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  1. #1
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    Default The horror under the chuck

    A month ago I got a Jones and Shipman 540 APR, details are in another thread in this forum.

    I've now had enough practice with the machine that it's time to dust the chuck, which is slightly tilted (about 0.01mm) from left to right.

    Before doing this I decided to take off the chuck. The problem with rust is that it occupies several times the volume of the iron that it replaces. So I thought that perhaps the tilt in the chuck was due to pressure from rust growing underneath.

    Here's what I found. I am sure that this chuck has not been removed since the machine was sold in 1986.





    So before dusting the chuck I am going to clean this up a bit. First step is getting off the rust without doing any further damage. A nice way to do this with Evaporust, which I have used for similar things in the past:



    Here is the chuck in its bath:



    and here is the table of the grinding machine:



    In a few more hours, these will be pitted but rust free. So here are a few questions for the experienced:

    (1) Before putting the chuck back, what should I treat the surfaces with so that they will survive coolant without too much corrosion?

    (2) The chuck is retained with two tongues right over the center line.



    Won't this tend to "twist" the table? Wouldn't it be better to support the table at three points, so it doesn't tend to twist the table?

    (3) I suppose the right thing to do is to regrind the top of the table and the bottom of the chuck. But I don't want to do this yet. I think the chuck was installed properly and professionally 30 years ago, and expect that after the rust is removed, the surfaces will again be flat. Anyway, I'll check the chuck on a surface plate. Any advice for the ignorant on these topics?

    I'll post some more photos after the Evaporust baths are finished and the surfaces are free of rust.

    Cheers,
    Bruce

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    Grind the top of the table and bottom of the chuck. That's my recommendation. It really doesn't matter if the face is tilted, but you want both of them flat. If the surfaces are flat and smooth, they will "wring" together and prevent moisture from wicking into any gaps.

    They probably used some god awful coolant. If you lightly oil the surfaces before clamping and practice good coolant maintenance, you should be able to avoid this problem.

    As for the clamping, two strap clamps is pretty much the standard. You have to dust the top of the chuck anyway so it really doesn't matter if there is deflection from the clamps as long as things stay where they are.

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    Blue the magnet and see how it touches the table
    If that rust slowly over time did bent the table a bit there is a chance the table is worn in the middle
    Now you remove the rust and the table gets its originl position again
    Perhaps you could blue the table with the magnet mounted and see how it touches the sadle
    But if you grind a test piece and it is within specs I would leave it


    peter

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    This is pretty common on surface grinders. Fact of life. In a perfect world you would pull the chuck every year, clean, possible dust the bottom of it if there is twist/bow, and reinstall.

    For our machines we use a mix of never seize and spindle oil to thin it out. This is the best formula I have found.

    This is what my surface grinder looked like after 10 years-

    Instagram

    The problem with this rust is it pushes the middle of you mag chuck up, to remedy it you grind the top of you chucks. Over time you then put a bow into your chuck. So on top of dealing with the rust you as well have a bowed chuck.

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    Known fact of life, sadly.

    The traditional recommended procedure is to grind the top of the table and the bottom of the chuck before re-mating.

    The problem with that is, typically grinders gradually wear such that they grind a hump in the middle of long work.
    Grind table, grind chuck, both using full or near full travel, and the error doubles when you clamp 2 humped surfaces together.

    So what I have done on several grinders is dust the table to clean up the worst pitting, and scrape it. Then flip do the same to the chuck. The chuck should be inverted and blocked to grind the bottom, chuck "off". Then put bottom down and block, turn chuck "on" and grind top. them flip again, on to ground/scraped table, and turn chuck "on" and re-grind bottom. Then scrape bottom of chuck.

    Stone both surfaces, put light grease between, and clamp. One end sort of tight, the other end snug. You want to align the rail/side of the chuck perfectly with travel, and the clamps need to hold well enough that that would not be a question. But the idea is that with the grease and the clamps, the chuck can slide a little as it warms or cools without bowing the table.

    I use LPS2 saturation coat to get in the nooks and crannies, then towel off and spray with LPS #3 before setting the chuck.

    Dust the chuck again before use after it is mounted.

    smt

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    Thanks for all the helpful replies!

