Lincoln 300D bearing / armature bad??

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I purchased a 300D a few years ago with around 3200 hrs on it for $3500.  Since then I have put a few hundred hrs on it.  It intermittently had 'electrical problems' that I traced to the brushes.  Now I found that the bearing at the front side (where the display is) is going bad and is wobbling.  Took it to a mechanic who worked on it and then said a machine shop would have to replace the bearing.  The machine shop said they could not do and subsequently a welding repair shop said they would probably have to replace the entire armature,  although they have not seen the machine.The est. price from him was $1800 for parts and $2500 total parts and labor.Is it true that a bad bearing can destroy the armature?  I want to make sure I'm getting accurate info.  Seems like a crummy way to design an expensive machine.  Why not have a removable part that houses the bearing???Any thoughts on this?  Thanks for reading.
Reply:A severely bad bearing might destroy the armature if it is so bad that it allows the armature and the stator to come into contact with each other, but the bearing would have to be extremely bad for this to happen, If it did happen the stator could be ruined as well. I'm not familiar with your welder, but the end cover with the bearing can be removed from smaller Miller welders to replace just the bearing and the entire welder does not have to be torn apart. to do it.  Our Miller 225NT only has one bearing in the generator. The motor end of the generator depends on the motor bearings for support. Since they haven't seen it yet they are likely just softening the blow by telling you about possible worst case pricing. The only way that you will get a more solid price from them will be to allow them to inspect it to find out how bad the damage actually is. Nobody is going to give you a good quote without an inspection.Good luck,CharleyHow about editing your profile to show where you are located. It's good internet manners.Last edited by CharleyL; 04-18-2012 at 05:47 PM.Miller MM252Miller Bobcat 225NTMiller DialArc HF / DIY Cooler2 Victor O/A TorchsetsMilwaukee 8" Metal SawMilwaukee Dry Cut "Chop" Saw 5 Ton Wallace Gantry Various Grinders, Benders, etc.
Reply:A bearing change for the most part can be done by yourself. A good puller and the replacement bearing( the old bearing will have the number on the race). Now if the housing is worn that will be more of a problem. A worn housing depending where/how it is situated "could" mean total dis-assembly to remove the worn part, but depending on how bad. A bad shaft depends on how bad, if slightly worn could be green locktit'ed, but thats just a quick fix. Eventually the shaft will need to be spray welded and ground back to tolerance. If the bearings we worn badly, that could explain the brush problem but also there would be a thinner and thick air gap for the fields as the armature is spinning. If there is a neutral position for the armature, you maybe able to feel if it has struck the fields or is rubbing there. If so that could mean alot or not that much work, depends on how badly the rub was.  An electric motor repair shop could also help in an opinion.
Reply:Thanks for the comments.Just trying to get a feel for the range of possibilities in terms of repair before I have the welding shop look at it.  The electric motor repair shop idea is a good one.Will give some follow up and / or pics when available.regards,dj
Reply:you might want to call bills welder repair in Oklahoma city and see what they have to say.   they are super nice people and great to deal with when it comes to Lincoln machines.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.