Hammy thin-o-matic micro rotor?

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  1. #1
    Member Will_f's Avatar
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    Hammy thin-o-matic micro rotor?

    I saw a NOS 69 Hamilton Thinomatic with the 620 micro rotor movement, and I was wondering what I would be getting myself into with this one. I assume the movement would need to be cleaned and oiled, but how is it likely to hold up? From what I've read the rotor bearing wears out early, but is it a pain to service? Is it accurate? Is the case any good?

    It's not cheap by any means, but I like the micro rotor concept and the intermatics are even more expensive.


    Thanks in advance,


    Will
    Last edited by Will_f; October 24th, 2011 at 06:22.
    Owner of a bunch of cool watches.


  2. #2
    Member DragonDan's Avatar
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    Re: Hammy thin-o-matic micro rotor?

    Vintage watches from a good company like Hamilton will last nicely, you shouln't worry about longevity. I have a watch from 1953 (Gallet multichron with Excelsior Park EP40 movement) that I wear quite often. It was given a full service last year. Keeps excellent time.

    I can't imagine that a micro-rotor movement would wear out the bearing surfaces faster than a regular automatic. The micro has less mass! The only thing I've heard about them is that they don't generate the same winding strength, so its power reserve wouldn't be as much as a standard auto when worn for the same time.

    I like micro-rotor movements, they are a unique entity in the watch world
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  3. #3
    Member TheJohnP's Avatar
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    Re: Hammy thin-o-matic micro rotor?

    Quote Originally Posted by DragonDan View Post
    The only thing I've heard about them is that they don't generate the same winding strength, so its power reserve wouldn't be as much as a standard auto when worn for the same time.
    I recently picked up a Hamilton Thin-O-Matic micro-rotor and had it serviced by my regular watch guy.
    Didn't cost me any additional to a regular servicing.
    And agree with DragonDan that I've found that it will run strong for a good while but doesn't seem to last as long as a regular auto.

    As far as accuracy, seems to keep good time for me.
    And the case on mine is a front loader, so no worries about wrist moisture (i.e. sweat) getting inside.
    I've got more Converse sneakers than watches, but it is a close race.

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  5. #4
    Member Outta Time's Avatar
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    Re: Hammy thin-o-matic micro rotor?

    There is an issue with the micro rotor. I haven't serviced any myself, but was told this by an older watchmaker. If you open the case and there are circular scratches from the rotor on the caseback, move on. It can be repaired, but parts are scarce. I can't remember exactly why this is an issue, I'll see if I can find out.
    OK, got it. The micro rotor is actually the achilles heel of the movt, developed by Buren (1280) and marketed in 1957, prior to being purchase by Hamilton. (calibre 628) Wear is marked due to extra stresses on the rotor arbor, and will typically wear out the bushing in the rotor bridge. Buren incorporated a floating pinion in the winding train, and this necessitated depthing controls on the switching gears, non-toothed round wheels to prevent over-engagement or too deep engagement of the gears. This increases friction and cause uneven wear on the rotor shaft, which will show up as circular scratches on the caseback. Apparently Buren addressed this problem in the higher jewel count versions of the calibre, but I can't find any indications that this solved the problem, although you would think it would.
    I, like many, would love to get my hands on one, and not break the bank in the process. The Patek versions of this and also LeCoultre, used solid gold rotors which would increase the mass of the rotor and possibly improve winding, but it occurs to me that this might also cause more wear on the shaft. If memory serves, the Patek Calibre is 310?
    Last edited by Outta Time; October 26th, 2011 at 00:01.

  6. #5
    Member eldarinn's Avatar
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    Re: Hammy thin-o-matic micro rotor?

    Outta time, I have to disagree with you regarding how quick to judge the condition of the watch according to some circular marks on the case caused by the rotor;

    You will have to excuse my 'invention' of technical terms, English is not my native language and I am not so familiar with the exact technical terms, I hope you get the point nevertheless;
    While normal rotors are either screwed or tight-pinned from above, or in other words have a blocking system preventing them from sliding vertically over their post,
    The micro rotor is designed with a pressure angle tightened over the post with a side screw. In other words, over time this post can have a vertical play and it's enough that it moves half a millimeter to leave marks on the case due to the low clearance and yet, this can be fixed VERY easily, by unscrewing the tightening screw, placing the rotor down in place and re-tightening.
    By the way the Buren initial development caliber was the famous K-1000. I serviced many of these, including the later variants, such as the ones with date in Bulova Ambassador movements, as well as pretty much the same idea Universal Polerouter. At the time these were made they were considered not less than rocket science in terms of technological breakthrough and I am always happy to see one, despite some mechanical issues that can arouse with this kind of engineering.

  7. #6
    Member Outta Time's Avatar
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    Re: Hammy thin-o-matic micro rotor?

    Thanks for that, eldarinn. I haven't had one under my loupe...yet, but hope to in future. So the telltale scratches can be from excessive endshake as well? Makes sense, of course. So there you have it, folks, it could be an easy fix, but possibly not. This is what makes the collecting interesting!

  8. #7
    Member Will_f's Avatar
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    Quote Originally Posted by Outta Time View Post
    There is an issue with the micro rotor. I haven't serviced any myself, but was told this by an older watchmaker. If you open the case and there are circular scratches from the rotor on the caseback, move on. It can be repaired, but parts are scarce. I can't remember exactly why this is an issue, I'll see if I can find out.
    OK, got it. The micro rotor is actually the achilles heel of the movt, developed by Buren (1280) and marketed in 1957, prior to being purchase by Hamilton. (calibre 628) Wear is marked due to extra stresses on the rotor arbor, and will typically wear out the bushing in the rotor bridge. Buren incorporated a floating pinion in the winding train, and this necessitated depthing controls on the switching gears, non-toothed round wheels to prevent over-engagement or too deep engagement of the gears. This increases friction and cause uneven wear on the rotor shaft, which will show up as circular scratches on the caseback. Apparently Buren addressed this problem in the higher jewel count versions of the calibre, but I can't find any indications that this solved the problem, although you would think it would.
    I, like many, would love to get my hands on one, and not break the bank in the process. The Patek versions of this and also LeCoultre, used solid gold rotors which would increase the mass of the rotor and possibly improve winding, but it occurs to me that this might also cause more wear on the shaft. If memory serves, the Patek Calibre is 310?
    The irregular wear is the issue that I heard about too. The version I'm looking at is the earlier version without the extra jewels, hence my concern. The real question is how long? Are we talking 5 years or 20 years?
    Owner of a bunch of cool watches.


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