I recently made a new workbench for my shop. The top consisted of several layers of MDF. After gluing the MDF panels together, I was faced with the task of trimming the ends to length. The benchtop was too big and heavy to run through the table saw. And it was too thick to make the cuts in one pass with a circular saw. Instead, I used this three-step process using my circular saw and router with a flush-trim bit installed.
First Cut
Using a straightedge, I set the circular saw for its deepest cut. I then made the first cut to final length.
Second Cut
Now, simply flip the workpiece over and reposition the straightedge so that the second cut is slightly longer than, but just overlaps, the first cut.
Clean Up
With your router, set a flush-trim bit so that the bearing rides against the first cut you made. This will leave a perfectly smooth edge.
