Nardiini Compound reconditioning
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    Default Nardiini Compound reconditioning

    On my lathe, the compound ranges from loose at one end of its travel to tight at the other. It appears as though there is a straight female dovetail, and a tapered male dovetail that matches the tapered gib, or did once.

    The female dovetail is about .002" narrower at one end than the other, measured over dowel pins with a tenths-reading micrometer.

    I have a few questions.

    1. Am I right that one dovetail is supposed to be straight? This would seem to make sense but I want to verify my assumption.

    2. How should I measure worn dovetails? Over ball bearings? Over short dowel pin sections? Some other way?

    3. What should be done as a first step? My first thought was to find someone to grind the worn dovetail straight or get a surface grinder and do it myself. (It would probably not be my very first surface grinding project.)

    4. I haven't accurately measured the male dovetail/gib combination yet, but my dial indicator shows it's a lot closer to the same dimension end to end than the female dovetail. Should I get that taper reground and get or make a new gib before trying to scrape or if things seem "a lot better," can I live with it as-is and try to get things to fit reasonably well?

    This machine is in a home shop, not in production use. I'm not after perfection, just good usability.

    Last, but not least, am I even thinking about this the right way, or am I way off-base?

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    A few photo's would be handy for me to advise better. First question id. Does your compound bottom have a cast in bottom stud or pressed in. Take some pictures of the cross-slide top, compound bottom and top both sides dove tail male and female and gib.

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    Quote Originally Posted by Richard King View Post
    A few photo's would be handy for me to advise better. First question id. Does your compound bottom have a cast in bottom stud or pressed in. Take some pictures of the cross-slide top, compound bottom and top both sides dove tail male and female and gib.
    Here are some pics. The narrower end of the straight(ish) dovetail is opposite the compound nut. The gib side of the compound appears unworn. The compound rotates on a pin that is a running fit with it and the cross slide.20190616_111455.jpg20190616_111500.jpg20190616_111503.jpg20190616_111510.jpg20190616_111517.jpg20190616_111455.jpg

    ...to be continued (5 image per post limit)...

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    And more pictures...20190616_111606.jpg20190616_111627.jpg20190616_111759.jpg20190616_111818.jpg20190616_111832.jpg20190616_111606.jpg20190616_111627.jpg

    A few more to follow...

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    20190616_111832.jpg20190616_112106_001.jpg

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    If I were you I would buy a dovetail cutter and mill everthing before scraping it. The compound bottom needs to be scraped flat against a plate. I suspect the area near the holes for the tee bolts are bent and that needs to be checked and scraped. Then indicate where the gib did not rub or the clearance surface. so the top is coplaner to the bottom. Then clamp it down to a mill table and kiss to clean up the top flats and dovetails. I will write more...to many chores today. Rich

    PS I will help here, no worried. Before you mill anything mike everything.

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    Quote Originally Posted by Richard King View Post
    If I were you I would buy a dovetail cutter and mill everthing before scraping it. The compound bottom needs to be scraped flat against a plate. I suspect the area near the holes for the tee bolts are bent and that needs to be checked and scraped. Then indicate where the gib did not rub or the clearance surface. so the top is coplaner to the bottom. Then clamp it down to a mill table and kiss to clean up the top flats and dovetails. I will write more...to many chores today. Rich

    PS I will help here, no worried. Before you mill anything mike everything.
    Richard, thanks!

    I started small, and checked to see whether area around the holes was bent. I have a small cast iron surface plate that I got with another purchase. If that's an acceptable surface, that's great because it's a bit larger than any of the things I need to work on at present.

    I put the compound on it, and it rocked perceptibly. I cleaned it thoroughly with a blade and scotchbrite and tried again. It still rocked, but less, about .001". I found burrs at the edge of one hole, and stoned them off. Now it rocks less than .0002". That's better than my mill is likely to hold, so I hope that's good enough and there's one thing off the list.

    I have dovetail cutters with the right angle already. I thought about having it ground or getting a surface grinder because the material is hardened and I thought surface grinding is more accurate than milling. However, the compound can still be marked with a file. When the time comes, I'll try one of my cutters and see if it will remove the small amount needed. If not, I'll get a carbide one.

    What should I use to find the clearance surfaces? Prussian Blue or something else?

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    min 5 and 8 is working on a compound. I start out a bit silly, but one of the guys behind the camera were making face sand I was playing along, He never said he was going to put it on you tube.YouTube The bottom top ...where the ways are be sure to grind or mill the area that is clearance minus about .010. Bluing around 6: 50 shows bluing up. https://www.youtube.com/watch?v=pO9GW0tAOIQI as far as blue goes I started with Permatex, then Dykem, then Canode and now I like the French ink. It's lake and I'll ad more tomorrow. YouTube

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    Quote Originally Posted by Richard King View Post
    min 5 and 8 is working on a compound. I start out a bit silly, but one of the guys behind the camera were making face sand I was playing along, He never said he was going to put it on you tube.YouTube The bottom top ...where the ways are be sure to grind or mill the area that is clearance minus about .010. Bluing around 6: 50 shows bluing up. https://www.youtube.com/watch?v=pO9GW0tAOIQI as far as blue goes I started with Permatex, then Dykem, then Canode and now I like the French ink. It's lake and I'll ad more tomorrow. YouTube
    I'll try to watch those tomorrow, thanks. Right now I'm waiting for the electricians to finish in the basement/shop. I was juggling contractors all day. Electricians, GC (for another project), and landscaper.

