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"A single casting machine will turn out several gun tubes in the time it takes to forge one," says Case, and machining time is cut 25 to 40%. "Reduction in weight is considerable," he adds, "and is used in many guns to regain mobility."
Centrifugally cast cylinder barrels will be used in all of Ford's Pratt & Whitney engines by this month's end. Both Army and Pratt & Whitney engineers-mindful of the old cast-iron stove lid, which was almost as brittle as glass-were leary of steel castings until Ford testers showed that, while forged barrels burst at 5,000 to 7,000 lb. per sq. in., centrifugally cast barrels burst at 9,000 to 10,000 lb. "Moreover," said a Ford engineer last week, "$10,000 worth of centrifugal dies will turn out as many cylinder barrel blanks as a $110,000 forging hammer." Landing gear for bombers is also centrifugally cast by Ford.
Armor. Casting U.S. tank turrets and hulls, heretofore riveted or welded together from steel plate, gets rid of another traditional prejudice against cast steel: that it couldn't successfully be toughened by heating and quenching. About one-third of U.S. tanks are now built of cast armor, and all of them would be, if foundry and machining facilities were adequate (see p. 53).
The advantages of cast armor are that
1) there are no rivets, which a direct hit may drive into the interior of a tank, where they ricochet, as deadly as bullets,
2) it allows a goodly weight saving by eliminating angle-pieces and overlapping necessary for riveting plates together. Unlike welded armor, cast armor has no seams of uncertain toughness. And, unlike both riveted and all-welded armor, cast armor can have rounded corners to deflect glancing shells.
*First used in the U.S. in 1902 in making railroad wheels at the American Steel Foundries plant in East St. Louis.