also hallowed on the back to help make sure the outer rim registers every time. They repeat extremely well.

[JRouche]

You can call it whatever you want, it acts as a drive key if the holder tries to move. And if that happens, you can kiss it goodbye as well as usually get some damage to the inside of the spindle from the mangled parts. They are a weak point. Most shops I've worked in remove them the first time they fail because of that. Leaving the key out prevents the key related destruction but a spin in the taper can potentially be even worse.

The guys bellyaching about not pushing a Bridgeport or similar mill to high horsepower levels are way off base.

Hmm? I didnt see any belly aches with the R-8 taper or HP. I might have said something but not even poopooing on the taper. It has been on more mills than any other taper maybe? Dunno.

The key? That is always in contention. Read many articles about the benefit of removing it. I am not one of those. The engineers have it there for a purpose. Its not a drive tang or key, we know this.

Only time I have seen (read) it fail was due to improper maintenance. The R-8 needs to be fully seated, with a clean seat then drawbar it on up.

When that doesn't happen there is not enough grip in the taper and it slips, shearing the lil tiny indexing piece.

And the indexing piece is not a tightening fixture. Snug up on the collet nose after the draw bar locks the taper in. JR

[JRouche]

Yes, that puzzled me about the TTS, because the collet pulls in, so it is not too well defined in Z.

Hmm. I dont know if I am doing it correctly but how I do it is define Z after my tool is set in its holder. Ill touch off on a method then zero. I cant afford Z axis errors. JR

[JRouche]

! That 3hp was in reference to the OP's talk of 3-5 hp being available where he was looking. If you read my entire post, you saw that I thought 1hp was enough.

Come on now, you know I would never throw a bus at you. I was meaning to make a "funny" comment. Not all jokesters work well. JR

[Bob La Londe]

This new machine arrived 3 or 4 years ago, 7 1/ 2 HP variable speed spindle with no gearbox.
At a suitable speed it will not drive a 1" HSS twist drill in mild steel without stalling. In order to prevent the Z axis drive from trying to push a non-rotating drill through the work it simply shuts down.

This piqued my curiosity since I fairly routinely TC tap in aluminum high pulley on the Tormach at 500 RPM. I know I know not the same. Anyway I started punching in numbers. I have 10-32 1/4-20 and 5/16-18 mounted in TC tap holders all the time. For a starting point I used 1/4-20. That's about 1/4 horsepower load according to FS-Wizard. I have to be honest, that's more than I thought was available at just 500 RPM from that inverter driven 1.5 HP motor in the high pulley range. It will break taps if I get a bad tap, but it does the job for any number of holes with quality taps so its within the capability of the inverter/motor combination.

So then I plugged in a 1" HSS drill and 1018 steel to see what it said/recommended 316 RPM @ 5.53 IPM and 2.06 HP load. That cut would be impossible with a Tormach of course , but it gave something for comparison. 0.25/1.5=0.166 vs 2.06/7.5=0.274666... That is a much larger power factor as a percentage of available power and a lower RPM which also must be considered. Just doing the most crude comparison it seems that a 1" drill would be marginal to much load for the machine you showed.

Now that's not the end of it though. Most people setup a machine and use the default power curve with a peak voltage and current at the peak of the power curve. Typically that's a slight drop off at the highest RPM and a fairly linear drop off to the lowest RPM. Motors are not so linear, and many can take higher voltages due to heavy windings. The inverter could be tuned to give more power at lower RPMs. Depending on the motor and how it is cooled. My Hurco has a separate fan motor inside the motor housing that runs continuously. I'm really beyond my area of more than general knowledge at this point, but when I was setting up an inverter VFD with the help of one of the guys at Drives Warehouse (he called me back from home on the weekend to help me) sometime back he touched on it a bit. It seems the motor isn't actually getting full voltage and current limit except at the peak in its power curve. Its all way over my head, but the gist is you CAN get more power at lower RPMs with some motors if you tune the VFD for the job. Maybe not enough for for application, but more.

