Strategy question: leave the area under the headstock alone? Or scrape everything? - Page 2
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  1. #21
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    I have ben following Jerry for years and he is a bright as anyone on here and he is free to do it anyway he wants. He I am sure has weighed the different ways (pun) to proceed. Plus he isn't ready for the home as some are.

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    Quote Originally Posted by Richard King View Post
    ....... As I said you have to assume it was good when it was built and you should be able to check much of it and it may not need scraping. I'm not there, I have to guess at most of this. If you like the front and it's not worn, of course use it as the master. The tops ends are probably like new so you can just scrape them straight down and get back to the new geometry. You need to check everything though. Good luck.. Rich
    There is nothing still "good" on it other than the headstock end, and to some extent maybe the tailstock end. All surfaces that were not under the headstock have damage.

    The damage includes "surface rust" (non-pitting as far as I can see), roughening from crud getting under the carriage parts, and some plain "thick discoloration" that is not quite rust, but is not "nothing" either.

    The prior owner was happily using it in a terrifically dirty condition, and he seems to have sometimes actually oiled the ways, although he was pretty good about oiling the spindle. If it were not a 608, with a price that would be low for an Atlas, I would have gone on my way.

    It's not going to print worth a hoot until I get it up on a bench and probably make a couple passes over it to "clean up" the surface problems and get some sort of real surface on the various contact or guiding ways.

    I'll straight up own to not having one clue how to get much information off of surfaces that have "coatings" of rust, etc on them. My usual procedure for those is to go over with a scraping pass so that the surfaces are brought to a condition I know how to spot with the usual blue. I can spot a smooth worn surface, even though it is usually smeary, but "gunk" that does not come up with solvents I have to scrape off to get anywhere.

    The upshot of that is that I probably won't really know what full surfaces are best until some work has been done.

    My concern with the side vs top is just that I've always found it better to make any misalignment show up on the shortest surfaces, or at least on the ones that are the easiest to scrape. Since the side has the dovetail, which is harder to scrape, I'd rather not have to do a larger correction on that. It has a taper gib, so everything needs scraped.

    So there is a part of me that says to start there, keep it as good as I can relative to the top, but do any needed realignment on the open and simpler top side. It's going to be enough of a job without making more trouble.

    I don't know if I am thinking wrongly with that.

    Meanwhile I have to go up to St Paul for another week of working on my late father's house, which needs a lot of cleaning and organizing before we can move forward.

    More later..... maybe the 608 bed will show up needing less work than it seems.

  3. #23
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    Quote Originally Posted by shapeaholic View Post
    ............
    The process I would recommend is as follows:
    1) scrape the face of the front surface flat,
    2) Scrape the top of the bed flat and square to the front face ( these can be done using a surface plate as reference)
    3) scrape the bottom dovetail straight and parallel to the top of the bed
    4) scrape the top dovetail parralel to the bottom dovetail.
    5) Scrape the carriage to fit the slideway, and make a new gib for the carriage. It will probably need one.
    6) Scrape the headstock tongue to fit the groove in the bed. Provided that you did not need to remove much off the top, you could scrape the back of the tongue only and the headstock will settle down nicely. Do the same with the tailstock.
    7) The cross slide way is actually attached to the face of the carriage, and does not bear hard on the top of the bed. Depending how much you had to take off the bottom of the front dovetail, you might have to scrape the bottom of the cross slide way to get the mounting bolts to fit into the cottage.
    8) scrape the cross slide and compound as usual.

    ........................

    Peter
    I like that, it's pretty much what I had in mind. It's going to depend on how much wear I find in the dovetail. Being a V that is open toward the top, it is a crap-trap, and no-wonder you found it to wear the worst.

    Yes, I assume the ground the beds and then tweaked it in to the last tenth by scraping and finally flaked it. This is a 1946, so I think old Mr Higgin was long gone by then.

    They bragged it up as within 0.0001" in 6 inches turning or boring in collet or between centers. I'd think it would need to be tweaked to get there.

    Tailstock taper? It did not seem to align with Jarno, although I think it was available with a Jarno option. It is given as Rivett "special", approximately a 3 degree taper.

    BTW, this one is just like yours in the photos, aside from the fact that parts of it are chewed and it will never look quite as nice. Idiots in the past managed to have the compound collide with a spinning chuck too often... and evidently did not notice for a while...... Also yours had steadies, which I lack, although I do have the original Rivett marked chucks that are in good shape.

    Yours in the pics is absolutely beautiful. Now I am afraid to ever post pics!

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    Quote Originally Posted by JST View Post
    Yes, I assume the ground the beds and then tweaked it in to the last tenth by scraping and finally flaked it. This is a 1946, so I think old Mr Higgin was long gone by then.

    They bragged it up as within 0.0001" in 6 inches turning or boring in collet or between centers. I'd think it would need to be tweaked to get there.
    Surely. And why not goal for it?

