SB9A restore and retrofit 3 phase/VFD - Page 2
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  1. #21
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    I was looking for an example of an appropriate motor. The revised speed ranges gets me into the slower speeds while the inverter rated motor supplies almost 100% torque down to 10% of 60 Hz. The original turnbuckle tension lever is used and there is a 2nd radius rod type stand off on the left side of the mount. So far, I have no vibration or flexing of the motor mount but have not yet taken any heavy cuts. A hall effect tach is mounted on the original switch holes on the left gear guard and the magnet is on the small cone pulley. I am having a hard time finding grease fittings with 1/4-20 threads, for the cone pulley and back gear shaft, if I decide to go with lithium grease over oil.

    The lathe footprint is more compact and portable, and I always have future options to bolt to a table. I'm sure there will be tweaks to this setup going forward, but my out of pocket dollars for this is so reasonable that I have taken a huge step up from what I had before.

    capture-519.jpg
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    _dsc2263.jpg

  2. #22
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    there you go....bad ass little motor ain't it? That price was a steal.

    1000ish rpm on a 9" is all you really need anyway IMO....and a 9" is not for hogging so as long as your mount is solid I think you will be fine.

    if you use grease make sure it is grade 1, although I just used the same oil I used for the ways.

    I do not see how the tach can work on the cone though, at least not while in back gear.

  3. #23
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    Quote Originally Posted by iwananew10K View Post
    That price was a steal.

    I do not see how the tach can work on the cone though, at least not while in back gear.
    Yes, Baldor confirmed that TENV motor is 6 pole. I have the TEFC 3 phase Baldor for sale on Southern Cal craigslist.

    Good catch on the tach placement for back gear use. I was going to do the "Whats wrong with this picture" if anyone noticed the hall sensor placement, but that is a dangerous thing to do on this forum.

  4. #24
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    life is dangerous...don't sweat it.

    can you do a video?

  5. #25
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    20190520_101527.jpg20190520_103814.jpg20190520_121223.jpg

    Getting back to one of the original issues of not having a flat belt motor pulley, I decided to turn down the larger of the original double V-belt pulley. I went with a 2 degree crown on each side with a 2.4" diameter.

    The photos shows the makeshift rubber caster wheel with the cast iron V-belt in the chuck. The 3" caster wheel next to the finished 2.4" cast iron pulley with both V-belt and flat belt pulleys. If I ever move to a V-belt cone spindle pulley this would work.

    Next is to take out the slack caused by the smaller motor pulley diameter.

  6. #26
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    you could have sold that pulley for 60 bucks.
    And then bought one for 20, or made it yourself for nothing....don't need a crown with poly v, don't even need the ribs, simply a lip on each side will do.
    You do NOT want v belts, they will never run as smoothly as flat belts and smooth is the key here!

    You're moving too fast!

    I "think" that motor has a 2 7/16" shaft? If so you could work out the calculations to use a 2 step motor pulley and given the spindle cone has 1" steps you could have a low and high range to cover the the full range of speeds if you wanted to....probably rarely need the high range but it wools be there if you did.

    keep the updates coming.
    Last edited by iwananew10K; 05-20-2019 at 05:44 PM.

  7. #27
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    Ha, I'm just happy I recouped $100 for a couple SB surplus parts, and still have a $100 motor and a couple more SB parts for sale.

    Excellent idea using the middle cone pulley for higher speed, using a 2 step motor pulley. I have a 3/16" broach for keyways and boring bar on my shopping list. I decided on oil for the cone and back gear lube, so no grease fitting to get in the way. For the time being, if I really need speed, I can go past 60 Hertz and approach 1000 rpm with the VFD, but the 700 or so rpm seems more than adequate. However, turning small diameter stock at higher speeds may be a smoother process with the higher gear middle cone pulley with lower rpm's.

    As the video shows, The .8" wide 36" circumference belt tracks perfectly due to the crowned pulleys and the belt tensioner on the right side and the turnbuckle on the left, to position the motor axle and spindle on parallel planes. In a no load scenario it is hard to tell the right tension on the belt, but with experience that should be evident. The spindle bearings are within spec at max .0015", but I detect drag in the quick change gears, and the back gears are loud. Hear anything funny?

    With the bull gear pinned to the cone pulley the rpm is accurate, but with the back gears divide by 5, so that is 60 rpm.
    https://drive.google.com/open?id=11S...HvPP5XuphKWD0W

  8. #28
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    I replied with a video focused on the VFD, but it didn't post and Brad's mail is full.

  9. #29
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    Uhhgg...yes, that is an issue.


    Anyhoo...what kind of results are you getting?

    And it looks like you could use a new chuck?? hard for me to believe that old 3J chuck could allow you to machine the OD of that pulley while maintaining concentricity to the pulley bore? At least not without some finagling.

    PS- if nothing else good pics will do, this is IMO a very useful thread as you will expose the pros and cons for those that consider the same...and if you successfully overcome the issues it will become a wealth of info for others.

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    Quote Originally Posted by iwananew10K View Post
    And it looks like you could use a new chuck?? hard for me to believe that old 3J chuck could allow you to machine the OD of that pulley while maintaining concentricity to the pulley bore? At least not without some finagling.

