The thread on millwrights got me to wondering about something.

I have seen one mill (I am sure mechanism was reconstructed) that
actually had wood crown and pinion gears (many mills required a right
angle change in shaft axis). And I see many diagrams of wooden gears in
history of technology books on mills.

Most gear sets I see are metal, from mid to late nineteenth century.

Now, I wonder if there was a complete, sudden transition from wood to
metal gears, or was there a transitional period with what we might call
composite gears- part wood, part metal.

For instance, we could have metal teeth mounted in a wooden wheel. That
to me would seem more reasonable than vis versa. Has anyone ever heard
of such a composite gear in a mill?