Lathe RPM with Babbitt bearings?
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    Default Lathe RPM with Babbitt bearings?

    Looking this up on original LeBlond brochures and catalogs from 1911 states between 300 and 350 as top speed. But going through some machinery forums I get conflicting numbers up to 1000. I'm not concerned with what type of cutters I'm using, rather concerned about burning up and or melting my Babbitt. My lathe and mill never even get warm but just worried....I've used 80/90 as a lubricant on all of my machines and as a thread cutting oil with great results for over 30 years but what's everyone's take on these two topics?

    Thanks, Jim

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    You should ask this question in the following forum as those guys see a lot more Babbitt in those Vintage Machines. You could also buy a Machinery or Machinist Handbook as those sorts of answers are listed there. Some Babbitting Suggestions - VintageMachinery.org Knowledge Base (Wiki)

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    The bearings are closely fitted - hopefully since Le Blond made their lathes to be precision - so a light oil like Velocite 10 (from Mobil) will do a better job of lubing than heavy glop like gear oil

    Here is that page from 1911 - though I don't know if yours is running the front journal in the chilled cast iron as described (clearrly this was for the Heavy Duty line)

    le-blond-1911-spindle-bearings.jpg

    Their "Regular" lathes were a bit different

    leblond-regular-1911-spindle.jpg
    Last edited by johnoder; 10-18-2021 at 09:53 AM.

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    The actual "RPM" is not very important.

    The key issue seems to be the "oil shearing speed" of the spindle vs the stationary bearing. That will depend on spindle diameter, so the slower speeds will be for the larger spindles, and vice-versa.

    A certain range of SFM in the oil works well. But too slow or too fast do not, as the "oil wedge" is not formed properly, and the oil gets overheated.

    I would suppose that it also depends on the "oil clearance" in the bearing, as well.

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    The type of bearing in the OP's LeBlond lathe headstock is known in engineering terms as a 'plain bearing'. JST correctly states the basis for how lubrication works in plain bearings. Herein lies the rub (sorry about the pun): when a shaft journal is running in a plain bearing, it 'rides up' on the oil wedge and is actually supported by that oil wedge. Metal-to-metal contact between the journal and the bearing is minimal and mostly occurs when a stationary journal is starts rotating within a bearing. Once rotating, if the factors JST speaks of are correct, the journal 'rides up' on the wedge shaped oil film and the 'rub' ceases.

    Now we get into the finer points of plain bearing lathe headstocks. Plain bearings (babbitted, bronze, iron, hardwood) for uses such as line shafting or machinery not requiring maintaining a precise shaft center location are designed with fairly loose clearances. Call it the 'cook book approach' with rules of thumb like 0.001" of clearance for each inch of diameter up to perhaps 6" diameter, then 0.0015-002" per inch of diameter. This sort of rule-of-thumb does not factor in things like load, surface speed of the journal, and assumes a mineral based oil about like an SAE 20 weight is used.

    Lathe headstock spindle bearings have to maintain the spindle on a precise centerline location in order for the lathe to have any kind of accuracy. As such, the bearings are setup to run tighter clearances. Adding to the mix are fairly high radial loads from the cutting forces, and possibly some additional radial loads from belt pull and back gearing.

    With the tighter clearances that lathe headstock bearings run, a thin oil is used, as John Oder correctly states. I cannot imagine running 80-90 wt oil in this type of bearing, particularly with the information John Oder posted. The LeBlond informations mentions that an 'oil reservoir' (also known as an 'oil cellar') is in place under each headstock bearing. Felt pads wick the oil up from these oil reservoirs and are in contact with the spindle journals. A heavy-bodied oil like 80-90 wt is not going to 'wick up' the felt (known as 'capillary action') too well.

    The tighter bearing clearances and the felt wick lubrication system are two reasons to run a thinner oil. Something like an ISO 46 oil will be fine in this application. ISO 46 oil is sold as "tractor hydraulic oil", and is what I run in my machine tool bearings. ISO 46/tractor hydraulic oil is also known as "DTE medium" oil. DTE is an ancient oil designation that predates automobiles and the SAE. DTE = "dynamo, turbine, engine". Plain bearings such as the old LeBlond Lathe have need a relatively thin, straight weight, mineral based oil free from most of the additives in automotive and gear lubricants.

    I am surprised the old LeBlond lathe in this thread has been running with the 80-90 wt oil in the headstock bearings. Assuming the lathe to be somewhere in the neighborhood of 12" swing-16" swing, I would expect the front headstock bearing (which will be the larger diameter of the two) to have a clearance of maybe 0.002"-0.003" and this is a WAG (wild ass guess) on my part.

