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Maudslay's Methods of Originating Screws (1856)
In a subsequent and stronger machine, the bar carrying the mandrel stood lower than the other, to admit of larger change wheels upon it, and the same driving ...
Mr. Maudslay succeeded by these means, after great perse-verance, in making a very excellent brass screw about seven feet long, and which, compared with standard measure, was less than one sixteenth of an inch false of its nominal length. Troughton, F.R.S., etc, who examined them by means of two powerful microscopes with cross wires, such as are used for reading off the graduations of astronomical instruments; applied like a pair of the most refined compasses, to measure the equality of some 20, 50, or 100 threads, taken indiscriminately at different parts of the length of the screws. * From this severe trial it resulted, that these screws, which to the unassisted sight, and for almost every purpose of mechanism, were unexceptionable, were found to be full of all kinds of errors, being unequally coarse at different parts, and even irregular in their angles, or "drunk."
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