Announcement

Collapse
No announcement yet.

Rivett 608 rebuild

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Rivett 608 rebuild

    I am starting a new thread, because the old one was not well titled, and this one will be easier to find.

    The previous thread was https://bbs.homeshopmachinist.net/fo...-rivett-report . In that, the progress from re-scraping the trashed crosslide assembly to the beginnings of evaluating the bed is covered.

    There was an original thread as well, from the time when I acquired the machine, which I will find and link here: https://bbs.homeshopmachinist.net/fo...lathe-a-rivett

    So, I have started evaluation of the bed using the new-to-me straightedge and feeler strips. The starting point on this machine will be the "side way".

    To review: This machine was trashed, by know-nothing dragster builders. I tried twice to buy it, once from the first dragster guy when he put it on Craig's list, then from the one he sold it to, and succeeded the second time. I knew it would be a long project in which I would probably fix, replace, or at least touch, every part and piece of the machine. The other two threads cover the original condition, and the repairs up to this point.

    The machine has 10 mating surfaces on 3 faces of the rectangular bed. The end of the bed is as per this picture:



    The red marked surfaces are all contact surfaces for the carriage. The green marked surfaces are used by the headstock and tailstock, and ones marked with both colors are shared.

    I cleaned off the "side ways", which have the dovetail, using a burr file to knock off the raised area of the many dings (see the "report" thread, toward the end). Then I stoned it lightly. After cleaning off dust etc, and getting handles on my "new" straightedge, I set that on the upper side way, centered, and started off with a 0.0015 feeler strip. I could get it under at least a short way in several places, but was unable to get an 0.002" strip to enter. The areas differed a bit as I moved the SE to one end and the other (it is a little shorter than the bed) and all the locations, even ones that are probably false, are marked (false because the "dip" in the middle causes the ends of the SE to be raised when the opposite end is somewhat into the worn area).





    Last edited by J Tiers; 04-16-2021, 11:18 PM.
    4357 2773 5647 3671 3645 0087 1276

    CNC machines only go through the motions

    "There's no pleasing these serpents"......Lewis Carroll

  • #2
    Then I did the lower way on the side. There, a short portion near the headstock would admit a 0.002" feeler, but not a 0.003".



    Overall, this confirms the measurements made with the "Kingway" type device, which indicated a bit over a thou or so wear on the side way, and the remainder of the almost 5 thou total on the backside way.

    The backside way is fairly small, and I do not mind hand scraping that.

    I also checked by sliding the existing condition carriage along the side way (where it runs) with some marker stripes on the dovetail bottom to check for contact, trying to get some idea of the condition there.

    There was some marking on the bottom of the dovetail of the carriage, along with a certain amount on the sides of it. So, a little uncertain, but clear evidence of some wear. The scraping process will take some off the ways, and some off the carriage, which should lower the dovetail into the recess and permit contact.

    Dovetail "bottom"


    Lower slideway of the carriage



    The upper slideway has a taper gib (should be fun!) which I will check much later in the process. I hope to take as little as possible off, with the idea of maybe using the same gib. That may not happen, I think it is a 10 to 10% chance it will work out.

    For the actual scraping, I will support the bed on the points which cause the minimum total bending of the bed. That is NOT the "Airey" points, BTW.
    Last edited by J Tiers; 04-16-2021, 01:53 PM.
    4357 2773 5647 3671 3645 0087 1276

    CNC machines only go through the motions

    "There's no pleasing these serpents"......Lewis Carroll

    Comment


    • #3
      So, the general plan is to do what is known as "scraping straight down" on each end. That involves scraping both parts of both ends the same amount, aiming to remove the same amount of material thickness from each section, maintaining the same "direction" of the surface, while reducing the level until it becomes a good flat surface at the right level and still at the same orientation relative to the rest of the bed.

      During that process, using the straightedge, as well as a small granite flat and angle references, should allow keeping things all co-ordinated.

