No I polished them from 600-1600 grit sandpaper wet
They are lubricated with graphite.
We followed the Mark Rober video
He also mentions a boeing engineer who did most of the science work. I have that video (purchased for my oldest to watch when it was his time) and my youngest watched it but it was a bit much for the kid. Next year we will do more with that video but I'm just using this to stretch his scientific knowledge and such. I mean how many 9 year olds do you know that can talk about potential energy, kinetic energy and other such things?