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这段话有用吗?
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To poise the hairspring we must first determine the angle between the point of attachment at the collet and the initial vibrating point. One of the ways to determine the angle is to lay out the hairspring and collet on a protractor-like scale. By lining up the point of attachment at the collet with the zero angle, the angle to the vibrating point can be read off the scale and used to determine how much of the hairspring must be cut off the innermost coil in order to repin it "in poise". If you're using the "wrap method" initially, establishing what constitutes the initially point of attachment (to line up with the zero angle on the scale) requires some experience and some guesswork. Since the hairspring leaves the collet fairly smoothly, deciding at what point it first starts vibrating is not cut and dried.
The formula for determining how much to cut off is: A (the angle between the two points) plus (the quantity) A over 3 minus 60 degrees equals B (the number of degrees to be cut off from the intial point of attachment). This allows for 60 degrees of the remaining spring to be tucked into the whole in the collet for pinning. The thought behind this formula is that a length of spring on the innermost coil is equal to a length of spring on the outermost coil that represents one third of the angular value of the portion at the innermost coil. This is only approximately true given the general geometry of hairspring coils but it's close enough to allow us to come within 15 degrees or so of pinning the hairspring in poise.
Ok, pinning the hairspring at the collet and then later at the stud requires the utmost precision and care. Not only is it incredibly easy to ruin the hairspring with a slight slip of the tweezers, but if it is not pinned flat, it'll create a world of troubles for you trying to make it that way. Also, if you pin it without the right amount of spring in the sharp curve where it enters the first coil (at the collet), it will resist centering vigorously.
It is absolutely critical that the hairspring be perfectly centered and perfectly flat at the collet if you cant to get anything like good performance out of it. As Henry Hatem (the first year instructor) said to me when he saw us struggling with this aspect, "That first coil is your whole world." He couldn't have been more right.
Each of us developed our own methods for holding the collet and spring, inserting the taper pin, cutting it to the right length and pushing it in firmly enough to hold the spring. For a little while I thought that holding the collet in a collet closing tool at precisely the correct height to let the spring lie flat as it enters the hole in the collet could insure a reasonably flat initial pinning. The problem being that the taper pin itself pushes the hairspring out of flat. There's really no perfect way to do it so you just have to practice, practice, practice until you can figure out a series of steps that works for you.
So after the spring has been pinned at the collet and made as flat as possible, we must shape the innermost curve to make the hairspring coils centered around the collet. This is incredibly difficult if the first coil is very tight (because you don't have room to get your tweezers in between the collet and the hairspring) and is also not at all easy if the first coil is very large (because it's hard to see how well centered it is). The actual size of the first coil is somewhat arbitrary as it is determined by the poising process.
One of the ways to check if the spring is properly centered and flat is to place the balance in the figure 8 calipers and spin it slowly. From the side, a slight up and down motion of the hairspring will indicate it is out of flat. From above, a perfectly centered hairspring will have coils that appear more or less stationary as it spins (or at least they will progress very evenly). One of the joys of this part of the process is that making corrections in the flat usually throws off the centering and vice versa.
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