For milling of worm wheels in economic conditions one should have the access to hobs with the same features as the worms that interact with the wheels.
These worm wheel hobs are highly accurate and costly. It is therefore advisable, when designing a worm gear set, to consult the list of existing tools.
When the correct worm wheel hob is not available a hob may be used that is close to the specifications.
Otherwise the tooth milling should happen with a cutting knife, which is a time-consuming and therefore expensive operation.