Correct oil level for Studer RHU-500 grinding head?

How much oil should I put into this Studer RHU-500 grinding head?



Stupidly, I filled it to the middle of the oil eye (Mobil Velocite #3) but then oil started to run out around the grinding spindle. I was stupid because just by looking you can see that the oil eye is well above the height of the spindle. I am pretty sure that the oil is fed by an internal pump, and the oil eye is to monitor the flow from that pump. So the required oil level is lower than this eye.

(Background: the spindle is from a machine that was parted out, and I want to run it for testing purposes before selling or trading it. But I have zero documentation.)

Edit: I've looked a bit more at the design. I think the way it is supposed to work is like this. The spindle bearing is solid, and when it's rotating there is a flow of oil coming out of it. This is "caught" by a grooved ring which then directs that oil into a hole directly ABOVE the spindle centerline. The oil then flows through that hole and back to the oil sump. (It might also flow through the oil eye that is shown, on the way back to the sump.) Does that make sense? Has someone seen a system like this before?

Answering my own question after a kind soul gave me a copy of the RHU-500 manual. The correct oil level can be determined by the oil eye shown above. The oil eye has a red circle in the center, and the correct oil level is between the bottom and the top of that circle. The oil ran out of my spindle because an axial oil seal was missing by the spindle mounting taper.

My next question: what's a reasonable operating temperature for a grinding wheel head like this? It has four speeds (pulley) for 350-400mm, 300-350mm, 250-300mm and 220-250mm grinding wheels. I have run it for several hours at each of the lower speeds, and it settles down to a temperature below 50C = 122 F. But if I run it a the top speed, after a couple of hours it gets up to 56C = 133F and I get nervous and shut it off. For reference, 60-65 Celsius is about the hottest that you can touch and hold without pulling your hand away.

I know that this is a solid hydrodynamic journal bearing, and that it has the correct oil and the correct oil level and plenty of oil flow (as seen through the flow eye). So what is the maximum expected operating temperature for such a head and bearing?

So I assume this is a sleeve bearing spindle?

My mattison sleeve bearings run up to 130 deg. F.

cash said:

So I assume this is a sleeve bearing spindle?

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Yes, the spindle is a single long tapered shaft running in a solid bearing shell. The small end of the shaft has a "screw" which draws oil through a microfilter and then pumps it over the shaft. The oil supports the shaft hydrodynamically, then exits from the large end of the shaft and returns to a sump.

My mattison sleeve bearings run up to 130 deg. F.

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OK, that's about 55C, similar to what I am seeing here. I also realised that this grinding head is missing the belt guard. I think that this guard has a second function: to direct cooling air coming from the motor so that it flows past the head. This should help to reduce the operating temperature somewhat.

Cash, I am thinking about regrinding the spindle taper, which has a "step" that I can feel. I could do this by removing the spindle from the bearing, lapping the center marks to get it running true, and then grinding the spindle taper between centers. Or I could remove the entire spindle capsule, mount that on V-blocks, and then grind it "in situ". How do you go about this?

As far as grinding the spindle- does your wheel flange fit tight? Maybe a small step but if your wheel flange fits proper, no wobble then my opinion would be leave it alone.

But if you do have issues and want to grind it- I think that both ways you proposed would get you the same result. But I think you would be better to remove the spindle and grind between centers. you would want to make sure before grinding you would be running true to the area of the spindle that runs on the bronze bearing. I am sure there may be some other input here which will confirm.

Whichever way you go- please let us know and take some pics!

cash said:

As far as grinding the spindle- does your wheel flange fit tight? Maybe a small step but if your wheel flange fits proper, no wobble then my opinion would be leave it alone.

But if you do have issues and want to grind it- I think that both ways you proposed would get you the same result. But I think you would be better to remove the spindle and grind between centers. you would want to make sure before grinding you would be running true to the area of the spindle that runs on the bronze bearing. I am sure there may be some other input here which will confirm.

Whichever way you go- please let us know and take some pics!

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I'd agree the first, 'fraid I'd actually disagree the second. But perhaps "not really".

Used spindle. He said "sell or trade".

If were to touch-up the wheel-mount taper in any way - presuming the wiser-yet course suggested of just leaving it TF alone was not quite good enough - I'd want to use the spindle in its own bearing just as presently assembled as my reference, and grind the taper in situ.