    Ewlsey: based on some of the other comments here, I'm going to go cautiously at first. Yeah, I think they used one of those paint-eating synthetic clear lubricants, which leaves an almost impossible-to-remove sticky coating on paint. (I remove it by wet sanding with soap and water followed by some polishing compound.) The deflection I am worried about is not deflection of the chuck, which is about 3" thick, but deflection of the table underneath it which is thinner. If that is deformed by clamping forces, it will make the machine inaccurate.

    Peter: I'll do what you suggest. I've got a surface plate that's the right size for the chuck, so I can verify the chuck on that, or scrape it if needed. Then I can use this as a master for the top of the table. Regarding table wear, I have now looked at the scraping marks underneath the table and they are perfect and pristine. So whatever might have happened with the rust, I don't think it wore the table in the middle.

    Cash: I would use Never-Seize but I don't know where to get it in Germany or in Europe. I am hoping that the bottom of the chuck will clean up with the Evaporust to leave the original pre-rust flat surface. Likewise for the table. So this way I can avoid the bowing.

    Stephen: thanks for the step-by-step. I'm a fan of LPS products, and Boeing T9, so will see if those can be had in Europe. I'm going to try and avoid the humping x 2, because I suspect that the machine as I have it is basically pristine. So I'll go slowly and do some measuring before anything else. (All the evidence indicates that this machine was used for some months in 1987, enough to wear/dress about 10mm off a 200mm x 20mm wheel, and then hardly ever used after that. The chuck controller had some problems that I repaired, it might have been that when that went south the owners stuck it in a corner and never got around to getting it fixed.

    Cheers,
    Bruce

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    Unfortunately that's what you get 90% of the time when you remove your magnetic chuck. In the past I've tried everything to stop coolant getting under the chuck without much success. Clean everything up, coat the the bed and base of the chuck with a the coat of water pump grease. Replace the chuck and grind the top face of the chuck lightly.

    Regards Tyrone.

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    never seize - aka copper slip here in the uk, metal (usualy copper, but also Nickle ££££) filled anti corrosion grease, a must have shop staple if your doing any threaded fastener going any were damp. Every thing i have used it on has always undone with out heat or messing. Commonly available online and at most auto places - farm suppliers. Don't know Germany, but am assuming like most of Europe theres intensive agriculture? Hence there’s tractor repair places?? Copper Grease | Maintenance Fluids & Grease | Euro Car Parts they list german as one of the languges on there site so presumably they post there too???

    IMHO pitting does not matter, all that matters is overall contact, so long as thats reasonably well spread out over the whole chuck it should work just fine. This is two large areas of mating contact, so pitting that removes even 80% of that contact surface is still going to leave plenty of contact points to carry any load this will ever see.

    Would love to see J&S own view on this, are the tables ground on the machine in the factory? With the V ways it would be hard to get great alignment any other way + the pad the chuck sits on on every J&S i have ever seen is reachable in the machines travels. Its raised clear of a lot of the rest of the T slots and is also at least on mine well clear of the rim around the table height wise too.

    Yeah theres the whole double bow argument, but on a typical worn machine, that would actually be lifting the table ends helping correct the age related error of middle of travel wear. Yeah, any one into high precision controlled engineering is probaly crying at the thought of it, but with most chucks circa 2" thick are pretty strong and most grinder tables about the same, that doubling of error might realy help cancel table bow more than you would think.

    On the OP's grinder its so low hours, i don't think the table wears going to be measurable, unlike the rust :-)

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    Just want to add my 2 cents worth. If you want to check for wear issues in the table. After you clean off the rust on the table top lightly stone it and with the table centered set a precision level .0005"/12" or finer on it and if the machine is not level all ready do so or use feeler gage under the level at the Airey points and shim until the bubble reads level. Then slowly crank or feed the table to the ends of the travel and watch the bubble.

    This will show you there is no issues with the scraping that you say is good. Depending on the use of the grinder if they ground long parts the top of the saddle will be slightly or worn a lot on the ends or if they ground short parts the ends of the table will not be worn to and it will get a double whammy when you reach the end of the travel. Knowing this figure of wear you will know you can not grind the table better then that error unless you scrape the machine.

