The problems of precision manufacture in Australia, arising chiefly from her geographic isolation, are first discussed. The paper then takes one particular problem from the field of optical manufacture and shows how it was solved for the conditions prevailing in the Dominion. The problem discussed is the production of graticules, or reticles, for range-finders, predictors, gun sights, telescopes, binoculars, microscopes, collimators, and many other such instruments. The first part of the paper deals briefly with methods used in reproducing the pattern, particularly the ruling and etching process. The second, and much the larger, part of the paper deals with the design of the high precision machines which were made for ruling the glass disks preparatory to etching the pattern into the glass. Two such machines were developed, one generating the pattern from the movements of the machine itself, the other, a pantograph, by copying the pattern from master plates. A series of self-checking tests is described by which the accuracy of the generating machine could rapidly be tested to an accuracy of much better than 0·0001 inch. A brief survey of the complete process, from glass blank to finished graticule, is made in the Appendix.
Active damping of vibrations in high-precision motion systems