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  1. #1
    SteveH8861 is offline Aluminum
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    Default Fitting bronze sleeves - 9" headstock.

    I had a thread going about this but it got lost with the new ubb software change.
    So from the beginning.
    A buddy gave me a 9" model A that was just collecting dust at his machine shop.(I'll return the favor by doing some work in his home)
    So first thing I did was totally tear it down. I figured I would start with the headstock and spindle.
    The bearings in the headstock were trashed. Badly scored on 100% of the bearing in the front and about 30% in the rear.
    I had read the article in HSM mag where a gentleman used his lathe ways to line bore the headstock in order to fit new bronze sleeves.
    I studied his method and it seemed sound. I had all the equipment needed for this task so I decided to give it my best shot.
    I used a mini mill head with a 1" diameter boring bar. The headstock was moved to the tailstock end of the bed where it was unworn. This is important as the line bore will only be as straight as the carriage can ride the ways.

    Here is what the headstock bearings looked like when I took it apart, ugly!-


    So here is the setup to line bore the front bearing-


    Here is the setup boring the rear, note the steady rest added -


    And here is the front bearing bored out ready for a new bronze sleeve-
    [
    The rear turned out just as good.
    Continued in next post,

  2. #2
    SteveH8861 is offline Aluminum
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    ok, so now it was time to turn some bronze sleeves. I used 660 bronze cores. This stuff machines easily. It sprays chips like rain. This is where you have to use all your skills and tricks as you need these to be nice and round, with a good fit to the head stock bores but oversized by about .0015" on the spindle journals. More on that later. I spent some time researching proper oil groove setup for plain bearings as well.

    Well first here are the finished bearings ready to be installed-



    I won't bother with all the tech involved in a plain bearing. But what I did learn is that what you do NOT want is a round bearing. This is why a certain amount of crush is used to create what is called a lemon shape. This shape helps control something called oil whirl and oil whip. Here is a primer on the subject-

    http://www.stiweb.com/appnotes/jb.htm

    And this is why my bearing sleeves were made a bit over sized in the I.D. I also studied oil grooved designs and went with a single axial groove 75% the width of the bearing. Now, here is where I made a big decision. This entire modification was a lot of work. Exacting work. One wrong move and your done and it's start over.

    The southbend oil wicking setup is nice. It was mainly designed to be very low maintenance. But it has some flaws. The oil the bearings is recycled and felt used to filter out the particles. And it does work of course and very well. However IMHO metered total loss system will be superior. It is adjustable, clean oil is always used and it's a simple matter of trying different oils. So I went with top oiling. The original oil return holes will still function, the oil fills now become oil drains.



    There is no need to split the bearings. They are thin enough to lemon shape to take up clearance with the pinch bolt. With a setting of under .0005" clearance, the spindle still turns smooth as buttered silk. I set my clearance to .001" for initial run in.

    I checked run out and now understand Southbend quality. The spindle run out is better than all of my other machines that used ball or tapered rollers for spindle bearings. I have a hard to time seeing .0001" run out. So here it is all assembled and ready to once again make chips, I use Benjamin Moore industrial urethane enamel mixed to the formula on Tony's lathe site for a south bend.





    Steve
    Last edited by Paula; 12-02-2007 at 11:48 AM.

  3. #3
    peterh5322's Avatar
    peterh5322 is offline Diamond
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    "... you do NOT want is a round bearing ..."

    Certainly true for hydrodynamic bearings, such as this on.

    However, for a top-of-the-line toolroom lathe, which generally employs ABEC 7 or 9 angular contact bearings, you DO want a round bearing.

    As round as is possible.

  4. #4
    flathead4 is offline Hot Rolled
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    Very nice Steve. I would be interested in seeing any pictures you took while machining those inserts. I doesn't look like you've left room in your inserts for felts. Will your top oilers have some kind of felt insert to keep out the crud and slow the oil flow?

    How did you apply the paint? Also very nice.