    Also be sure to use coolant when you grind the table and chuck. The table will bend a little / tenths when you kiss the table top as that metal is "work hardened". Be sure to use a course wheel dressed fast and open/rough so it grinds cooler. Also check to be sure your diamond dresser is sharp. You can clamp the dresser on using the Tee slot. As Stephen said turn on the magnet when grinding the chuck and I tighten the left end of the chuck and put a lock washer under the right end and tighten it but not tightened down tight as Stephen said the chuck gets hot and expands. This is not as bad when it is a manual chuck. Rich

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    I've also used " Copper Grease ". It's OK as is " Water Pump Grease ". I've never tried " Silicon Bath Sealant " , maybe that's worth a try. The only sure way is to remove the magnet and clean the area about every 3 months or so.

    Regards Tyrone.

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    Silicone is not listed as an adhesive, but from one that has used it for a similar application, you will play hell getting the chuck off later. A common way to get a chuck or similar off is to slide it to break the seal. No can do with silicone. I had to pry the two surfaces appart.

    Tom

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    Adama-

    That is an interesting perspective and may have some merit. Thinking further, it kind of surprised me that "your" suggestion even accommodates twist, though it will not correct it at all. (low diagonal corners on chuck bottom will mate with high corners ground on table surface when chuck is flipped back in place).

    I think like Richard describes, best is to indicate and see what you have, then make a decision. I have always (3x) scraped the table & the chuck to match, considering it the foundation. But on a worn grinder in future will have to consider what you observed. I do think it may make the table unstable, though. Because the top apron ways will have a hump, so you will be bringing the ends of the table ways up out of contact &* fundamentally the long axis of the table will be teetering on center.

    No can do with silicone. I had to pry the two surfaces appart.
    I've seen some at auctions that were siliconed on. Just out of curiosity, in your experience did it solve the problem, or did rust get under anyway?

    smt

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    You might try silicone Grease as used for electrical heat transfer applications or Stopcock grease. They are Not adhesives.

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    Quote Originally Posted by stephen thomas View Post
    Adama-

    I've seen some at auctions that were siliconed on. Just out of curiosity, in your experience did it solve the problem, or did rust get under anyway?

    smt
    No, there was no rust. One approach if you want to do silicone is to wax both surfaces before applying the silicone. Some one part formulations cure in the presence of moisture unlike the "crazy" glues. So even if you squeeze the material down by rubbing the two surfaces, enough moisture will penetrate over time to cure it. Another consideration is that there are different chemistries for one part silicones. One of the oldest formulations releases acetic acid (vinegar) during curing. Other one part formulations do not. I don't know which products produce the acetic acid, only by putting a dab in air will you know. If in doubt use a two part system.

    Tom

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    Thanks for all the responses. I am done with the Evaporust. Here's the bottom of the chuck:



    and here's the top of the table:



    Here's a photo with the sheet metal shielding removed:



    As Adama has said, the raised pad about 455 x 155mm. The machine travels are enough to cover this area completely.

    I've stoned both the chuck bottom and the table top using a medium-grit diamond plate and some oil to knock off any remaining high points/rusty bits.

    First step in assessing the condition of the parts: I've put a 0.01mm = 0.0004" indicator on the wheelhead and run the table back and forth and in/out. The high points are right on the money over the entire surface. The low points are running into the pits and valleys. These look worse than they are, about 0.01 - 0.02mm low. So I think the table and ways are in factory condition, apart from the rust pitting.

    In fact the machine looks like a low-mileage car driven only on Sundays to church, look at the condition of the paint! (As an aside, it is very tempting to repaint the areas where the paint is peeling. I need to order some 2K paint in the right colour to do this.)

    I'm going to be on the road for a couple of days, but when back I'll blue up a surface plate and print the bottom of the chuck.

    Tyrone, I hear you, I guess any solution is only temporary, the area needs to be cleaned from time to time.

    Adama, I agree about the pitting being irrelevant if the tops are OK, the main problem is that it provides a place for coolant to collect. The next time I call J&S to ask about parts I'll also ask them how it was originally done. They seem pretty helpful on the phone. I can't see why they would not grind the tables on the machine, it seems like a smart move. I agree that the double bow is not an issue, this machine has no significant wear as far as I can see.

    Richard, thanks for looking at this. I'm a fan of your scraping and reconditioning posts here and have read many of them and tried to follow your suggestions and tips in scraping. But I don't think the base I have is stable enough for your test.

