The behavior of self-excited chatter after an excitation is studied by introducing the new idea of a multiple regenerative effect. This considers not only the effect of one turn before, but that of two or more turns before. The analysis explains well some characteristics of the chatter, such as the finite amplitude after the onset, and the generation of chatter marks. Increase of the stability at low cutting speeds is also discussed in terms of a resistive force due to the relative motion between work and tool.

A flying toy called Aerobie r was invented by Adler in the US. The flight range of the toy is rather enormous, and it is one of the Guinness book world records. The authors were interested in the aerodynamic characteristics of the toy, and experimentally investigated annular plan form flat plates from which the toy was developed. It was found that L/D was improved and the center of pressure moved toward the center of gravity as the inner radius was increased.