Plain (Bronze)Spindle Bearing Q?
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  1. #1
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    Default Plain (Bronze)Spindle Bearing Q?

    Not my SB- 11" Sheldon but the same rules apply (just acquired).

    Bronze spindle bearings, and spindle were in excellent condition upon disassembly and inspection (surprisingly so, looked new).

    Replaced reservoir wicks after cleaning up the headstock and then dropped the bearing caps on. Manual says to torque to feel, as it was before assembly.

    I thought it odd at disassembly that it took so little torque to loosen the cap screws, just kind of "twisted on" torque. On reassembly, I torqued them "snug" to start- and couldn't turn the spindle by hand. The screws on the front bearing in particular needed to be tightened just a few degrees beyond contact- any more and the spindle would bind.

    My concern is that with so little torque on them one or more will just vibrate completely loose and cause problems without me being aware of it. Is it odd to have such tight bearings? I was thinking of dropping some Loctite 290 down into the threads?

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    in the case of Sheldon, that is good and indicative of very little wear.

    as weird and counterintuitive it seems, that is how they are, just barely nipping the cap bolts, and although I have never heard of an issue I can understand the concern, that said,If you want a thread locker to prevent vibration from loosening its a non hardening one you want...sometimes very slight adjustments are needed for some things - non-hardening will allow "adjust on the fly".

    edited due to bad memory. here is what I was thinking of-

    https://www.amazon.com/Vibra-TITE-21...52427989&psc=1

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    I'd suggest maybe the bearing caps are not shimmed correctly and that adding a couple "thou" to the shim packs might make it so that the cap bolts can be tightened.

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    Might light-tight the hold downs and feel openings with a feeler-set gauges as a starting point. add .005 (or .010) to the feel number and then take out by .001 till you get a .003 or so with wood 2x2 pry lift movement under an indicator checking both ends..yes with not having all kinds of shim stock dry copy paper can be used for the test (with having a micrometer to measure shim stack)
    Then run with care to see not too much heat.

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    Try to remember it isn't some old sloppy automobile part. They are put together sloppy so maybe they will last awhile - no precision needed or intended.

    Entirely different in machine tool spindles which need the very LEAST amount of slop to make any pretense at being capable of close work. If you can turn it by hand but it still warms at speed you are getting there

    Example - my number 4 B&S grinder - wheel head runs at about 1500 RPM for the 14" wheel, gets warm to the touch and makes finishes like the thumbnail. That's a little under 800 FPM on the 2" journals - which run in bronze "boxes"
    Attached Thumbnails Attached Thumbnails p1000616sm.jpg  

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    Speaking of automobiles, connecting rod and main bearing clearances are pretty critical and they can be checked with a product named "Plastigage" which is a small piece of plastic "string" that gets put in the bearing and squashed when the bearing cap is tightened. The cap is removed again and the width of the squashed piece of plastic is compared with a chart supplied with the product. This gives you the clearance in the bearing in thousandths of an inch. I don't see why it wouldn't work on a lathe journal bearing and would answer your question about bearing clearance.

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    SHeldon didn't use shims.

    tob, PLEASE correct me if my memory is off! I don't want to put erroneous info out there...
    Last edited by iwananew10K; 07-19-2019 at 03:31 PM.

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    Rummaging around on the "Lathes.co.uk" website archives, I find mention of early Sheldon's running spindles directly in the headstock casting but using bronze shims under the bearing caps. I didn't find anything mentioned about bronze split shell bearings. I have a fairly old Sheldon 10" with single tumbler gearbox but it runs the spindle on taper roller bearings--something I wish South Bend had decided would be a good idea. It's a lot easier to replace taper roller bearings than it is to mess around trying to get spindle and bearings fixed on a South Bend if they get messed up.

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    Quote Originally Posted by iwananew10K View Post
    SHeldon didn't use shims.

    tob, PLEASE correct me if my memory is off! I don't want to put erroneous info out there...
    Spot on. No shims at bearing caps were used.
    The only part missing on the entire lathe was one of the flat way wipers, so I've got to fab something similar on the mill. The lathe is eerily similar to my SB, with a few twists. I do like that there are 4 pressure oilers on the saddle to get a bit of oil under. Cleaning up the underdrive motor assembly, run another 220 line to it and see what it does...

    headstock.jpg

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    Looks great! Love the E drive on those, a real work of engineering art....incredibly efficient with the dual v belt spindle drive.


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