    You didn't choose to start with a white-bread Logan, SB, nor Rockwell.

    But if you do NOT start with the "leg up" of a high-grade regrind?

    Will you have the "spare time" left before punching-out to even get to one-tenth as righteous?

    Tailstock taper? It did not seem to align with Jarno, although I think it was available with a Jarno option. It is given as Rivett "special", approximately a 3 degree taper.
    One does have to wonder "why?"

    What is it they gained - or thought they gained - vs making it harder to tool quickly and affordably than Morse, B&S, or jarno?

    HAS to be more to that than "force them to buy tooling from Rivett", because that trick usually fails.

    Folks good enough to have NEED of a newish Rivett would DIY.

    Those not so good would DWO.

    And Rivett would have already known that.

  5. #25
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    Thermite:

    Your option what you THINK of it, the specs give it as I mentioned.

    Jarno IS "about 3 deg", depending on how the taper is given, being 2.8624......... deg (0.6" in 12"), but this example did not fit a Jarno, quite. No guarantee that the taper in this one is not special/worn/modified/etc. When I get there, I will do a cerrometal cast and see what that tells me.

    As for grinding, it's a good idea. The issue is that they normally like to grind off "plenty", so as to get to a flat surface. That will probably involve being somewhere between "able to fit as-is", and "enough space to use Turcite". Not a useful range, no options left then.

    A decent assessment of the surfaces will tell that story, once I clean them up to where it is possible to measure things.

    Also, Rivett being who they were, each 608 seems to have been ground to fit with all mating pieces ground to fit each other, as opposed to being ground to a production standard. (quite a number of years they seem to have made only one every several weeks). Getting THAT done is hardly affordable, even for a 608.

    Looks like shapeaholic hand-scraped his, it's do-able.

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    Quote Originally Posted by JST View Post
    Thermite:

    Your option what you THINK of it, the specs give it as I mentioned.
    Let's say I'm "favorably impressed" with the precision, just curious about their TS taper choices.


    Jarno IS "about 3 deg", depending on how the taper is given, being 2.8624......... deg (0.6" in 12"), but this example did not fit a Jarno, quite. No guarantee that the taper in this one is not special/worn/modified/etc.
    Well that isn't as easy as might be. I had a 5MT didn't hardly fit atall.. until I hand reamed the hammer welts around the edges of the release drift azures!

    But at least a decent and brand-new 5 MT reamer was easy to find and not terribly costly. In HCS. Soviet Bloc NOS outta Moldava, IIRC?

    I'm a cheapskate about seldom-used stuff, only owning three 5MT "holes", only ONE in-need, and NONE as will likely ever again see that sort of accumulated abuse. If it really IS an odd taper? I'd prolly aside the OEM ram, untouched, fab new in a common MT taper.

    That keeps any "sacrilege" reversible.
    When I get there, I will do a cerrometal cast and see what that tells me.

    As for grinding, it's a good idea. The issue is that they normally like to grind off "plenty", so as to get to a flat surface. That will probably involve being somewhere between "able to fit as-is", and "enough space to use Turcite". Not a useful range, no options left then.

    A decent assessment of the surfaces will tell that story, once I clean them up to where it is possible to measure things.

    Also, Rivett being who they were, each 608 seems to have been ground to fit with all mating pieces ground to fit each other, as opposed to being ground to a production standard. (quite a number of years they seem to have made only one every several weeks). Getting THAT done is hardly affordable, even for a 608.
    You aren't doing but the one. Hardly anybody else does, either. On ANY lathe. Complex as a 618 IS, ISTR a 10EE actually has two MORE surfaces?

    They just aren't as critcal w/r to what works WITH each set having such a narrow range of options.

    So I'm not sure it is all that much of a departure cost-wise from "ordinary" setup for the grinder hand?

    We have several professional bedway and not-only grinding mavins on PM.

    Can't hurt to ASK the experts what costs "might" run?
    Looks like shapeaholic hand-scraped his, it's do-able.
    So is building a wooden boat from standing timber. Or raising 12 kids all yer own "production".

    All it takes is time ... resources...and dedication enough to keep at it long enough to see it through.

    You can DO that. But is money really more expensive than time?

    So... should you do it?

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    Quote Originally Posted by thermite View Post
    ...........
    You can DO that. But is money really more expensive than time?

    So... should you do it?
    I'm the only one who needs to ride that horsie.......

    But, when I get back in town (I'm up near Mr King at the moment) We'll see

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    Hi Jerry,
    I followed your thread with some interest!
    The armchair putzers are making it sound like a huge difficult job. It is not!
    It takes patience and skill, and is time consuming, but I expect you are quite capable.
    Some people seem to think they need to "idol worship" Rivett lathes. They are nice, accurate machines, but quite quirky.
    Just like the tailstock taper, do the math, it's a Jarno, within a few .0001" by my calculations.

