It won't be cast at that thickness, but like said of its flat enough it will be suitableAt a quess 6-7mm. If it turns out to be cast will it still work? I've never used a table always earthed straight to the work!
if it is cast, your weld tacks with m/s rods will only just hold-not much resistance to breaking.Great news! I'd love to be able to upload photos but me and technology don't have the best relationship! Haha. What do you mean by webs? One side is flat and one side has diamond patterning on it!