Getting gears to appear smooth by explicitly assigning indices to the generated facets got me thinking in more detail of how to accomplish this result in general, for any facets drawn in face mode by turtle graphics.
As an update to the 2d involute (curved teeth) gears, I modified the program to produce 3d (extruded) gears. This required a change in drawing tactics.
Finally, not perfect at all but working gear set in 3D. Thanks to asplech's blog about involute gear and this Spur Gear document, I finally get to know better about these cogged wheels.
Following the circle involute blog, I thought about creating a gear procedure for easy creation of different gears. The method used is quite differnt to the involute idea but the turtle geometry way of thinking and doing the gears. This prototype procedure utilised a simple regular poygon formula (repeat :sides [ fd 1 rt 360/:sides ]) and some built-in commands such as TOWARD and SETHEADING to rotate the turtle and get the directions needed.