Today's "What is it?"

[Superburban]

I jst haven't ever had any interest in messing with gas engines, so it's brand new territory for me.

Now you have a reason, start looking for a small engine to rebuild.

 

[Lo-Fi]

Yep, valve seat cutter. You put a mandrel in the valve guide bore and the cutter rides on that. The machine drives the cutter via the hex with a flexible coupling. Means you don't have to faff setting the machine lined up perfectly central or concentric with the valve guide.

 

[hman]

Makes a lot of sense. Thanks!