Basics of joints

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Beginner here, and wondering if there is a rule of thumb on good, better, best joints for general fabrication with guidelines on which to use, why?For example, I assume 45 degree miter joints are stronger than a butt joint, similar to woodworking.  Correct?  If you imagine a recatangle cube, is it stronger to place the tube in a lap joint? or butt them up so it's seemless without overlap.
Reply:Strength usually goes by weld length. A straight butted corner has less weld length than a mitered corner does. If you are coping angle, then that has even more weld joint length than the mitered corner does.Note however that in many cases it doesn't take a huge weld to exceed the strength of mild steel. Anything else is "extra". That extra can be both good and bad. It gives you more places to screw up, but it also helps spread out the stresses so a "bad" area isn't as strained.Some joints also help to resist other forces. A socket type weld would be more resistant to bending than just butting two tubes together and welding them for example..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Fillet welds are the typical joint configuration of structural erections but the weld strength is solely dependant upon the filler metal used. Far as mitering/butting/coping corners of angle iron frames, butting is a horrible idea. Cope or miter the corners for full strength. I would miter then because there is less grinding and less welding.-Hillbilly