DIY Bush Hog

A bush hog is a farm and garden implement used to cut brush and heavy grasses. These are both walk-behind and tractor-towed machines that can cut saplings up to several inches in diameter. Bush hogs are often dual- or triple-deck assemblies, but smaller ones are comprised of only a single spinning blade. Commercial bush hogs are high-performance machines, but they can be pricey. For beginners in the area of clearing heavy brush, making a bush hog by converting a heavy lawn mower is often the ideal solution.

Tape measure

5-hp lawn mower

Wrenches

Socket set

Straightedge

Permanent marker

Acetylene torch and tanks

Heavy steel file

Steel vise

Hammer

Select a 5-hp heavy lawn mower as the candidate of conversion. Drain the oil and gas from the mower, and leave the cap off the gas tank for 30 minutes. Flip the mower over and measure the vertical distance between the upper surface of the cutting blade and the underside of the mower's cowling or cover.

Use a wrench or socket set to remove the blade from the mower.

Place the mower on concrete or another work surface that can handle torch use in its vicinity.

Use a straightedge and marker to draw a straight line across the front of the mower's upper surface. Make it 3 inches in front of of the blade spindle and parallel to the axles. Draw a pair of lines perpendicular to that line, 2 inches from the front wheel connections on the mower, extending forward from the horizontal line.

Use a pencil-flame nozzle on the acetylene torch to cut along the three lines, and remove a front quadrant of the cowling of the mower. Use a heavy file to clean up and smooth the edges.

Set 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. Mark the same spot on the other end of the blade. Use a 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 outside half of the blade about 1 inch from its previous vertical position when mounted in the mower.

Mount the blade on the mower and check its blade height in relation to the cowling or cover. The vertical measurement of the distance between the top of the blade edge and the cowling should be the same on both ends of the blade. 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. If it vibrates 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.

Remove the handlebar from the mower and set it up to be towed behind a tractor. This is optional, and varies by both the make and model of the mower, and the tractor's towing hitch. Most mowers have a two-part handle that can be disconnected and welded to an assembly that connects to the tractor. If not, use a torch and cut the mower handle level with the tractor hitch, and weld a yoke or a standard hitch to it.

For saplings over 1 inch in diameter, cut a custom blade from 3/8-inch steel bar stock.

Use caution when working with power tools.

Do not walk directly near the front of the bush hog while it is running.