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Title: |
1895 Article-Pratt & Whitney Co., Measuring Machine |
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Source: |
Modern Mechanism 1895 pgs 497-498 |
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Insert Date: |
6/21/2011 3:16:23 PM |
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Measuring-Machines.—The Pratt & Whitney 12-in. standard measuring-machine is shown in Fig. 5. The screw is 50 threads per in., and has adjustments for compensation for wear in nut and shoulders. The index-circle is graduated to 400 divisions, giving subdivisions of 1/2000 of an in.; while, by estimation, this may be further subdivided to indicate one half or even one fourth this amount. Delicacy of contact between the measuring-faces is obtained by the use of auxiliary jaws holding a small cylindrical gauge by the pressure of a light helical spring, which operates the sliding spindle, to which one of these auxiliary jaws are attached. The behavior of this "sensitive piece" readily determines the uniformity of contact of the measuring-faces at zero, and upon the gauge which is measured between them. An adjusting device for the index-line is provided, to allow for slight variations of position of the measuring-faces at zero, or for any convenient reading on the index-circle. |
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