Report No. 94. The efficiency of small bearings in instrmnents of the type used in aircraft by F. H. Norton, aerodynamical laboratory, National Advisory Committee for Aeronautics, Langley Field, Va. Io pages, illustrations, plates, quarto. Washington, Government Printing Office, I92O. This report deals with the construction and properties of hearings and pivots for use in instrumt'nts. The static and running friction for both thrust and radial loads was determined for a number of conical pivots and cylindrical and ball bearings. The static rocking friction was also measured for several conical and ball bearings under a heavy load, especially to determine their suitability for use in an N. P. L. type wind tunnel balance. In constructing conical pivots and sockets it was found that the pivots should be hardened and highly polished, preferably with a revolving lap, and that the sockets should he made by punching with a hardened and polished punch. It was found that for a light load the conical pivots give less friction than any other type and their wearing qualities when hardened are excellent. When the load exceeds about moo grams ball bearings give less friction than pivots and will stand shocks and wear better. Very small ball b'earit~gs are unsatisfactory because the proportional accuracy of the balls and races is not high enough to insure smooth running. For rocking pivots under heavy loads it was fotmd that a ball and socket bearing, cousisting of a hemispherical socket and a sphere of smaller diameter concentric with it with a row of small balls resting between the two was superior to a pivot resting in a socket. It was found that vibration such as occurs iu a'a airplane will greatly reduce the static friction of a pivot or hearing, in some eases to as little as one-twentieth of its static value.