SPLITTING HAIRS

Shannon News, 14 April 1927, Page 1

SPLITTING HAIRS

WONDERFUL MACHINERY To most people a hair's breadth denotes extreme narrowness, al though in reality it is twice as thick as a cigarette paper, which measures a 2-1000ths part of an inch. A visiting card is quite a bulky affair in comparison, as it is no less than 25-1000th of an inch thick. Thinness, however is merely a matter of comparison, and to the engineer aiming at extreme accuracy the splitting of a hair or even a cigarette paper is quite an every-day affair. For instance, an erro r of l-1000th part of an inch is all the margin allowed in many of tho larger and clumsier parts of a modern motor-car, this fine limit ac- ! counting for the long life of the better class of British cars (says the ‘•British Commercial News.”) Whe nit comes to other and more vital parts, such as the gear wheels an error of only 2-10th of a l-1000th part of an inch being allowed the amount being registered by. an Instrument that can read to l-10th of a l-1000th. In other words the degree of thinness measured by this marvellous instrument is equal to the splitting of a cigarette paper into 20 layers! . Another aspect of the case is presented by the fact that the ordinary film of oil that separates, say the crankshaft and its bearings is quite a fat affair measuring some 3-1000ths of an inch. To maintain these extraordinary fine limits grinding and lapping machines are employed. In some cases, in spite of their marvellous dexterity. they are automatic In action the operator only having to set the machine to take off material up to a few thousandths of an Inch, and the machine noa only performing this work, but also stopping itself 1 when the job is completed. These remarks are prompted'as the result of a visit to the Armstrong Siddeleymotor works in Coventry, where the™ latest and most accurato machinery is in action.