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  1. #1
    Larry Condon is offline Aluminum
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    Default Repairing Half-Nut Threads

    Hello Everyone

    A couple of questions about S.B. Heavy 10
    How do you remove the snap ring (ITEM #5,Parts List Book) of the clutch sleeve assembly? It appears to be captivated around the shaft and inside of the worm gear. Iím thinking of making a round tool that will fit over the clutch sleeve (item #2) that will spread the snap ring to remove the sleeve. Has anyone ever taken one apart?

    Also the half nuts are worn almost to a sharp on the threads. Iím planning on making new and was wondering what material to use. The nuts appear to made of cast steel now. Any one ever had the same problem? Iím sure it will be expensive to purchase new from LeBlond or Parts Works.

    Thanks

    Larry

  2. #2
    Paula's Avatar
    Paula is offline Titanium
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    Hi Larry,

    I don't think I can help with the snap ring question, but I have some suggestions on the half-nuts issue.

    My guess is that the original half-nuts were machined from cast iron, as this provides a superior bearing surface (superior to steel, anyway) against the steel lead screw. One way I've heard of to repair worn half-nut threads is to build up the surface with brazing rod, and then re-cut the threads. However, I recently came across another method that I like better.

    It consists of boring out the old half-nut threads, threading a bronze sleeve to fit the leadscrew, and then epoxying the sleeve to the inside of the installed half-nuts. The new half-nut "assembly" is removed, locking pins added, and then split in two and re-installed in the lathe. I would think that a mill would be almost a necessity for this job.

    Here is a more detailed description of the process, as described by Brett Flemming on the southbendlathe Yahoo! forum (His description applies to the 9"/10k model, put the principle should apply to larger lathes):

    Part of my machining hobby is restoring worn machinery to usable condition and getting those machines in the hands of people who want to make chips. A recent reconstruction of a South Bend Model A involved restoring completely worn out (as in completely gone) half nut threads.

    I cannot figure how these half nuts were worn out so badly on a Model A, but there was no disputing what they were. I bored out old threads to a .900" bore. Made a bearing bronze spool to .895" to allow for epoxy to fill gap and account for misalignment. Then I single pointed the threads till spool threaded on leadscrew easily. I then made few passes on the spool outside diameter at 4tpi to rough-up for epoxy to grip. I then installed the bored half-nuts on saddle, put saddle on lathe, screwed spool onto leadscrew, replaced lead screw end support to line things up, then clanked half nuts closed on spool to test fit.

    Once it looked like it would work, I coated spool with epoxy, clanked half nuts closed, then let cure for a few days. I then removed saddle by running lathe screw backwards. I then drilled and roll pinned (1/16") on each end of spool lip. I then clamped the half-nut assembly in the mill vise and split it with a big slotting saw, drilled oil holes, and Voila. Half nuts live again.
    And here are a couple of pictures Brett included of the finished product:





    Paula

  3. #3
    peterh5322's Avatar
    peterh5322 is offline Diamond
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    HSM featured an Acme thread repair using Moglice some time ago.

    Although somewhat more complicated due to the split nut, such a repair should still be feasible using this material.

  4. #4
    Sea Farmer is offline Titanium
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    Hi Larry. I own a Logan 10" and lurk on this forum because the machines have some similar parts. But your snap-ring question is the first one I've tried to answer [img]smile.gif[/img]

    As best as I can tell, the snap ring assemblies on the ends of the clutch knobs are similar on the SB and Logan. The snap ring on mine had deformed and partly pulled into the gap between the clutch shaft and hole in the center of the clutch knob. How it happened I don't know. Probably a jammed cut.

    Anyway, snap ring pliers only succeeded in breaking off the tab at one end of the ring. I ended up buying a set of picks in the automotive tool section at Sears. NAPA has them too, much more expensive. The useful one was the circular pick (Sears part number 47174). I picked away for quite some time, eventually breaking up the snap ring into several pieces before it all came out.

    Good luck!

  5. #5
    Larry Condon is offline Aluminum
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    Hello everyone
    I have some questions concerning this quote.

