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Flame Hardening
Heat-Treatment by the Shorter Process
Automatic Machines for Straight Surfaces, Shafts, Gears, Camshafts and Crankshafts

This article first appeared in the Volume 4, Number 44 (June, 1942) issue of Aircraft Production magazine, and is presented here through the kind permission of Flight International. Thanks also to Bruce Vander Mark for furnishing volumes of Aircraft Production for scanning.

All forms of heat-treatment which involve the heating and quenching of the entire component are liable to result in work distortion unless special precautions are observed. It is in this connection that the Shorter flame-hardening process is particularly successful since, due to the fact that only a very small area is heated at any instant, and this is immediately quenched, distortion is almost entirely eliminated. The chief appeal of the process to the aircraft industry is in the toolroom and maintenance departments, but as it has proved so successful in the production branches o f other engineering industries it could undoubtedly be applied to many aircraft components.

In its earlier days there was considerable prejudice against the employment of hand-operated flame-hardening for accurate work, but the results obtained from the modern mechanical methods can be controlled to such close limits that the former rather haphazard process is now replaced by a comparatively accurate science. Apart from the general-purpose equipment covering practically all types of work, a number of automatic special-purpose machines have been developed for quantity production use in the automobile industry. All these are built to machine tool limits.


Heat-treatment in one form or another plays an important part in the manufacture of aircraft, and elaborate furnace equipment has been developed for this work. There is, however, another branch of the aircraft industry where heat-treatment is of equal importance. This is the toolroom, where such parts as dies, jigs, tools, filing templates and gauges are made, and where cams, sprockets, feed rollers, machine slides and other components for repairs and special-purpose equipment are produced. Sometimes comparatively large batches of similar articles require treatment, whilst in other cases there are only one or two. Work of this nature often presents considerable difficulty, as it may not be desirable to heat the entire component merely to harden one comparatively small surface, particularly when dealing with thin material or sections of varying thickness that are liable to warp or distort very easily.


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