Reballing Linear guide block? Brother TC
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    Default Reballing Linear guide block? Brother TC

    I have an older brother TC-S2a that I'm trying to get back into shape. I already replaced the ballscrews and there is no longer any backlash.
    I'm having surface finish issues which I believe are from worn linear guides.
    The rails themselves are in good shape with no visible damage. Is it worthwhile to remove and reball the linear guide blocks with balls slightly oversize (+.0001) to increase preload and rigidity?
    I would buy new rails and blocks but the mounting hole spacing is non-standard and I can't find any for a reasonable price.

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    No...........

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    You might be better off really digging in and determining that it's definitely the linear rails before committing to reballing. Even if the rails look good, they may have uneven wear or minor brinelling, and reballing alone might not give the desired results.

    Did you change the thrust bearing along with the ballscrews? And are you sure the servomotors and drive aren't introducing "jerkiness" or other issues that can cause poor finishes? Or maybe there's a global feed smoothing setting that's set too loose in the control?

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    I did all 8 trucks on an Akira-Seiki 4020 VMC. It machined very abrasive non-metals. The trucks were worn, but the rails were fine.

    It was a lot of time. Had to machine a mock rail so I could load the trucks with balls then slide them on. The trucks that machine used had spacer balls and load balls so I couldn't just dump a handful of balls in. It was one then the other forever and don't lose count!!

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    Default Reballing Linear guide block? Brother TC

    The linear guide blocks are case hardened about .080" (2mm) deep. Use a carbide tool to cut through the hard layer, then the steel beneath is easily drilled, tapped or reamed.

    I've modified the threaded hole pattern on THK blocks to fit older Mazak Quick Turns (we run 7). Mazaks of old (maybe new as well?) use non-standard mounting hole patterns on the blocks. As an attempt to force users to purchase replacement linear guides from Mazak. (Not me...haha)

    Tape up your new blocks to seal out chips before machining. I had to machine reamed locating holes for adapter plates on my QT28 rebuild, so I indicated each truck before machining.

    Make sure you know where you're drilling in the blocks, as you don't want to break into a ball/roller raceway. (Case on that end would probably end your tool anyway...lol)

    Mazak also went as far to have the lube system for the linear trucks pass though holes in the machine casting, and then through a non-standard hole in the truck, rather than follow lube lines around to the end of each truck as standard.

    Needless to say, I've installed standard lube lines on linear guide replacements, bypassing the original Mazak BS.

    I use THK's linear guide system where the trucks and rails come separate, so you buy what you need piece-by-piece. Although not factory-matched as factory replacements are, these modern generation guides offer phenomenal precision and rigidity.

    THK builds linear guides in Ohio, and have a great website with online ordering, check it out. (No affiliation, just a satisfied repeat customer.)

    For a new linear guide install on a 30-year CNC lathe, if I lose a tenth or two of accuracy over the travel of the machine when done, I'm going to be happy as a lark! Because the machine will have NEW guideways that are RIGID as hell.

    New generation linear guides have far-better specs for rigidity, precision, etc. than those of just a couple decades ago. Today's universal series linear guides offer precision of yesterday's matched sets, all the while taking rigidity and damping up a huge notch!

    The rail holes should be standard regardless.

    ToolCat
    Last edited by cnctoolcat; 12-04-2021 at 09:55 AM.

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    Which guide rails are you talking about? X or Y? or both? It seems to me that the Y often takes the worst beating on these because of neglect of keeping chips cleaned out and build up in the Y axis area.

    I had an older Brother TC-S2A-O that came to me in pretty rough shape. Part of the problem is that Brother didn't use the little hole fill caps on the rails on those machines, at least not mine and another I know of. Anyway, mine were packed with chips and the trucks were too. Not sure about the short travel machine but the -O machine (27" x travel) leans to the side when you tram it to the extreme in X. I put a level on the table and trammed it one way and the bubble went off the side a little and trammed it the other way and the bubble would shift the other way. I took the linear rails and trucks off the machine, took all the balls out of the trucks, cleaned everything, put new seals on the trucks (NSK brand). I also installed the hole plugs. Basically made it as new as I could on the cheap. Didn't change the balls though. I wound up buying new Y axis rails and installed. The table still leaned to the side when trammed to the extreme even with new Y rails and trucks. Personally I think it's a design flaw of that generation machine. My TC-S2D-O or S1000 don't do this. My TC-S2A-O worked really well but it did introduce a slight error in z at the extremes.

    Anyway, I think the suggestion of checking the thrust bearing is very good, I had to replace that on mine. And I do think it may be worth taking it all apart and cleaning. Maybe Motion Industries can get you new seals for the bearings.

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    Going to do both X and Y while I have time. I also have the TC-S2A-0, I'm curious to test the tram now. I replaced the thrust bearings with the ball screws so shouldn't be that. I'm going to pull the trucks and try replacing the balls, no harm if it doesn't work I'll just get new rails. Hopefully will be able to work up to a newer generation machine, but for now, this is within the budget.
    How did you access the rails? Propped them up or remove the whole table casting?

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    Quote Originally Posted by cnctoolcat View Post
    (skipped)

    The rail holes should be standard regardless.