    As for speed, I would not expect the fastest speed of the headstock spindle to be much over about 600 rpm. Again, this is a WAG on my part without knowing the swing of the lathe. These lathes were designed at a time when most cutting tools were made of high carbon steel. As such, the cutting speeds were quite a bit lower than those used with high speed steel tools. 600 rpm would be the speed with the back gear pin "out" and belt on the smallest step of the headstock cone pulley/largest step of the countershaft pulley.

    Another factor to consider is the 'dynamic balance' (or lack thereof) of the headstock spindle assembly. The headstock spindle with cone pulley and back gears was never dynamically balanced. Maybe LeBlond gave it a static balancing. Add a chuck, particularly with an odd shaped job, or a job setup between centers with a lathe dog, and there is an imbalance. Run with any kind of speed and the lathe will develop heavy vibration and the work may be turned or bored out-of-round.

    600 rpm maximum spindle speed is plenty for this kind of older lathe. It is a good speed for running High Speed Steel toolbits, and will let you do plenty of work.

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    I am surprised that the spindle would turn at all with the heavy gear lube in the bearings. I had a Lehmann lathe with close fitted bronze bearings. They were drip lubricated. If someone mistakenly put way oil in the lubricators the spindle would lock up stalling a 10 hp motor.

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    img_3019.jpgThanks everyone for the responses. Even though my 80/90 has served me well for years, I'm gonna switch to a lighter oil just for safety sakes. I don't want to risk ruining my old buddies.

    Jim

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    Back then, "babbitt" was most likely just lead.

    Modern babbitt(mostly Tin), can sustain shaft speeds many times that of what was likely originally poured into that headstock. This is probably why you have read conflicting answers.

    The real answer to you question requires a bunch of variables that not easily found without disassembly. The main ones being babbitt composition, roundness, surface roughness, and especially oil clearance.


    I agree with everyone else in that a lighter oil is ideal. As a plain journal wears and the oil clearance increases, the pressure on the oil film is exponentially increased. Sometimes using an oil with a higher film strength(heavier) can help, but this is really a band-aid rather than a cure.

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    John and Joe Michaels, would Universal trans-hydraulic fluid work? The bucket says used in transmissions, hyd, wet brakes, final drives and power take offs. No mention anywhere what weight oil it is. Sold by Orchelns in these parts. I use it in my 56 ton log splitter.

    I just edited this. Just found this oil online and the description says weight- 16.00000. Assuming this means 16 weight?
    Jim

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    Jarhead Jim:

    You are correct about our recommendation for the oil. Tractor hydraulic Oil is what is known as a "DTE" oil. DTE is an ancient designation that predates the automobile. DTE = "Dynamo, Turbine, Engine". DTE oils are a straight weight, mineral based oil and come in grades: Light, Medium, Heavy-Medium, Heavy. An ISO 46 grade tractor hydraulic oil would correspond to a DTE Medium and is fine for plain bearings in your LeBlond Lathe. Tractor Hydraulic Oil has anti foam and anti corrosion additives, and these are OK for your lathe bearings.

    ISO 46 or ISO 68 are the common weights for tractor hydraulic oils. ISO 46 is roughly equivalent to an SAE 20. SAE = Society of Automotive Engineers. The SAE did not come into being until automobiles were fairly well established and being produced in considerable numbers. Dynamo is an oldtime term for a Direct Current generator, and engine refers to steam engines, while turbine refers to hydroelectric turbines or steam turbines. ISO is the most recent system of oil designation and stands for "International Standards Organization", something that came into being in more recent times as industry became more global. Quite a little bit of history in the development of oil designations. Your LeBlond lathe likely predates most automobile manufacturing and was designed at a time when hand forged carbon steel lathe tools were the most common thing. Working on these old machine tools, it helps to put ones self in the mindset of the era the machine tools were designed and used. Carbon steel cutting tools = low cutting speeds, and oil would be a loose spec, probably something like: "Use a good clean engine or machinery oil in the spindle bearings..," Where 'engine' was likely referring to a steam engine with babbitted bearings, hence a DTE oil.

    Gear Oil, the 80-90 wt you mention, is too heavy for the bearings. The bearings may use a felt wick to bring the oil up from reservoirs in the headstock beneath each bearing. These reservoirs are also known as 'oil cellars'. The felt wick utilizes capillary action to cause the oil to 'climb the wick' and wet the spindle journals. A heavy bodied oil like gear oil, is going to take its sweet time in climbing up the wick.

    If the lathe seemed to run OK with the gear oil lubricating the headstock spindle bearings, I find myself thinking the clearances on the bearings may be a bit on the loose side. A heavy bodied gear lube and the close clearances a lathe headstock bearings should have seem like a bad combination that would result in the bearings running hot.

