How to Cut Octagonal Moldings

Octagonal molding is used almost exclusively to trim around octagon windows.

As its name implies, this type of window has eight sides, so trimming it out can be very tedious work. With the proper tools and the right angle measurement, though, these pieces can be cut out and fit together to go perfectly around a window.

Count the number of sides on the window to make sure there are eight and divide 360 by 8 to get the measurement for each angle that will need to be cut.

Run a tape measure along each side of the octagon to record the measurement. All measurements should be the same length, but verify just to be sure.

Measure out the distance for the first piece on the desired type of molding. Mark it with a pencil. Slide the piece of molding into the miter saw and turn the blade of the saw to 45 degrees in either direction. Plug in the saw and line up the blade with the mark on the molding. Turn on the saw and pull on the lever to bring the blade down through the molding to completely cut the piece. Release the lever and let the blade go back up to turn off the saw.

Mark the next piece at the same length and turn the saw to 45 degrees in the opposite direction. Cut the molding in the same manner as the previous step and line up the two pieces to make sure they fit together properly.

Cut the other six pieces of molding the exact same way, making sure to turn the blade of the saw so that there are four right-handed, 45-degree angles and four left-handed 45-degree angles. Line up all of the pieces in the octagon shape around the window to verify that they butt together properly.

Things You Will Need

  • Safety goggles
  • Tape measure
  • Miter saw
  • Pencil
  • Molding
  • Paper

Tip

  • The number of sides is divided by 360 because that is how many degrees a complete circle is and this number also equals the number of degrees an octagon would have.

Warning

  • Always wear safety goggles when working with a compound miter saw to prevent wood or other material from entering your eyes.

About the Author

Alexander Callos began writing in 2005 for "The Lantern" at The Ohio State University and has written for various websites, including Bleacher Report, Top Ten Real Estate Deals and Columbus Sports. He has published articles for CBS Sports, SI.com and other websites. He graduated in 2007 from The Ohio State University with a bachelor's degree in public affairs journalism.