Page 334 - Gear Technology Solutions

without a step. However, in the complex case shown in Figure 2, stepping and
top slope are required to ensure root bottoms without fins and steps.

Due to the large distance between inside and outside blade tip reference point,
the step between S890IB and S890OB is significant. The formal calculation of
StepIB and StepOB required the blade point radii, the blade pressure angles and
the length crowning tilt component as documented in Figure 2. Although the
combination of top slope angles and stepping in Figure 2 presents the ideal
case to achieve a flat and stepless root bottom, there is one inconsequential
obstacle. This obstacle occurs at the inside blade because of the negative top
slope angle which results in a clearance side tip higher than the cutting-edge
tip. Cutter head blade stick outs are achieved with a flat blade height setting
surface as shown in Figure 3 [1, 2]. In Figure 3, the clearance side tip contacts
the surface of the blade setting stop, but Figure 2 shows that the theoretical
datum for the blade height above the cutter head face is the tip reference IB,
which is causing a blade stepping error. This error can be calculated and
compensated by an increased StepIB amount. However, practical cutting
experience has shown that the cutting results of cutters with blades stepped
according to Figure 2 deliver optimal results regarding smooth and stepless
root bottom.

Figure 3: Blade height setting at clearance side tip

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