Most of the things I build are cube-ish frames, made from 1/8" thick angle iron. These typically are formed by 12 pieces cut to length, and then 45s cut into both edges of both sides. I use a Dragon Wagon and (Table Kit 2) fixtures to secure the material to the table. I’ll use a pair of 1" tall shims under each piece of angle, and use either a Quick Clamp or a Swivel Plier to hold it, pressing down exactly over top the shim under it - to prevent bowing. For two of the sides, I use a pair of table blocks (positioned oppositionally to prevent block lean). The other two sides are held in place with Extension blocks/Tooth Blocks for the additional adjustability - always with at least one tacking bolt to ensure fixture rigidity. I’ll tack these 4 pieces together as the top of the cube, allow to cool, then repeat the process with the next 4 pieces to form the bottom of the cube. I’ll clear out all the fixtures and redesign the layout to allow the top form to sit fixtured to the table upright, the bottom form will be set in a mirrored stance across from it, and I set in 2 of the 4 “stringers” that connect the Top and Bottom forms. Tack, allow to cool, then rotate the entire form 180 degrees so I can attach the last 2 stringers to form my cube.
This works pretty well at tacking the cube together. Most of the time, I can take my completed cube, place it on empty table, and try to test for flatness and I’ll get no “teeter-totter” (probably a better term for it) on any of the 6 sides.
Then I go to actually fill in the welds and all bets are off. Using as many fixtures, shims, and clamps as I had in the kit, I always seem to warp. I’ve watched Jason’s videos about the order I should do the welds - and followed it - but its always seemed that I’m short on clamps. I recently added four 13" Extension blocks, plus 6 C-Clamps, and 6 or so locking C-Clamps. The form gets so busy with clamps everywhere that even a 20"+ cube gets a crowded and tough to get up inside with torch and helmet on.
Going with idea to try to have 2 clamps on every surface (in other words 4 clamps holding each piece of angle) to 2 immoveable plains (table and fixtures) seems to have helped. I’m also allowing some cooling (not very scientific with my testing here, but when a laser thermometer says no point of or around the weld is above 130 degrees - that’s cool enough) before I remove any clamps. In this cube scenario, I’d have 4 table blocks and 4 Extension blocks positioning the cube on the table. 8 one inch shims between the cube and table, with Quick Clamp or Swivel Pliers holding them in place.Now I can add two 13" Extension blocks to 2 of the 4 lateral sides of the cube. I’ll clamp the “stringers” to the Extension Blocks in a high and low spot. Each corner will need a total of 4 beads I need to weld - going from center out. I’ll do one corner, then the opposite corner. Once the laser thermometer reports the hottest weld is down to 130 degrees, I undo clamps and flip it. Once I’m done, I’ll grind down any weld that may have fallen through a gap - or is otherwise exposed to the outer plains of the cube.
Even with these extra clamps, I’m still not reliably creating cubes that are as straight/square/flat/plumb as I would like. Still a little teeter-tottering.
I’ve only got about 5 years experience as a hobbyist - so I’m sure my form or method can be improved. If I need to add more clamps to these forms, IDK how I’d be able to get up inside the form with a helmet.
Any experts have some free advice?