Does touching bearing surfaces ruin them?

Chopshop13

Chopshop13

Member
When i first worked in a performance automotive workshop where as well as fabrication(my trade), engines were built. The owner told me never to touch the surface of a new bearing (such as a main or big-end). And i understood it was to do with the oils and acids on the skin interacting with the surface and generating a hot spot.
So, the other day my co-worker pulled a new main bearing out of a box, which is part of my 286cui flathead rebuild, planting his big greasy sweaty thumb right on the surface.
So is it stuffed? What are your thoughts?/
 
I wouldn't say total nonsense... Ask any Numismatist about the effects of oxidation on coins. Having the choice between a shiny NOS bearing and one having old darkly oxidized fingerprints, the choice is easy even if without significant or measurable damage.

Additionally, dirty hands can transfer grit to the bearing... Doesn't everyone assemble engines in a clean room? ;)
 
Hey guys....do you reckon the engine assemblers in car plants of years gone by wore surgical gloves when fitting rod/main bearings?

Somehow, I dont think so, especially before OH&S.

Musta been a miracle that all those millions of cars did millions of miles with "contaminated" rod and main bearings.

Nothing wrong with being super clean during engine assembly (I know I am) but dont you add wipe the bearing clean then add bearing lube to the bearing before you drop in the crank/fit the rod ?

BFD
 
Is that similar to not touching the the porcilin part of a spark plug for the same reason?

I remember being told that also.
 
I have heard that touching a main or rod bearing will shorten it's life. Also, never store a crankshaft horizontally, don't halogen light bulbs, don't rotate radial tire side to side..... ! It's easy enough to follow some of these ideas, and someone must have had a problem or why would they even make them up.
 
chuck stevens said:
I have heard that touching a main or rod bearing will shorten it's life. Also, never store a crankshaft horizontally, don't halogen light bulbs, don't rotate radial tire side to side..... ! It's easy enough to follow some of these ideas, and someone must have had a problem or why would they even make them up.
Click to expand...

Bunk about touching a bearing
Possibly true about crankshaft, although I think you would cause more damage knocking one over that was stood on end.
True about halogens - skin oil creates a hot spot, even the bulb manufacturers include this warning on the box. If you touch the glass clean it with alcohol wipe
True about radials.
 
I remember back in the 60's, in a shop I was working in, we had a Y block crank standing on end on the floor. Someone walked by and touched it and it fell over and broke right in two. It must have been his finger print that caused it. Walt
 
In engineering I was taught that people have "rusty fingers" if you touch a machined ferrous surface, that will be the first part to show rust.

I suppose how long between touching and assembling is important, if touched, oiled and assembled straight away there would be no problem, if touched and left on a shelf for a couple of years that would be a problem. Touching the bearings is probably not a problem but a quick wipe clean and fresh lube should be applied on assembly anyway so again no problem.

What your mechanic said was based partly in truth, but had suffered in the handing down of the info. Ferrous items will rust after touching if not cleaned and kept oily, but not really for bearings. There may be rusty fingerprints on the backs of bearing shells after 60 years on the shelf, but nothing really to worry about.

Mart.
 
I was taught the same thing (don't touch bearing surfaces) when I went through my Machinists Apprenticeship and then, many years later received the same instruction during my Tool & Die apprenticeship.

I would like to add that "touched" bearing surfaces when placed beneath a microscope in the metallurgy lab did show definitive signs of erosion. Whether or not this would reduce the miles obtainable on the exact engine had they not been touched is still a theory as far as I am aware.
However, if folks would see what I had (microscope) you would be more diligent in the way you handled bearings.
As Robert Dip (below) has pointed out, this is appearing to be yet another of those things that separates the true craftsman from the simple "back yard" mechanic.
 
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The difference between a ‘craftsman’ which in this case is engine re-building machinist related, one has to work with diligence, thought, respect of the parts one handles, and so on. You just don’t throw an engine together….you have to do it with precision. This is also why we use the ‘Ford Barn’ to obtain information and guidance. I believe that the ‘finger print’ discussion has more to do with working with eyes, hands, mind, etc. and the proper approach to the work involved. Handle the parts with care. All are important in the ‘mindset’ of professional working techniques. The engine may not cave-in, but your work ethics will. I have guided younger people in this pastime of ours, and this is what I have taught them. Robert
 
If an engine were machined to perfect smoothness and tight tolerances, it could theoretically run forever without wearing out. We're not there (yet).
 
All metals you will find in your car will react to the acid in your fingers over a long time, i always handle my bearings very carefully, and i have never felt the need to fondle the bearings all over.
The need for a tidy and clean engine assembly is obvious and the piont that we lubricate everything very well during assembly is good and all these oils and temperatures will wash away all foreign tiny "contamination" later anyway.
 
We were told by a factory rep from Federal Mogal that the bearings were coated with a protective coating before they were packaged. This prevented oxidation an discoloring. They said to clean and remove the coatings before installing them.
 
GREAT! im so glad to have touched on a topic which brings about some real healthy discussion in these important/unimportant issues.
So ive decided the bearing in question is not a throw away item however to some degree there must be an effect, SO.
Do you think i should take it back out of its box and give it a gentle wipe (WITH WHAT) then re-lube it (AGAIN WITH WHAT) and pop it back in its box. Its possibly going to sit 1-3 years max.
 
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This is just a guess. I think you could wash them in alcohol,let them dry, then spray them with something like WD40 wrap them up and put them away. Later the WD40 can be washed off.
 
I do hank my cranks from a rack to hold them vertical and safe. I also use a fine scuff pad on all my bearings, gives the surface a texture to hold oil during initial run in, then wash is soapy water.. Not sure if it works, but can't hurt. Been doing it for 60 years. Doesn't mean I'm right, just old.
 
My first day of work at North American Aviation was to test some titanium samples for strength after some stretching. knowing nothing I had my fingerprints all over the sample. We cooked the sample somewhere around 720 and the fingerprints ruined the samples. Somehow they kept me on.
 
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