Sandvik Coromant Silent tools - How to reduce vibration in metal cutting - Manual (Page 23)

Sandvik Coromant – How to reduce vibration in metal cutting 19
Internal machining theory
Internal turning
Many external turning operations are also found in boring, as per-
formed with stationary turning tools, (as opposed to boring operations
with rotating tools, such as in machining centres). With external
turning, the tool overhang is not affected by the length of the work-
piece and the size of the tool holder can be chosen so that it with-
stands the forces and stresses which arise during the operation. With
boring - internal turning - the choice of tool is very much restricted
by the component’s hole diameter and length as the depth of the hole
determines the overhang.
A general rule, which applies to all machining, is to always minimize
tool overhang and to select the largest possible tool size in order to obtain
the best possible stability and thereby accuracy. Stability is increased when
a larger boring bar diameter is used, but possibilities are often limited, since
the space allowed by the diameter of the hole in the component must be
taken into consideration for swarf evacuation and any radial movement.
The limitations with regard to stability in boring mean that some extra
care must be taken with production planning and preparation. Selecting
the right boring bar for the operation, applying it correctly and clamping
it properly has considerable effect on keeping tool deflection and vibration
to a minimum, and consequently the quality of the hole being machined.