The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . ?^^ ^^ .^).«,<io MEASUREMENT] TOOL ^4-5 Micrnmetcr Calipers are the direct offspring of the Whitworthmeasurins pwchine. In the original form of {his a screwof 20 threads to the inch, turned by a worm-wheel of 200 teeth™nd single-threaded worm, had a wheel on the axis of the worm with-SO divisions on its anadjustmentol »olan inch was possible. The cosily measuring macliines made to-dayhave a dividing wheel on the screw, but they combine modificationsto ensur
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . ?^^ ^^ .^).«,<io MEASUREMENT] TOOL ^4-5 Micrnmetcr Calipers are the direct offspring of the Whitworthmeasurins pwchine. In the original form of {his a screwof 20 threads to the inch, turned by a worm-wheel of 200 teeth™nd single-threaded worm, had a wheel on the axis of the worm with-SO divisions on its anadjustmentol »olan inch was possible. The cosily measuring macliines made to-dayhave a dividing wheel on the screw, but they combine modificationsto ensure freedom from error the fruits of prolonged machines are made by the Whitworth. the Pratt & Whitney,the Newall (fig. 71). and the Brown & bharpe firms These areused for testing purposes. But there are immense numbers of smalinstruments, tTic micrometer calipers (fig. 72). .made for general ? ._ j; » »^ .1 nf an inrh ami in the instruments, tne micrunicLci ^..pw^o v-t,- ,-,. —-- —- <?-----shop use. measuring direcUy to xoVtj of an inch, and m the. pitch is 40 to the inch, and the circular divisions number 25. so thata movement of one division indicates that the screw has been ad-vanced ^ of iS or loSo of an inch. Provision for correcting ortaking up the effects of wear is included in these designs { ata in fig. 72), and varies with different manufacturers. A vernier issometimes fitted in addition, in very high class instruments, to thecircular divisions, so that readings of ten thousandths of an inch canbe taken. Beam micrometer calipers (fig. 73) take several inchesin length, the micrometer being reserved for fractional parts of theinch only. , . r , Deplh Gauges.—It is often necessary to measure the depth ofone portion of a piece of work below another part, or the height ofone portion relatively to a lower one. To hold a rule perpendicularlyand take a sight is-not an accurate method, because the sameobjections apply to this as to rule m
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
