welding a center into a bullgear

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Hey guys, I have a dilema here, I need to weld a center into a bullgear for a grain elevator leg.  The gear is about 24 inch diameter with a center that is about a 2 inch hole.  The center piece has the same 2 inch with a shoulder - a hole in it that is about and inch and a quarter in diameter with the keyway cut in.  The cut down shoulder part is the thickness of the gear, about 3/8 inch thick. My worry is; what is the best way to weld the center in?  I am afraid of screwing up and getting a warp in it, distorting the center or keyway, or what ever else I may not be seeing.  Since this is a fairly critical part to be welded up and seeing as how it sits about 150 feet in the air and runs 300 plus foot of grain belt, I don't want a problem.Any idea of what process to use - mig or stick or tig - what rod and heat would be best - any other information you have would be extremely helpfull!!!I know that for the most of you out there, this is boring stuff But I really appreciate the help. Thanks
Reply:Sorry to answer your question with a question.Is that bull-gear cast with spokes or is it low carbon plate, more like a sprocket?The hub, is that a wedge type, like a taper-lok bushing, or bored to size mild steel?Some hubs seem to be made of high carbon steel and are very difficult to work with.If these parts are cast or high carbon, getting a warp in it, or distorting the center or keyway will probably not be as big an issue as cracking.Maybe test by welding a tab to each part and then break it to see what kind of failure you have, base metal fracture and pull out or tab and weld bend first.Last edited by denrep; 07-03-2007 at 01:20 AM.
Reply:it is a sprocket, mild steel or low carbon, the center has no taper to it - it is milled to size and seems to be the same material, but I am not sure.  I am going to find out for sure of the actual make up of it, but I was told by the millwright I talked to last night that I just need to weld it and don't worry about it.  That's easy for him to say
Reply:With a key in the keyway, the weld only needs to hold the sproket on the shaft.  No torque load.TIG it and be done.Zap is the expert on this type of stuff.  Maybe he will post.  Can you get a picture of the parts so we can all have a look?Favorite right now is a Miller Syncro 200.Tons of tools and I blame at least one of them when things don't go right.
Reply:Originally Posted by denrepSorry to answer your question with a question.Is that bull-gear cast with spokes or is it low carbon plate, more like a sprocket?The hub, is that a wedge type, like a taper-lok bushing, or bored to size mild steel?Some hubs seem to be made of high carbon steel and are very difficult to work with.If these parts are cast or high carbon, getting a warp in it, or distorting the center or keyway will probably not be as big an issue as cracking.Maybe test by welding a tab to each part and then break it to see what kind of failure you have, base metal fracture and pull out or tab and weld bend first.
Reply:I've welded a few hundred or so of them thru the years. That's actually a pretty common weld when dealing with sprockets.  ALOT of sprockets come like that so you can weld in a center hub that fits the shaft diameter you have without have to have a machine shop bore out and re-cut the key way.    You can weld it with stick, tig, or mig, your choice, most I do are in the field, and I use a stick.  Usually 1/8th" 7018 at around 140amps.     You shouldn't have a problem with warping enough to case a problem.  Bottom line is these pieces are designed to be welded.  Weld it and don't look back.  ~JacksonI'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Scratches head?You have a gear with an approx 2 inch diameter hole in the middle, and you want to install a collar that goes into that 2 inch hole?  And the collar then has a 1.25 inch diameter hole through it for the shaft, and the hole has a keyway as well?  And you need to attach, by welding, the collar into the 2 inch dia hole in the center of the gear/sprocket?  Sort of like http://www.surpluscenter.com/item.as...ame=powerTrans this, except you have a 24 inch diameter gear instead of that little 9 5/8 inch sprocket?Like denrep said, step one is to find out what the materials are.  That will help determine whether you can weld it, and if so what procedures and processes you can use.If what my description and mental picture of the parts is correct, then Mr. Philla is wrong about the torque needs.  The torque from the shaft will transfer through the key into the hub, and then from the hub through the welds into the gear/sprocket.  So -ALL- the torque will be going through the weld between the hub and the gear/sprocket.My simple answer is to ask the engineer or designer what the weld needs to be and what the materials are.And also find out what rpm and torque this whole thing is spinning at and transmitting.  High rpm stuff would need to be balanced and trued better than lower rpm stuff.  And it might help if you knew what the needed precision is for the machine.  It doesn't sound like super high precision is needed, but it also isn't just a job to slap it together.  You -may- have to true (size and runout, more the runout than the size I think) the center hole in the bushing after welding, maybe not.Got any pics so we can see what you are talking about?  A pic is worth a thousand words, after all.If it's a weld-in hub like I picture, I'd say to chamfer the corner of the hub and the corner of the shoulder on the hub and both edges of the center hole on the gear/sprocket.  Insert hub into hole, align, then weld.  If it's all mild steel, then MIG or TIG or stick should be able to do the job.  With the appropriate machines of course.And a rotary positioner would probably help to spin the work as you weld it all up.
Reply:I'll wait for pics thank you.....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:Hammack was right, the millwright came out and showed me what he wanted.  He wasn't supposed to come by.  Wasn't that big a deal, he pulled out the leads on the ranger 10000 plus, fired it up, started it with 7018 and tacked it, let me have at it.  I was worried about warp and such, he just laughed and said that I needn't be worrying about the small stuff.  I appreciate all the feedback, it really helps.  Thanks all!!!!!!!!!!!!!