    Without knowing the size of your lathe and the nominal sizes of the spindle journals, I am taking a rather big WAG to try to give you any kind of bearing clearance values. I would not be surprised if LeBlond did not set the headstock bearing clearances at something like 0.002-0.003" for the smaller bearing, and perhaps 0.003"-0.004" for the larger bearing (closest the chuck). Time and an unknown history of owners and how they maintained (or did not maintain) the lathe all work against the bearings having those tight clearances at this point in time. Opening the bearings by lifting the bearing caps may tell some of the tale when the condition of the spindle journals and the bearings can be seen.

    Checking the bearing clearance is easily done with a pry bar and a dial indicator. The method is:

    1. slack the drive belt and back off the thrust adjusting nuts on the spindle. Disengage the feed/threading gearing (neutral position of the lever).

    2. Set up a dial indicator so it touched the collar of the spindle (between the threaded spindle nose and the bearing cap) at 12:00 and put some pre-load on the indicator. Zero the indicator.

    3. Stick a piece of hardwood such as a hammer handle into the spindle bore and push down hard. The indicator may move in the 'minus' direction. What you are doing is squeezing out any oil film between the bearing and spindle journal.

    4. Zero the indicator with the spindle in the 'down' position. Visualize the spindle journal touching the bearing at the 6:00 position. In theory, the contact between
    two circles of slightly different diameters, one inside the other, is "line contact". In actuality, it will be a large contact area.

    5. Using a pry bar (and a piece of copper to protect the spindle threads or machined collar surface) and a piece of wood blocking on the lathe bed as a fulcrum, pry the spindle upwards (prybar contacts the spindle at 6:00).

    6. Note the indicator reading. This is the bearing clearance.

    The proof is in how the lathe turns a piece of stock held only in the chuck. Without benefit of a tailstock center, the stock held in the chuck is cantilevered out from the chuck. If you can take a fairly heavy cut on a piece of 1 1/2" diameter steel and get a good surface finish with no signs of the work 'climbing up' on the lathe tool bit (as would happen if the spindle bearing clearances were too loose), and if you can face off a piece of stock with no center tit, this is a general indication that the spindle bearing clearances are 'in the ball park'.

    My own 'druthers would be to check the bearing clearances. Plain bearing headstocks are 'simple but elegant' in their design and there is more to the workings of the plain bearings than one might think. If the lathe headstock uses the 'felt pads' as described in the catalog pages John Oder posted, I'd be concerned as to the condition of the felt. Who knows when, if ever, the felts were checked or replaced ? Worn felt pads or felt pads that are dirty are not going to raise much oil to the spindle journals.

    A note about some automotive gear oils: these oils contain additives which may be harmful to 'yellow metals' such as brass or bronze. It is a good idea to avoid using automotive gear lubes on old machinery which may have brass or bronze working parts (such as a worm gear in the apron or bronze bushings in the apron or quick change gearbox).

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    Joe........ Damn. That was some intense reading! I appreciate the time and intelligence of your response! My lathe seems to have no play as I can face off a shaft in the chuck to a disappearing point. I've yet to do the dial indicator test, however I have had the entire lathe apart when I got it and cleaned all of the old crap out of it. The Babbitt seemed to look like new. I don't remember seeing any oil cups? I think it was just 2 Babbitt halves. I oil them from a couple of Lunkenhiemer number 4 drip oilers. When I got it there were grease zirks where I replaced them with oilers. Dripping one drop every 6 seconds. Often times I would forget to shut the valves when I finished a job and they drained out onto the pan underneath and dripped back into a recovery jar with a 0000 steel wool filter. The entire 110 year old lathe is in beautiful shape so luckily previous owners took great care of it. This winter I might do the dial indicator trick and see what play there is in it. I did thread a muzzle break on my .300 Win Mag rifle so it must be pretty accurate.

    Thanks again for the heart felt dedication to this profession, and your in depth response. I really appreciate it.

    Jim

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    Just to toss some numbers into the mix, here.... A prior employer had an old 13" SB lathe in what passed for the toolroom.

    That machine had a spindle clearance spec which allowed from 1.5 thou down to 0.75 thou clearance using a test like Joe M described. They specified a 50 lb up force and an 18" bar (as I recall), for what that is worth.

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    Tried the lighter oil. One thing I noticed right off...... It slings this stuff all over! Lol

    Jim

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    Maximum permissible speeds of bearings is an interesting topic. I believe a lot of engine turbochargers use plain bearings for speeds of tens of thousands of RPM. Of course the surface speds are not so high, becusev these are small diameter ...and lightly loaded.
    But I would love to hear from someone who understands the physics of plain bearings better than I do, what actuallly limits maximum permissible speed. I would suppose that it is heat from viscous drag, so the higher the surface (oil shearing) speed, the thinner the oil needs to be, and/or more cooling or oil circulation.
    I suppose at extreme speeds the shear in the oil film could cause cavitation where the inner and outer boundary layers meet. Perhaps at that point the oil could be pressurized to prevent cavitation.....non-contacting labyrinth sealing would be needed, I guess because at that point contacting seals would be impractical, too.

