The art of Fabrication: Jig making

No matter the welding process you choose, whether it's MIG, TIG, Stick, or even Flux-Core welding, the key to fabricating success is a good jig. No, a jig isn't an Irish dance to bring you luck... It's actually a template that is made to hold or restrain metal in position while welding it. The jig is essential to making and reproducing the same weld over and over. It can be a time saver as well. Jigs are similar to a "negative" that a photographer uses to make a final picture. The way a jig is constructed, everything seems reversed.

Let's say you wanted a jig to make a square out of tubing that you needed as a smaller part of a larger frame, say a 4 sided box. Each leg of the frame would need to be held in a perfect 90 degree angle to the other, while the other legs were being welded, to prevent them from drawing from the heat. A simple jig may be nothing more than a few pieces of angle iron welded as an outline around the outside dimension of the square frame. The flat side would be turned to the inside. Then, the precut pieces of tubing could then be laid into the frame repeatedly without having to take second measurements. Then the pieces of tubing could be restrained to hold them in line with simple C-clamps clamped to the tubing and the angle until the parts could be tacked up. The edges of the angle iron need not meet at the corners of the square so that the tubing can be welded or tacked on the outside of the frame.

Rarely will a jig need to be made out of heavy metal. Most items welded in a jig will be only partially welded, so lighter material than the component itself, as long as it can do the job can be used. Scraps, and drops from the waste pile come in handy when making a jig. A little experimentation may be needed, so when constructing a jig, make sure everything is only lightly tacked at first. And most jigs never need full welding. If a joint needs a full, heavy weld on a jig, a second jig may need to be made to assure the jig components themselves stay in line. When constructing a jig, before and after ever weld, components pieces of the jig should be checked for warping or incorrect alignment. Never weld a jig all at one time. Allow time for each component to cool. Covering a jig with anti spatter spray is a good idea to prevent build-up of spatter, and material on the jig itself to prevent misalignment that can be caused by buildup of weld material.

Depending upon the way the jig is made, some jigs require a backing, others are made to be open. Some will have clamps, others will have restraining pieces that secure the sub component on either side. It's not uncommon to see a jig welded to a welding table in a welding shop. This is typically a heavy table with the jig components lightly tacked to its surface. Still others may be bolted to a special fabrication table or held with a special fastening system that allows the jig to be adjusted or created as needed. Others, may be permanently welded to a sheet of plate, if this jig will be used repeatedly for an extended period of time. If a jig needs a backing, it should be made out of good, true plate steel.

A jig can be one of the most stress relieving items in a shop that does fabrication. It can cut fab time down greatly, and serves as a method of quality control. If you never have made a jig, start with a small item, before tackling a larger one. Jig making is a skill that is learned. It takes a creative thought process and analyzing and visualizing of the finished product to be able to master it.