  5. #5
    SteveH8861 is offline Aluminum
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    Peter, yes of course for a Tapered roller or A.C. or deep groove ball bearing, roundness is every thing!! That's why we have big dollar abec 7 bearings. Apples to kiwi's though! The plain bearing rides and relies on a film of oil. When that oil film breaks down it's game over and bearing damage results. A 100% round shape is the worst possible to retain that oil film at speed for a plain bearing. A total round shape with consistent oil film thickness becomes unstable.
    But.... a plain bearing has much more damping than any roller style bearing. We have trade offs going on here when comparing plain to roller type.

    Mark, this is just an initial setup. Pipes will be added and a drain pan to collect the spent oil. I will also add larger oil reservoir's and perhaps a needle valve to regulate flow.

    But that is all to be done when the machine is back running. Now it's on to the rest of the machine.
    I forgot to add, the sleeves have been bonded to the headstock with high strength loctite retainer good to +400'F.
    The axial oil gooves in the bearing shells were cut with a 1/4" reamer that I ground into a T-bit and then used the quill on my mill. The oil return holes in the headstock were hand radiused using a dremel and tiny round bit to aid oil return flow from the groove dams in the headstock to the oil return ports.
    I don't like oil slinging.
    All in all it was a very fun job. It's not like building a mini 12 cyl rolls royce engine. Just use common sense and think perfection or at least down to the tenth with every machining setup and it will turn out great.
    Steve

  6. #6
    SteveH8861 is offline Aluminum
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    Tom, ask away with any machining questions for this mod.
    Here is a shot of a semi finished bearing next to the raw bronze cored stock.


    I turn the the O.D. first and then bore the I.D.
    I use a modified solid carbide boring bar that can easily skim off .0002". I can take a pic of it anybody wants to see it. I sharpen it with a diamond hone to a razor edge.
    As the bearing gets thin I add a layer or 2 of rubber tape to dampen the ringing.


    Steve

  7. #7
    SteveH8861 is offline Aluminum
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    no felts, no need . My artisan lathe is 100 years old with a 2 1/8" spindle , has no felts, total loss oiling, not a single score mark on the bearings and still has original scraping marks on the bearings and an un hardened spindle with almost no scoring. Probably 100 times better looking than this S/B was before repair.
    Now what is needed is good maintenance with this type of setup. You have to remember S/B did their best to design a spindle lube system that was fairly maintenance free, good for a shop or school where proper total loss oiling maintenance would never be followed and cleanliness might not be followed as well.
    It is actually hard to over oil a bearing. You can certainly kill off some rpm with to much oil but with proper design you want a good oil film at all times.
    An automotive plain bearing operates under great load with changing oil pressure.
    The real negative is oil slinging. To much oil will just be thrown all over the place. In an engine it is contained. On a lathe you'll wear it.

    I used a Purdy brand brush for oil paint. I have to admit I am a painter by trade and have a brush in my hand 5 days a week for the last 13 years. So I might have a little advantage in this dept.
    Steve

  8. #8
    jim rozen is offline Diamond
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    Very sweet. I was worried about the roundness of your journals because they were not
    ground at all, just polished (right?) but if things work well then you did good.

    Did you machine the fit of the shell oversize for the journal, taking into account the
    press-up in the cast iron headstock, and also the idea that you would be adjusting
    the running fit by crushing down on the shell even without a split?

    Watch out if you try to remove these after using the locktite. You will need to
    machine them out or get them very hot to break down the bond. That must have
    been a bit of a white-knucker installing them with it.

    I personally think that bronze lunkenheimer oilers would be very attractive on top
    of that headstock.

    Jim

  9. #9
    SteveH8861 is offline Aluminum
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    Hi Jim!
    Roundness? the spindle? it's ridiculous. I'm floored by the accuracy and runout. Honestly I am. I must have checked it 20 times today as I could not believe it.
    Hey I am happy to see .0002" on any of my machines. But when I can't even see that on the internal mt3 taper on this spindle I am amazed. The spindle register is just as good. The spindle bearing surface, forget it. Nothing shows up.
    Ahh well nothing is perfect though. The flat belt 3 step pulley on the S/B has about .002" run out. Hate to say it my Artisan has only .001" on it's 3 step cone pulley . But OL' artisan's spindle run out is not as good as the S/B with near .0002".

