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Thread: My Taiwanese Shenwai SW-900B Lathe Clean/Repair Thread

  1. #11
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    Looks like a previous owner ran it without knowing what they were doing. Ive never seen a lathe that requires grease, they all use oil. Its easily fixable, you could count gear teeth and diameter, then take a look at the Boston Gear catalog. Or scrounge eBay. I like to soak parts like that in a mixture of kerosene and baby oil -- youd be amazed how well it cleans and penetrates, dirt cheap too.

  2. #12
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    State the tooth counts and diameters of the paired gears.

    the other one is a worm wheel, but willing to bet can be sources from similar lathe...need tooth count and diameter, and also a measure of the worm it mates with.

    ps- Eisen Machinery may be able to provide replacements too....worth a call.
    Last edited by 1200rpm; 03-08-2019 at 07:49 AM.

  3. #13
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    Helsinki, Finland, Europe
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    Quote Originally Posted by 1200rpm View Post
    State the tooth counts and diameters of the paired gears.

    the other one is a worm wheel, but willing to bet can be sources from similar lathe...need tooth count and diameter, and also a measure of the worm it mates with.

    ps- Eisen Machinery may be able to provide replacements too....worth a call.
    With a bit of luck its the similar gear as in this Grizzly
    https://www.grizzly.com/parts/Grizzl...16T/P4003G0320

    16/32 tooth count is already a match to OP's gear.

    19T? sheared bronze gear is non-existent in grizzly.

  4. #14
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    May 2006
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    Well looks like someone got past the moping around and took some major action! Kudos, im with the group trying to find a replacement gear(s) before having one made, looks like all the other stuff can be brought around and she's going to purr like a kitten when your done,

    can't wait to see it all fixed up and working which would not surprise me will be in short order at the rate your going...

  5. #15
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    If teeth are cracked, that's obviously more of a problem.*

    The idea of boring out and pressing in a replacement for the smaller gear is certainly a possibility. To make one, you would have to, as mentioned, get the tooth count and outside diameter, so as to find the diametral pitch, or module if it is metric. For comparison to a prospective replacement, , you would just need the count and diameter.

    Those double gears are often made by pressing together two, either with one having an extended sleeve, or both may be pressed over a sleeve that connects them.

    I can't quite tell if the bronze gear has the teeth at a slight angle to match the worm, but it is not formed to wrap around, as many are. It may not be an actual "worm gear", one made specifically to fit that worm.

    * Some might fix the gear by removing the broken teeth and filling the area with brazing material, then shaping, or just filing the tooth form again. That's troublesome on a double gear, but not impossible.

    I think I'd suggest the "assembled" type, boring the larger one out and pressing in a replacement for the smaller, assuming there are no broken teeth on the larger gear of either pair. If one has broken teeth, you have to wonder about the one that mated with it.

    Alternately, if one of the two double hgears is good, you can put the bad one in the "last position" and just not use it at all until you find a replacement. Those gears produce the slow-down for the various ranges of threads and feeds. If you put the bad one in the "last" (finest end) position, you will only lose the very fine threading and slowest feeds. That may be tolerable for the moment, it would let you fix other things and use the machine while you look for a replacement.
    1601

    Keep eye on ball.
    Hashim Khan

  6. #16
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    May 2006
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    I have to comment on your average lathe transmission and Junkaddict don't take this personal as it's just an observation of all the lathe trannies iv seen down on this site,

    They have to be about the crudest transmissions out there, all in an area where you would think they would want refinement due to the transfer of gear pattern frequencies ending up directly into your work, now I know straight cut gears are rated very strong but are there some precision lathes that use helical? having more than one tooth engaged at a time can do wonders for smoothing out the power transfer, just accelerate any manual trans car in reverse to hear that vibrating winding in comparison to taking off in first gear,,,

    I know it's a huge factor, even Mill heads that have the high/low speed option run through a gear system that introduces chatter and gear pattern into the work, My mill is total step pulley and does not have anything but a belt drive and I was pleasantly surprised at the amazing finish I get out of it esp. when using it as a lathe...

    Guess that's why lathes like the Hardinge super precision have nothing but belt between the motor and the tooling...

    it makes sense - sense enough to wonder if there are manufacturers that utilize helical with side dog engagement for the power transfer... like a very light duty auto trans...

  7. #17
    Join Date
    Dec 2016
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    Quote Originally Posted by A.K. Boomer View Post

    it makes sense - sense enough to wonder if there are manufacturers that utilize helical with side dog engagement for the power transfer... like a very light duty auto trans...
    Big monarchs:
    https://www.practicalmachinist.com/v...monarch-87682/
    Even some imports:
    http://bbs.homeshopmachinist.net/thr...aiwanese-lathe

    And the double-helix or herringbone gears on Sidney:
    http://www.lathes.co.uk/sidney/

  8. #18
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    Jan 2004
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    AK....

    Most good lathes did use helical gears in the headstock. Monarch, for ine.

    Maybe some used them in the QCGB, which is where the gears the OP is showing are from, but mot I have seen of the regular Norton type have spur gears. The shifting transmission type QCGB (not the ones with the drop levers like this one) I think may use helical gears, just as the headstock gearing.

    But there is a difference between low cost machinery and the better grades, such as Monarch was.
    1601

    Keep eye on ball.
    Hashim Khan

  9. #19
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    May 2006
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    Wow guess iv never seen a monarch down - very nice - just how I imagined the engagement and what beefy looking shift dogs to boot...

    Holy man that one sidney takes things even further, no need for the needed thrust bearings/washers that helical gears produce, herringbone eliminates all that just in the gear design... it's the best of both worlds but very expensive...
    Last edited by A.K. Boomer; 03-08-2019 at 11:29 AM.

  10. #20
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    May 2015
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    That much damage is probably not any fault of the poor lathe, but deliberate butchery by earlier operators or small kids. Hopefully the gears can be replaced and shafts remade. If you have a mill, then some of the plain bearing bores could be opened up and bushed.
    Best of luck to you, a lot of work will result in a reborn machine.

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