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Bad bearings? Dah Lih circa 1976 Taiwanese

Discussion in 'QUESTIONS & ANSWERS (Get Help Fast Here!)' started by Ropata, Aug 9, 2017.

  1. Downwindtracker2

    Downwindtracker2 Canada Active User Active Member

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    I have used a lot of 7200 series bearings. They are mostly a thrust bearing, one side is cup, one side is cone. So how you put them is important. I've seen millwrights put them in backwards. Sometimes it's pretty easy to look good. On one common use ,we used two, back to front. We never had any 7200 with seals. Your top bearing should have a seal to close in the cavity . I wouldn't worry about the bottom. But I would use a super premium grease like Mobil 101. A problem that is in some designs the preload is governed by the dimensions of the nut and housing. When either wears or is over tightened and hammers out, the preload is reduced. I've seen that slop more than a few times.
     
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  2. Ropata

    Ropata New Zealand Active Member Active Member

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    Yes the top bearing I got was reasonably cheap and sealed both sides. The 2 very top 6208 bearings I also got sealed both sides but the 2 7207 angular contact bearings only came non sealed. They said if I wanted them sealed they would have to make some enquiries overseas and were talking big money. Here is the grease I got which they said was the "Rolls Royce" of bearing grease.
    20170821_140256.jpg
     
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  3. Downwindtracker2

    Downwindtracker2 Canada Active User Active Member

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    Over the years, I 've used a few hundred of that brand of bearings. I would trust them. That's OK grease, but it's not the RollsRoyce, just priced like it. I've used it, it was specified in the new German machines. I didn't notice that you are kitty corner across the ocean from me, so that was why I recommended the American Mobil 101. In machine design, there is a lot of common practice . I've joked " A chunk of iron is a chunk of iron." You are going to want some axial preload on the 7200s, none on the 6200. One of those empty beer cans roaming around your shop can be used for a trial shim. Much like car wheel bearing, it's a feel. If you need a shim, use steel, or at least brass.
     
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  4. Ropata

    Ropata New Zealand Active Member Active Member

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    How would you pack the grease? 1/3rd pushed right through?
     
  5. Downwindtracker2

    Downwindtracker2 Canada Active User Active Member

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    If the design doesn't allow for preload, so be it. But do check for wear in the housing or the nut.
     
  6. Downwindtracker2

    Downwindtracker2 Canada Active User Active Member

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    The standard advice is pack the bearings and fill the cavity 1/3.
     
  7. Ropata

    Ropata New Zealand Active Member Active Member

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    So I'm going to have a crack at fitting these new bearings tonight. When I took the old ones out, the side of each bearing with the writing on and thicker outer race were facing each other. These new ones have the writing on the inner race on the other side. Does anyone know if the thicker outer race's face each other? Photo attached of new bearings.

    20170824_170608.jpg 20170824_170617.jpg
     
  8. Downwindtracker2

    Downwindtracker2 Canada Active User Active Member

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    It's a cup and cone, the outer race is the cup,the bottom of the cup is the fat side. This has to bear against something, like a housing. Machines are many simple parts, so think about what it supposed to do. As my old partner would say "What are you hoping to accomplish?" There is no guarantee the guy before you put it together right.
     
  9. mikey

    mikey Active User H-M Supporter-Premium

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    Maybe this will help:
     
  10. Ropata

    Ropata New Zealand Active Member Active Member

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    Yes, very helpful. Thanks.
     
  11. mikey

    mikey Active User H-M Supporter-Premium

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    Hey, Ropata, did you ever get the quill sorted? Just curious how things turned out.
     
  12. Ropata

    Ropata New Zealand Active Member Active Member

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    Yeah It's all back together. Thanks for the guidance all you guys.

    20170831_113637.jpg I'm tossing up weather or not I get into scraping it in for a better fit due to there being a couple of hundredths of wear in the bed. I'm not as enamoured with it as I was with my lathe so I may wait for a better quality machine to fully restore. It'll do for the projects I have planned coming up. I started another thread for some tooling advice. I have no idea about milling so heaps to learn.
     
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  13. Ropata

    Ropata New Zealand Active Member Active Member

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    By the way, It's amazing how quiet a belt driven machine is with new bearings :)
     
  14. mikey

    mikey Active User H-M Supporter-Premium

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    I have zero experience with scraping but my understanding is that when you're in the hundredths, it is better to have the surfaces ground. If it was a couple of thousandths, then maybe scraping would work but it is going to take a LOT of scraping to even out hundredths of an inch. If a machine in better shape comes along, that might be the way to go.

    In any case, glad you got the quill rebuilt. New bearings make a huge difference, especially when they aren't living in muck and rust like the old ones were.

    Happy for you, and now you get to play with your milll; have fun!
     
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  15. Ropata

    Ropata New Zealand Active Member Active Member

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    Ha ha, sorry mate, that's hundredths of a millimetre. So I think a couple of thou in your old ways. So not unworkable.

    Sent from my SM-N920P using Tapatalk
     
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  16. mikey

    mikey Active User H-M Supporter-Premium

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    Should have figured you meant metric measurements down there! Old ways, indeed! :)
     
  17. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    I was thinking hundredths of an inch as well. Scraping that would be a long slog!
     
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  18. Downwindtracker2

    Downwindtracker2 Canada Active User Active Member

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    Good luck with your mill. I find my mill to be the only machine that's paid for itself as a hobby machine. While we are officially metric, we work in thou. From my days in college as a pre-app, I found using a metric verneir much trickier than an imperial. Your hundreds are even finer then the caliper's fifties. So between the fine measurement and the Bridgeport style's naturel sloppiness that could be your frustration.
     
  19. jaded13640

    jaded13640 United States Active User Active Member

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    I tried to read every post of this thread but I'm not very patient and seem to have lost track of what happened. I'm guessing the cap screws that you didn't know what the deal was, it looks like they hold the assembly or support or bearings on the inside. It looks like they come out and then the whole rotating assembly comes out throw the housing. Is that what happened? I'm curious.

    If that was something on a car, I would assume it needed to be disassembled from the back, then the cap screws removed and then, either the shaft would then come out or it allows the bearing/support assembly to come out after the shaft is out. Is that what went down?

    Thanks,

    Wayne
     
  20. Ropata

    Ropata New Zealand Active Member Active Member

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    It all came out the bottom just like a Bridgeport set up. The end cap was left hand thread, it had a little L marked on the cap and housing on the inside! Go figure what good that does anyone. All back together now, made my first chips yesterday with a terrible blunt end mill that came with it. Now the expensive tool up phase begins.

    Sent from my SM-N920P using Tapatalk
     
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  21. jaded13640

    jaded13640 United States Active User Active Member

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    What was the purpose of the cap screws? What did they hold in?

    Wayne
     
  22. Ropata

    Ropata New Zealand Active Member Active Member

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    Just a seat really for the bottom spacer against the bottom bearing and the only way to get the spindle out.

    Sent from my SM-N920P using Tapatalk
     
  23. Ropata

    Ropata New Zealand Active Member Active Member

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    Oh sorry, thought you meant the cap. The two grub screws one over the other locked the preloaded nut on top of the contact bearings and the 2 other Phillips head screws were grease ports.

    Sent from my SM-N920P using Tapatalk
     

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