Science: Honing Hard Steel

The skilled human hand lost another small round against the machine last week, and U.S. industry thereby took an important stride toward solving one of its most acute wartime bottlenecks—cutting tools. Such tools (used to cut gears, shafts and engine parts from hard alloy steels) are themselves made of even harder tungsten, cobalt and molybdenum steels. Nevertheless, they dull quickly, must be constantly reground. Previously such grinding was done by hand. This method is maddeningly slow, and even the most efficient hand grinding produces a cutting edge which, viewed through a microscope, looks like the blade of a saw. Red-hot metal caught between these minute saw teeth causes cutting tools to overheat quicker, wear out sooner.

Last week Wright Aeronautical Corp. announced that it has developed a machine grinder which hones 18 cutting tools at once to a razoredge impossible with hand grinding. Result: the tools heat much more slowly, wear from 10 to 20 times as long.