    ToolCat
    they might not be, Chiron as an example, they use 45mm rails (Y and X) on the "12" size mill, NSK double full groove ball rails - cars have the standard hole pattern and overall dimensions, but the rails have 80mm hole spacing instead of the 105mm on any standard 45mm rail, and you can only order them through Chiron ar a set, two 1050mm rails and 4 cars will set you back around 4500EUR

    I'm seriously thinking about buying a piece of a 45mm roller rail to redrill them to the 80mm hole spacing and check what distortion is there if any

    before reballing the cars I'd first take a good look at the bearing surfaces on the cars, they might be pitted (even when the rail still looks good), and if they are, reballing won't help at all

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    Quote Originally Posted by jz79 View Post
    I'm seriously thinking about buying a piece of a 45mm roller rail to redrill them to the 80mm hole spacing and check what distortion is there if any
    I've thought of doing this, not for a direct replacement, but for some bespoke applications I have in mind. Some of the linear rail I buy has the "short pitch" spacing from the factory, but most is the standard (and what I consider to be too long for ideal stability).

    before reballing the cars I'd first take a good look at the bearing surfaces on the cars, they might be pitted (even when the rail still looks good), and if they are, reballing won't help at all
    Good point. Wear from a rolling element is less likely to be uniform than with a box way.

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    For the x I just took the table off. For the y I did one side at a time. First take all the screws out in the rail and the trucks. Then used a little starrett (199?) jack screw to just barely unweight the loose side then slide the assembly out. I put the jack screw down in the coolant trough.

    They are great machines to start with. I did the same.

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    Quote Originally Posted by jz79 View Post
    they might not be, Chiron as an example, they use 45mm rails (Y and X) on the "12" size mill, NSK double full groove ball rails - cars have the standard hole pattern and overall dimensions, but the rails have 80mm hole spacing instead of the 105mm on any standard 45mm rail, and you can only order them through Chiron ar a set, two 1050mm rails and 4 cars will set you back around 4500EUR

    I'm seriously thinking about buying a piece of a 45mm roller rail to redrill them to the 80mm hole spacing and check what distortion is there if any

    before reballing the cars I'd first take a good look at the bearing surfaces on the cars, they might be pitted (even when the rail still looks good), and if they are, reballing won't help at all

    Dumb question-

    Wouldn't it be infinitely easier to drill and tap the machine casting so it accepts the standard rail spacing?

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    Quote Originally Posted by Garwood View Post
    Dumb question-

    Wouldn't it be infinitely easier to drill and tap the machine casting so it accepts the standard rail spacing?

    Well, you can sorta' get away with having a through hole with a partial eclipse due to spacing values when redrilling, but it's a lot harder doing the same with a tapped hole...

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    I absolutely wouldn’t start down the replacement path first. Pull the way covers and clean stuff as well as you can. Then look the rails over well. You’ve probably done much of this if you’ve already replaced ball screws. Then if you can’t see anything horrible pull one of the y axis rail assemblies off. Take it apart and clean it and see what you’ve got. If they look good I’d stop there.

    How’s your spindle?

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    Quote Originally Posted by Milland View Post
    Well, you can sorta' get away with having a through hole with a partial eclipse due to spacing values when redrilling, but it's a lot harder doing the same with a tapped hole...
    that is exactly the reason, there is one hole with the 80/105mm pattern that will partially intersect no matter how you try to position the rest, so on top of having less mounting points, one of them would be compromised, and on top of that I don't quite fancy taking off the probably 500+kg saddle (and the column) to do that, mag drill might be an option, but then there is lack of machined surfaces there, so a fixture would have to be made etc etc etc

    redrilling/milling the rails seems the easier option of the 2, if you drop the option of overpaying 3 times for the oem rails

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    Quote Originally Posted by Milland View Post
    Well, you can sorta' get away with having a through hole with a partial eclipse due to spacing values when redrilling, but it's a lot harder doing the same with a tapped hole...
    Plug hole with threaded rod, drill new.

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    This spindle is in great condition. I cleaned out one of the trucks and it has a decent amount of preload and smooth motion, nothing visibly wrong except that the seals are falling apart.
    I received a quote from yamazen for the OEM X & Y rail assemblies at over 5k. I am contemplating Hiwin rails but the clearance from the bottom of the truck to mounting surface is only 5.5mm and the machined reference for the rail is 6mm in height. Don't want to have to shim the entire length of the rail.

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    Quote Originally Posted by Dilettantism101 View Post
    the seals are falling apart.
    Did you check on new seals? was able to buy just the seals and replace them.

    I spent the money for the new OEM Y axis bearings on mine and it did nothing.
    Last edited by Pete Deal; 12-07-2021 at 08:35 AM.

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    Quote Originally Posted by Garwood View Post
    Plug hole with threaded rod, drill new.
    in my case that rail holds the column on it (traveling column machine), tall heavy thing = high dynamic loads (40m/min rapids, not that I would need to use that all the time, but still), regular x/y table rail will see much less loading, so instead of having a secure fastener every 80mm, I will have a place on the rail that has 2 good fasteners 210mm apart, and a weak one in the middle - in a place where there would have been 4 good fasteners - that is creating a weakness I wouldn't like to see

    this was my reasoning for dropping that idea, the overlap is 50/50 aprox. (M10 thread), so it would be quite tough for the the threaded plug to hold there while half of it is drilled out and then threads are cut, I don't see it holding there without a glue, and I wouldn't be comfortable relying on the glue to make it work, if that is the choice, I very much would risk ruining a rail than a big casting

    drilling the casting for a much larger plug could be done, but then again it would be M20 at least, not a great option either IMHO

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    It's too bad one can't buy the rail with no holes at all, but perhaps they're in place to account for distortion from bolt loading during grinding.

    I'd mentioned that I much prefer fine pitch holes for machine tool applications, with some of the standard rails I have I intend on drilling "in between" holes to help with securing the rails, but they'll be smaller than the OEM holes/cbores.

    So for instance, if the rail uses M10, I'd be adding M8's as the middle hole. My reasoning is the smaller bolt will still help with securing the rail, and its smaller size will lessen the distortion at the bearing surfaces. It may not be worth a lot, but I don't think it will hurt.


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