A MICROMETER FOR INCHES OR CENTIMETRES.
Page 22
If you've noticed an error in this article please click here to report it so we can fix it.
A Useful Instrument for the Engineer and Foreman Repairer.
A NEW form of micrometer has been II introduced by the Micro-Inch Micrometer Co , of 26, St. Stephen's House, Westminster, London, SAVA. The instrument is the invention of a French engineer, but is of British make, and has, we understand, been passed as satisfactory by the National Physical Laboratory. The main feature of the instrument lies in the fact that both decimal fractions of the English inch and of the metric scale can be read simultaneously, without any calculations or reference to tables of equivalents. In all moO work one has often to deal with both English inch and metric measurements On the same piece of 'work, as, owing to the motor having developed earlier on the Continent than here, many metric sizes are still used for such parts as cylinder bores, ball bearings, etc. This is the case in the making of new parts, but is experienced to an even greater extent in the making of replacement parts and in repair work. The result of this mixing up of the two scales is that a mechanic has always to be bothered by the use of two micrometers, or is still more bothered by constant reference to tables of equivalents. By the use of this very ingenious instrument, the work of the mechanic M reduced to simplicity itself, as both scales can be read at a glance, both indices being visible at all times, and the equivalent of metric to inch is plainly shown at all Parts of the reading line. The difficulty of devising a reading line that will enable a mechanic to read at a glance both scales will be realized when one recollects that the inch is equal ,to 2.539954 centimetres. The inventor has overcome this difficulty by making his reading line for the metric seals in the form of a helix, and providing two separate divided , edges to the revolving thimble, the front one of which is divided in radial lines so as to match up with the straight line
of the English inch, whilst the lines which are read for Metric measurements are tangential, so as to match up -with the helical line. By this means it is impossible for any confusion to take place whilst using the instrument. A very neat lock is provided, as is shown. in the illustrations. The milled faces at the button shown are gripped between the thumb and finger, and a slight turn actuates an eccentric which forces a plunger up-Wards so that it grips the screw for t locking purposes. We think this new micrometer should be installed in all works and garages where motor work is undertaken.