What is Back Cutting

A Back Cut is Commonly Used When Installing Trim

By Mark J. Donovan

Question: Mark, In your video on “How to Cope Inside Corners with a Coping Saw” you mention a term I am not familiar with, “back cutting”. Can you please clarify what back cutting accomplishes?

Answer: E.M., when installing any type of trim molding, such as baseboard trim or crown molding, back cutting is a commonly used method for ensuring perfectly tight joints along the front edges of the seams. The process of back cutting can be done using a coping saw or miter saw, depending upon the type of cut you are making, e.g. a coped cut or a mitered cut.

The process of back cutting simply involves cutting a little more off the back side of the cut so that there is less material towards the rear edge of the trim piece.

By removing slightly more material from the back side of the trim piece when making the cut you ensure that the front side extends out such that only the front edges of the two adjoining pieces of trim actually touch. This enables a tightly joined seam.

To make a back cut with a coping saw, you simply position your coping saw over the line on the trim piece that represents your outer edge, and then back cut at a 45 degree angle. The front edge should then lead the back trailing edge when the cut is complete.

Similarly when making a back cut with a miter saw, if the required angle is 45 degrees you want to steepen the angle one or two degrees so that the cut is actually at 46 to 47 degrees. This will ensure that the front edges of the adjoining trim pieces fit together perfectly at their outer edges.

Yes, there will be a slight gap towards the back, however you can minimize the gap by limiting the back cut to just under 46 degrees. Also, caulk or wood filler will hide any slight gap towards the back of the cut.

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