If I had the revenue work for it, and the Studer in need of it, then the former Pope spindle krew, ELSE Penn Technologies (Parker-Majestic), ELSE Fi$cher $pindle for the best rebuild I could get, balancing included, ... and mortgage the damned Jaguar!



Used sale? Trading material?

I see simply "good condition" and with TIR figures offered as lower risk on an uber-spindle of putting-off the sort of folks who NEED such than "seller refurbished" might do.

I'm risk averse on stuff like that.

Those three firms I cited are "in the business". Or were when last I looked ( you may know many more).

If it ain't right? They can correct it. With Out Fail.

Now.. if it happens that PM's "ballen" IS Fischer Spindle ....or similarly equipped, clean room and all..

Cash, Bill,

No, I'm not Fischer Spindle or similar. Just someone who enjoys using and fixing up old machinery. If this was a greased needle or ball bearing spindle I would probably not contemplate working on it myself. But this type seems easier.

The step in the taper does not interfere with proper hub engagement and there is no run-out that I can measure. The hubs engage at the large and small ends of the taper, but are relieved in the middle. That's where I can feel the step. Probably the right thing is just to leave it as it is.

On the other hand I've gotten good enough with my cylindrical grinder that I am confident that I can get the hub taper spot on and keep everything concentric to under a micron. So it's tempting to make it better.

Cheers,
Bruce

ballen said:

Cash, Bill,

No, I'm not Fischer Spindle or similar. Just someone who enjoys using and fixing up old machinery. If this was a greased needle or ball bearing spindle I would probably not contemplate working on it myself. But this type seems easier.

The step in the taper does not interfere with proper hub engagement and there is no run-out that I can measure. The hubs engage at the large and small ends of the taper, but are relieved in the middle. That's where I can feel the step. Probably the right thing is just to leave it as it is.

On the other hand I've gotten good enough with my cylindrical grinder that I am confident that I can get the hub taper spot on and keep everything concentric to under a micron. So it's tempting to make it better.

Cheers,
Bruce

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Bruce?

Think through what you just wrote, there.

If "there is no runout that I can measure"? Be happy. Someone did their job well. Really well.

So how on God's Green Earth do you expect to "make it better", and how TF would you even know.. unless - it does happen, y'know ... you made it WORSE? And THEN had runout you COULD measure?



Lybarger's Corollary applies to this one:

All else being equal, you lose.

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"the right thing very much is just to leave it as it is"

thermite said:

So how on God's Green Earth do you expect to "make it better", and how TF would you even?

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By eliminating the step on the taper. That step surely matches the hubs used on this spindle for the past decades, but won't match other hubs, which will then either mess up the spindle taper or be messed up by them. So "better" would be to have no measurable runout, no step in the taper, and the correct taper angle.

But you and Cash are probably right that it's better left as is for the next owner to either live with or deal with.

PS: who is/was Lybarger?

ballen said:

By eliminating the step on the taper. That step surely matches the hubs used on this spindle for the past decades, but won't match other hubs, which will then either mess up the spindle taper or be messed up by them. So "better" would be to have no measurable runout, no step in the taper, and the correct taper angle.

But you and Cash are probably right that it's better left as is for the next owner to either live with or deal with.

PS: who is/was Lybarger?

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Schoolmate, Audiologist, businessman.

ISTR it was a Science class and we had just done the usual on Charles' Law, Boyle's Law ==> the "Combined Gas Laws", which started out with the one TARGET variable and:

"All else being equal..."

Murphy's Law // Sod's Law was at the time expanding into posters and posters full of permutations - all with much the same message, of course.

Ed took the gas laws example as a means to simplify the entire lot with "Lybarger's Corollary" (to Murphy's Law or Sod's law..):

"All else being equal, YOU LOSE!"



NB: The relieved center portion is so common on 50 Taper hubs for grinders (and not-only), that Hong Kong Harbour could very well freeze solid before that Studer spindle ever sees one that does not have that feature.

If the ridge bugs you, all it needs is stoning. No need to sweep the rest of the taper at all.

Monarch 10EE #12 Jarno has the reverse problem.

The relief is in the female taper. Back edge of it gets bumped as tapered goods are inserted, and it needs stoned.