    (Here is a more detailed description of the process, as described by Brett Flemming on the southbendlathe Yahoo! forum (His description applies to the 9"/10k model, put the principle should apply to larger lathes) [img]smile.gif[/img]


    (quote:
    --------------------------------------------------------------------------------
    Part of my machining hobby is restoring worn machinery to usable condition and getting those machines in the hands of people who want to make chips. A recent reconstruction of a South Bend Model A involved restoring completely worn out (as in completely gone) half nut threads.

    I cannot figure how these half nuts were worn out so badly on a Model A, but there was no disputing what they were. I bored out old threads to a .900" bore. Made a bearing bronze spool to .895" to allow for epoxy to fill gap and account for misalignment. Then I single pointed the threads till spool threaded on leadscrew easily. I then made few passes on the spool outside diameter at 4tpi to rough-up for epoxy to grip. I then installed the bored half-nuts on saddle, put saddle on lathe, screwed spool onto leadscrew, replaced lead screw end support to line things up, then clanked half nuts closed on spool to test fit.

    Once it looked like it would work, I coated spool with epoxy, clanked half nuts closed, then let cure for a few days. I then removed saddle by running lathe screw backwards. I then drilled and roll pinned (1/16") on each end of spool lip. I then clamped the half-nut assembly in the mill vise and split it with a big slotting saw, drilled oil holes, and Voila. Half nuts live again.)

    I sure would like to try this repair but have several questions.

    Has anyone else ever tried it? Any reports of success/failure?
    There are numerous alloys of bronze. Maybe I'm making a big concern of this, and just use an oil impregnated bronze. Also a lot of different grades of epoxy. I would think a good strong grade for bonding metal.

    Anyone have more thoughts?

    SEA FARMER
    I made a tool that slipped over the clutch sleeve and spread the snap ring and removed the shaft from the worm gear.

    Thanks

    Larry

  6. #6
    Paula's Avatar
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    There are numerous alloys of bronze. Maybe I'm making a big concern of this, and just use an oil impregnated bronze.
    Larry, I would go with SAE 660 bronze (alloy 932) for this application. It is probably the most widely available non-sintered alloy, with excellent bearing qualities. Oilite would not bond very well to the epoxy.

    Also a lot of different grades of epoxy. I would think a good strong grade for bonding metal.
    I would use JB Weld. Has excellent metal bonding strength, and a steel filler to fill gaps. I use it a lot. Because of the "spool" design of the replacement half-nuts, plus the 1/16" roll-pins, the epoxy joint is not subject to very much stress in normal use.

    Paula

  7. #7
    Larry Condon is offline Aluminum
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    Paula

    Thanks for the input of information.
    I quess I'm a skeptic of this repair but I'm going to try it anyway. I'm not in a big hurry to do it as what I have is still working. I can do this as I have time. You seem to know what you are talking about so I'm going to follow your suggestions. No one else has responed. If it doesn't hold I will just have to make the half nuts new out of a bronze block if I can purchase one.

    Thanks
    Larry

  8. #8
    Paula's Avatar
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    Larry,

    This is not what I would call a simple repair -- certainly not something a beginner should attempt -- but it will work, and should hold up as well (if not better) than the original cast iron threads.

    The primary force on the half-nut threads is along the axis of the leadscrew, and the flanges on the replacement nut halves take all of this thrust. The epoxy and the roll pins are to resist the radial pulling force when the nuts are disengaged from the leadscrew. The epoxy also offers some forgiveness in aligning the threaded bronze "spool" to the bored out half-nuts.

    The trickiest part is probably setting up the half nuts to accurately bore out the old threads. This could be done on a lathe, using an angle plate on a large faceplate, but I think it would be a much simpler task on a mill.

    Good luck, and let us know how it goes.

    Paula

  9. #9
    Larry Condon is offline Aluminum
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    Paula

    Thanks for the information. I don't have any problem in trying to tackle this repair I have a mill and the use of my lathe and have already thought how I would fixture the half nuts. What I was worried about was the new threads holding in the bored half nuts. After reading your last post I looked closer at the pictures and could see the shoulder flanges at each end. This makes more sense to me and I think the new threads should hold. When I read Bretts explanation he just said to turn spool to .895 diameter. I thought that this method would over time let loose. It pays to talk things over before proceding.

