I have an Indian made HMT automatic wrist-watch,it is written on it "21 jewels".What does it mean?

That watch does not need any battery or manually winding to run it. Its winding is done automatically merely with a few hand movements while wearing it on the wrist. Is 'JEWEL' any kind of standard or grade or unit in wrist-watch mechanism? Please describe it in detail what is a JEWEL.

4 Answers

  • 7 years ago
    Best Answer

    Jewels serve two purposes in a watch.

    First, reduced friction can increase accuracy. Friction in the wheel train bearings and the escapement causes slight variations in the impulses applied to the balance wheel, causing variations in the rate of timekeeping. The low, predictable friction of jewel surfaces reduces these variations.

    Second, they can increase the life of the bearings. In un jeweled bearings, the pivots of the watch's wheels rotate in holes in the plates supporting the movement. The sideways force applied by the driving gear causes more pressure and friction on one side of the hole. In some of the wheels, the rotating shaft can eventually wear away the hole until it is oval shaped, and the watch stops.

    More details on source link.

  • annino
    Lv 4
    3 years ago

    Hmt Automatic Watches

  • 7 years ago

    Rubies are used for the bearings in the watch. The link below will give you more details.

    The type of watch you are talking about is called a self winding watch since it uses the movement of your arm to keep the watch spring wound.

  • 7 years ago

    watches can have metal on metal bearings, or bearings where a jewel is used to isolate the metal to metal contact - classically this has been a preferred way to reduce wear, but modern metallurgy makes it kind of academic

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