repair cam journal

Ronnie and others, I again re-iterated to the machinist about repairing the damage by grinding journal, hardchroming back and grinding to size. He reckons the gouge is too deep to do so successfully. I disagree, I think he's thinking of the cost, which he'll have to bear, to put on so much buildup. It's gonna cost him a damn side less to execute a proper repair via that method, than it is to find another steel cam, send it to the USA to get it ground, and ship it back. I am a finicky *******, when it comes to building these things, if it's not 100% right, ie, if any lobe has the slightest runout, I can see things getting ugly. And I don't want that!!
Years ago, when I worked in a machine shop, I had to make a pin to suit a big Caterpillar, to replace the original which had fractured. I used 4140, and got it hard chromed oversized, and ground it to size. It was returned within a week, cleanly broken in half! Metallergical examination of the pin showed this was caused through hydrogen embrittlement. Subsequent reading up on the subject tells me that such a phenomonon can be substantually be reduced through a post bake process, ideally as soon after the plating process as possible.
Obviously, this particular job involves only plating a relatively small portion of the entire object, which allows easier escape of any atomic hydrogen introduced to the parent metal, but I was still uncertain of the outcome. And, I didn't want to do any post-bake, which very likely could bend the shaft! Ronnie has obviously been down this path, subjected the camshaft to a good test, and reported great results. Oh...if only I could convince my machinist. Maybe I'm getting too concerned too early; just allow him to fix HIS mistake as he sees fit. But if I'm not happy with the result it will just create a lot of angst for all parties.
Thank you everyone for participating in this dialogue, I'll let you know how it all pans out.
Brian
 
Any spray/plasma/flame welding includes a LOT more heat then using a mig welder.
Some of the methods include preheating to get a good bond of the added material.
Do you know what material the cam is made from ?
We are talking serious money here and guessing a lot about if its weldable or not.
Sending a bit for analyze isnt cheap but if youre gonna spend all this money it takes a bit of guessing away.
 
flatheadmurre said:
Any spray/plasma/flame welding includes a LOT more heat then using a mig welder.
Some of the methods include preheating to get a good bond of the added material.
Do you know what material the cam is made from ?
We are talking serious money here and guessing a lot about if its weldable or not.
Sending a bit for analyze isnt cheap but if youre gonna spend all this money it takes a bit of guessing away.
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I don't believe that to be the case. While it is true the spray will be at a very high temperature the substrate temp stays low preventing distortion or warpage. Thirty years ago a union steward I worked with had a Chevy powered fishing boat with a severely worn distributor shaft in a Mallory marine distributor. Tool room supervisor would not help him so I suggested metallizing, as there was a local shop I was familiar with. Worked out perfectly for him, they not only sprayed but had facility to finish grind too. I would at least look into it as a possible fix.
 
Fordors said:
I don't believe that to be the case. While it is true the spray will be at a very high temperature the substrate temp stays low preventing distortion or warpage. Thirty years ago a union steward I worked with had a Chevy powered fishing boat with a severely worn distributor shaft in a Mallory marine distributor. Tool room supervisor would not help him so I suggested metallizing, as there was a local shop I was familiar with. Worked out perfectly for him, they not only sprayed but had facility to finish grind too. I would at least look into it as a possible fix.
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What youre spraying is metal and for it to bond with the base metal you need to heat that metal to a temperatur high enough to bond.
With a shortarc wirefeed you have less loss of heat into the material in the time you need to melt the base material.
Not starting an argument here and metalspraycoating is excellent for adding a wearshield to another type of basematerial.
But most crankwelders for example use a wirefeed often with a powdershield.
 
Im not to damn good at explaining but ill have another go on backing my statement.
The most heat efficient way of melting a filler and basematerial togetter is with a direct arc between them.
Using a secondary heatsource like a tig/plasma/flame gives you some advantages like better control of the weld but have a bigger heatloss into the basematerial.
All of this is based on that you want to add the same type of filler material and have a full bondage between them to create an as uniform endproduct as possible.
And if i get to loud just give me a good smack on the head and tell me to shut up :o
 
The other day I needed a sector built up the machinist suggested hard chrome were talking 1/16 ,here in Auck there at least two who do it .Ted
 
Ha! 68 posts and nobody's user name begins with a "D"!

I'm not sure of the rules in this game Pete.

Lonnie
 
Find a shop that does metelizing spraying powderd metal to build the journal up and the maching or grinding it to size in a lathe it is only brougt up to 250 deg. and won't warp and will last for ever . I have built up pump sleeves electrete moter shafts and more .
 
There are various "metal spray" processes and I am not familiar with all of them. However, the metal spray unit I use in my shop requires the base metal to be red hot for the powdered metal to properly bond. I would not try to "build-up" any precision part where no finish machining could be done on the entire piece.
 
Me - I'd first put it in my lathe and check it for straightness . . . could be bent from the incident.

Then, I'd find a crankshaft repair shop that has the welding machines for journal repair. I'd have them weld up the journal, straighten it if needed after welding, then regrind it back to size. If done correctly by a competent outfit, can't see this not working.

They may want to turn it down on the bad section, such that they are getting the same amount of heat and weld throughout the journal during the welding operation. (This is just my guess).

Pete probably knows more about this than all of us combined - I'd just ask him his opinion! :)
 
Pete said:
65 posts and no workable solution that meets the parameters.
TSK TSK....
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Pete do you believe this can be repaired without welding,plating,jb weld or others. .Thinking outside the box I think it can,just a little creative machining and them back to the grinder to finish off the repair. :D

R
 
Ronnie said:
Pete do you believe this can be repaired without welding,plating,jb weld or others. .Thinking outside the box I think it can,just a little creative machining and them back to the grinder to finish off the repair. :D

R
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Hi Ron, not Pete, but there MAY be another option. It would involve a Bridgeport and a decent lathe.

This would be a "long shot" for sure, but feasible.

The bad section could be machined flat across and a new piece machine to fit in place. It would be semi-ellipitcal and fastened with 2 (very small) socket-head screws, possibly like some 10-24 threads. I would only do the side of the cam journal that needed it and NOT across both sides of the journal.

Thanks, Gary in N.Y.

P.S. This attempt would depend entirely on being able to drill & tap safely into the core, if not it will not work!
 

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Yes it could work if the hardness isn't too deep to discourage drill and tap.

This could be an alternative if hardness comes to play. They only require grinding no drill and tap and are available in many sizes.Just another avenue to explore. Install screws with loctite and grind to finished dimension. Same approach as you only deal with 1/2 of journal. That's my 2¢.

R
 

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Bored&Stroked said:
Me - I'd first put it in my lathe and check it for straightness . . . could be bent from the incident.

Then, I'd find a crankshaft repair shop that has the welding machines for journal repair. I'd have them weld up the journal, straighten it if needed after welding, then regrind it back to size. If done correctly by a competent outfit, can't see this not working.

They may want to turn it down on the bad section, such that they are getting the same amount of heat and weld throughout the journal during the welding operation. (This is just my guess).

Pete probably knows more about this than all of us combined - I'd just ask him his opinion! :)
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I have fixed at least 20 of this kind of botch over the years. Half hour job. No warp, but I wouldn't give the guy the time of day.
 
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