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    I watched the video, bought a granite surface plate, and borrowed (!) some scrapers.

    So to start, if I understand correctly, I should put Dykem or Prussian Blue on the surface plate to indicate the bottom of the compound. Then, scrape it in (re-indicate, rinse and repeat) so it's flat. That will probably keep me busy for a few calendar days, at least.

    What's next? To actually cut the dovetails I'll need to clamp it to the table upside down. Should I scrape the largest surface on the top side so that it's parallel with the bottom? Or, work out a way to clamp it using the bottom as the reference surface?

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    According to Connelly the next step would be to scrape the surface that the tool post mounts to (above the T-slot). Might as well work on a surface that counts. (Richard is skeptical of Connelly, so if he disagrees follow his advice. After all, Connelly isn't here's to answer follows up questions.)

    When setting up in the mill you'll want to indicate off the freshly scraped bottom, rather than just assume that clamping your scraped top is adequate. Of course, once you start indicating and shimming you'll start to wonder if it's necessary to scrape the top at all before machining.

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    do keep in mind when you work the dovetails you are also changing the relationship of the feed screw to the nut...plan accordingly.

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    Quote Originally Posted by iwananew10K View Post
    do keep in mind when you work the dovetails you are also changing the relationship of the feed screw to the nut...plan accordingly.
    Good tip. The nut floats up and down in a bore perpendicular to the thread axis. I can easily mill a couple mils off the top if necessary. A future project is making a new nut to reduce the backlash. I have not measured the threads, but to the eye it looks OK.

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    Sorry I have been busy.

    First off this isn't rocket science and Connelly was the organizer if the book and not the total author. He organized the book as you can see on the first few pages he acknowledges several companies. I sell the books as it is a great book but there are some parts of it that are not exactly the way many machine builders, rebuilders who get paid to do it would do it. I sure as hell would not be selling the books if I didn't agree with the majority of what's in there. And as what I have been saying on here for years, there is always different ways to skin a cat. Back to the compound 10kis right on as the top is longer and you always (there is a few exceptions on this rule, if the top longer part is flimsy) scrape and then match scrape the longer one first, but as I said you need to prepare the short one to accept the long one to get the correct readings and bluing ups when you scrape. An analogy would be you clean the long side and not the short one. It is obvious you would not do that. Are you prepared (Boy Scout Motto), Do you have a dove tail straight-edge prism or camelback type? You will need that to scrape the top and bottom sides straight on the long side and straight on the bottom. Now you need to learn to rub and hinge the straight-edges. If you watched the Swedish video you saw how we rub and the pivot so we assure the part is not high in the middle and resemble a rocking chair or high on the ends.

    In the one photo of the long ways of the top you can see where the ends are not as worn as the middle. Remember your a detective and have to investigate everything before jumping in and making a mess of it. This is a real pain trying to tell you how to do this vs showing you in one my classes or in a you tube show. I won't be doing a you tube show. If I was 20 years younger I would. It took me years to do my scraping video and it cost me $11,000.00 back before the filming revolution as I had to hire a pro who used 3/4" video tape and we had to edit hours of video to get 60 minutes.

    Back to the compound. Once you see from your tests and looking for unworn area's of both sides you use those unworn area to guide where and hw much you scrape off. After looking at you pictures again I see your acme screw is mounted in a fixed hole and that complicates it a bit more compared to a bolt on bracket that many other brands have. Plus your bronze nut can move up and down as you said, but it won't be easy to move it sideways. The easiest way I am not thinking would be to glue a piece of Rulon 142 (same as Turcite B) or some grade linen Phenolic to bring it back to the factory alignment. I am assuming the factory drilled the hole in the nut after the ways were match fit scraped.

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    I figure I need to start a new post before I hit the wrong keys and loose when I wrote, that happens to me sometimes and that up-sets me a bit...lol

    I looked at the pictures again and it's hard to figure out what side the tapered gib attaches to The gib is no doubt bent and will need to be straightened . You will also have to think about the width after you mill off the flats plus the thickness as it will slide in and one side of the short side will need to have Rulon to or the wear side of the gib. All this needs more thinking as I said because the fixed screw on the top side.

