Well I am not sure Pat. He pushes 3/4 stock through it into the router which gets it to 3/8. As it catches the pick up block going out it is still 3/8 but has three other blocks of hardwood, I assume with different gradual hole sizes that compresses, burnishes and when done, no sanding or anything, just a good clean 11/32 shaft. I am just going to have to try some different woods to see how it works. Got the side rails and the pick up hole blocks cut today, no looking for some hard wood to make the other blocks.