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How to Cut Wood Beams

Shane Grey

If you incorrectly cut a wood beam, you might need to buy a whole new one. When wood timbers cost upwards of $10 per foot in 2010 prices, buying more pieces than you need becomes a big deal. Fortunately, you don't need a sawmill to properly cut wood beams--with proper planning and care, even your average circular saw will do the trick. Save money and time by making the first cut right.

A wood beam, also called a "timber"
  1. Determine the beam's final length and use a tape measure to mark the measurement on the beam's surface. Hook the tape measure's tang onto an end of the beam. The tang is a metal clip at the end of the tape.

  2. Stretch the tape the desired measurement and use a pencil to draw a "v" shaped mark on the beam's surface. The intersection of the "v" mark's lines should point directly at the desired measurement. Carpenters call the "v" mark a "crow's foot".

  3. Lay a framing square's broad side flat on the marked surface of the beam and butt its lip against the beam's edge. The framing square forms a triangle--one side features the lip that now rests parallel with the beam's edge, another side runs at a 45 degree angle from the beam's edge and the last side runs at a 90 degree angle from the beam's edge.

  4. Position the "straight" side, or 90 degree angle side, directly over the center of the mark made in Step 2. Run a pencil along the straight side of the square to draw a mark that runs across the entire face of the beam and directly through the center of your mark. Remove the square from the beam.

  5. Flip the beam, rolling it away from you, to expose the face of the beam adjacent to the marked face. Lay the framing square on the upward facing side as in Step 3. The lip that holds the square snug to beam's edge extends slightly onto the adjacent face--the previously marked face. The end of the lip should be precisely square, or "in-line" with straight edge of the square's triangle.

  6. Position the framing square so that the end of its lip rests directly over the line marked in Step 4. Run a pencil along the straight side of the square and across the entire exposed face of the beam. This line is a direct "transfer" of the first line and more reliable than marking each face with a tape measure.

  7. Flip the beam and transfer the line to each of its two remaining sides.

  8. Put on your safety glasses and gloves. Cut through each of the four marked sides of the beam, directly across the lines, with the circular saw. Cut entirely through a face, flip the beam, cut the adjacent face and repeat until the waste portion of the beam severs from the rest.