Repair Job using weld

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Hello thereRight we have a big problem.we currently manufacture large parts for the oil rigs.and we have a problem with one of the parts.its 406mm x 406mm by 191mm square block.our problem is that one of the boys has faced one of the parts down to 401mm x 406 mm by 191mm.so we have a block there that is 5 mm under the size.my question is, is it possible to weld the entire face to add say 6 mm of weld across the face and then face it using the horizontal mill?im sure its possible but i need to know what sort of things to look out for. Also im trying to do this without there being any signs that we have done this. Is it possible? or am i just dreaming.the other options i have is possible bolt a 5mm plate on to it using countersink screws and welding around the edge and over the screws, then try to blend it all together.im a CNC Mechanical Engineer and i know a little welding, but i think it will be somethign i would send off to another company, but i just want to know if its possible and there not just gonna laugh at me like im thick.anyway if anyone can give me some information on my problem then i would be very gratefulThank you for your timeFraser
Reply:how much stress is the part going to be under? and if i'm not mistaken, milling through a weld is tough the rapid heating and cooling of the metal during a weld  distorts the physical properties and hardens the metal. it wouldnt be impossible, just tougher than regular steel. i don't think you would want to try and fill 5mm across an area that large(164,836mm sq.)your other i think is a bit better. but rather than using screws, do plug welds. plug welds will hold much better than the tiny screws you would have to use. i would try and use maybe a 10mm plate and mill it down so that you have room to work when milling down the face to hide the welds.those are just my thoughts. i'm going to school for this kind of stuff and i'm only in my second year, so i'm not an expert, but if this was a problem presented to me on a test, thats how i would answer it.
Reply:You should be able to weld and machine without a problem.  We have a few members that do this stuff every day...zapster redoes stuff as big as all outdoors and machines the surface so that it looks as good as new.  I have several welding texts that detail the process of building up and resurfacing all kinds of stuff...it gets done all the time.  Send zapster a personal message and get his advice on this...my guess is that with a picture or two, and a good description of the metal involved, you will have a solution.  Base materials matter in how you do it, but if I remember correctly, there aint many metals that leave you SOL.Last edited by smithboy; 10-31-2006 at 03:01 PM.Smithboy...if it ain't broke, you ain't tryin'.
Reply:Smithboy...You give me tooooo much credit.. well in my best guesstimation,the part should not warp / distort because of the size anyway..The only trouble i see is in the "make it look like nothing happened" deal..the hard part is welding around the edges..and that has to be done FIRST..once the border is done then filling the inside is just time consuming.. when doing the edges weld with the lowest heat setting possible to keep the "undercut" down to a minimum..Stick weld it with 7018 rod..3/32 for the edges and 5/32 for the surface..only use as much heat as needed..your not welding something together that needs strength..after each pass chip and wire brush..make sure the weld overlaps the previous weld by 1/8" so you know there will not be any "missed" areas..Option #2 is what you suggested in the begining..a new plate about 7mm thick is the answer..instead of flat head screws, drill a bunch of 1/2" holes in it and weld the holes up...put holes in the corners and then space them out in 3" X 3" spaces..MAKE SURE YOU CLAMP IT DOWN REAL GOOD before you start welding..gotta keep it flat yaknow..then re-machine the surface to spec..i do this stuff all the time..a good welder should have no trouble at all with it.. good luck.. ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.