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Rivett 608 rebuild

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  • #31
    Well I need to do some re-thinking on the methods.

    The plan was to use the presumed-to-be reasonably un-worn center V on the top of the bed for alignment. The V is more worn than I thought. Found that out when I was using the V as a reference for scraping the side. I guess I had not taken as good a look at it as I needed to.

    The only thing I can do is use the two ends as reference surfaces for the side ways, since the middle area is worn to a (currently) unknown degree. The ends still have flaking on them, "real" flaking, so I can be reasonably sure they are good.

    They could still be worn, since flaking is fairly deep. But I have to call something a baseline, so that is it. That adds a nuisance factor to the equation here, but it is not a deal-killer by any means.
    4357 2773 5647 3671 3645 0087 1276

    CNC machines only go through the motions

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

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    • #32
      Simpler approach. I can use the ends of the dovetail way. That is a lot more accessible, and is even less worn at the extremes. I think I will end up using that.

      Edit: I did, and found that I am relatively close to parallel now. But I have not managed to clean up the surfaces I am working on. I may leave some defects in order not to take off too much material.

      No idea why it did not occur to me earlier to use that dovetail way surface. Maybe it did, I have gotten little enough time to work on it, and have wasted too much time on nonessentials, including this forum, and checking out other equipment.

      Because every surface needs attention here, there are no reference surfaces that will be left alone. With that situation, there is always the problem of how you keep the new scraping or grinding as parallel with the original surfaces as you can.

      My original plan with the center V, was because that is the original ground/scraped surface (I thought). And because I really did not want to have to scrape it, as that gets into both the headstock and tailstock, which are guided or located by that V. I REALLY wanted not to need to mess with them, as that would affect the headstock etc alignment to the ways.

      But cleaning off the grime, I see that it is worn all the way to the tailstock end, and only good at the headstock end. So no cigar on that idea. I WILL be scraping those.

      I'll have to do something to the tailstock, anyway. I may be able to leave the headstock alone, but even that may end up taller than the tailstock, and need adjustment.
      Last edited by J Tiers; 12-30-2021, 01:48 AM.
      4357 2773 5647 3671 3645 0087 1276

      CNC machines only go through the motions

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

      Comment


      • #33
        Everything else in the world seems to be conspiring to keep me from working on this, but I temporarily foiled them all by doing a fair bit more scraping work.

        The areas that are as low as the lowest part of the side flat are expanding, and I only have a couple thou to go on most of the rest. So far, "scraping straight down" * seems to be working. I am holding the different areas within a few tenths measured difference. Right now, I am only scraping on the basis of measurements, I am not bothering to use the straightedge. I figure the straightedge would only be somewhat confusing the issue, since I KNOW it is "out", about how much it is "out" and about where that is. The rest I can correct at the same time as other things, once I am fairly close. No sense trying to refine things when I have quite a bit to remove.

        That should allow me to get the upper flat roughly straight, ready for the straightedge. At that time, I will also be correcting the surface to be at 90 deg to the top surface, so that I have the minimum amount to remove there.

        The reference is the back side of the bed, which is a finished surface, but is far less worn than the "front" side that I am working on. Again, any problems there I will fix as the surfaces are refined.

        * "Scraping straight down" is just making sure to scrape the same amount of passes at the same pressure, scraper angle, and the same amount of coverage all over a surface, so as to remove a consistent amount of material across a large area, to the best of your ability.

        To help out, I leave notes written on the surface of where to avoid, where I have worked, how much the measurement is, and what direction I scraped last. That lets me take it up where I left off even after some delay.
        4357 2773 5647 3671 3645 0087 1276

        CNC machines only go through the motions

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

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