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  • Need suggestions for repairing ways

    Last October I got a great deal on a large Polamco lathe (21x70) it has normal wear and tear and overall is in good shape except the front way close to the chuck, about 24" of the way is scored. I really haven't used the machine a lot but I'm assuming the front way wiper is bad and chips got under the carriage. Is it possible for a HSM to repair this or do I need to tear down the lathe and have the bed rescraped or ground? I don't know anything about scraping ways and these are about 84" long overall. The tailstock rides on it's own set of ways and they are in great shape. The rear carriage way is also in great shape and the tail stock end of the front way is perfect. I'm planning on doing some long work over the winter and I just know that bad section of the way will cause me trouble, any suggestions? Approx what does it cost to have a bed of this size reground?

  • #2
    I'm not sure the details, but I've heard more than once "a couple of hundred dollars" thrown around. Of course, depending on how the head stock is mounted this may mean shimming up the saddle and reseating/scraping the head stock. Certainly doable, but finding a place close by to do the work may be the hardest part, otherwise you add shipping along with the accompanying delays and risk of it getting lost or ruined.

    Fortunately, my new lathe seems to have a fine bed, but the cross slide ways turned out to be very badly scored on the bottom side. I’m currently investigating getting them ground and scraped, or possibly laminating with Turcite, or building up with Moglice which are low friction synthetic polymers that have become very popular for VERY low friction ways in the last few years. I think I prefer grind/scrape, but if it turns out to be too bad for that, then the others become more attractive. These are also options for the main bed ways that you might look into...
    Russ
    Master Floor Sweeper

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    • #3
      Could I fill up the scoring with moglice or something similar? I haven't really looked under the headstock covers but I know it's complicated in there. The total bed length including the area under the headstock is about 10 feet, still think "a couple of hundred dollars" is possible? Fortunately I'm in Ohio so i have to think with all the machine shops and tools around there must be a refurbisher within reasonable driving distance and I do have a flat bed trailer that I hauled the lathe on when I bought it. I'd love to get it professionally done but I can't spend much more than $1000 at this time. The upside is that while the machine is torn down I could clean it all up, attend to some details and repaint the machine.

      I really like this lathe and it has served me well when I have used it, nothing like taking 0.500 off the radius of 303 stainless in one pass! I had to make a stepped roller for a coating machine at work, it was a shame to make all those stainless chips but the roll had to be solid.

      Hmmm wonder who has a 10' surface grinder

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      • #4
        No idea on how the cost compares, that's just some numbers people threw out talking about having a bed reground.

        I also don't know details on the Moglice as I'm only beginning to sniff around in that direction. But here is a link to their web site that shows examples of where Moglice has been used to repair various machines...
        Russ
        Master Floor Sweeper

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        • #5
          The first question is does the lathe provide the accuracy needed? If it is working within the requirements of your application, repair is not needed. Scoring does not necessarily affect accuracy.

          Make sure the lathe is installed on a solid surface and properly leveled. If it was leveled at installation, recheck it. It can change. Make some test cuts and determine the accuracy of the lathe. There is no point in fixing it unless the problem warrants it.

          If it is scored from trash under the carriage. Clean it and the carriage well, and lightly stone the ways to remove any high spots. It might be a good idea to remove or at least raise the carriage to make sure nothing remains to cause farther damage.

          Install new wipers and keep the ways well lubricated. Unless there is wear in the ways, the scoring will not affect accuracy.

          Scraping is not cheap, and with the size of the machine, you will have to have someone come to you to repair or incur shipping costs which will add even more to the expense. It can be done by the HSM, but experience, lots of practice and some specialized tools are needed.
          Jim H.

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          • #6
            Jim's reply was spot on. Make sure that the ways or saddle are actually worn enough to affect accuracy before going into the grinding and way material process. And a 'couple hundred dollars" won't get you far along that path once you're moving, it'll be more like a thousand before you're finished with just the ways. Generally, if you find that much wear on a lathe there's going to be other problems that'll pop up in the process of fixing the ways.

            I went though this with a Monarch 10EE - stripped the lathe down and took the bed, saddle and cross slide to Commerce Grinding in Dallas. The were able to clean up the bed with .007" grind and reground the cross slide dovetail ways on the saddle and squared up the cross slide and top of the saddle (the latter simply cosmetic). After remounting the bed I had to scrap the tailstock into contact with the bed, use that as a gage to scrape the headstock back into alignment and contact with the bed.

            Once the headstock was in place I made little jackscrews for the corners of the saddle to work out the alignment. It needs to be a particular height for the apron to have the appropriate height for the leadscrew, feed rod and switch rod and you want the cross slide to be perpendicular to the spindle. Once that was done I could use feeler gages to get the existing clearances (wear and the bed grind) and calculate the work. I had to mill the ways on the bottom of the saddle to give clearance for Moglice (minimum thickness is .032") about .012 on the leading edge and .019 on the trailing edge. After putting tape (oil grooves) and release compound on the ways I was able to mount the saddle with Moglice putty on the bed, and in testing the result it came in better than .001 on height and .0001 on cross slide alignment.

            I then had to measure the wear on the cross slide, I'm not sure if there was an easier way but I simply measured the height from the top of the cross slide to the cross slide screw, and subtracted the thickness of the cross slide. That should have given the distance from the top of the nut to the screw centerline, and it's what I used to calculate how much material to take off the bottom of the cross slide to get it to the proper height for the screw, taking into account the .032 for way material and .004" for glueline. It came in .001" low when all was said and done, but no scraping was required. The repair of the drop eliminated a makeshift fix on the gib with a .007" shim, so if the cross slide gib is loose the cause is likely wear on the bottoms of the cross slide ways.

