How to Build a Brush Cutter

Drain all gasoline and oil from the mower and leave the cap off the gas tank for 30 minutes.
Measure the vertical distance between the upper surface of the blade and the underside of the cowling or cover on the mower.

Remove the blade from the mower with an appropriate-size wrench.

Set the mower on a work surface that can handle torch use in its vicinity or near its surface.

Draw a straight line across the entire front of the mower's upper surface. It should be 3 inches forward of the blade spindle and parallel to the axels. Mark it with a straightedge and permanent marker. Draw another pair of lines perpendicular to that line, 2 inches from the front wheel connections on the mower and extending forward from the horizontal line.

Cut along the 3 lines with the torch to remove a front quadrant of the cowling or cover of the mower. Use a heavy file to clean up the edges.

Place the blade in a steel vise and measure and mark a point midway between the center of the hole in the blade and the blade tip. Do this on both ends of the blade. Use an acetylene torch to heat the midpoint of the blade to a steel-work temperature -- recognized by its cherry red color. Use a heavy hammer to pound an angle that effectively lifts the blade about an inch from its previous vertical when mounted in the mower. (Note: this distance must not allow the blade to come within less than 1/2 inch of the cover.)

Mount the blade on the mower and check its blade height in relation to the cowling or cover. If necessary, reheat and adjust the cant in the blade.

Refill the fuel and oil tanks on the mower and start it. Check for excessive vibration -- indicating a needed adjustment in the blade cant. If it is vibrating badly stop the mower, remove the blade and hold it level to determine the source of the vibration. Reheat and alter the blade as necessary.