    I hope you have good luck doing it!
    If you have any questions that I can help with, feel free to send me a PM.

    Peter

    BTW your PM box is full ;-)

  9. #29
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    Inbox has been partly cleared.

    Yeah, we'll see eventually why this one did not seem to be Jarno... may have been modified, have a ding I did not spot, etc. A Jarno taper is not the easiest thing to find in available shanks, I may need to make all the pieces to fit, or make it into an MT if it is metal-safe for that.

    Your procedure seems reasonable, so long as the dovetail is not too bad. If it is, I may need to make a "sled" to cut it straight vs the other surfaces. Someone on the Rivett group did that and it worked well. I had a compound top that would have done that nicely, and I gave it away, didn't know I might need it..... I sure don't want to have to scrape 0.01" off parts of the dovetail, that's a real pain... don't ask how I know that.

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    Quote Originally Posted by shapeaholic View Post
    The armchair putzers are making it sound like a huge difficult job. It is not!
    The career decision-makers are simply pointing out that for ANY project, it pays to prioritize for greatest gain at least cost in blood, sweat, tears, time, and treasure.

    Retains more flexibility as to options. Gets you better outcomes faster and cheaper. Let's an entity complete more on OTHER challenges.

    And even be healthy and happier more of the time.

    Not just rebuilding machinery.

    Anything and everything.

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  12. #31
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    Quote Originally Posted by shapeaholic View Post
    ..............
    The armchair putzers are making it sound like a huge difficult job. It is not!
    ...........
    Yes, there are a limited number of angled surfaces.... and two of those are easily accessible on top. So of the 10 total, 6 are flat outside surfaces, and 2 are easy angles.

    Flat surfaces are pretty easy, and if you need to remove much material, you can make the chips fly without too much trouble. It's the inside surfaces like the dovetail that are a pain for more than a touchup, they can take as much time as several flat surfaces, just because of the limited working room and angles.

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    I’m by no means an expert scraper, but I have done enough to know I respect someone who can scrape as many surfaces parallel and to bearing quality as this lathe has. I’m finding overshooting geometry correction happens more often than I’d like when shooting for that last tenth. No problem on a mill- just go a little deeper on both sides. But on this lathe? Fussy work!

    Regards,
    L7

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    Incidentally, initial examination suggests the V on top is in original condition aside from some "bite marks" (dings etc). A session with the burr file knocked them down flat, and it looks as if those will be a reasonable reference as far as getting things straight along the bed as a whole.

    The wear looks to be perhaps 6 thou, distributed between surfaces.

    The ends of the bed, measured across the top of the bed, are exactly equal to within 0.0001" as measured with my 3-4 mic (Polish origin), measured in unworn areas. (unworn as evidenced by surface condition and original flaking).

    I expected no less from Rivett. It's a high standard to sustain.... I will be doing my best to uphold it.

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    Some more initial investigation (using a "Kingway" type device) shows that the wear is concentrated on the "back" side of the bed, and that relative to the "V", the dovetail side is worn barely enough to remove the flaking. Possibly 1 to 2 thou there, 4 to 5 thou on the "back side".

    That is good if confirmed by other checks, since it means the real work will be on an area that is both small and very easy to work on. Also that there may not be much disturbance in relation to the leadscrew and feed rod.

    We will see.
    Last edited by JST; 03-20-2021 at 12:20 AM.

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  18. #35
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    Thanks Jerry, You are gifted on how to do it. Explaining your work. :-)

    I'm not sure if I said this before. But many times I shim the opposite side to figure out how much I need to scrape off the high side. When checking long test bars you can get multiplication of errors and you will be flipping back and forth. I have my students also check how much the scrape off, so they can use the shim stock to know how many times they must scrape it to get it close and then sometimes you can do some precision stoning to get a good static fit (more percentage)and a few millionths. (I never like leaving a shim under there, I just use it to calculate error.)

  19. #36
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    Someone commented that the Rivett were ground, and so grinding is the best way.

    I am not sure of that. The pics I got are not very good, I'll try to get better ones, but after hitting the existing surface of the "side ways" with the burr file to knock down the dings, and going over it with a stone, it looks to me as if it may have been ground, but it was also scraped somewhat. There are marks that are nothing to do with the flaking, but look like scrape marks. The flaking appears to cut through them.

    It appears that it may have been ground, but that indeed, as I thought, the surface was further refined by scraping. This is obviously from looking at areas where the flaking is intact, and which are at the ends of the bed, where the carriage could not go, or probably rarely if ever went.

    Stoning etc is just me trying to get a decent surface to measure from. There are dings etc in places on the surface, even in the unworn areas. I am thinking of getting a check on the carriage by trying it in those areas to see how the wear is. Not sure if any info will come of it, but those surfaces will be going away, and I need to get as much from them as possible while they are still present.


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