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Gauges and Other Tools - Shop Talks with the Young Mechanics by W. H. Vandervoort, 1899

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There is nothing more confusing to the young mechanic than the use of the several systems of gauges used in designating the sizes of wire, machine screws, drills and plate thickness. Unfortunately, most of these dimensions differ from each other for corresponding numbers by comparatively small amounts, yet an amount sufficient to cause error if the one is mistaken for the other.

The following table gives for comparison values for only a few numbers under each of the several gauges in most common use.

The dimensions are purely arbitrary. The American, or Brown & Sharpe gauge, was brought out in the production of a gauge to overcome the irregularities in spacing of the Birmingham wire gauge. In this gauge the dimensions increase by a regular geometrical progression.

The largest dimension is No. 0000, which equals .46 of an inch. The next smaller number, 000, is obtained by multiplying .46 by the constant .890522. This product again multiplied by the same constant, gives the next smaller number, and in like manner each number is the product of the preceding number and this constant. A comparison of the English and American gauges is best shown in Fig. 225, where the peculiar irregularities of the former are plainly shown.

The imperial wire gauge differs but little from the English. It was adopted by the English Board of Trade in 1884 as a substitute for the Birmingham gauge. The Stubsí steel wire gauge differs materially from those above cited. Its range carries it from No. 1 to No. 80, variations in dimensions being indicated to the nearest one thousandths of an inch. The difference between consecutive numbers differ in dimensions from one to at most only a few thousandths, the eighty number carrying it through but .214 of an inch.

It is extremely unfortunate that a single standard gauge could not be adopted and used to the exclusion of all others, at least in our own country, and thereby avoid all confusion incidents to the promiscuous use of the several so-called standards. Even the manufacturers of brass and copper stock, who have adopted the American standard, do not confine themselves exclusively to this gauge, as much of their product is still gauged by the English system.

The Stubsí drill gauge varies from the Stubsí steel wire gauge by from 0 to 3 thousandths of an inch over size, which is simply the average oversize determined by a great number of measurements of wire drawn through Stubsí wire gauge dies, and might be compared with a maximum limit gauge, as the dies, when worn to such an extent as to produce wire over the sizes indicated by the drill gauge are replaced by new ones.

It will be noted that as the designating number of gauge increases the dimensions decrease for all except the steel music wire and machine screw gauges, which increase in diameter as the number increases. This also tends much towards confusion, and may be looked upon as another anomaly of the present gauge systems.
The gauges, or tools for indicating the gauge of wire or plates, are of two forms, the angular and the notch. The angular gauge is shown in Fig. 226.

With this tool the measurement is made by passing the screw, wire or plate into the angular opening until it touches both sides; the reading opposite the point of contact giving the gauge of the material. When used for gauging plates, this gauge should be made with open end, as shown at C. on the one side is graduated the English and American standards, and on the other the machine screw gauge and parts of an inch. The notch gauge is shown in Fig. 227.

In using this tool the article measured should just pass through one of the slots, the number opposite indicating the gauge. These gauges may be had with the decimal equivalent of each size stamped on the back of the tool, which will frequently be found to be a great convenience.

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