            The rest of the work was pretty straightforward repair stuff (but a lot of it), I just wanted to summarize the way work. Since the Moglice is using the work as a master in the molding process it really does need to be straight and clean, something very freshly scraped might work but all the examples I've seen have used ground surfaces. You can't use a thin layer of it anymore than you can use a thin layer of glue to build up an exposed surface, and that's all it is - very brittle glue at that. It worked very well on the saddle but would not have worked on the cross slide, so I used way material for the latter.

            Harry Bloom has written a couple of articles for HSM on the process of reconditioning a lathe, with a focus on scraping the bed and other bits into alignment. It might be a good idea to read all that to have a good grip on the process before jumping in.

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            • #7
              Well I suppose it only makes sense to determine if the accuracy is being effected before fixing something that might not need fixing. I'll get a long piece of stock and make so test cuts to determine if there is a problem before proceeding.

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              • #8
                RSR,

                You might also look up the machine tool reconditioning book, read about way checking procedures and do some indicator tests comparing the unused portions of the ways with the scored ones. This would tell you whether the geometry has changed and by how much.

                Jan M.
                .
                "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

                Comment


                • #9
                  Originally posted by rsr911
                  it has normal wear and tear and overall is in good shape except the front way close to the chuck, about 24" of the way is scored. I really haven't used the machine a lot but I'm assuming the front way wiper is bad and chips got under the carriage. Is it possible for a HSM to repair this or do I need to tear down the lathe and have the bed rescraped or ground?
                  It depends. If the ways are just scored (and not depressed from wear), then you can just (very) lightly scrape the raised scores back into the trough and stone everything flat, and use the lathe as-is. However, since the front way close to the chuck is the area of most use (and swarf), it's more likely that it's just worn more on that side from use. If this is the case, then the cross-slide and compound will be worn more on that side as well.

                  Note that Moglice, Turcite-B, Rulon-142 et al are meant for the female bearing slide. The most common use for these PFTE bearing materials is to insert under the saddle of a lathe or mill, which wears a lot faster than the male ways if you have hardened (or chromed) ways.

                  As RKlopp mentions, Harry Bloom (who is a poster on PM, and possibly here as well) has an outstanding article on rebuilding a Monarch lathe with worn ways. I don't know how experienced you are, but Harry's restoration involved extensive scraping with a Biax power scraper -- i.e., it was a heroic effort, and not something a newbie would want to attempt.

                  First thing you're going to want to do is clean up those scores with a scraper, file, or india stone, and measure the alignment of the ways, carriage, etc.

                  As others have suggested, Connelly's Machine Tool Reconditioning is highly recommended, but it's not for the faint of heart
                  "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                  • #10
                    I don't mean to hijack, but since it seems we are dealing with similar problems and questions, I'll link some pics of my problem scoring for comment, and perhaps it will help Christian as well. If nothing else, maybe it will make him feel better about his damage? Or comment that his is better/worse for discussion?

                    The first is the bottom of my slide. The next 2 are a side angle shot of the saddle for perspective and a close up shot of the details of the same area.

                    Edit: Oh, and my expectation was that the saddle would be surface ground smooth and then Moglice/Turcite the cross slide.





                    Last edited by BadDog; 08-12-2006, 06:59 PM.
                    Russ
                    Master Floor Sweeper

                    Comment


                    • #11
                      What Jim Hannun says is a good point(as always with JIM ) might be better to clean up and leave alone if the accuracy is good enough.I wouldn't like to take my lathe to pieces to do this but then maybe my being unwell doesn't help still it needs a guy with a big heart to undertake such a re grinding task good luck whatever you decide I hope it all turns out well for you kindest regards Alistair
                      Please excuse my typing as I have a form of parkinsons disease

                      Comment


                      • #12
                        If the score is a depression, and most of the surface is OK.....

                        Then you really DO need to fix it, as it will continue to tear up the saddle as stiff gets in the score, and then under teh saddle.

                        The good news is, you can stone down the edges.....

                        Then give that area a really good bath in solvent, wiping and re-applying, until all oil is gone.

                        Then, get any un-filled epoxy that suits you, and fill in the score. Get it all teh way full, and above.

                        When hardened well, use a burr file and cut it down flush. A stone will just fill up, and a regular file may damage the surface.

                        Did it a couple years ago, all is still fine and dandy, way oil has not caused any trouble. I used 5 minute epoxy.....
                        1601

                        Keep eye on ball.
                        Hashim Khan

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                        • #13
                          The scoring on my ways looks similar to the above pictures. Filling the scores with epoxy sounds like and option if the machine is still accurate enough. I won't know much more until I take a long cut on the machine.

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                          • #14
                            Right now I think you should take a test cut on a long piece, to see if you have a problem that you can't live with
                            The next thing you can do now is to obtain a copy of Connelly's book "Machine Tool Reconditioning", if for no other reason than to see what is involved in leveling and checking the lathe out. There are nuances in the book that only experience teaches, and that Connelly was able to put into words.
                            One way to check the bed is with a Master Precision Level. It is one of the ways I verified the Monarch's bed in the article. The way I did it is quite involved, and is detailed in the article. In short I checked the front way against the other 3 ways. I then did the other 3 ways in the same manner. That was for the transverse direction. I also checked the ways longitudinally. I recorded all the readings and then did a comparison. When I got done I had an excellent idea how "good or bad" the bed was.
                            Harry

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                            • #15
                              20 years ago when I worked for a re-builder in Toronto

                              HI! 20 years ago we were charged $ 100.00 a foot. That's the cheap part...By the time you re-scrape in the saddle and tail stock plus re-shim the tail stock to proper height will take hundreds of hours. A complete re-build without much headstock work would be 1/3 to 1/2 the cost of a new machine.It's a real big job and a challenge time wise. Hope this helps...If you need more info, feel free to ask...

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