I've seen a lot of people building frames against a piece of plywood or even OSB and I was wondering if the jig I plan on building will have any advantages/disadvantages to the board jig.
Working in apartment maintenance I've amassed a pretty sizable collection of bed frame angle iron, I can never let a piece stay in the dumpster because it's so darned handy and free angle iron is great.
I plan on laying down two lengths parallel then bolting them to some 3/4 fiberboard and making fixtures for the rear dropout, crank tube and building a triangulated head tube brace out of a fork. Basically the fixtures will bolt to the frame and be able to slide along the angle iron rails and clamp into place so once I cut the frame in two I can just slide the halves apart to my final length then lock everything down to weld in the new tubing.
The main advantage I can see is I will be able to weld both sides of the frame without removing the frame from the jig.
you can make a jig out of just about anything, but it needs to be stronger than the frame you are building. i have yet to build a jig for a bicycle frame, but i have built a few harley frames on this boat anchor. the way i figure it, if you can build the jig, you can build the frame.