    Thanks

    Larry

  10. #10
    Larry Condon is offline Aluminum
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    Hello
    Finally finished repairing the half nuts on my Heavy 10. Just thought I would share some pictures with everyone


    Picture of worn nuts



    As the nuts were machined in lathe. I fabricated a fixture using scrap metal I had. Used the removable gib from lathe apron mounted on fixture to locate the nuts, made another gib to hold nuts tight to fixed gib, had 1/8" dowel pins on center line to locate nuts on center, set screws to hold nuts from sliding out. Had a indicating block on fixture to locate on center when mounted to lathe face plate.




    Nuts before cutting in half



    Used bandsaw to split and then machined in mill flush.
    When mounting to apron to see if everything fit I noticed that the thread cutting dial had to be timed by turning the bronze nut and lead screw in the machined casting. Used 660 bronze alloy and JB Weld epoxy to hold together. Nuts are installed and working fine.

    Larry

  11. #11
    540i928 is offline Aluminum
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    nice job Larry! we shure have had the weather for these projects lately. did you use a boring bar to cut the threads.

    Tony

  12. #12
    Larry Condon is offline Aluminum
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    Tony
    Yes I single pointed the threads. First I measured the leadscrew using the three wire method. Made a sample screw.Then I cut the internal threads to fit the sample screw. Worked very well. Yes April has been cold and a stay inside month so far. Finishd several projects this winter.

    Larry

  13. #13
    twalsh341's Avatar
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    Default How to fixture this

    Hello all,
    Paula, when you talked explained the process it seems really simple. I partially took apart my apron yesterday and was attempting to get the half nuts off, I unscrewed the hex bolts on the front side but was unable to get the rest of the half nut assembly off, how do I do this?

    The new half nut "sleeve" turing, fitting, epoxying, and slitting is pretty straightforward; how though do I bore the half nuts out? will they clamp easily in the 4 jaw just bearing against each other or os some crazy faceplate+angle plate for needed here?

    Thanks Paula, or anyone who will help me with this.

  14. #14
    Larry Condon is offline Aluminum
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    TWALSH341

    I repaired the half nuts for a heavy 10 machine. Not sure if this is the same as yours. I did fixture the half nuts and turned them on my lathe. The post did have pictures of the process I followed but are now deleted. If you can send a email I can send you the pictures that I had.

    Larry

  15. #15
    sicero is offline Stainless
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    I bolt mine to a piece of 3/4" plate and clamp the plate in an 8" 4 jaw and bore the old threads out then make a bushing from cast iron and epoxie the bushing into the bored out nuts. I also have one with a new bushing or a used set for sale for a 10L. New bushing nut for $45 shipped or used set for $35 shipped. Kenny

  16. #16
    Brett by Portland's Avatar
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    Paula,
    Wow, I nearly forgot about my half-nut repair method. Thanks for reviving it. I kind of miss having a South Bend 9 around......anyone around Portland have an extra? I am in the mood for a rebuild. biketools@me.com

    For what it's worth,, I have done it 3 times, and it is perfectly effective, and yields a near zero-backlash result, plus guarantees absolutely perfect alignment.

    I feel I should clarify that I inserted roll pins through the flanges into the cast iron in an axis parallel to the leadscrew on both ends top and bottom(4 total).

    I think it would be nearly impossible to dislodge the bronze thread inserts, even without the roll pins.

    Additionally, I do the clamping of the spool dry and check that there is no contact so as to ensure that there is no mechanical deflection, and i do the clamping using mixed epoxy with half-nut assembly as close to lead screw bracket as possible to also minimize chance of deflection.

    When done, the half-nut action feels beautiful.

    Brett

  17. #17
    jayhawkman is offline Stainless
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    Default half nut repairs

    If any of the 16" owners are wanting to do this I have inserts for sale with the 1.125-6 thread. I will be listing them in my ebay store but PM members will get a discount just give me a call or PM me. 913 636 6107. Price will be $65 including shipping. Thanks Mike
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