Handlewanker, christoferIn my very humble opinion, a mill comprising of a fully welded and braced steel plate box section framed body would make a far more interesting design,
If you welding together, using thin plate (maybe <0.5 in) you need to stress relieve.
That is true, I experienced like that on my previous build. Use thick plate or steel block and bolted together is cheaper and faster way and alot heavier.you have any trouble with warping or inaccuracy of the rail supports