Cutting MDF Corners

• 1). Place your MDF crown molding upside down on the base of your miter saw. Place the top of the molding flush with the base of the saw, and the back of the molding flush with the fence of the saw.
  
  
• 2). Measure the wall on the left side of the inside corner. Position the crown molding to the right of the blade. Measure from the right end of the molding and make a pencil mark on the bottom of the molding, which is currently pointing up, at the same distance as your wall measurement. Set the saw to 0 degrees and cut the MDF.
  
  
• 3). Measure the wall on the right side of the inside corner. Place a different piece of MDF crown molding on the saw, aligned in the same way as the first piece. Position the molding on the left side of the saw and mark your measurement from the left end of the molding. Position your miter saw to the left at 45 degrees, and make the cut.
  
  
• 4). Move the crown molding piece you just cut to your table and position it so the cut end is hanging over the edge. Make a pencil mark along the top of the cut, just under where the face of the MDF is. This line will help you visualize your coping cut. Take your coping saw and cut away the bevel on the end of the crown molding. This cut will allow this piece to fit flush against a non-beveled piece of molding. Be sure to follow your pencil mark as you cut.
  
  
• 5). Cut outside corners with the MDF molding situated upside down, just as you did with the inside corners. For the right side of the outside corner, position the molding to the right of the saw and set the saw to the left at 45 degrees. For the left side of the outside corner, position the molding to the left side of the saw and set the saw to the right at 45 degrees.
  
  

Installing MDF Crown Molding

• 1). Use a stud finder to locate the wall studs and ceiling joists. Place a piece of painter's tape on the ceiling and wall a few inches from the corner between the two areas, directly over the center of each stud or joist.
  
  
• 2). Hole the first piece of MDF crown molding in place between the ceiling and wall. Drill 1/16-inch pilot holes 1/2-inch in from the top and bottom of the molding, wherever it intersects a stud or joist.
  
  
• 3). Place an 8d nail in one of the pilot holes and drive it in with a hammer. Once the nail is almost all the way in, place a nail set on the end of the nail and hit the nail set with the hammer. This process will allow you to countersink the nail without damaging the MDF molding.
  
  
• 4). Apply wood filler over the nail holes and in any gaps in the corners. Scrape the filler with your finger to make it even with the rest of the MDF molding, then sand it down flat by hand using a sanding block.