    Anyhow I have been into model engines for a while and am used to making small bores. It was trial and error over the years that I happened on solid carbide boring bars with quite large modifications in my quest for a cutter that could take off much much less than .0005" per pass even on what many would call a junk machine. I even modified my 9x20 lathe tail stock to a lever feed to use as a hone. But honing proved unsatisfactory to me as of course the quill needs to be perfect. I have also used a tool post grinder. But I found a razor sharp solid carbide boring bar is hard to beat. I mean so sharp you have to be careful touching it.
    It has to be solid carbide. Steel stemmed bars with carbide tips are like rubber and totally 100% useless for precision work IMO. I sharpen until it will cut like a hot knife through foam. I run a right hand spring pass feed (towards tail stock) to use the large lead angle on the boring bar for the smooth finish in the bearing. There will be no "thread" to be seen after this pass. Bronze rains chips. A sharp bar will cut .0002" no sweat.
    Note when I line bored the headstock I shimmed and tightened the pinch bolts. This gave me a round bore at that initial setting. I made the bearing shells to fit that setting but left the ID .0015" Over. So the bearing shells must be crushed to bring clearance down to the needed .0007-.001". This creates the needed lemon shape.
    I am an oldie to loctite. Used it for 15 years at least.You probably already know this but others may not, There are many an article proving chemical bonded bearings superior to press fits. The secret is in the self alignment before curing. This allows the shaft to settle in perfectly and once the loctite cures the alignment is locked in and there is less friction.A few papers have shown increased motor RPM from chemical bearing retainers vs machined press fits. But one has to work quickly!
    But the drawback is the new bronze bearings will never ever be removed unless the headstock is heated to 500'F. High strength loctite is just crazy strong. I have destroyed many parts over the years learning just how strong it is unless broken with heat. I am confident though that I'll out live the need for new bearings on this machine. And had I not taken possession of this machine it have would be scrapped anyhow.
    I am new here so my skills are in question and I certainly understand that. I have just built a bench top cnc lathe with linear rails mostly from scratch right before I took ownership of this lathe. Z axis is good to .0001" over 10". I am quite involved in the cnc aspect of the hobby. However I think I have found I enjoy older manual machines even more.
    And also any work I have done or posted is all manual for this project.
    I hope to learn from everybody here about the S/B lathe. From I have seen so far it is quite a nice machine. It's 3 times the machine that a new 9x20 is. Maybe 6 times. I'm very happy to now own this machine. It will be rebuilt with pride.
    Steve

  10. #10
    kdc
    kdc is offline Hot Rolled
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    Looks like you know what you're doing from where I'm standing. You've done a remarkable job of fixing a badly damaged headstock(which is something more than one owner has had to face).

    Thanks for the pictures and the information on how you accomplished this--I wish I had the ability (and tools)to do what you've done. Mine is still in pieces on the workbench since I dismantled it and then got entangled in something that is more pressing at the moment.

    Dave

  11. #11
    jim rozen is offline Diamond
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    Just remember you could always line bore the old bearings back out the same
    way you did the headstock in the first place. Yep, I'm impressed by the anerobic
    adhesives. I take it you used one of the 600 series (green) locktites. Those are
    wicked strong.

    What I was getting at when I mentioned the journals, were the cylindrical surfaces
    on the exterior of the steel spindle itself. Proving that they are truly cylindrical, and
    also coaxial, is toughter than one might imagine.

    For example, did you mike the OD of the larger journal, at various places along its
    length?

    It's easy to imagine a nearly perfect reading on a test indicator resting inside the
    spindle taper bore, as the spindle is turned 360 degrees - but the total amount of
    contact between steel journal and bronze bearing ID could still be pretty small.

    My guess is the setup is pretty forgiving -the machine was probably in use, making
    parts, while it was self-destucting from lack of lube. At this point the variation in
    journal height is much less than the oil film thickness - so even though it may be
    large than X amount from end to end, the bearing works fine because it rides on
    that oil film.

