This woodworking tool was bought at an auction. It has a cutter on handle and an adjustable stop, with a clamp for dowel. What is it for?
This is a valve stem face cutter. It is essentially the old time equivalent of a bench mounted valve grinder; used for the repair of valve faces of internal combustion engines.
You can see in the photo how the mechanism is set up. The valve stem is clamped firmly but free to turn with the blade and stop adjusted to the desired depth and angle of cut. The crank (inevitably separated from the unit over time) would hold the small end of the valve stem and the user would turn it with the face (part of the valve that nests in the seat) contacting the blade. Then, the user would adjust the depth stop incrementally until a clean face of the desired dimension is formed.