      What has to be kept all happening at once is:

      1) The flat outer surfaces (2) of the "side way" must be made flat, and on the same plane

      2) Those two surfaces must be aligned parallel with the centerline of the V-ways on the top of the bed, which are essentially unworn and usable as a reference.

      3) Those two surfaces must also be at 90 degrees to the flat ways on the top. There, the reference is the area that was under the headstock, and therefore is un-worn.

      After that is done, and the top flat ways are brought to the same condition relative to the side ways, then the bed will be re-evaluated to determine what needs to be done to the dovetail, which must be made parallel to the top flat ways as well as to the side ways. That also affects the carriage location.

      All the scraping removes metal, which changes distances, clearances, and relationships between parts. So the carriage may move relative to the leadscrew and feedscrew. Since those are not movable o the 608, at least not without a ridiculous amount of trouble, the carriage will have to be returned to it's original position relative to the screws.

      Finally, the "carriage angle" must be scraped or "adjusted" so that it has the correct relation to the top flat ways of the bed, and the back surface where a gib runs.

      To make sense of all this guff, the picture below may be helpful:



      The picture shows the carriage in place on the "side way" of the bed. The box on the right holds the half nut mechanism. The bump at the bottom holds the rack gear shaft, you can see the rack at the bottom of the bed.

      The crank at left is the feed crank. The lever above it is the "trip" lever for stopping the automatic feed, which is via the lower rod set into the face of the side way. The lead screw is above the feed rod.

      The rods are down in the dovetail area, running in the recesses which you can see looking at the end view of the bed as shown above. In that view, all the contact surfaces are shown.

      The large thing bolted-on to the left of the half nut box is the "carriage angle", which holds the crosslide, and rides along the top flat ways of the bed. There is an extension of the "carriage angle" over the top of the bed.

      I anticipate that getting all this aligned is going to be a total "zoo". It's a ridiculously complicated way to make a lathe, but it was done for decades. The folks at Rivett did it, so someone else can do it also.
      Last edited by J Tiers; 04-16-2021, 11:56 PM.
      4357 2773 5647 3671 3645 0087 1276

      CNC machines only go through the motions

      "There's no pleasing these serpents"......Lewis Carroll

      Comment


      • #4
        Bessel points?
        BTW I like the way you explained and illustrated the situation. I can actually understand it on an unfamiliar machine!

        I am willing to bet that each individual surface or plane was scraped in by a different (junior) "hand" at the factory, and then the final scraping and fitting done by a master. Both the lathe and your mill represent a non-trivial amount of work -- you should be proud!
        Last edited by nickel-city-fab; 04-17-2021, 12:34 AM.
        25 miles north of Buffalo NY, USA

        Comment


        • #5
          Does the vertical relationship between carriage and carriage angle have to be maintained? (Does this lathe have power cross feed?)

          I’m thinking WAY ahead to which surfaces need moglice/turctite.

          Comment


          • #6
            You betcha it does...... and the machine has power crossfeed. It's going to be great fun to deal with. I already figure that the carriage angle will need something, and very likely the lower part of the dovetail on the carriage. Not sure about the rest.

            Material? Not sure. You mentioned the usual these days, but there are others, like linen micarta
            4357 2773 5647 3671 3645 0087 1276

            CNC machines only go through the motions

            "There's no pleasing these serpents"......Lewis Carroll

            Comment


            • #7
              Damn...

              I can’t get my head around so many constrained surfaces and only two gibs. (I think it “needs” a third on lower dovetail. In my vast expertise. 🙄)

              The shared surfaces remind me of flat tail stock way on 10EE among others that can touch saddle but shouldn’t bear “hard” and become a third saddle way.

              Comment


              • #8
                Originally posted by SVS View Post
                ..................

