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  • SB Model 9 Rails

    Looking at a South Bend model 9, the lathe was in reasonable condition given the age. The most obvious issue is the front guide rail. I understand its a point of heavy wear given that it has the bulk of the carrier weight. The front guide rail had worn to a point it was roughly .375 wide intead of coming to a point when it was new.

    Is there a cost effective repair or just move on? I was mad at myself for forgetting my staight and a feeler gauge, this was bad enough it was quite obvious.

  • #2
    Move on.

    if I understand you correctly, it is severely worn, probably way past the "scrapeable" type of wear. As a "point" of information, the ways do not come to a "point" but rather typically have a flat about 0.125 wide at the top. I have no clue how it could get to be a 0.375 wide flat, that sounds crazy.

    S-B typically wear so that there is a "ridge" at the top of the V-way, so you can judge the wear amount. Some other machines, like Logan, do not show this ridge.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #3
      The top of the front vee way is 1/16 wide when new. It shouldn't wear at all since it isn't normally a contact area. The carriage ways bear on the sides of the vee way. That is why it develops a ridge when worn. If the top is also worn the lathe is trash. Look for another. It must have been used for grinding.
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      • #4
        For my personal knowledge, any chance they can be welded and reground. All though it would more then likely cost more then the lathe is worth.

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        • #5
          Its cast iron so welding is out. It could possibly be plasma sprayed and ground but it isn't worth the money.
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          • #6
            Originally posted by majohnson View Post
            For my personal knowledge, any chance they can be welded and reground. All though it would more then likely cost more then the lathe is worth.
            I've heard of successful and unsuccessful attempts at flame spraying material on the ways and regrinding to the original spec, more unsucessful with material peeling off. Additionally the process will be expensive if you're paying someone else to do it for you.

            Something that might be done would be to regrind the ways to eliminate the wear and then refit everything on top, using way meaterial like Turcite or Multifil to take the saddle back to the original height (for leadscrew alignment). Still an expensive process but you end up with a lathe with a new bed Not sure that it'd be worth it unless the lathe would be worth quite a bit new.

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            • #7
              Usually, the wear is at the headstock end. Can you shorten the bed to get to an area that is not worn as badly? One of my friends bought a huge lathe and cut the bed length down to fit into his garage.

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              • #8
                It isn't worth the trouble unless there are sentimental reasons to make it functional. The lathe has been very badly abused to be worn in that manner. I point out to the OP that I have the same lathe and have used it a great deal for about 30 years. It shows almost no wear on the bedways, just enough to make the original scraping marks invisible. With the amount of wear on the front way that you describe there must be other less visible areas that are also badly worn, especially the mating surfaces of the saddle. If it was used for grinding, which is very likely, then there will also be wear elsewhere. I would also suspect the spindle bearings as they are plane bearings. That means bearings that are plane (but curved) surfaces, metal on metal, cast iron on steel. If they are not lubricated according to schedule severe damage will occur quickly. The same goes for all other bearing surfaces on the SB9. There are practically no rolling element bearings in the lathe, just the main thrust bearing in the headstock.

                A South Bend lathe must be lubricated on schedule without fail or it will fail. I suggest you have another look. Observe the long leadscrew at the front underneath the front edge of the front bedway. Look at the width of the acme thread crown over the entire length. If the width of that crown varies considerably, especially at the area near the maximum wear of the front way then the lathe has been used extensively for grinding and is worthless.
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                • #9
                  If you need manuals and other data on Soutn Bend Lathe try
                  http://finance.groups.yahoo.com/group/southbendmanual

                  Dave

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                  • #10
                    A photo would be a help in determining the actual wear to this lathe. I find it very hard to believe the ways are worn as badly as the description seems to indicate. I would think the carriage would be down to the flats on the bed well before the V ways would wear to this extent.
                    Jim H.

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                    • #11
                      Originally posted by JCHannum View Post
                      A photo would be a help in determining the actual wear to this lathe. I find it very hard to believe the ways are worn as badly as the description seems to indicate. I would think the carriage would be down to the flats on the bed well before the V ways would wear to this extent.
                      My thoughts as well. Meaning no disrespect to the OP, but it sounds like there is some confusion and maybe a lack of knowledge. For instance, we normally call those "rails" "ways" and that "carrier" a "saddle" (sometimes called a carriage, which carries the apron, cross slide and compound). The ways have to support not only the weight of the saddle, but also handle the forces generated when cutting material. Usually the headstock end wears more because that is where most of the work is done; the saddle moves back and forth in that area much more than at the tailstock end. As others pointed out, the width of the way when it was new was not a point but a small flat. As they wear, they normally end up looking sort of like a "top hat". There has to be a huge amount of wear before it bottoms out on that top flat and to then wear that top down to 3/8" ... well that seems like a train wreck.
                      Last edited by Fasttrack; 11-29-2012, 02:05 PM.

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                      • #12
                        I also have trouble with the description. Assuming the description is accurate then the only thing I can think of is that the lathe was more or less permanently set up for a particular grinding job and run that way until it was useless.

                        In business all tools are also consumables.
                        Last edited by Evan; 11-29-2012, 02:37 PM.
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                        • #13
                          I'm pretty certain everyone who owns a lathe would like to have a machine that will turn a cylinder true to within .0001" over a 12" length, but most here probably don't have machines that will do that. Feel free to correct me if I am wrong on that count.

                          That said and assuming that the OP isn't going to be making parts for NASA, some pretty accurate parts, to within +/- .001", can be turned on some pretty worn lathes, particularly over the short distances usually required (hence the headstock end of the lathe being worn the most). Many home shop machinists would probably be pretty well pleased to hold those tolerances, and some would have difficulty measuring a bore to to the thousandth.

                          Some of the ability to hold tolerances on a worn machine has to do with the geometry of the lathe where the tool meets the work and some with the skill of the operator and the level of his "oneness" with that particular machine. Not being particularly good with Trig (actually not good at all) I can't give a formula that would allow the calculation of how much the diameter of a shaft would change per .001" of wear on the ways, but no doubt someone here can. Just off the cuff I would guess that ways worn .010" would only change things at the tool point a very small amount and .010" would be considered quite a bit of wear I'd think.

                          All this said, if the OP just needs a lathe for general home shop work and is just beginning in his machining hobby, a worn machine with the remainder of the parts functioning well may be a great starter machine. In fact after some use and experience with he he may actually learn that it's all the machine he requires. If it turns out it isn't he can always resell it to another beginning machinist or strip it for parts sales and likely get a bigger return on his investment than he paid.

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                          • #14
                            I would really like to see a picture or two. I can't see that .375 number. What? What?
                            Gene

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                            • #15
                              From the description this lathe isn't just worn, it is utterly destroyed. A picture would be very helpful.
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