    Right now the machine is sitting on my shop floor, which is 22mm OSB on top of 50mm of rigid foam insulation on top of 6 inches of concrete with an embedded mesh. The foam is rated for 3 bar pressure (about 40 pounds per square inch) so it's no problem driving a car onto it. But I suspect it is not stable enough for the testing you propose. My lathe sits on four concrete "pillars" that pass through the holes in the OSB/foam and then are bonded to the concrete below. So the lathe sits directly on the concrete. Once I have settled on a final location for the surface grinder, I intend to make three more pillars like this, so that the surface grinder is also sitting directly on the concrete, and then bolt it down. (By the way, the J&S operators manual calls for a concrete pad that is larger than the base all around and 600 mm (!!) thick. I won't be able to provide that.) Anyway if I can scrounge up some steel plates I'll try putting those under the feet and levelling the machine, then seeing what happens when I walk around it. If that seems stable enough to resist tilting as the table moves back and forth, then I'll try your test and report here.

    I'm shopping for some coolant now, the problem is that the one I want (which is human- and environment-friendly) is only available in 25 liter bottles, I need about 5 liters. Anyway I won't grind table and/or chuck until I get coolant in place. The chuck is electromagnetic, but is a "permanent electromagnetic chuck". So you magnetise it and demag it, but when it is holding there is no current running through it and so no heat being generated there.

    Tyrone, I'm not going to use silicone sealant (RTV, bathtub caulk). No way. But I am thinking about using silicone stopcock grease. It has the right consistency to fill the pits but will also flow out when clamped. And it's completely inert and won't be bothered by any of the chemicals in the coolant.

    Tom, agreed, no silicone caulking/sealant.

    Stephen, yes I will go slow. I am not going to grind/scrape anything until I have understood the current status. This machine is in nice shape, it has survived 30 years, and I don't want to screw it up because I didn't first spend the time to first figure out what if anything is needed.

    WHHJR: I think stopcock grease is a good idea, and readily available to me.

    Tom, the idea of waxing the table and chuck is a good one. Ten years ago I waxed the cast-iron top of my Delta tablesaw, and that has protected it from rust and made the saw work better. Wax and grease sounds like the best approach I have heard.

    Cheers,
    Bruce


    PS: very tempting to remove the rusty SHCS from the bottom of the chuck and replace them with new non-rusty ones (one at a time, of course). But my gut says to leave well enough alone. Is that right?
    Last edited by ballen; 09-06-2016 at 04:28 AM.

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    I put lanolin grease on my chuck and table.

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    My only experience of using silicon to seal a machine element was years ago. I'd been re-building an Hor bore spindle frame. Everything was back together again and I'd left my apprentice to replace the covers. He used silicon sealant and plenty of it.

    About 12 months later the covers had to come off again. I had a really difficult time using fox wedges all around the the thing to loosen the covers. Never again. He was still my apprentice but only just.

    My idea with the magnetic chuck was to grease underneath the chuck and then run a bead of silicon all around the edge of the chuck.

    Regards Tyrone.

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    I would go carefull with the silicone grease, silicones used in a lot of anti foam chemicals, it may well play ok chemically with your coolant, but mechanicaly it may not get on so well with the emulsion!

    That said, silicones as resistant as hell to wash off, if you get the HT (high tack not high temp) it will stick and work in orings in things like shower valves for decades. my only concern would be it flowing out and letting the chuck make metal to metal contact + unexpected coolant issues.

    Worth adding, never use silicone oils or grease on metal parts as a lubricant, just causes em to gual up near instantly! Great for seals running on parts, but mechanical sliding parts, bad things happen fast!

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    I still think it would be worth testing with a bubble. Also if you think your floor is bad. Lay a flat bar on the floor and set the level on it shimmed to read level and move the grinder table and see if it moves. Your assuming to much here, I have discovered in machine tool rebuilding you can't assume anything, you have to prove it. Many cases if you have a week floor you set the machine leveling jacks or feet on a 1/2" x 12" x 12" plate to spread out the weight.

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    I wonder what some Hylomar would do? I use it from time to time when I need to seal something like a bearing flange but I don't want to fuck up the pre-load. It works just like Permatex #2 or #3. It's a non-hardening gasket replacement. But, layer it forms is only about .001 thick and very consistent.

    Don't use RTV. God I hate that stuff. A trigger happy maintenance man armed with a tube of RTV is my arch nemesis.


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