# Help with welding crankshaft



## oldgascar (Nov 25, 2013)

I am rebuilding my 1904 Brennan 2 cylinder engine  (opposed cylinder). One end o the crankshaft has a keyway milled in it, but is it in very bad shape. I want to weld it up, turn it down and cut a new keyway in it. This end of the crank is about 1-1/2" diameter and about 3 inches long. Can I sucessfully mig weld this shaft (as long as I keep the rest of the crankshaft cool)

Any thoughts, suggestions , ideas ?

Thanks 

Bob F.


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## xalky (Nov 25, 2013)

Pictures are worth a thousand words. Can't give any usable advice without them. :thinking:


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## oldgascar (Nov 25, 2013)

I will post a picture or two tomorrow of the crankshaft. 

Thanks,

Bob F.


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## Tony Wells (Nov 25, 2013)

Actually, you should heat up the entire end where you weld instead of keeping it cool. Welds shrink as they cool, and create stress by "pulling" a shaft into a banana shape with the weld on the inside of the bend. It minimizes the effect to heat, and hence expand, the shaft all the way around rather than concentrate the heat only where the weld bead is. 

I have repaired shafts with keyways and used minimal filler by using some carbon rod, ground into a faux key, and welding all around it. If the keyway is any good at all, there is no real need to fill it up simply to mill it out again. The weld puddle will flow all around the carbon, but form a roughed out keyway as welded. Go slightly undersized with the carbon. Then you can do a good cleanup on the mill.


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## oldgascar (Nov 25, 2013)

Here is a picture from one of my older post about the engine showing it as  I 1st started to disassemble it . I hope you can see this picture , if not I will post pics tomorrow. In this pic, you will see the end of the keyed crank at the bottom of the picture.

http://www.hobby-machinist.com/attachment.php?attachmentid=60411&d=1378843906 


Bob F.


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## pjf134 (Nov 25, 2013)

Is milling out a bigger keyway a way to fix it? A bigger key would be easy to make or buy. I assume a new crank would be hard to get and would be less chance of messing it up by using heat ect. Just a thought since no pic yet to see how bad it is.
Paul


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## astjp2 (Nov 26, 2013)

You need to put the crank into a bed of hot charcoal before welding it (dull red color if possible).  Weld it with a stick welder using the right alloy of rod (depending on if cast or forged) and then put it back in the charcoal and cool slowly (anneal it).  Once you have it welded, you need to go to an automotive machine shop and have them grind the crank and polish it.  It will not like turning on a lathe because you may have different hardnesses of materials.  I would get it close, within .010 and then cut the keyway and have a final grind to the correct dimension.  This is a specialty in the automotive world, not many shops like dealing with welded cranks so shop around.  Tim


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## GK1918 (Nov 26, 2013)

When in doubt, I would go along what Paul said, the next size Key.  Or mill another keyway.  Looks like this is on the front for a pulley. I still
would mill it bigger.  Example we did this on a 6-71 Detroit crank.  These have a keyed gear that drives the oil pump. This key is not fit even
for a lawnmower. Its so small its worthless.  So we re milled it for a 'real' key and did the drive gear on a shaper. Didnt have a broach that big.
That would be my first choice rather than welding something that rare.  Next if whatever goes on the shaft (gear/pulley) is ok and you do not
have a broach for that, then you could mill a key that would look like a Tee nut.


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## rgray (Nov 26, 2013)

Hard to tell from the pic. But can you just mill a new key slot on the opposite side. Timming markes or TDC mark could be resribed easy enough.


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## iron man (Nov 27, 2013)

We use to repair crankshafts like this all the time we never tried to heat up the entire crank for fear of warping it. We would protect the bearing surfaces and just built up the end stick or wire feed it did not seem to matter after we where done we would heat up the end until it was a dull red and let it cool. We would then machine it and cut keyways or splines never had one fail. Ray


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## xalky (Nov 27, 2013)

Another alternative would be to build it up with bronze brazing. Its easy to work with and machine and the heat won't be so localized or intense. Let it air cool slowly.


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## Kernbigo (Nov 27, 2013)

Mill it out oversize, and make a step key, did it all the time on other application


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## iron man (Nov 27, 2013)

xalky said:


> Another alternative would be to build it up with bronze brazing. Its easy to work with and machine and the heat won't be so localized or intense. Let it air cool slowly.



 That works good too. Ray


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## Guv (Dec 5, 2013)

xalky said:


> Another alternative would be to build it up with bronze brazing. Its easy to work with and machine and the heat won't be so localized or intense. Let it air cool slowly.



When a key way is worn it can only be due to the pulley being loose(loose nut,bolt). When the pulley is loose it wears the inside of the pulley as well as the outside of the crankshaft. It does not help to cut another key way opposite as the key does not secure the pulley,it is only for timing marks to be in  the right position. You have to replace the pulley and braze weld the crank point and cut the key way in the correct position.


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## Kernbigo (Dec 5, 2013)

If  the pulley is worn just make a over size key for both the pulley and the crank, if only the crank is worn make the step key, no brainier, why weld something and take a chance of it warping.


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## Spirit20 (Dec 5, 2013)

What about just reducing the end a little to clean it up & make a new pulley. If you do this first you can still try & get the crank welded if it does not work.:thinking:


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