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Hi Red, The dump bed will have alot of stress in the bed sheeting from fabrication and only gets worse as the bed is used. This means when the bed is cut, metal is going to move, alot, and be very difficult to realign. To help stop this, pretack weld some 1/4" x 4" bar stock on the outside of the bed skin on both side of the joint, leaving about a 1/8" gap between the bars once refit. This lets you use finger grips on the 4" bar to set the joint gap for welding. I would cut the skin with a cut off wheel on a 5" Makita side grinder. This will leave a almost preped edge for fit up after cutting. Preclean the base metal before cutting and marking as it will clean eaiser than after it's cut. Use steel wedges with dogs to align the skin surface working from inside the bed. Rule of thumb for tack weld spacing is 50times metal thickness maximum. If the sheeting has more than average stress then I will tack weld considerable closer, every 3/4" working on 10ga and sometimes on 1/4". You want to leave a root opening 1/2 the metal thickness as this allows the skin to shrink as the joint is welded without warping the skin. Skip weld the joint from the inside. When the inside weld is conplete, then take off the 4" bar stock, then peen the weld with a single jack on the inside while using a double jack hammer on the outside as a dolly bar. This will stress relieve the skin before the outside is welded. Think of the outside weld of more for "looks" than a structual weld. To much heat here can cause the metal to "pouch" or "V", to the outside. T_Bone
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