| 摘要 |
The central part of the instruments of the boring set, prior to the portion having the cutting edges, has a section of a polygonal shape. The lateral faces of the central part are either convex, for the instruments of small diameter, plane for the instruments of middle diameter and concave for the instruments of largest diameter, in such a way that the curve of the bending moments of the instruments of the set is substantially rectilinear. Thus the variation of the bending moments of the instruments is linear, while, in previously known sets of instruments, the curve is exponential. Hence, the flexibility of the instruments of the set is satisfactory for the entire set of instruments, while; in the known conventional sets, if previously flexibility of the small instruments of the set is satisfactory, the instruments of largest diameter will be too rigid, and vice versa.
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