Mikron Traversing drive chain
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  1. #1
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    Default Mikron Traversing drive chain

    I have been refurbishing a Mikron WF1 and have an issue with the main traversing drive chain.

    The chain looks like it's the wrong pitch, it works but makes a clicking sound as it feeds onto the lower sprocket. The tighter the chain the more pronounced the click, so there is definitely a pitch issue. The length is correct as the adjustment is in the center of it's range.

    It would appear to be a 5/8" pitch chain and I wonder if a BS standard chain is correct. The sprocket looks ok and the chain has very little play either side or length ways. Are there any other chain standards that could have been used on a Swiss machine.

    When I got the machine the traversing was not working and it turned out to be the usual motor phases wrong, so I have no idea what state this chain drive was in originally.

    Ciao Adrian.
    Attached Thumbnails Attached Thumbnails wp_20210512_001.jpg  

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    I think Mikron (which is Swiss) would have used a metric pitch chain, not an imperial/inch one. Perhaps someone replaced the metric chain with a similar but incorrect inch/imperial one? If so, it's an easy fix.

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    That is due to wear Wear changes the pitch slightly The chain liesa bit deeper Therefore the nominal diam of the sprocket gets smaller Therefore the pitch gets smaller In addition wear of the chain makes the pitch bigger If you look at the wear you will notice most wear is at the front side of the teeth
    Eighter use it with some slack Or replace all sprockets and chain
    On really worn sprockets the chain cando wierd things Like tightening up all of a sudden Then it starts to ride on the worn more forward and outer secrion of the teeth insted of that the rollers are in the bottem between the teeth So never tighten a worn chain
    Peter

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    The odd thing is the sprocket looks fine, the shape is uniform on both leading and trailing edges.
    The clicking sound is the sprocket tooth tip hitting the oncoming roller. To me this would indicate either the chain pitch is wrong or it's going too deep into the sprocket groove due to wear on the sprocket.

    Interestingly all the chain I have seen advertised as metric is just inch chain i.e 0.625" or 15.875mm

    Ciao Adrian.

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    Perhaps the wear is in the chain mostly
    Metric size chain was very rare in the days the machine was build Even now it is


    Peter

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    Quote Originally Posted by adrian View Post
    Interestingly all the chain I have seen advertised as metric is just inch chain i.e 0.625" or 15.875mm
    You're right --standard metric types around that size are:

    08B = 12.7mm pitch = 1/2"
    10B = 15.875mm pitch = 5/8"
    12B = 19.05mm pitch =3/4"

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    I'm with Peter on this..the chain may be worn. A standard test is to remove the chain, lay it on its side on a flat surface and pull it as if trying to make a circle. It should move very little, there are specifics at chain mfg's sites. A worn out chain acts the same as a worn out sprocket, the pitch is wonky and it won't mesh properly with the apparent good sprocket.

    A good sprocket and a good chain move smooth and fairly silently, so you only two possible culprits..actually three culprits, as there are two sprockets.

    Stuart

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    One work around for the sprocket that works sort of is to rotate them

    Peter

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    My only experience comes from bicycles and having made a few sprockets for bicycles but when the root of the tooth becomes worn the chain sits lower on the sprocket causing it to interfere or rub on the crest of the tooth. As the roots wear the teeth become effectively taller.

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    Better explanation as I see it
    If you get wear in your chain the pitch gets longer on the pulling side of the chain On the slack side it can adapt a bit
    If you look closely at a worn sprocket you see wear in a tangential direction That way you have a bigger nominal diameter of the sprocket therefore a bigger pitch of the sprockets teeth
    The sprocket wears to the pitch of the chain so to say


    Peter


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