Place the angle iron rails parallel to each other in the diameter of the largest logs you plan to cut, from 20 inches up to 36 inches. Weld 1/2-inch-thick steel plates every 5 feet, leaving at least a 3-inch overhang on the plate facing outward.
Drill two holes into the overhang of the metal plates, one close to the angle iron and the second about 1 inch away from the other hole.
Set the angle iron rails into 2-by-4-inch boards, with the second hole in the steel plate overhanging off the wood. Place screws into the first hole in the steel plate that is closest to the angle iron rail.
Drill the screws into the wood to secure the angle iron rail.
Drill holes into the ends of the metal support beam. Place a flat-head bolt through the second hole in the steel plate and into the metal support beam.
Twist a nut onto the end of the bolt. Tighten with an adjustable wrench.
Set the cutting apparatus and the power unit onto the angle irons rails. Tighten the fasteners enough so that it can roll up and down along the angle iron rails.
Make the log holders, also called log dogs, by placing rebar into a vice clamp.
Set the welder flame 8-inches up the rebar from the end. Heat the rebar until it turns red hot.
Clamp a plumber's wrench on the rebar, and bend until you make a 90-degree angle. Do the same with the other end of the rebar.
Grind a blade shape into the ends of the rebar, using the angle grinder. Pound the blade edge into the logs with a hammer, as you hold the log in place while sawing.