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POSITION:  Home -> About watches -> Why does not require the watch -> Details
Why does not require the watch the second hand must be aligned scale?
Published: Caister    Date: 2014-04-28  

A pointer alignment problem watches, watches the industry standard is required, this is called, the coordination error. In the relevant industry standards QB/T1249-2004 inside, there is a, is defined as follows: "the minute hand and dial" 12 "character overlap, observation, 6, 9 and 3 hour, 12 character of angular displacement, its value should be less than 3 degrees". But just said, the minute hand, but no requirements on the second hand.

In the early period of the planned economy, such as watches, light industrial products, the watch factory have business representatives, called "in the factory". Commercial and industrial perspective is different, the general business certainly hope that the product quality standard of the higher the better, and the industry is in the hope of "within the scope of". I have heard about at that time, when the coordination error, this standard has triggered a fierce debate between industrial and commercial sides, because the commercial square in any case can not accept, the clockwise and dial "12" character overlap, and the minute hand allow plus or minus 6 minutes, deviated from the "error 12" character of this provision, finally the result of compromise deduction that appear in: "the minute hand and dial" 12 "character overlap, observation, 6, 9 and 3 hour, 12 character of angular displacement, its value should be less than 3 degrees". In fact, inside and outside is still the same, which belongs to the typical chop and change, in fact, is only a simple conversion problem.

When the minute hand coordination, error is easy to control, manufacturing tolerance is a small problem, mainly lies in the needle assembly. Now some consumers to watch, very strict quality requirements, and even proposed correspondence problem of second hand, minute hand, second is to coordinate error requirements; second walk in a circle, the minute hand is to accurately move scale, at the same time, and the second at run time, to align the index or character.

As far as I know, the current major watch all producing countries in the world watch standards are not the rule, so, I consider the following factors:

(1) between the second hand and the minute hand in hand and hand, which belongs to the "dead engagement", a minute wheel, wheel and wheel trans positions are relatively fixed, under normal circumstances will not be dislocated or mobile. And between the second wheel and the minute wheel is not the same, because the minute wheel will "slip", as long as a needle will appear.

(2) the tooth gap, in order to ensure that the gear meshing and transmission of normal smooth, smooth, watch basically use modified cycloid tooth profile, tooth in meshing angle and the nip angle, must also have a backlash, otherwise it will appear in top gear or gear shaving phenomenon. A pair of gear's tooth gap is very small, but turned into a number of the gear backlash, added together, it becomes obvious. After the idle angle of a tiny, the pointer will be promoted, which often have to dial needle in one direction, the most typical is the two needle quartz watch, lane is bad to the instruction always slow half a minute.

(3) belonging to the dial, dial character and calibration error in installation and printing, cannot guarantee absolute scale of each part are indexing concentric and uniform; the most important is that the two wheel claw under the dial, a positioning tolerance wheel claw, a perpendicularity, there is the movement above may have radial move the tiny.

(4) quartz watch second hand are basically skip, second para seems more obvious, especially the surface of quartz clock, is often the second hand is on the scale of a part of the dial, and another part is not so positive, this is very normal. In fact, the second operation of mechanical watches, is intermittent, also has a pause. It depends on the balance wheel oscillation frequency, if it is the 28800 /, that every seconds, seconds will "trembling" 8.

(5) requirements (Zhong Biao) watch second hand completely accurate to scale, in life seems to be no specific application significance, only sports stopwatch is necessary, but it requires a very fine tooth and high oscillation frequency only, and must be able to stop second, only when the second hand is stopped, to accurate observation data. But such special purpose or need time timer, will now use digital quartz watch. Pointer type meter code function watch, in the center second installation time, is in need of positioning, so the stopwatch started the initial position and fly back to zero position, can be aimed at "12" character; and the radio controlled clock hand also has installed positioning requirements, they have requested second timing accuracy, in addition to the above two, generally watch the second hand is free to install.

(6) the second highest position, far from the dial, so easy for observation angle sake visual error.

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