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    I just took apart a turbo from a small diesel car engine and the ~3/8" diameter bearings are fed oil from the engine at 40-60 psi at 4 locations around the bearing, and the bearing is about a 1:1 ratio for length to diameter. there are two journal bearings about an inch apart on the same shaft.

    120K rpm at 3/8" diameter corresponds to about 45K rpm for a 1" diameter journal.


    anyhow regarding lathes with 2:1 length to diameter bearings, drip fed.. well there is no where for the oil to go. it heats up gets too thin spindle locks up after it heats up too hot. the actual clearance isn't that much tighter than that of a modern car.

    typical 22R toyota engine camshaft has about a 1:1 ratio for the diameter to length of the bearing, its fed oil in one location through a small hole and runs 10w-30 oil. they run probably less than .001" clearance on the camshaft.

    typical 5w-20 modern engine camshaft will have the same diameter camshaft but will have oil fed in two locations on that bearing such that the effective length to diameter ratio is 0.5 and the oil can flow out of the 1" long journal bearing from 3 places instead of just both ends.

    nascar has been known (from what i hear) to have used bearings on the crank shaft as narrow as .25" .. and they change them every race. why? to reduce friction.

    thinner oil, thinner bearings, less clearance = lower losses, which means you can run them higher rpm.


    now if your oil clearance is so high that you can develop oil whirl.. something is wrong. lathes or car engins should never have that much slop in them.

    typical shaft journal bearing for a 3600 rpm 1 gigawatt turbine is how many inches? more like 2 feet.

    oil is fed into the bearing in the middle and the oil flows out at both ends. (which keeps the 4 atmospheres of hydrogen inside the generator)

    so.. someone has clearly figured out how to spin a 100 ton rotor at 3600 rpm at a shaft diameter of like 2 feet (i know its more than 1 foot).. without over heating, or wearing out.


    problem with a lot of lathe spindles is the bearing isn't round.

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    Just seen this...

    I bought a 16"x120" leblond with babbit bearings 40 years ago. Still have it and use it at least once every other year. Has 600 RPM top speed. An old timer, 40 years ago, told me to loosen the bolt caps if running top speed. This lathe comes with oil glass fill above each bearing. Got to fill it every day it runs.

    This was the first lathe I ever owned - kind of like a first girlfriend = I will never part with it.

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    That was the rule with big grinders too....loosen the bearing caps until the machine heated up.....generally a 30 minute run,...the tighten the caps ....mostly preWW2 grinders had plain bearings ....my actual WW2 Landis has "microsphere"....and the Cincinnatti that I had to scrap ,unfortunately,had rocking contact self adjusting shoe type bearings ......in fact I scrapped two Cincinnattis with the "Filmatic" bearings.

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    I am finding the posts related to be bearing lubrication interesting since I don't know a lot about plain bearing lubrication.
    One thing that hasn't been mentioned but that one might want to consider is the overall effect on the gear train and apron components when speeding up an old lathe to perhaps double or more of its original speed.
    Focusing on the spindle bearing lubrication is no doubt important and fine if you don't plan to use any power feeds or do any threading .
    Most of these old lathes as far as I know didn't have many shear pins or slip clutches that would drop out if there was too much strain somewhere .
    Broken and stripped bevel and worm gears often found in the apron not to mention the half nuts are not so easy to reproduce if they get worn or wrecked.
    The occasional short over speed may not cause much problem but having a crash at high speed might produce a lot of collateral damage.
    Jim

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    I would probably experiment with synthetics. I know, don't mess with something that works, but synthetic oils make a huge difference in gear life, so it would be interesting to see how they work in a lathe spindle.

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    Quote Originally Posted by EmanuelGoldstein View Post
    I would probably experiment with synthetics. I know, don't mess with something that works, but synthetic oils make a huge difference in gear life, so it would be interesting to see how they work in a lathe spindle.
    There seems to be a lot of concern by folks about detergents in the oil.

    A test that I did with my southbend 9 was to chuck up a 56 pound steel bar with a center of mass about 2 feet away from the spindle. this would have put about 150 pounds of downward force on the front bearing and about 100 pounds upwards thrust on the rear spindle bearing.

    I then turned the bar with my fingers slowly and tried to figure out the minimum speed needed to maintain an oil film. I found the result to be about 40-60 rpm. clearances are i believe a maximum of .0015" up and down.

    The spindle oil I use is low viscosity synthetic atf I believe is 6 cst at 100C.
    It warms up but not more than 110F at 1450 rpm.

    sometime I might buy some velocite 10 and compare. velocite 10 is 4 cst at 100C.

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