How to Cut Mitre Joints

Step 1

1

Secure a mitre box to your work surface with screws. Mitre boxes are U-shaped guides that have angled slots on top so you can line up a saw easily. Set the mitre box on your work surface so it sits flat and locate the screw holes on the front and back. Feed screws into the holes on the mitre box and secure them to the work surface using a screwdriver or drill.

You can buy a mitre box from your local hardware store or online.

Variation: If can’t screw directly into your work surface, place a piece of scrap wood underneath the mitre box and screw into it. Clamp the scrap wood to your work surface so it doesn’t move around.

Step 2

2

Mark the line you’re cutting on your piece of wood. Find the length of the longest side you need for your mitred board, and measure the length from the end of your piece of wood. Draw a line across the board so it lines up with your measurement. Align the bottom of a protractor along the long edge of the wood so the line you drew points to 90 degrees. Set a 45-degree angle on the protractor, and trace the angled line to the other side of the wood.

Make sure the end of the angled line doesn’t extend further along the board than your initial measurement, or else the piece won’t be the proper size.

Step 3

3

Position the piece of wood in the middle of the mitre box. Slide the piece of wood through the middle channel of the mitre box so the finished side faces down. Continue guiding the wood until the guide line you drew aligns with the slots on the mitre box that have the same angle. Hold the piece of wood securely against the front side and bottom of the mitre box with your nondominant hand.

You can also clamp the piece of wood down with a C-clamp if you want to keep your hands free.

Don’t keep the finished side of the wood face-up since it won’t leave as clean of a cut.

Step 4

4

Line up a back saw with the slots matching the angle you want to cut. A back saw has a rigid top so it’s less likely to bend while you’re cutting. Position the side of the back saw closest to the handle in the slot at the front of your mitre box. Slowly lower the front end of the saw into the slot on the back side of the box that follows the same angle.

You can buy a back saw from your local hardware store.

You can also use a regular handsaw, but it may flex easier and make a crooked cut.

Usually, mitre boxes have 2 slots that are 45-degree angles and 1 slot that cuts at a 90-degree angle.

Step 5

5

Saw through the wood to cut your joint. Hold the piece of wood steady with your nondominant hand so it’s pressed firmly against the front and bottom of the box. Use long, slow strokes to ensure the saw doesn’t jump out of the slot or make a crooked cut. Continue cutting through the wood until you’ve broken through the other side. Remove the saw from the mitre box before you grab your wood pieces.

Make sure your fingers aren’t in the way of the saw blade, or else you could seriously cut or injure yourself.