Installing prefinished doors can be a very time consuming task. Protecting the finish is one thing, but cutting a door to precisely fit an opening that is less than perfectly square or out of plumb is usually a one shot deal. If you make a bad cut you can turn into public enemy number one, or be faced with starting the project all over again on a new door. That kind of drama could be the catalyst for an evening TV series but it’s hardly the kind of thing the average carpenter wants to be remembered for.
The “Old School” way to cut a prefinished door is to first cover the face with masking tape so you do not scratch it with your saw. Mark the cut line on the door, and 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. If you have to take off another 1/16″ you go thru the process again.
On one particular project I was building a house that required us to set quite a few 8ft tall, solid core, 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 with 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. I hate to tell you how much time was allotted for this task, and, it is not something you want to rush and take the chance of destroying with a bad cut. Needless to say we were always looking for a better, faster way to merely hang a door.
The solution was found by cutting a _” thick sheet of ridged plastic into 8″ wide strips and attaching a straight edge to one face to act as a fence. Next, we used a circular saw and ripped the plastic strip the entire length holding the saw base plate tight to the fence.
The guide was then clamped to the door and the saw rode on top of the guide, never touching 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 or a rail saw to the job!Since the guide was clamped to the door, it trapped the cutting surface. Just before cutting the door we took a razor knife and scored the door along the cutting edge of the guide. We dramatically reduced the amount of surface lifting, splintering and most importantly, there were no scratches on the door.The process for cutting doors with this guide set up was now about a 5 minute job.
From that point on the guide was dubbed “the door trim guide”. It wasn’t long before the crew started finding more ways to use them. Pretty soon they were making quick work of cutting counter tops, ripping plywood and wet sawing concrete. Door Trim saw guides are available in 4 foot and 8 foot lengths.