How to Make a Crown Molding Jig


Crown molding often frustrates beginners because the compound angles involved can be confusing. The molding sits at an angle with the bottom against the wall and the top against the ceiling. The back of the molding is cut so it rests flat against the wall and the ceiling. The angles required for cutting don't seem to make sense either. The angle at which the crown sits might be 45 degrees, or it might be 38 degrees. A simple solution is to place the crown molding on the miter saw at an angle and cut it at a 45-degree angle using a jig.

Things You'll Need

  • Tape measure
  • Table saw with fence
  • 3/4-inch plywood
  • Miter saw
  • Scrap crown molding
  • Wood glue
  • 1-1/2-inch wood screws
  • Pencil
  • Drill with countersink bit and screwdriver bit
  • Clamps
  • 5/8-inch wood screws
  • Measure the width of the fence on your miter saw. This determines the jig's width. You can add a few inches to the jig's width if your miter saw has a very small table and fence.

  • Measure the miter saw slot the blade fits into when you lower the blade. Measure from the fence out toward the front of the table. Add 2 inches to this measurement to determine the jig's table depth.

  • Place a scrap piece of crown molding against the miter saw fence with the ceiling side resting on the table and the wall side resting on the fence. Ensure the flats on the back of the molding rest perfectly flat against both surfaces. Mark the fence where the crown top ends. Remove the molding and measure from the table to the mark. Add 1 inch to the measurement for the jig's fence height.

  • Cut three pieces of plywood on the table saw. Cut one piece to the jig's table depth, another to the jig's fence height, and another at 1-1/2 inches. Cut the length of each piece to the jig's width determined earlier.

  • Lay the jig's table on a flat work surface. Stand the jig's fence on edge and against the jig's table to make an "L" shape. Drill countersunk pilot holes through the back of the jig's fence into the edge of the jig's table. For safety, do not put a hole or screw within 2 inches of the center point where the blade will cut. Run a bead of wood glue between the two pieces and screw them together.

  • Place the scrap piece of crown molding on the jig with the top part against the table and the wall side against the fence. Get the alignment of the molding flats perfect on both surfaces. Place the 1-1/2-inch wide piece of plywood on the jig's table against the crown molding and draw a pencil line to mark its location from end to end.

  • Place a bead of glue on the back of the 1-1/2-inch plywood strip. Place the strip back on the jig fence and clamp it in place, aligning the strip with the line made previously. Immediately verify the crown molding is correctly held in place by the strip and make any adjustment necessary. Allow the glue to set up for an hour.

  • Screw the jig to the miter saw fence with 3/4-inch round-head wood screws. Place the saw table at 45 degrees left and make a cut down into the jig. Turn the table to 45 degrees right and make another cut. The jig is complete. To use the jig, place crown molding in the jig upside down and make your cuts.

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  • "Miter Saw Jig for Crown Cuts"; Workbench Magazine; December, 2004
  • Photo Credit Images
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