Abstract
Abstract The papers forming this symposium deal respectively with electric drive for planers, special drilling and tapping machinery, precision grinding machines, and lathes. F. E. Cardullo first describes the types of electric motors adaptable to planer drive and states that because of superior electrical and mechanical advantages, practically all reversing planer motors are of the adjustable-speed direct-current type and fall into constant-voltage and variable-voltage classes. He describes these motors and their control apparatus and computes such factors as the loss of time due to reversal. He then compares the reversing-motor with bell drive. He closes with a description of the space-time diagram and its use in studying planer drive. J. H. Mansfield discusses the application of motors and controls for special drilling, tapping, turning, boring, and facing machines. He compares the times required in the operation of a single-purpose turning and facing machine equipped with single-speed motor and the same machine equipped with a multi-speed motor. In discussing the application of electric motors to woodworking machinery he shows a double-end turning machine equipped with 15 motors. R. E. W. Harrison traces the development of motor-driven precision grinding machines from the countershaft bell-driven type. He then discusses motor bearings and motor mountings. From a study of a load-cycle chart which shows (a) period in which stock is reduced at maximum rate of metal removal, (b) ending of metal-removing period and beginning of finishing operation, and (c) period for finishing and accurate sizing, the author shows what are the chief characteristics desired in a motor driving a grinding wheel. The paper closes with a brief discussion of “across-the-line” motors and its advantages. Chas. L. Cameron deals first with methods of mounting motors on lathes and lists the difficulties which arise from lack of standardization of motors. He then points out why it is best for the manufacturer of the lathe to provide the motor to drive it rather than relying on the purchaser to buy the proper motor, and discusses the tendency to use motors larger than practically required, pointing out that the use of anti-friction bearings has reduced the power required to drive the lathe. The paper ends with a discussion of motor types and an expression of the desirability of developing an alternating-current, variable-speed, constant-horsepower motor.
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