If you cut out joint pieces that are supposed to fit together and the joint is too tight, that could be because your actual bit diameter is smaller than what you have told Easel. It also could be that your X and Y steps per inch are off.
Do the following…
Design a rectangle in Easel that is 1 inch by 2 inches. Place your bit in the router and tell Easel to cut on the line of your rectangle, not inside or outside. Cut your piece all they way through to the waste board and then measure it precisely with calipers.
Your rectangular cutout will be smaller than 1 inch by 2 inches by exactly the diameter of your bit. Subtract the length from the width and you will have the amount your X carve actually moves when it thinks it is moving one inch. If that is too big or too small, adjust your steps per inch accordingly and try again.
Also measure across the diagonal of your rectangular cutout. This will tell you if your X axis is square to your Y axis. You would think that you could just find the diameter of your bit with your calipers but the bit actually cuts a path slightly wider than the bit itself thanks to belt give, runout and a host of other factors.
When you’re finally ready to do joint work, don’t forget to leave a tiny margin for the fit and for glue.