                The shared surfaces remind me of flat tail stock way on 10EE among others that can touch saddle but shouldn’t bear “hard” and become a third saddle way.
                That is one "theory" of the top ways vs the "carriage angle". There to "touch" and prevent downward movement, but not to have completely solid bearing. A very delicate balance. I am not sure I believe in that theory, but I do not have a good alternative, either. The carriage angle is bolted on, not part of the solid carriage. And that extension is not a thick beam, it is relatively thin for what it does supporting the crosslide.
                4357 2773 5647 3671 3645 0087 1276

                CNC machines only go through the motions

                "There's no pleasing these serpents"......Lewis Carroll

                Comment


                • #9
                  So, I should be posting to this, since I have already started on the scraping, and have a bunch of "passes" done, even though I have been out of town a bunch. Pics, such as they are, to come.

                  I started from the idea that the ends are at least a thou and a half less worn than the middle (so they are higher), AND that there are some linear scratches, as well as dings in the worn area. So, I have split the thing up into several areas. I have ones at the ends, which get scraped every pass, and the ones closer to the middle get scraped less, and the middle the least. "Step scraping".

                  That should bring the side flat ways to generally flat, at which time I can scrape the entire length every time until I have the side ways flat, at 90 deg to the top ways, aligned with the top V ways, and have removed as much of the scratches and dings as I practically can with hand scraping. That is a number of simultaneous considerations, but is do-able.

                  4357 2773 5647 3671 3645 0087 1276

                  CNC machines only go through the motions

                  "There's no pleasing these serpents"......Lewis Carroll

                  Comment


                  • #10
                    Some pics, no big deal. I'm only working on the outer and uppermost surfaces right now. The middle is for later.

                    Here is one of the ends, where the step scraping is set up to do more passes. I'm not quite to the point of bothering to do any spotting yet. Just shoveling off excess material. Lowering the ends, and getting the middle worked down to remove the worst of the defects.



                    Further down in the middle. You can see the linear scratches on the left side. I don't know if I am going to get those eliminated, some of them are fairly deep. Same with a few of the dings.

                    4357 2773 5647 3671 3645 0087 1276

                    CNC machines only go through the motions

                    "There's no pleasing these serpents"......Lewis Carroll

                    Comment


                    • #11
                      Looking good so far. That is a lot of work, but it will be worth it in the end. There sure is a lot of surface area in contact at once on that carriage, must be one stiff S.O.B. in terms of rigidity, probably makes for a very nice machine. I didn't read back; are you hand scraping or power scraping?

                      Regarding the gib, I would re-use it regardless. Glue on a bit of turcite or whatever you end up using for the carriage and bring it back to where you need it size-wise.
                      Last edited by eKretz; 06-28-2021, 10:22 AM.

                      Comment


                      • #12
                        X2 that is one beautiful machine. I think it'll be OK if the surface isn't perfect, so long as the asperities don't stick up through the oil film after scraping. But that's what stones are for, after scraping. I bet she'll glide like oiled glass.
                        25 miles north of Buffalo NY, USA

                        Comment


                        • #13
                          Hand scraping.

                          I have filled depressions before with epoxy, and it has lasted long enough that I am not sure anymore just how long.
                          4357 2773 5647 3671 3645 0087 1276

                          CNC machines only go through the motions

                          "There's no pleasing these serpents"......Lewis Carroll

                          Comment


                          • #14
                            It's almost impossible for me to see those surfaces as concave. I see convex & when I force myself to see concave, they snap back to convex when I look at their intersection. Usually when you "get it", it stays gotten. Not this time. Witchcraft!!
                            Click image for larger version

Name:	sn5hKLJ.jpg
Views:	575
Size:	76.5 KB
ID:	1949075

                            Comment


                            • #15
                              Checking indicates that the ends are not coming down fast enough, so I need to do more on them relative to the middle areas. Plenty of exercise in my future.......

                              The optical illusion: Never saw that until you posted.... now I do!. Must be more Rivett magic.
                              4357 2773 5647 3671 3645 0087 1276

                              CNC machines only go through the motions

                              "There's no pleasing these serpents"......Lewis Carroll

                              Comment

                              Working...
                              X