Most especially for test bar use when I am about to put a 20 Millionths Mahr or the 10 Millionths Hamilton to it to see how good, bad, or indifferent the bearings might be.

Ignorance was bliss, by comparison. But there you have it.

If you cannot measure any <wotever>, it isn't perfect.

You just need better instruments!

thermite said:

The relieved center portion is so common on 50 Taper hubs for grinders (and not-only)...

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FWIW, the Studer taper is not a "standard 50". It has a 10-degree included angle, going from about 33.8mm to 43.4mm over a length of 55mm.

If the ridge bugs you, all it needs is stoning. No need to sweep the rest of the taper at all.

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I have heard and read that one should never try to touch up a precision taper by hand.

Here the "ridge" is ~2cm (3/4") wide and ~10cm (4") circumference. Since I can feel it with my fingers it must be at least 25-50 microns (0.001-0.002") high. That's 50 to 100 cubic mm of metal! I do have a pair of flat-ground toolroom stones, but they are for removing burrs off of machined or ground surfaces, not for substantial stock removal.

If you cannot measure any <wotever>, it isn't perfect. You just need better instruments!

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Agreed. My take on this is that if I can get the taper precise at the 1 micron level, then it will be more precise than the hubs, so "good enough". The dressed wheel surface is what counts, and not affected by these taper and hub errors.

ballen said:

FWIW, the Studer taper is not a "standard 50". It has a 10-degree included angle, going from about 33.8mm to 43.4mm over a length of 55mm.



I have heard and read that one should never try to touch up a precision taper by hand.

Here the "ridge" is ~2cm (3/4") wide and ~10cm (4") circumference. Since I can feel it with my fingers it must be at least 25-50 microns (0.001-0.002") high. That's 50 to 100 cubic mm of metal! I do have a pair of flat-ground toolroom stones, but there are only to take burrs off of machined or ground surfaces, and are not suitable for substantial stock removal.



Agreed. My take on this is that if I can get the taper precise at the 1 micron level, then it will be more precise than the hubs, so "good enough". The dressed wheel surface is what counts, and not affected by these taper and hub errors.

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All the discussion aside, yah cannot measure an error, and you aren't even going to keep the spindle and use it?

Fess up!

You are just trying to manufacture any excuse you can to go play with the grinder!

Just do it. You don't need a hall-pass from any of us.

thermite said:

Fess up! You are just trying to manufacture any excuse you can to go play with the grinder!

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Guilty as charged. My natural inclination is to make it as good as I can, and since I have not done this type of fix before, it's an appealing challenge and learning experience. But the advice I get here is useful, since it makes me reflect carefully and in this case reinforces one of my dad's favourite sayings, "if it ain't broke, don't fix it!".

Anyway, let me turn this back to your earlier advice to "stone it off". Do you agree that the situation I describe, 50-100 cubic mm of metal, does NOT qualify as a "ridge" and is NOT a candidate for hand stoning on a precision taper mount?

ballen said:

Guilty as charged. My natural inclination is to make it as good as I can, and since I have not done this type of fix before, it's an appealing challenge and learning experience. But the advice I get here is useful, since it makes me reflect carefully and in this case reinforces one of my dad's favourite sayings, "if it ain't broke, don't fix it!".

Anyway, let me turn this back to your earlier advice to "stone it off". Do you agree that the situation I describe, 50-100 cubic mm of metal, does NOT qualify as a "ridge" and is NOT a candidate for hand stoning on a precision taper mount?

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Stoning is for burrs.

Or crows - if you never learned to point-shoot the aerobatic rats with a .22 pistol for lack of money for shotgun-shells.

And you are heading into working to Dickie Smother's rules, not yer Dad's:

If you borrow it, BREAK it!

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cash said:

So I assume this is a sleeve bearing spindle?

My Mattison sleeve bearings run up to 130 deg. F.

Click to expand...

I ran the oil filter and microfilter (sintered bronze) through an ultrasonic cleaner with a heated brass/bronze cleaning solution. At the highest speed the head temperature now stabilises at 56 Celsius = 133 degrees Farenheit. So I think all is well.

I've talked to a Swiss expert on these machines, who says that this head has a hydrostatic spindle bearing. When the spindle is running, there is no metal-to-metal contact: an oil film separates all moving parts.