welding a gear

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i was called to do a job welding a gear for a friend. i said that i could weld it i just dont know the propper way. i told him that the gear is hardened and requires someone who knows what they are dealing with. Which was not me!  i did not take the job do to the fact that i have never had to weld a gear before.  the gear in question is 5'' I.D. and is going to be put on a shaft and welded to the shaft......i just read back over and it sounded like i was talking about a broken gear that is not the case. brand new gear brand new shaft. .... my friend works for a machine shop. i was wondering what is the propper way to weld a gear of this size to a shaft.does this require preheat and or post heat?is there a special rod (filler metal) in particular that you would use?such as wearsheild mm or somthing elese?63' Lincoln SA200 2008 miller trailblazer 302fibre-metal pipelinermiller camo BWEand all the guns and ammo a growin boy needs
Reply:Do they know what the gear and the shaft are made of? Anything special?Yup
Reply:not that i know of. it goes inside of a pump and is not out in the open and is covered in oil. i called to see but he did not pick up. i will try to find out. well i was able to get in touch with him before time to edit ran out............ he does not know what they are made of they were brought to him by a customer and the shaft needed to be cleaned up due to it being banged up in shipping.Last edited by usmcgremlin; 05-24-2008 at 12:17 PM.63' Lincoln SA200 2008 miller trailblazer 302fibre-metal pipelinermiller camo BWEand all the guns and ammo a growin boy needs
Reply:gremlin,It all depends.Mostly it depends on what the gear is made of and what the shaft is made of.The shaft could be pretty much any alloy of steel, from plain old low-carbon 1018 steel(weldable) to a free-machining leaded/resulfurized steel (not weldable) to a super-hard exotic high-carbon high-alloy steel (maybe weldable or maybe not).The gear could be the same thing.  It could also be cast steel, or cast iron, or powder-metal.  Some of the possible materials can be welded, some can be welded with difficulty, and some can not be welded well.  Then there can be the possible post-weld heat-treatments or remachining of things, depending on how critical dimensions and material properties need to be.So, the answer is ....It depends.To do it right, you really-really-really need to find out first what the materials involved are.
Reply:A spark test would be in order if nothing else.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Yes you can weld that gear onto that shaft.The steel gear probably is hardened but it is only hardened to a certain depth.The middle of the gear is not as hard. That is why it will work.Trying to weld a broken tooth on the gear will NOT work,When you weld the gear onto the shaft make sure you have a press fit.You said you have a 5 inch ID and that is a lot of inches of welding.Obviously since you are welding it, and not broaching splines, cost must be an issue. Sounds like a prototype. Right?I have welded gears onto shafts. TIG welding is best but you can use other processes also.Weld both sides.You said it will be used in a pump. I do not see a problem. If the gear is steel.If it is cast iron that would change everything.SMAW - use 7018.FCAW - use NR211MP.GTAW - use ER70s2.GMAW - use a structuraly rated wire.Last edited by Donald Branscom; 05-24-2008 at 02:07 PM.
Reply:ER70S6 is fine, but I would use tig. You would do well to preheat everything as evenly as possible. Tack in opposite locations on both sides, like 3 places each side, maybe 4. Then weld in opposite quarters from 12 oclock to 3, then from 6 oclock to 9, and skip to the other side. Start from 3 oclock to 6, then 9 to 12.... just like tightening lug bolts on a wheel.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:I'm with Moonrise on this one.  Until you know what the composition of the shaft and gear you are asking for trouble by just welding it.  There's more to think about than just the welding.  how much distortion will you wind up with after the welding it done?    If he works for a machine shop then suggest he try to key the shaft and gear, and lock it with set screws, or he could cut a key way and then possibly turn it for a shrink fit.  If he has room he can run another set screw behind the first one to lock them and stop them from backing out.  maybe I'm wrong but there are better ways in my mind to attach a gear than just welding it to the shaft.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:As stated before i did not take the job .... the reason for welding it is because the damaged gear that is being replaced was welded on to the shaft the gear shattered when the pump locked up and both the shaft and gear are to be replaced. i am not set up to tig yet. but money is being set aside and it is in the works. thanks for all the input fellas i am not afraid to let someone know my limitations. especially when my name is on the line.  i missed out on some money but i dont feel bad cuz i know i didnt screw anything up. They said they were happy that i was up front with them. i just felt it was the right thing to do!63' Lincoln SA200 2008 miller trailblazer 302fibre-metal pipelinermiller camo BWEand all the guns and ammo a growin boy needs
Reply:I agree with dave spark test and then if it looks good 7018 I have a customer that brings me gears with teeth broken off so I build them up then grind them down
Reply:most important thing to know is what material its made from....if its a lower carbon steel then and your doing stick i would lay in a 6010 first and put 7018 over top of it...or if you used wire maybe a flux core that digs like T9?(of course tig would be nice but $$$)....also if your concerned about warpage then heat the whole gear up....maybe as high as a dull red and then weld it up...thats how i would do it if i had to. heat the whole thing up and weld 'er up. i cant say that i have a huge amout of experience but...that what i would do