    I'd be interested to get somebody's take like Miller machine and fabrication, on this
    sort of rebuild approach. They line bore and I think hone the cast iron bearings, and
    than hard chrome up and grind the steel spindle journals.

    Until you showed those photos, I had never even conceived of repairing a headstock
    in such a fashion.

    Jim

  12. #12
    aboard_epsilon's Avatar
    aboard_epsilon is offline Titanium
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    Roundness? the spindle? it's ridiculous. I'm floored by the accuracy and runout. Honestly I am. I must have checked it 20 times today as I could not believe it.
    Hey I am happy to see .0002" on any of my machines. But when I can't even see that on the internal mt3 taper on this spindle I am amazed. The spindle register is just as good. The spindle bearing surface, forget it. Nothing shows up.
    Ahh well nothing is perfect though. The flat belt 3 step pulley on the S/B has about .002" run out. Hate to say it my Artisan has only .001" on it's 3 step cone pulley . But OL' artisan's spindle run out is not as good as the S/B with near .0002".
    Were you levering and pushing on the spindle with a bar when you were measuring ...if not ...the measurements don't count.

    all the best.markj

  13. #13
    APD
    APD is offline Hot Rolled
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    epsilon-
    I think he's measuring roundness of the spindle journal (how far the journal surface deviates from a true cirlce), which is a different thing than the lever bar test you suggest.

    The levering bar test measures bearing play (the gap between bearing and journal surface)...some gap needs to be there for oil, expansion, etc.

  14. #14
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    Looks good like the photo of your job too.

    David Smith

  15. #15
    Paula's Avatar
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    Steve,

    Beautiful work, and very inspirational!

    Thanks for taking the time to document this project for us!

    Paula

  16. #16
    SteveH8861 is offline Aluminum
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    Jim, I used a high quality Vernier Micrometer to measure the spindle journals. I can not measure a .0001" deviation along the length of the journals.
    It is pretty amazing the bearings were so bad and yet the spindle still so perfect. When I polished it, I made darn sure not to remove any measurable amount of material.


    Mark, yes I set and measured bearing clearance by first seating the spindle to squish away the oil film and then levering it upwards and with a T.I. on the spindle register to note the clearance. I have a max of .0015" clearance and it is adjustable with the pinch bolt to 0 clearance where it will clamp the spindle tight and lock it. Very simple procedure.
    I will need to shim the split housing to be able to firmly tighten the pinch bolt and retain the bearing clearance setting.

    Again though, I did not come up with this method of repair. I got the idea from the article titled " Line boring a South Bend lathe headstock "in the jan/feb 2007 issue of Home shop machinist magazine. The Author was Jack Butz.

    Jack, if you are out there and reading this, thanks for the idea!

    Steve

  17. #17
    jim rozen is offline Diamond
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    Yes, you should shim the splits in the bearings, it will give you a bit more rigid
    setup I would think.

    And yep, I bet the oil filim on that bearing is bigger than a tenth, and if you cannot
    measure a height variation bigger than that, it should work just fine - and it does!

    Jim

  18. #18
    J Grainger is offline Aluminum
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    I dont see any small scale replica of an angular milling head.. so just how did you cut the oil groove on the inside of the bearings?

    J Grainger

  19. #19
    SteveH8861 is offline Aluminum
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    J Grainger, cutting the groove was simple. I took a 1/4" reamer and ground it down leaving only the tip intact. Then the bearing shell carefully held in a vice after marking out the groove distance and centered up the cutter inside the bearing. Then advance the bearing into the cutting bit and used the quill on my mill to stroke the cut. I did this is in several small cuts. I could have ground down a end mill instead of a reamer but I felt the reamer type bit would be a lot less aggressive and allow me to sneak up on a nice groove. It worked very well in the bronze.
    I practiced on a piece of scrap before grooving the real shells.
    Steve

  20. #20
    jim rozen is offline Diamond
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    Oh! Now I get it, missed it the first time. I though
    you were running something in "shaper" mode.

    But the key of course is to realize that the cross-section
    of the oil groove is not rectangular. It's semi-circular.

    Another nice idea filed away for the future....

    Jim

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