1928 "Ehrlich" Lathe - Spindle teardown (Help request)
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    Default 1928 "Ehrlich" Lathe - Spindle teardown (Help request)

    Heyho!

    I've recently posted about the restauration of my new(old) Ehrlich Lathe.
    The one thing I didn't dissasemble and clean was the spindle itself.

    I've done that now and it turns out its enough of a topic in itself for a new Thread.

    Since you can only upload 5 pictures here I made an Imgur link with high-res versions of all Photos:

    PHOTOS ---> Ehrlich Lathe Spindle Teardown - Album on Imgur <---

    I also added some more notes by some of the Pictures.


    An interesting feature of this spindle is beeing able to "select" between two speeds.
    There is a knob on the big gear on the very right; if you pull that out it disengages the Flatbelt Pulley from the rest of the spindle. By flipping a tumbler on the headstock two more gears are engaged - which in turn results in a (roughly, need to measure it later) 10:1 reduction between pulley and spindle.

    I'm assuming this is used for either very large work or thread cutting, since it reduces the speed to roughly 10rpm on the slowest setting.



    Help request
    Joe Michaels has posted a very nice, detailed instruction for setting the bushings properly, beeing tapered bronze bushings and all that.
    I am going to tackle this next weekend, but nevertheless:

    If any of you awesome people is living in Germany near Koblenz and would be willing to come over and help me a bit with setting the spindle up properly, - That would be just amazing, and greatly appreciated.



    Either way I will post a quick update after everything is finished.
    Thanks for reading!

    -Marco

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    The "back gears" or "lay shaft" gears were done for over a hundred years. It is a nice surprise to actually see how it works, right there and slightly greasy fingers. Yes the tapered bearings; first clean but don't use brake cleaner or caustic element on them. They are porous and that will disturb the lubrication film that you need. Remember that everything takes a "set" or settles in place after tightening those rings. They can't be perfect until it has run a tad. just right may be too tight and the worse thing to happen.

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    Marco:

    Thanks for the kind words. If I lived close to you, I'd be helping you get the lathe assembled and bearings adjusted.

    I took a look at your photos. The spindle journals (portions of the spindle which run in the bronze bearings) look quite good with no obvious scoring (cutting of grooves due to uneven wearing). A good test to determine if a spindle journal is OK for re-use is to lightly drag your fingernail along the surface of the journals, axially. If any scoring, ridging or grooving catches your fingernail, it should be put right.

    Typically, what we do is called "stoning" the journals. This "breaks the ridges" on any scoring. We use a small oilstone, called an Arkansas Hard Stone, or a "Washita" stone. These are very hard smooth white stones. If you feel them, you would not think they would cut any metal. Using the stone and some light oil (ISO 46 oil or thinner), or some mineral spirits, you take the stone and rub it at about 45 degrees to the centerline of the spindle, working your way around the journals. This takes down any slight ridging and cleans up the journals without taking enough metal to affect runout or roundness of the journals.

    When you put the lathe back together, as noted, the journals and bearings have to "Bed in" (a term us old timers use). Kind of like a person getting into a new bed, having to get used to it and not quite settling down to rest until the bedding and their body conform to each other.

    Even though the lathe parts will be put back together as they came apart, the fact is the bearings and spindle were taken apart. Reassembly and readjusting the bearing clearances will put things in slightly new positions, hence the "bedding in" process. As I wrote, your first runs of the lathe are "bearing heat runs", done to make sure the bearings- while having correct amounts of clearance by dial indicator testing- do not run hot.

    After you have used the lathe for a week or two (depending on how heavily you use it, types of jobs, etc), re-check the bearing clearances. As the bearings bed-in to the headstock and the spindle journal beds-in to the bearings, clearances may open slightly. A very small amount of re-adjustment might be needed at that point.

    A lot of this work is done by instinct or feel, since there are usually no manuals for these old machines. Learning how an apparently scored spindle journal can still function in a lathe doing accurate work was something I remember well. Old-timers taught me, and I was fortunate to learn from them. All of what they taught is never found in books. Those oldtimers are all dead and gone now, so I suppose I am now one of the oldtimers. I've worked with bronze and babbitted (white metal) bearings in anything from small machine tools to steam engines and hydroelectric turbines and generators (bearings 0ver 1,5 meters in diameter). Even on the big hydro turbines, we'd get things taken apart during a repair or inspection/maintenance outage and I'd be asked to take a look and determine what work was needed. Usually, we'd just run our fingernails over the shaft journals, do the same with the babbitted bearings and give the babbitting a good visual inspection (and maybe some ultrasonic testing to determine that it was still bonded to the steel bearing shells). After that, we'd get the oil stones and stone the journals lightly (stoning a 1,5 m diameter journal takes a few men some time to do), and we'd give the babbitt a light scraping (we'd call it a "shave", such as you do with a razor on your face) to "break the glazing". Put 'er back together, adjust the clearances and return the turbine and generator to service following a bearing heat run. 18-24 months of running until the next inspection/maintenance, and we always got things put together right.

    Plain bearings, such as are in your Ehrlich lathe are a science unto themselves. In engineering terms, we say these sorts of bearings are "simple but elegant", and the principals of how the oil film is formed and maintained has always fascinated me. As I said, were I living anywhere within driving distance of your place, I'd come over with my tools and supplies and we'd get your lathe put to rights. I learned the machinist trade from German immigrant machinists a LONG time ago as a kid. These were men who came to the USA around 1923 to escape the currency inflation and economic collapse and hardships in Germany at that time. Some came from Bavaria and some from the Schwalbenland. I wound up speaking a workingman's German, ungrammatic, and definitely not Hochdeutsch. I can handle a days work in a machine shop without speaking English, but it is hardly the German you'd learn in college. I get kidded by some Germans when I speak "Bauerndeutsch". The oldtimers who taught me were in the USA, but in their shop, they spoke German and I picked up enough of it to get by and learn the trade. Those oldtimers were great teachers in so many ways, and they saw something in me when I was a teenager and took me into their shop and taught me. Other older men taught me in other shops and then on powerplant jobs after I got my engineering degree. I like to say that the best professors were the old machinists and other craftsmen, and the best post-graduate education I got was on the shop floors and on the powerplant jobsites.

    So, viele gluck und mach's gut !

    Joe Michaels

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