How to Make the Perfect Miter

How many times have you... throne a piece of trim away because it would not fit?

Cut the perfect miter using an electric miter saw and using wood shims. First, check to see if your door or window frame sets out Passed the finish wall or sets in from the finished wall. You can use a straight edge to check.

Set miter saw at a 45-degree angle and lay the trim on the Saw table, if the frame sets in from the finished wall put a Shim under the thick edge of the trim next to the fence. (Example if frame sets in 1/4” then use a 1/8” shim under the thick edges of trim next to fence and make cut.)

If the frame sets out from the finished wall put a shim under the thin edge of the trim away from the fence.

If the frame is flush with the finished wall, I use a 1/16” Shim under the thin edge of the trim Away from the fence. This gives back relief to miter cut.

For windows I start with the bottom trim first, miter both Ends as required and install. Next miter left and right Sides as required and install. Finally, measure and cut top Trim.

For Doors, start on one side then the top and finish on the other side.

TIP: After I install the first piece of trim I take a scrap piece of trim and make the cut as required. Butt it up to the First piece of trim to check the fit, if the fit is good then make the cut on your next piece of trim. If the miter doesn’t fit you may have to use a thinner or thicker shim. Just practice using scrapes of trim and you will master the idea. The object is to cut the trim as it will set on the wall and frame.