    What I would do is match fit everything with the screw out. If you follow your detective work when you mill everything your not changing the top and side of the screw alignment with the axis of the ways and hole or center of screw alignment. Also what complicates this is as you mill and scrape the flats that will move the dovetail over and out of original alignment. The way I would do it is scrape everything and assemble with a new screw and nut then use plastic shim stock under the ways to get the alignments right so you know how much Rulon will be needed. You should use a minimum of .030" thick Rulon ( I usually use .047") but more milling would be needed to get the proper fit.


    You can buy plastic shim stock in different sizes. Plastic Shim Stock, Color Coded Shim Stock: Artus Corp so you cut narrow way size x say 2" long until the screw when screwed closest to the nut doesn't bind up. Slide in the plastic shim without glue and the use math to figure out what size Rulon will be needed and how much will need to be milled or ground off. You will also have to figure in the epoxy glue which is approx. .005" plus you need a little extra for scraping. This is where the experience and skill take over. This why you first timers need to measure twice and cut once. I'm getting finger cramps. Will write more later or one of the students or pro's can take over. Rich

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    Richard et al, thanks again.

    Let's leave the screw and nut off the table, so to speak, for now. I'll have to make the parts anyway; they are not available new from what I've read, unless you live in Brazil and perhaps not even then. If they don't have enough slop from wear to absorb the material loss from milling and scraping, I can trim and shim the nut or turn it down and make an eccentric sleeve for it. That should serve, I think, until/unless I get around to making new parts. Please! Tell me if I'm wrong about this now. Backlash is definitely the least of the two problems I can see with the compound.

    No, I don't have a prismatic straight edge. I've been poking about online but haven't bought one yet. I wondered today about getting a piece of cast iron, milling it at a 40* or so angle (less? exactly 45*?), and then scraping both working sides flat and even end to end. Would that serve, or do I really need to find one? And, how long does it need to be? "A bit longer than the compound dovetail," or considerably (1.5x, 2x) longer?

    Likewise, new gibs are likely unobtanium unless you know where I can find blanks or I make a new one. I did a quick measurement of the taper, which I've now forgotten, but it's either 1* or 2*. My thought was to scrape the worn side straight, and at the correct angle to the back side, and shim behind it to make up the space created by wear and the material removal on both sides of the dovetail. If I do make a new one, what material should I use for it? Brass? Bronze? Something else? If you or anyone else knows where I can get a blank (presumably already tapered), I suspect I should wait for it and then scrape it and the dovetail into each other.

    The compound gib is retained by a screw with a collar that passes through a slot in the top side of the gib and screws into the top of the compound. It is done very similarly to the way a gib is retained on a South Bend 10L or 13 cross slide. (The Nardini cross slide has the same kind of screw but there is also a stop screw on the other end that is not present on the compound.)

    I will have to look into Rulon. I'd heard of turcite but know nothing about either of them (what they're made of, how to apply them, etc.). I do have a question, though. If the nut is offset to accommodate the movement of the dovetails down and toward the gib side of the compound, and the space created on the gib side is taken up with a new, thicker gib or a shim, is the Rulon still needed?

    In the meantime, indicating and scraping the bottom flat will keep me occupied for a while. Maybe long enough to digest everything you've said already.

    As this project progresses through its steps, the compound will be installed and used in between those steps, which will involve more tool acquisition and thus time. I can always lock the compound if it gets too sloppy before it's all done. (Anyone got a taper attachment for a Nardini, cheap?)

    I am certain I will have more questions as this goes on. But thanks to you I am visualizing the geometry better already.

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    You need to think 3 steps ahead when rebuilding. This is not my first rodeo and I have rebuilt several machines that I had never heard of, so no need to fly to Brazil. They are all the same design for the most part. The new screw and nut is simple as you can buy a new screw and nut and cut and fit the gear and handle to the new screw. If you use the Rulon or Turcite no need to calculate and no need to make an eccentric. Gluing Rulon is simple. And forget the idea of making a new gib. In my 50+ years of doing this I have made under 5 gibs. I have bought a handful, but for the most part I either used Phenolic or Rulon as a wear strip on the wear side on the old gib. Also Moglice could be used. Green Bay Manufacturing
    Last edited by Richard King; 06-24-2019 at 07:52 AM.

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    Quote Originally Posted by Richard King View Post
    You need to think 3 steps ahead when rebuilding. This is not my first rodeo and I have rebuilt several machines that I had never heard of, so no need to fly to Brazil. They are all the same design for the most part. The new screw and nut is simple as you can buy a new screw and nut and cut and fit the gear and handle to the new screw. If you use the Rulon or Turcite no need to calculate and make an eccentric. Gluing Rulon is simple. And forget the idea of making a new gib. In my 50+ years of doing this I have made under 5 gibs. I have bought a handful, but for the most part I either used Phenolic or Rulon. Also Moglice could be used. Green Bay Manufacturing
    Richard, I am trying to think ahead. Honest! That is why I am asking so many questions. This *is* my first rodeo, but I want to know where I am headed, and more importantly, why.


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