IO2
CURRENT TOPICS.
[J. F. I.
the heat treatment of steels and the preparation of alloys with better mechanical properties and corrosion resistance." He demonstrated the magnetic experiment recently before a meeting of the Schenectady Chapter of the American Chemical Society. R. H. O.
Photography Utilized to Break an Aircraft Bottleneck.--The big bottleneck in airplane manufacture has been the loft, the department in which the draftsmen's renderings of construction details are enlarged into full scale drawings on huge sheets of plywood or metal. Layout men use the loft floor as their drawing board and crawl around on their drawings as they work. The practice, handed down from that far time when magnificient clipper ships were born in New England lofts, was carried over virtually intact into the aviation industry. It served its purpose well--as long as demand for airplanes was relatively small. Under leisurely schedules of peace time aviation manufacture, lofts could turn out enough full-scale drawings and templates made from such drawings to keep productive departments running. But increased war time demands turned lofts into bottlenecks. As demands accelerated, it became necessary to call upon the automobile industry to supply parts and sub-assemblies for fighters and bombers. These parts and subassemblies, made in scattered automobile plants, had to fit with absolute accuracy. To get such close fits the needs for the number of templates were multiplied beyond the combined capacities of all the lofts to supply them. At that crucial juncture the solution of the precision-loving pattern maker's problem was applied to the new problem. Now automotive and aviation engineers are lopping incalculable numbers of precious hours out of the once laborious job. Briefly the process works as follows: The original drawing is made on a sheet treated with phosphorescent chemicalswhich glow with blue light after bombardment by X-rays. A coating of cellulose nitrate lacquer now goes on the metal sheets which are to serve as working drawings or which are to be cut out and drilled as templates. Underred light the coated sheets are then faced with photosensitive film. This film having a nitrate skin, is locked to the surface of the metal by use of nitrate cement and pressure of rubber rollers. The phosphorescent drawing is then placed in contact with the photo-sensitive metal and the image is transferred. The exposed metal sheet goes successively through the developer, stop bath, hypo, wash tank and drying racks. With the immediate use of glass plates the resultant prints can be made positive and negative, as right and left templates. After close checking for fidelity,