The cutting boards started out as rough-cut slabs of walnut and maple. Among other things, they went through a Delta jointer, then a Powermatic planer and then sanded with a Milwaukee ROS (generally moving only with the grain direction). I started with 80-grit and moved to 120, 150, 180 and 220. Between each grit I used a sanding block (again with the grain) wrapped with the corresponding grit. They were finished with Butcher Block Conditioner, and you can see faint, diffuse lines that run perpendicular to the grain.
The other project is a plant stand top (I only took pictures of the back). There, I started with dimensional lumber from Lowes (red oak). I sanded it with a Makita ROS with the same progression of grits and same mid-grit hand sanding. It was finished with a MinWax oil-based stain. You can see somewhat sharp lines that run perpendicular to the grain.
Any idea what I’m doing to put the lines in? How to avoid them or remove them before finishing? And how do I know they’re still there or gone before I start finishing?