Suppose I want to weld a box and fuse the inside corners as well. How do I go about adding filler metal in those tight corners where 3 sheets meet? There obviously is no room for adding filler metal under the standard angle.
As you approach the corner, add a little more filler than normal, then withdraw the wire, and use the arc to pull the excess filler into the corner. Once past the corner, continue to add filler as normal.
Does anyone know why it is so important to add the filler metal under the prescribed angle? I mean, can’t you play and fiddle with the angle a bit (or a lot) so that you have easier access to those hard to reach places. If you do tamper with the angle, would you seriously compromise the weld quality?
The fillers angle of attack isn't going to effect weld quality directly. If the filler is introduced too steeply it tends to melt and ball up before reaching the puddle causing a mess. As long the angle is kept low filler can be added from the side for example
For accessibility you can just bend the end of the filler to keep your arms from getting crossed up. Picture a tube to plate fillet weld that you can't move around- to get the filler in at the rear of the joint your filler arm is going to be across your body, close to the torch hand and the filler is gonna be 'sprung' against your body but if the end is suitably bent...
the weld becomes a lot easier, especially if there are other obstacles around too