Simple in its design, the Ring Ruler allows you to make circles by deciding exactly what diameter you need. Its design enables you to make perfect circles (although irrespective of a central point) and the diameter can be increased (at increments of 0.06 inches) or decreased by just snapping the ruler at the desired point. BUY NOW!
Welding table with leveling feet. More
Welding tools (Think intergalactic asteroid mining anime sketch)
3-Axis Welders Welding Angle Clamp - From a post all about welding clamps.
Acetylene Torch Cutting Jig by Justin Edwards -- Homemade acetylene torch cutting jig constructed from angle iron, threaded rod, bar stock, nuts, worm clamps, and an electric drill. http://www.homemadetools.net/homemade-acetylene-torch-cutting-jig
Homemade metal bender constructed from flat steel bar stock and steel rods.