Abstract
DURING the War, the danger that New Zealand might be cut off from supplies (and the difficulty of getting any) led to considerable effort to find substitutes. The short article in Nature1 on “Meter and Instrument Jewels and Pivots” reminded me of a good substitute we found for the sapphire-steel combination used in prismatic compasses. The jewel was made by press-moulding a molten drop of Pyrex glass in a two-piece chromium-steel mould—it emerged almost a finished article with a fired surface that proved very good. The pivot was made by turning softened silver steel (Stubbs, gauge 17) by means of projection turning and then hardening, electro-cleaning, polishing, etc., and finally electroplating on the tip with chromium. The radii of the pivots and of the jewels were measured by microscope projection for the former and mirror-image formation for the latter2.
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