Question on repairing a shaft

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I have a shaft out of a combine, it's about five feet long 2 1/2" diameter  has splines on booth ends. The problem is the brg. on one end got loose and cut into the shaft about 1/4", this is behind the splines and about a foot from the end of the shaft. I told the boss we could probably have it welded up and turned and be good as new, I checked and could cut about any place on the shaft with a file easily.Well he came back from the machine shop and said they told him it couldnt be done as the shaft was hardened and would break right beside where ever they welded on it. Is this true or did they just not want to do it?I have welded up a lot of small shafts, even spliced two to make one longer and never had any problems before.
Reply:I think it can be done, but its gonna be hard to keep it straight.   If you can file it, try the spark test and weld away.  A positioner would be nice.  We would chuck em in the lathe with the ways protected and weld them that way.  Just like a driveshaft.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:You should consult with Zap on this one.  He's the king of building up and machining down parts.  If it can be done I'm sure Zap can tell you.  Pics would probably help.Michael
Reply:If it's a splined shaft the splines may be the only part of the shaft that's hardened which may or not include the bearing seat. The shaft itself may be 4140 which is hard but can be welded as long as you pre/post heat enough. As said above the most difficult part may be keeping it straight. Price and time wise it may not be worth the effort though.
Reply:The other thing you can do is to cut the bearing seat down and then sweat fit a sleeve over it. keep the cut to a minimum so you only have about a 1/8' to 3/16" sleeve thickness. Ice (co2) and heat the sleeve for a super tight fit then turn the sleeve for brg fit.
Reply:Thanks for the replies, the machine shop that he took it to has all sorts of large lathes and figured he could weld it and turn it too.I could weld it, but as you said without a lathe it would be hard for me to keep it straight.I'll try to get some pictures tomorrow.
Reply:There are alot of variables here.  Which shaft in the combine is it.   Depending on the usage, the way it is loaded, as well as the material of the shaft will decide if it can be done.  I build up shafts on a weekly basis on Ag equipment.  Ag equipment repair is 90% of my work in my shop.  A few things to think about is if the shafts breaks what will be the extent of the damage.  How much down time will it take to repair when it goes?  Sometimes its just not worth chancing it.   Also how much is the replacement shaft?  It is possible that it could cost close to or even more than the new one to repair the one you have.  The hardness of the shaft now is not the problem.  How it will get after welding is the key.  Some shaft material will crystalize when welded and become very brittle. 1045 shaft will do this I have found.  Don't ask how I found out.    If they are a reputable machine shop I would take them at their word.  Just my opinion.  ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:10 to 1 Its only hardend by the splines and its only case hardned at that..If the whole shaft was hardned all the way thru it would snap in no time...If a file "cuts" into it then its not hard where you put the file to it..My answer is do it..But do a pass on one side then flip it over fast and do the other..Like this..12:00 first pass..6:00 next pass..3:00 next...9:00 next..Then fill in the rest of the o'clock positions..That keeps the bending in check..Repeat untill done and make sure the weld is higher than the shaft so you won't have to re-fill the areas that are still small..Have fun!...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.
Reply:I would use cold weld rods and only do short passes and let it cool before anothe pass... It might take you forever to get it done but it wont hurt the shaft...