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Plain bearing spindle design

Sorry, I meant high dn grease, just a high speed rated grease. N and M are pretty close together on the keyboard. I didn't have any trouble with that link. It does have ads. Don't know if it helps, but I use a free highly filtered DNS service that might be protecting me- https://github.com/Ultimate-Hosts-Blacklist/Ultimate.Hosts.Blacklist Generally it won't let you access a problem site at all. Highly recommended. If it blocks a site I really need to see I just change the DNS to Google or whatever, then change it back when done.
 
I would look for the additional spindles for ID grinding on a ID/OD grinder
Plenty available New or used
There is more into making a plain bearing for a grinder as meets the eye
If it is for fun?? Please go ahead

Peter
Well, it's sorta for fun but not exactly. I've got a mid-80s Studer S20 that get used a couple times a month for grinding some oddball parts that we use in-house. Instead of installing and aligning the workholidng fixtures each time, I'm making a couple spindles that will have the workholding fixtures more or less permanently attached. This machine only has 80mm from the spindle center to the table, which is what drove me to roll my own spindles instead of just bolting a punch grinder to a baseplate and calling it good. I looked around for some S20 spindles. The only ones I saw were for the later 100mm center-height machines and the pricing was, uh, yeah, that's not gonna happen. I've got a mechanical engineering background so I figured what's stopping me from making a spindle similar to what was getting cranked out by dozens of machine-tool makers a hundred years ago? And within a minute or two, I realized, I don't know the first thing about designing precision plain-bearing spindles. Nice chance to learn something new about something old, I guess.

Is this occasionally used or a production set up?
As mentioned above, a couple times a month, and only to finish or regrind a few parts at a time.
 
I have to disagree that turbos are highspeed bearings. They are more like medium speed.

The one foot or even larger journal bearings that support the generator shaft of 1 gigawatt 3600rpm turbo generators are running at a higher specific speed than most consumer level stock turbos.

A 10mm diameter journal bearing 1 cm long spinning at 100k rpm, feed from the middle from a 2mm wide groove with 4 oil holes, around a .001" clearance... Not actually that hard to design.

Compare to a surface grinder spindle, 30mm at 3600 rpm and a ten thousands of an inch clearance with water thin oil.

Or any main bearing in any half liter or larger per cylinder, vehicle engine able to sustain 5k rpm for triple digit hours.. 8cm diameter main bearings 2 cm wide at .002" clearance. The same engines can run at higher loads with admittedly more clearance at double the rpm, but not for very long- but that seems to have nothing to do with the main bearing oil film breaking down, rather fatigue limits of everything else.

I heard that an off the shelf but otherwise turbo or supercharged sbc engine can twist the whole block a 1/16th of an inch under the torque produced by the engine itself.. and i wonder if that is actually the reason why .003" clearance is needed for some engine builds. The whole block is twisted causing point contact on the bearings needing that extra .001" of clearance to avoid metal on metal contact.

Certain 1.9L vw tdi engines can handle 5.5k rpm and the 6cm diameter connecting rod bearings can handle as little as half a thousandths of clearance. factory spec is 0.4 to 2.4 thousandths clearance.... Rarely do they go bad.

My south bend 9 can handle 1500 rpm at 1.5 thousandths clearance without warming up much, using low viscosity atf (a little thinner than velocite 10 spindle oil). A 200 pound load downwards on the spindle needs a minimum of about 60 rpm to reach a true oil film of low friction.
I have tried proving that number from older texts on journal bearing design and its not easy, didnt get anywhere.

Also my southbend prefers to spin in one direction
.. it probably takes double the rpm under 200 pounds load in reverse, to reach a point where you can keep it going with just one finger pressure turning the weight.

I doubt i have the ability to measure how out of round the headstock is. It may only be half a thousandths, enabling oil to flow from the wick into the journal but preferably in one direction.
 
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A hydrodynamic spindle bearing may not be practical for the low RPM of a grinder work head.

A used internal motor Setco block spindle operated with a VFD will work for your application at a fraction of the cost of a homemade spindle.


Setco also makes pulley driven block spindles which will match your height restrictions. The bottom of the block spindles are keyed to allow quick alignment when swapping blocks.


The Setco spindle catalog lists the block dimensions and runout specifications:

The spindles can be supplied with air purge seals.
 
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I looked into plain bearings for a milling machine spindle at one point, partly as a thought exercise - I was working out a BOM cost for a DIY machine and considering all the options.

And I was given a bunch of reasons it couldn't be done, but I discovered that a researcher at a NASA facility in the 90's has done exactly what I was thinking - a hydrostatic bearing and a hydraulic motor. Incidentally, the patent documents talk about how effective it is at low rpm.

