I made a 3/8" box joint jig and have it mounted on an Incra miter guage. I am using a Freud dado blade on a 3650 TS. This is my first attempt at making drawers. I have been working with scrap 3/8" scrap stock for practice. As I go across the 3 5/8" width, I find the slots are getting tighter across the stock. The pins all measure 3/8", I have moved the key closer to the blade to increase the slot width. The distance between the pin and blade is approximately 19/32". What am I doing wrong?