Hi all,

I am in the process of building a fabrication table 1200 x 1200 x 20mm thick and having sides extending down 200mm, also 20mm thick all round. I want to machine the top and 4 side faces true and square and have fixturing holes on all faces.

I am looking for advice for welding the table prior to machining as I haven't done a lot of heavy fabrication. I want to have a minimal weld bead to reduce machining costs and have good penetration for strength. I was thinking of welding the sides onto the top plate with a 3mm gap and a light chamfer ground on both edges, say around 2mm for the butt weld and fillet weld the inside. Does this sound reasonable? Also, what would be a ballpark amperage to start, I own a Esseti 320 amp synergic pulse mig. I will probably try welding it in single pulse to start with.

Thanks

I would clamp the sides down and build up a 6mm bead measured from root to the face of the weld on both sides, 50mm long bead, staggered, 50mm gap, the other side being the opposite. Gaps are great for insuring proper fusion (I hate the word penetration, welders don't penetrate), but having a gap is going to be begging for warpage and distortion, clamping it down is a better idea if possible.

I would use an ARC welder, 7024 rod 1/4" diameter, 200a.

If I was to MIG weld it, turn the welder up until you start to undercut, then back it down a bit. And don't be afraid to pre-heat, it never hurts anything and helps A LOT on thicker sections, even with steel.

MC

And for your butt weld, grind a V-groove minimum 80% deepth of the thickness to assure proper fusion if you can leave a gap, otherwise, grind a groove to full depth if possible, leaving just enough material to locate the 2 pieces.