I had a sense it was feasible after seeing a large cylindrical grinder ( 500 HP ) get it's spindle rebuilt. The place I was working has originally built the machine, I think, in the 60's.

Then there's the Ingersoll machines from the same period - the HVM600 and another in the same series. Interestingly, I think those were hydrodynamic and used water as the fluid.

Not that milling machines are your application, but I would run with it. Design guidelines, I don't know. I don't remember seeing anything about design of plain bearing spindles in any books beyond some generalities.
 
I have to disagree that turbos are highspeed bearings. They are more like medium speed.

The one foot or even larger journal bearings that support the generator shaft of 1 gigawatt 3600rpm turbo generators are running at a higher specific speed than most consumer level stock turbos.

A 10mm diameter journal bearing 1 cm long spinning at 100k rpm, feed from the middle from a 2mm wide groove with 4 oil holes, around a .001" clearance... Not actually that hard to design.

Compare to a surface grinder spindle, 30mm at 3600 rpm and a ten thousands of an inch clearance with water thin oil.

Or any main bearing in any half liter or larger per cylinder, vehicle engine able to sustain 5k rpm for triple digit hours.. 8cm diameter main bearings 2 cm wide at .002" clearance. The same engines can run at higher loads with admittedly more clearance at double the rpm, but not for very long- but that seems to have nothing to do with the main bearing oil film breaking down, rather fatigue limits of everything else.

I heard that an off the shelf but otherwise turbo or supercharged sbc engine can twist the whole block a 1/16th of an inch under the torque produced by the engine itself.. and i wonder if that is actually the reason why .003" clearance is needed for some engine builds. The whole block is twisted causing point contact on the bearings needing that extra .001" of clearance to avoid metal on metal contact.

Certain 1.9L vw tdi engines can handle 5.5k rpm and the 6cm diameter connecting rod bearings can handle as little as half a thousandths of clearance. factory spec is 0.4 to 2.4 thousandths clearance.... Rarely do they go bad.

My south bend 9 can handle 1500 rpm at 1.5 thousandths clearance without warming up much, using low viscosity atf (a little thinner than velocite 10 spindle oil). A 200 pound load downwards on the spindle needs a minimum of about 60 rpm to reach a true oil film of low friction.
I have tried proving that number from older texts on journal bearing design and its not easy, didnt get anywhere.

Also my southbend prefers to spin in one direction
.. it probably takes double the rpm under 200 pounds load in reverse, to reach a point where you can keep it going with just one finger pressure turning the weight.

I doubt i have the ability to measure how out of round the headstock is. It may only be half a thousandths, enabling oil to flow from the wick into the journal but preferably in one direction.
Lots of uncategorized data and opinions.
What is the take away points for the original
posters question about a plain bearing grinding
spindle ?

-D
 
We need to design and build a couple small spindles for some grinding operations. They need to be reasonably but not exceptionally accurate: 1 tenth TIR would be perfectly adequate. I have one small Blockhead air bearing that's the right size, but it's overkill for the task and I don't want to risk putting it in harm's way when we usually use it for special measurements. I thought about using a Harig grind-all spindle, but the center height won't work out with the mounting arrangement.

I can design and build a spindle with a couple pairs of preloaded angular contact bearings for this. That wouldn't be a problem. Before commiting to that, I wanted to consider a plain-bearing spindle. Years ago, I had an ancient Hendey conehead lathe with plain bearings that turned exceptionally round. Thousands of SB lathe spindles had plain bearings, and the old Crystal Lake Grinders claimed to achieve sub-0.00001 TIR with their conical spindles riding in scraped bronze.

Can anyone point to a reference that discusses the design of plain-bearing machine-tool spindles in some detail? I've never disassembled a precision plain-bearing spindle and I'm unclear on several details...for instance, how are thrust loads resisted in both directions, and how is the oil-gap maintained as the spindle warms up? It seems like the spindle will get hotter than the housing, which would cause the spindle to grow faster and for the oil-gap to increase.
In the 16th edition of Machinery’s Handbook they have over twenty pages dedicated to plain bearings, and a few more to the lube best used in them in various applications. Not all editions of the reference are equal in content. The 16th is from about 1962 as I recall and is one of the best for old hard knowledge. Good luck
 
And lap the spindle Also often the bushings are 3 lobbed And the bronze quality And the steal quality And the lubrication oil To make a really good one takes a lot of trail and error
Peter
 
I don’t know much about plane bearing design but have used grinding machines using them. I could be wrong but thought they were limited to a highest RPM of 6000 or what.
They seem to run smoother and give a better surface finish then a beringed spindle. They take 15 minutes+ (or so) to warm up, and perhaps more horse power (energy) to run.

Qt Dave: (In the 16th edition of Machinery’s Handbook they have over twenty pages dedicated to plain bearings,)
I will have to take the time to read that.
 
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