Got a pair of disc spindles off of a '71 Coronet in a 'yard. After cleaning 'em up found one has rust pitting on the shaft, but none on the bearing surface. It extends all the way around the shaft. Ok to use? Let the debate begin.

Why not? No issue in that area

Looks OK to me?

I would use that, not a problem.

Yes, and if there was to be pitting, that is the least stressed section IMO.

Thanks guys.

Another vote for using it.Rocky

Pitting on the bearing surface wouldn't be an issue either - the bearing doesn't spin on the spindle. The seal area is what you have to be concerned with. FWIW, mine are way worse than that.

I'm not convinced that that area was bright and shiny on the spindle when new. I suspect it's an area where the forging was only big enough for the machining to take off the top of the bumps, leaving the bottom of the bumps as-forged. In service that area is usually covered with grease.

R.

No issue with that. USE IT!

Hmmm....never thought of that. I was wondering how it could have gotten rusty in the first place, since it should been covered in grease.

Yup I'd use it

Nope. I know the stresses are not great in that area, but that pitting is a great source for stress risers. Significantly increases the chances of cracking and breaking. I personally would not risk it.

That's exactly what I was wondering about when I posted this.

Grind them out then.

Sorry, but we are starting down a path that could very well make this worse for the OP. It appeared to me, and not if addressed already, seems like the spindle has already had some mechanical surface de rust prep in posted pic. That was smart, and only improved matters. Going further with grind marks, causing minor localized heating, and/or grind marks orientation, etc, are a risk, and not worth it. Additionally any metal removal is hard to see as a plus. If there was one or two serious depressions, which I don't see, there would be the issue of concentrated stress riser. The fact that there are numerous rust cavities, actually spreads the stress out over a larger surface area, minimizing any single large stress concentration. As also already mentioned, I always coat the area shown pitted with grease, for this very reason, due, to exposure some how, by immersion, or condensation.

Granted the stresses are much higher, but in my career I have seen many rotating shafts break because of stress rises caused by that kind of corrosion. Each one of those pits has stress risers.

Yes, I agree, but I believe I have taken that into account correctly in my thinking. On a related note, ever seen a fully "knurled" (literally hundreds of stress risers) rear axle shaft, and know why?

Stress risers......... You realize these are forged steel, not cast?

yes

That area was machined - just not to a fine finish. Usually looked like fine threads because the cutter ran down that area at a higher feed rate.

Stress risers ... seriously ?!?!?!

Would I use it?

After polishing the seal surface...yep.

i have used spindles like that in the past, but i first taped off the bearing and seal areas with a few layers of duct tape, then blasted the center area with steel shot. i don't know if that "improved" the pitted area, ie. stress riser prone, but said spindles are still in use after many, many years with no issues.

No but not because of the rust. The A body knuckles are stronger and the late model rotors are a lot cheaper so I'd switch to the later model stuff.

Un
Sarcasm is cool, no

It doesn't spin but it does move. As to stress risers, they are more of a concern with cyclical stresses. I'd run it.

"stress risers"

Boy do we know the terms.

You actually think that someone who had the car before you de-rusted the spindle? Seriously? Even cars that sit in scrapyards have the hubs on, most of the time. How do the knuckles get rusty? And if you are in a scrapyard that has a rusty knuckle lying there, wouldn't you pass it by and get a different one? So this derusting talk is all nonsense to me.

Does it have original ball joints? Did the previous owner do all his own mechanic work? Because no shop worker is going to do anything more than clean with a rag and maybe some solvent before adding new grease and bearings and reassembling. Even in the 0.1% of the time that it's rusty. It just wouldn't happen. They're all trying to beat the flat rate, not that there's anything wrong with that.

Then add to that the fact that I've taken apart hubs and seen that exact surface texture, many times. Under the grease. My conclusion is that hundreds of millions of cars left Detroit with that same surface texture in that area.

Now on to how the member is stressed. The spindle is a cantilever beam and the maximum moment is at the root of the spindle, tapering off to zero at the point where the outer wheel bearing exerts a force on the spindle. If the vehicle is rolling straight the upper side of the member is in compression, which does not affect the "stress risers". It's only where the tire is trying to tuck under the car that there is a possibility of this area being in tension, and that tension is opposed by the weight of the car. So the amount of tensile stress in that area may be quite a bit less than imagined.

So what happens IF all the planets line up and the spindle fails? It bends. Yes, that would probably lock up the wheel, but in such an extreme case there would be warnings as the spindle bends through its elastic region before going into the plastic (yielding) region.

So I'd certainly use that spindle and not give it another thought. On my daughter's car.

R.

As the others say , use it.

But...But, this is Moparts, someone has to come up with the crazy answers. Didn't we all sleep at the Holiday Inn?

"Now on to how the member is stressed. The spindle is a cantilever beam and the maximum moment is at the root of the spindle, tapering off to zero at the point where the outer wheel bearing exerts a force on the spindle. If the vehicle is rolling straight the upper side of the member is in compression, which does not affect the "stress risers". It's only where the tire is trying to tuck under the car that there is a possibility of this area being in tension, and that tension is opposed by the weight of the car. So the amount of tensile stress in that area may be quite a bit less than imagined."

That tuck under you mention, in a high performance application can occur under braking, in a high g turn, and depending on other suspension variables, could be 70%? of the weight of the car, and then add the potential dynamics of bumps, etc, I think the loads can be higher then imagined. Failure will likely be at a point of maximum stress, not over time, when subject to only the rolling weight of the car you brought up. Are we also assuming all the rust the OP is asking about is only on the upper surface pictured that under ideal normal conditions as you described iis n compression, and not underneath? We are also assuming, I believe safely, the COG on the car is above the centerline of the spindle, and therefore the "tuck under" mention helps to reverse load the spindle.

Bottom line ANY surface irregularity is a potential stress riser, all should be avoided, the consensus here so far, which I agree with, in the OP's case, its an insignificant stress riser. Why are beating this to death again?

If you plan on using it for serious corner burning or wheels up drag racing, get it shot peened.l If not put it on and sleep easy.

Once you've been on Moparts,you have all the stress rises you need !!