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  • Spindle design - seals

    I've been sketching out a spindle I want to make and am trying to decide on seals for the business end. medium speed, light milling, to take ER20 collets, angular contact bearings at one end - very typical light spindle layout.

    What I need some design perspective on is seals at the business end. Should I use a labyrinth seal and a lip seal, or is that a machining faux pas, akin to braces and a belt. Would you ever use both, ever seen both used.....and if not which would you use and why?

    thanks

    PS....George, a little help, worlds worst typist did it again.....should be Spindle in title
    Last edited by Mcgyver; 09-17-2016, 10:40 AM.
    .

  • #2
    Figgered you meant spindle and not some obscure Norse god.
    Labyrinth is tried and true, but what sort of materials will you be light milling?
    What about a positive pressure air flow.

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    • #3
      What RPM?
      Lips seals have friction.
      Lots of it at high speeds.


      -D
      DZER

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      • #4
        Originally posted by Doozer View Post
        What RPM?
        Lips seals have friction.
        Lots of it at high speeds.
        -D

        good point. <8000, but nothing finalized. At what rpm's do you think think the lip seals cease to be a good idea?

        Carm, as for what, all the usually suspects; steel, AL, brass, plastic etc. Think bench top mini mill, making a new spindle for my BCA benchtop jig borer.
        Last edited by Mcgyver; 09-17-2016, 12:08 PM.
        .

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        • #5
          You need to consult technical resources from a particular seal manufacturer. Either literature or by contacting application engineers. You will learn something.

          metalmagpie

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          • #6
            To select a seal you need to look at the linear speed at the seal lip and the pressure.
            The higher the speed or the contact pressure, the more expensive seal material you need:
            NBR-HNBR-ACM-Viton
            8000 rmp is not prohibitive. Automotive drivelines have 15krpm shafts running in ~35mm seals into the transmission.

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            • #7
              Lots of info in tbe New Departure handbook of bearings. Copies are around in the US, no idea there. Long out of print,but useful.

              I would say labyrinth for that. Make sure the diameters are such that there is air flung out, and not sucked in at the bearing.

              Oil or grease?

              If oil, it will likely be total loss,and some provision to catch excess when not running is good. No good way to recirculate with a spindle in a quill.

              Grease would be better, and I assume you will use it.

              Lip seals are not just about RPM, but also rubbing speed... and heat build up can be different at different diameter/spindle mass.
              1601

              Keep eye on ball.
              Hashim Khan

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              • #8
                nothing to add about the seals, but I'm interested in the spindle design. Are you going to be making it from scratch or repurposing one of those long straight shank ER20 chucks?

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                • #9
                  I'll start a thread on it when things get more refined, wanted to keep this about seals. There's a few I'm thinking of making.
                  .

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                  • #10
                    Can you just use sealed bearings? http://www.skf.com/binary/98-136761/...l-bearings.pdf

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                    • #11
                      McG
                      What do you have against braces and a belt?

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                      • #12
                        Originally posted by Illinoyance View Post
                        McG
                        What do you have against braces and a belt?
                        lol....nothing if it keeps the dirt out
                        .

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                        • #13
                          Originally posted by Mcgyver View Post
                          I'll start a thread on it when things get more refined, wanted to keep this about seals. There's a few I'm thinking of making.
                          fair enough, I'll keep my eye open for it.

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                          • #14
                            Cheapo double sealed bearings on automobile fan belt idler pulleys last for more than 4000 hours at speeds in excess of 8000 rpm. Temp range"0" F too 190 F ,Edwin Dirnbeck.

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                            • #15
                              The cheapo bearings do not have to be very good, nor do they have to be well sealed.

                              For this usage, bearings are good, likely angular contact, less easily available sealed. Separate seals , such as SK carries, have a speed rating, and the spindle-sized ones I recently used were rated around 4000 rpm, as I recall.
                              1601

                              Keep eye on ball.
                              Hashim Khan

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