
320 Fundamentals of Machining Processes
including the type of workpiece material and the method of US tool feed. In
general, USM accuracy levels are limited to ±0.05 mm.
Conicity: The conicity of holes is approximately 0.2º when drilling of a
20 mm diameter hole to a depth of 10 mm is achieved in graphite. The conic-
ity can be reduced by the use of tools having negatively tapering walls.
Out of roundness: The out of roundness arises by the lateral vibrations of the
tool. Typical roundness error is about 40–140 μm and 20–60 μm, respectively,
for glass and graphite materials.
10.1.5 Surface Quality
As shown in Figure 10.15, the larger the grit size, ...