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US Patent: 287,420
Micrometer
Patentee:
Samuel Darling - Providence, RI

USPTO Classifications:
33/813

Tool Categories:
metalworking tools : machinist tools : measuring tools : micrometers

Assignees:
None

Manufacturer:
Not known to have been produced

Witnesses:
John E. Hall
Jacob Kettner

Patent Dates:
Applied: Mar. 01, 1883
Granted: Oct. 30, 1883

Patent Pictures:
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Description:
The object of this invention is to make a micrometer having a screw and a nut in which there shall be no perceptible play between the threads of the screw and the nut, a micrometer in which the screw will revolve much farther relative to the motion of the cross-hairs than in the micrometers heretofore made, and a micrometer having a substitute for the common cross-hairs, (spider's web,) by which measurements can be made with greater accuracy and uniformity and it consists in making a micrometer having a V-thread screw and nut, the nut being split at one end, and using a screw for tightening the nut; in making the frame that carries the cross-hairs with a very small hard abutting-piece that shall come against the end of the screw, which is also to be made hard and preferably small; in making a micrometer having two screws on the same piece, each made of a different pitch, and a whole or split nut for each part of the screw, one nut and the corresponding screw being attached to the frame that carries the cross-hairs; in making a micrometer having small wires, which may be of glass or any suitable material, instead of spider webs, and in making a micrometer having short cross-wires parallel with and opposite to each other, leaving a space between them, and in various positions, so that the operator can have several points to guide him in adjusting the micrometer to the line on the article to be measured, and in making a micrometer having one or more movable pieces to hold the wires for the purpose of adjustment, all to be constructed and used as more fully described in the folio wing specification. It is well known to mechanics that a screw loose in the nut cannot be depended upon for great accuracy and uniformity in measurements, notwithstanding the slack may be taken up by a spring, as particles of matter are liable to get between the threads and cause errors. That difficulty is avoided in this improved micrometer. From experiment it is believed that the cross-hairs in a micrometer made according to this improvement can be adjusted to a line a number of times say five, more or less, within an error of .00005 of an inch. It greatly facilitates the adjusting of the cross-hairs to a line to have the screw move a considerable part of a revolution for each division of the index-wheel. It is difficult to move the screw made in the ordinary way little enough to adjust the cross-hairs in the most accurate manner, and the difficulty in moving it little enough often influences the operator to accept an adjustment as correct with which he is not fully satisfied.

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