    PS- if nothing else good pics will do, this is IMO a very useful thread as you will expose the pros and cons for those that consider the same...and if you successfully overcome the issues it will become a wealth of info for others.
    I'm getting .006" run-out on the crown crest while pulley is on the motor shaft. I suppose I could use the 5/8" rod referenced below to return the pulley. How does that sound? and is .006" at the pulley enough to cause vibrations because I'm not getting any up to 1150 motor nameplate rpm.

    I was thinking the 3J chuck was pretty good. . .
    I'm getting .003" run-out on a 5/8" stainless rod, 1 inch out and .002", 3 inches out in the small external chuck fingers. Radial run-out of chuck outside diameter is .002. Axial run-out of chuck face is ~0.
    20190523_122511.jpg

  12. #31
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    if it works,it works....if it ain't broke...

    but once you use a chuck with 2 piece jaws you will never go back, the ability to use soft jaws solves a lot of issues.

  13. #32
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    Yes, a 3 jaw 2 piece chuck would be nice. Original SB items are so pricey, at least eBay sellers think so, maybe I can trade up to one of those.

    If my video of the VFD in action ever gets posted, I comment on load resistance in the quick change gearbox on some gear combos. I removed the QC gearbox today and with the tumbler levers disengaged there was no resistance on either side of the gearbox. South Bend being a model of good American engineering, everything only fits together one way, so I saw 2 identical looking tumbler levers and didn't note which side each was on during disassembly. Upon inspection, everything looked good.

    The only thing to do is swap the tumbler levers, which I did. After screwing in the tumbler lever guide bar to the base and hand turning the different gear combos, all were free turning. Also, the tumbler lever pegs went into the position holes easier. I suppose there could have been torque in the lever that caused binding in the gears.

    One of the parts list show 2 parts #s for each tumbler, so there must be a difference. My photo, the near one says "1" and the back one says "2".

    So, issue solved for your information. . .
    20190524_153114_001.jpgcapture-524.jpg
    Last edited by JimBuchanan; 05-25-2019 at 12:15 AM.

  14. #33
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    https://drive.google.com/open?id=11S...HvPP5XuphKWD0W
    This is a 2nd attempt to get this video up for viewing. And the link seems to work!

    The general layout and mechanics are shown. About 2/3 thru, the gears driving the quick change box are rumbling due to the resistance described above when the 2 tumbler assemblies were installed backwards. Once swapped, the tumblers could select gear combos easily and the resistance in certain gear combos were gone.

    The back gears are certainly loud. Maybe playing with the mesh adjustment would reduce it. Until I change the hall effect tach sensor, back gear spindle rpms are divided by 5.

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    you're getting there...I still think the mount will prove unsatisfactory, but will be happy to be proven wrong.

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    https://drive.google.com/open?id=1t1...JjMhYlkYWZlz1w
    This shows how the motor mount is located. I'm not saying I will not redo the mount in the future, but the lathe is operational now. On the left side is a turnbuckle radius rod and on the right is the original tensioner handle. The 2 locate the motor axle parallel to the spindle, counteracts the weight of the motor, and tensions the belt. Notice how straight the belt tracks.

  17. #36
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    https://drive.google.com/open?id=1-1...spQ-aIn_swtIN6
    There are 3 parts, motor at 100% of 60 Hz with no belt load, 100% of 60 Hz with belt/spindle
    load, and 100% of 60 Hz with belt/spindle/Cushman chuck load. Vibrations of the chuck start at 85%. There is very little runout on this chuck. The spindle bearings are within spec, .0015". Out of balance chuck?

  18. #37
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    now you KNOW what I am going to say...

    isolation,stability, pulleys near as perfect as possible, no crown with poly v...

    it's not the chuck...imagine grabbing a non symmetrical part in a 4j and trying to machine it...that's the kind of stability you need.


  19. #38
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    Quote Originally Posted by iwananew10K View Post
    now you KNOW what I am going to say...
    isolation,stability, pulleys near as perfect as possible, no crown with poly v...

    it's not the chuck.
    I knew someone was going to say something about the mount! Spell it out for me because I'm a machinist impostor.

    Isolation? The new breed Taiwanese lathes are gear headed right? Where's the vibration in that system? Maybe the vibration is in the BELT system? My rebuilt Craftsman table saw with v-belts and fiber-link belts are as smooth as silk.

    For "low" speed HSS turning on SB9, I'm not seeing a problem.

  20. #39
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    The Taiwanese machine has another 600 or so lbs...and that mass can cover many sins.

    the saw spins a lightweight blade at a single speed.

    Apples and oranges.

    keep going, continued experimentation will get you there, the concept has promise, the implementation may take a few tries..

  21. #40
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    Quote Originally Posted by iwananew10K View Post
    The Taiwanese machine has another 600 or so lbs...and that mass can cover many sins.
    The Precision Matthews 10" weighs more than the SB9A and more than my iteration. Your comparing a 350 LB SB9 to a 1000 LB lathe? I guess so.


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