I am much more crude than than. I have figured some of my power curves by when I hear the spindle bog down, or when I broke a tool. Kind of like your machine just shutting down because either the current was to high (servo drive or motor drive) or the following error was to large from the servo drive. "It don't feel right. That's the limit. OFF!"

I'm not sure I added anything to the conversation except to satisfy myself that its not unreasonable to have issues punching a 1" drill into mild style with that machine at recommended speed and feed. It would be nice if the machine manufacturer provided a tested RPM/HP/TORQUE power curve for your guys to use in calculating cuts. Of course it doesn't help if its more than the servos can handle.

I hesitated to post this because I'm not an expert on this, and it would give the nit pickers the opportunity to do the judgmentalism they so enjoy, but hey. Everybody has to have a hobby right? Even if its just being an internet troll.

[Bob La Londe]

I hesitated to post this because I'm not an expert on this, and it would give the nit pickers the opportunity to do the judgmentalism they so enjoy, but hey. Everybody has to have a hobby right? Even if its just being an internet troll.

I'm halfway tempted to make that my new sig line.

[old mart]

When I converted the Tom Senior light vertical from MT2 to R8, I deliberately left the spindle bore clear, no locating pin. Without the pin, a 30 size taper cleaning plug can be used. The only thing that needs to be good when there is no pin is the smooth engagement of the drawbar threads. If the threads have tight spots, then the tooling will want to turn with the drawbar before and after the taper is tight. This does not matter much for most tooling, but the direct fitting R8 collets have nothing to get hold of. I have run a 7/16 UNF tap into the tooling and cleaned and greased the threads with moly grease. This makes them less troublesome. So far, the advantages outweigh the disadvantages, and I'm in the pinless camp. It would be easy to drill three axial holes it the end of each collet and make a loose fitting pin spanner to hold them. Maybe one day I will do that to the full set of metrics and about 5 imperial collets that the museum has. Most sizes have never been used.
This mill has only got a 1hp 6 pole three phase motor with a VFD set for 25-75 Hz. The original motor was 1/2hp. I would think that R8 would be at its limit power wise with 2hp.

[nickel-city-fab]

I'm halfway tempted to make that my new sig line.

Originally posted by Bob La Londe View Post

I hesitated to post this because I'm not an expert on this, and it would give the nit pickers the opportunity to do the judgmentalism they so enjoy, but hey. Everybody has to have a hobby right? Even if its just being an internet troll.


That is Excellent!!

[tom_d]

There are also master holders for KWIK 200 from R8, so I could run my KWIK 200 holders, but it all hangs down below the quill. I had one for a while on an RF45 style mill.

As soon as you start hanging tools out and away from bearing support you trash any advantages of a quick change set-up. This is further exaggerated when the quill is extended. Those things are just a gimmick as far as I'm concerned.

R-8 tooling doesn't require anything more than 1 to 1.5 horsepower. Only reason for 2 horsepower on the old 2J heads is for the power sucked up by the variable speed drive. The R-8 system is a wonderful way of holding tools, and its longevity in the field is testament to that, but if you can go with a #40 spindle I would recommend it. No need to go broke buying tooling on day one. Pick up holders as you need them. Buy or build your own tool setter so you can swap out cutters and retain Z position with ease and you're off and running.

[Bented]

I'm not sure I added anything to the conversation except to satisfy myself that its not unreasonable to have issues punching a 1" drill into mild style with that machine at recommended speed and feed. It would be nice if the machine manufacturer provided a tested RPM/HP/TORQUE power curve for your guys to use in calculating cuts. Of course it doesn't help if its more than the servos can handle.

I suspect that some manufacturers like to use a wide speed range in their marketing. A claimed 200-5000 RPM range for this machine.
The spindle is amazingly quiet at all speeds however, the cooling fan is far louder then the motor itself.