When installing large prefinished solid core doors it can be a very time consuming task cutting a door to precisely fit an opening that is less than perfectly square or out of plumb.
On one particular project I was building a house that required quite a few 8ft tall stain grade highly lacquered, mahogany doors. The doors and frames were built as close to our field conditions as possible then finished in a spray booth at the mill shop.
The door frames were installed before the flooring went in and wrapped to protect their finish. Once the flooring was installed the doors were brought to the site. We wanted to fit the doors to very close tolerances for the hardwood and stone floors.
Our goal was to provide the client with a very precisely cut door, splinter free edges, and no scratches to the lacquered finish.
The “Old School” way to rip a prefinished door is to first cover the face with masking tape so you do not scratch it with your saw. Then you scribe the cut line with a razor knife deep enough so that when you make your cut you avoid splinters. Next, you measure the backset on your saw blade and clamp a straight edge to the door allowing you to follow your knife cut. Once you have made your cut, you remove the tape coating from the door and clean the surface.
The solution was found by cutting a ¼” thick sheet of ridged plastic into 8″ wide strips and attaching a straight edge to one face. Next, we used a circular saw and ripped the plastic strip the entire length holding the saw base plate tight to the straight edge.
The guide was clamped to the door and the saw rode on top of the guide, never touching the door. The guide trapped the wood from lifting, splintering and most importantly, there were no scratches on the door.
We now had a guide that was custom fit to the saw. Wherever the guide was placed was exactly where the saw blade would cut. We just took our layout and prep time out of the picture without having to bring a track saw to the job!