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Show Sensitive Springs Spun From Quartz; Tiny Threads Give Precise Measurement Quartz, which looks like glass and is a sort of glass, is the last material mate-rial most of us would use to make a spring. But the scientists in the General Research laboratories find nothing but quartz will do for springs in making precise measurements, measure-ments, says a writer in the New York Times. Steel springs rust; quartz springs don't. Steel springs are affected by changes in humidity; quartz springs are not. Steel springs begin to lose their temper at about 250 degrees Centigrade (482 degrees Fahrenheit); Fahren-heit); quartz springs never lose their temper except at temperatures not attained in ordinary practice. A quartz spring has a sensitivity of one milligram. In other words, it can detect a difference of weight as little as one 28,350;h of an ounce. And it always snaps back, after stretching, to exactly the original point of rest. Suppose it becomes necessary to measure the amount of moisture absorbed by cotton or cellulose. The cotton is suspended at one end cf the spring and the weigh: of the sample determined by the stretch of the spring. By introducing more and more water at varying pressures pres-sures it becomes piii.bie to deter mine just how much moisture cotton can absorb. Making a quartz thread is something some-thing of a fine art. The first step is to spin a fine thread no more than six one-thousandths of an inch in diameter. This is done by heating a fused quartz rod to more than 3,000 degrees Fahrenheit and pulling threads from the rod. The threads are measured by calipers. All within with-in a quarter of a mil of the desired six-mil size are saved. (A mil is a unit used to measure the diameter of a wire. It is equivalent to a thousandth of an inch.) The final step is to place the thread in a long brass trough which leads to a mandrel (technical term for a drum of the right diameter). As it passes over the mandrel the thread is heated to 1,800 degrees Fahrenheit. The mandrel makes two revolutions a minute. After cooling, the coils are ready for use |
