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

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

    I'm sure most of this kind of stuff is common knowledge to most of the members here, but I thought I would make a thread of my trials and tribulations as I try and get this thing back into working order. Also maybe someone thinking of buying one can get an idea of what may be wrong, and the work involved when hashing out a price. I have lots of experience repairing cars, and have taken on repairing just about anything with a motor, jacks, hydraulics, but with off the shelf parts. I took a couple of semesters of machine shop back in the stone age(well, the 80's, so not that long ago), I know a little, but I'm mostly flying blind when it comes to anything past threading shafts, and making bushings. I am ready to learn though, and if anyone has any useful info, it's welcome. I have a pretty thick skin, so criticism if I'm doing something stupid is fine, and of course, nomenclature corrections.

    This thing was never oiled, so I'm going to go though and clean/check/lube everything. The grease on this thing has degraded into a hard glue, and the cosmoline was never cleaned off. I'm not going for a resto, just a clean up and get it running. The gear box has a drip system with a piece of felt to slow the flow. The gears were packed with grease when I got it, as some alternative to oiling, so the shafts and bushings just went dry. Starting with the lead screw, it was impossible to turn by hand. I had to use a puller to get the end block off, and it was galled with a piece of metal that had come off the shaft and ground around in the bore. I knocked down the burr on the shaft with a small file, and the burr in the cylinder with a few turns by hand with a hole lap. Lead screw turns freely now.




    Other 2 shafts just held on with pins. The set screw on the lead screw did not release it, so I just removed it with the box to get a better angle.



    Flat way has some dings on the inside that almost look to have been surfaced over. The carriage does not bind or slow here, and it is flat with the opposing sides with a straight edge, so I'm not going to worry about it. I can still see the grind marks on all the way, so I don't think there is much wear there.



  • #2
    Gear box came off with 3 bolts. I don't know what the selector gears/handles are called, but the shaft came out by taking off the snap ring, and pushing the opposing bearing out with the shaft(vise grips on lead screw have copper inserts, in case anyone was wondering)




    There is a snap ring on the end of the center shaft, and it pushes out the opposing bearing, right through all the gears.




    The driving shaft comes out with 3 bolts. The lead screw shaft comes out when the center shaft is removed, and the gear goes back far enough to get the shaft key out.

    Comment


    • #3
      The set screw on the lead screw shaft holds on a collar that was really stuck. Had to use a puller to get it off. Its also the race for the thrust bearing. It reveals a pin that releases the lead screw.



      Damaged gears



      Box disassembled.



      Metal transfer from 2 of the bronze bushings. Looks like this got dry and hot.



      Small spur gear, one of the transfer points, gear is good, but bushing spun in the bore, and oil hole is no longer aligned.

      Comment


      • #4


        One of the damaged gears, and the other transfer point on the shaft. Again, spun bushing.





        The drip oiling system, bone dry.



        The two bad gears. They are one piece with bushings in the center. Not sure how to go about these, as I do not have any gear making equipment.

        Last edited by junkaddict; 03-08-2019, 02:26 AM.

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        • #5
          Carriage off



          Half nuts look good.



          Snap ring came off under pressure of the gear seizing.




          Gear is stripped and bent.

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          • #6

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            • #7
              Dunno for sure, but it kinda looks as if the honked-up gears other than the one bronze worm gear could be brought to working condition with a careful job of filing on any deformed teeth. That's if there are no actual missing teeth on the others, and I did not see any in the views above except for the bronze gear. Maybe I missed them , maybe they are on the other side, or maybe no teeth are broken off.

              The bronze gear will need replaced, yes. But if it is for crossfeed, as you said somewhere above, it is not essential, and you can go for years without it. Boston Gear may have something that will work, or maybe the Grizzly folks have parts, since someone suggested there was a very similar Grizzly machine. ( "The two bad gears. They are one piece with bushings in the center. The other one is for the worm gear drive on the power cross feed. Not sure how to go about these, as I do not have any gear making equipment. ") I think you edited the pics and removed part of that statement while I was composing this.

              Looking again at it, it is not a real worm gear, by the look of it, and should be fairly easy to find. Looks like a plain spur gear in several of the pics.

              The spun bushings can be pressed out and replaced, either with ones you make, or possibly with "oilite" type pre-oiled bronze bushings. McMaster-Carr has metric sized oilite sleeve bearings, which I suspect those may be. If they are inch size, of course they have those as well.

              The oilite would not need oiling through a hole like that, although light oil will not hurt them.

              The machine looks well-designed and made, it's issue is having been operated by a low-grade barbarian.
              Last edited by J Tiers; 03-08-2019, 02:56 AM.
              1601 2137 5683 1002 1437

              Keep eye on ball.
              Hashim Khan

              If you look closely at a digital signal, you find out it is really analog......

              Comment


              • #8
                The two gears that need repair were done on a gear shaper.
                You might be able to make new ones, if you can bore out the bigger gear till the small one fall's off. Then make the small one the regular way gear cutting with a wheel cutter, plus a shoulder, then press into the big gear and tig weld together.
                The bronze one looks easy to make..

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                • #9
                  The one where the small gear is damaged, a couple of the the teeth are cracked at the base.

                  Comment


                  • #10
                    Originally posted by 754 View Post
                    The two gears that need repair were done on a gear shaper.
                    You might be able to make new ones, if you can bore out the bigger gear till the small one fall's off. Then make the small one the regular way gear cutting with a wheel cutter, plus a shoulder, then press into the big gear and tig weld together.
                    The bronze one looks easy to make..
                    Looks to me that you can get one good gear out of the 2 bad ones by cutting them in half, boring and inserting over sleeve. They seem to be made of steel so you don't need to worry about wall thickness like with cast iron gears.

                    With a bit of luck the gears are some standard size and you don't need to cut your own. Folks here can help fiquring out the type if you get enough measurements form the gears.

                    Crossslide bronze feed gear could be more difficult to find and some speciality size but you can easily live even without crosslide power feed. Many if most garage size hobby lathes don't have one in any case.
                    Location: Helsinki, Finland, Europe

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                    • #11
                      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.

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                      • #12
                        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, 08:49 AM.

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                        • #13
                          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.
                          Location: Helsinki, Finland, Europe

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                          • #14
                            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...

                            Comment


                            • #15
                              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 2137 5683 1002 1437

                              Keep eye on ball.
                              Hashim Khan

                              If you look closely at a digital signal, you find out it is really analog......

                              Comment

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