repair cam journal

Brian

Brian

Well-known member
My machinist has had a bad day!! I had him grind the journals .010" undersized to suit the cam bearings. The cylindrical grinder he uses has a fast traverse in to within a few thou of the journal to be ground, from where he uses regular infeed to achieve finished size. He was in the process of setting machine up and got distracted by a customer, returned to job, thinking he'd done the initial setup, and promptly rapid fed the grinding wheel into the centre cam journal, taking out a bit chunk, probably about 1/8" deep! Never done that before in 30 years said he!! [although, at the time I'll bet the language was a tad more colorful!!]
So, he asks if I've got another cam. Normally, that would be the quick, easy solution; to merely use another cam. Not this time though....This is a steel camshaft that I shipped from New Zealand to our collegue on here that put his rendition of the 'famous' L100 grind on it, and shipped it back. This was not a cheap exercise by any means.
So...any suggestions on the best method of repair of the damaged journal? Bear in mind, it is a steel item, not cast iron. Mig welding is a solution, but I'm worried about keeping the thing straight. Admittedly, it can be straightened prior to finish grinding, but every cam lobe needs to maintain perfect concentricity too. What do you guys think of some form of epoxy repair? There is an oil groove through the centre of the journal, and the damage is confined to one side [half the journal]. Does anyone know of a suitable 'cold process' of building up the gouge? All opinions appreciated, thank you.
 
I like the heat shrink sleeve idea that way you or your machinest can make the sleeve out of a material close to the original and not worry about expansion differances.
 
I would just weld it. The journal is so massive compaired to the cam, it is not likely to warp anything.
 
Brian , trust me it "WILL" warp if you weld it & these steel cams are a mutha to straighten !!!!!! The engineers at my work have well educated me on camshafts .
I would like to see pics also . Can we maybe grind down bearing journals & make bearings ?
I am here to help you !
Cheers
Tony
 
Depending on how big a piece is missing you may be able to just dress the edges of the chip and carry on with the machining.
 
Depending on the size of the "gouge", and if only half the center journal is affected, welding should not cause a problem if properly performed.

I would do some serious investigation into the accuracy of the cam before beginning any repair so as to have a basis for evaluation after the repair is completed.
 
Brian,
Yikes......After a whack like your cam has suffered I would place it
between centers and indicate the unwhacked area of the journal. Once it's running
true , his responsibility not yours , I'd direct him to grind the main to eliminate as
much of the whack as possible WITHOUT going smaller than the lobes will allow. The
next step of course is to turn up ring of something like 1035 med carbon steel and
shrink it in place, leave at least .025 on the OD for finish. This is a ,shall I say , cold
repair and my comfort level is quite good going this particular way. One thing of
paramount importance with a hot repair ,aka welding, is the journal will always have
a bit of runout and to achieve a 100% cleanup during regrinding the journal will
loose some diameter.
Nightmares like this happen and your guy will no doubt make things right,
please keep us informed.
Charlie ny
 
Any repair done at this point assumes the camshaft was originally straight when the L100 grind was put on it. If it had some runout on the center journal when reground (by Kiwi's guy) and it is now straightened to zero r/o what effect does that have on it? Couldn't that tend to compound any error in base circle runout? I think I would attempt a repair of the damaged journal, straighten it and then check the base circle of the lobes for runout.
I wonder if the best course of action is another cam.
 
Brian I think you could weld it with mig then grind it true. I welded every lobe of a Model B four banger cam to grind it for more lift and it moved slightly, which was easily sorted on the press. That is a chill cast iron cam. Your steel cam will take the weld better and be easier to correct if it moves which I dont think it will. If it does it will only be in one plane, so will be easy to press straight. Weld it!
 
If it was pre regrind i wouldnt be so afraid of welding it.
But adding heat can set any built in tension free.
Its a gamble can work perfectly or not, all depends on if youre willing to take a chance.
Why didnt the bearing surface get ground when regrinding if it was needed ?
Have you checked what the impact from the grinder has done to it this far ?
Most available chemical repair materials are not intended for a bearing surface.
Electroplating adding hardchrome is a safe way of adding metal but 1/8 is to much to be realistic.
 
You cannot shrink a sleeve on the center journal unless you do one of the end journals in the same fashion.

Welding small nuggets with adequate cooling between each will be a safe procedure.
 
Charlie ny said:
Brian,
Yikes......After a whack like your cam has suffered I would place it
between centers and indicate the unwhacked area of the journal. Once it's running
true , his responsibility not yours , I'd direct him to grind the main to eliminate as
much of the whack as possible WITHOUT going smaller than the lobes will allow. The
next step of course is to turn up ring of something like 1035 med carbon steel and
shrink it in place, leave at least .025 on the OD for finish. This is a ,shall I say , cold
repair and my comfort level is quite good going this particular way. One thing of
paramount importance with a hot repair ,aka welding, is the journal will always have
a bit of runout and to achieve a 100% cleanup during regrinding the journal will
loose some diameter.
Nightmares like this happen and your guy will no doubt make things right,
please keep us informed.
Charlie ny
Click to expand...

How are you going to get your sleeve repair over the end journals???
The repair sleeve will have an "id" smaller than the end journals "od".


R
 
You have to grind down the end journals to sleeve the center.
Next issue with a sleeve is if its to small inner diameter it will get stuck on the camlobes when you try and get it into center position.
Somewhere in all this work it might just be better to try welding it and if it goes bad the machinist has to pay the bill to replace your cam....
 
At 1/8 inch you probably can't get a sleeve over the lobes, --at least not the lobe next to the journal, that lobe tip is probably higher than the reduced diameter if the journal---perhaps a split sleeve could be made and the ends brazed together in place, cooling the brazed area first it will shrink in place, then pinned for insurance

Have you asked the machinist how he proposes to fix his problem?
 
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