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Figure 13: Cutting edge spacing j
Three-face ground blades result in a spacing angle j x, which will according to
Figure 10 lead to a tooth thickness error Ne. As previously mentioned in sec-
tion “Length Crowning and Flank Twist Phenomenon”, if the correct tooth
thickness is re-established with small cutter point radius changes, then a
length crowning side effect of gears cut with such a cutter will occur which
cannot be corrected (without changes in blade geometry and alterations of the
machine settings).
An uncommon solution was developed, which achieves the correct blade spac-
ing angle j instead of j x (see Figure 13) and at the same time delivers the de-
sired values for the effective cutting edge hook angle, the effective side rake
angle as well as providing a complete front face clean-up.
The new method is based on the idea that j x in Figure 13 can be increased, if
the IB-blade receives a larger front clean-up thickness and j x can be reduced
if the front clean-up thickness of the OB-blade is increased (see also Figure 8).
Only increasing the front face clean-up thickness is permissible because only
then the minimal clean-up is preserved.
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