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Bearing composition


nicole

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I happened on some large roller bearings and am trying to figure out their composition.  Their physical dimensions are ~1.425 D X 2.9" height, with a slight 0.050 taper.  Using the tools available I calculated their density was 7.45 g/cubic centimeter.  They showed some attraction to a magnet.  Picture is attached.  I looked up steel density and it is usually near 7.8 for a carbon steel.  Chromium is less dense however and the density I determined suggests these bearings may be stainless steel; but I thought they would not be magnetic.  Further reading showed that while only austenitic SS is non-magnetic, even it can become magnetic from cold working.  An old bearing could be considered to have been cold worked?  This seems to leave me no further along, and while this is not critical because I am just going to play around with them, it would be nice to have a little more insight into their composition.  Any thoughts out there?.post-46507-0-15085800-1392524892_thumb.j

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Searching "roller bearing" in the search bar gives 72 results of related topics. Did you try searching this forum for any information yet? What I gathered from a quick search was that many ball bearings are made from 52100. Roller bearings are sometimes made from 9260 case hardened steel. Sometimes a lower alloy that is case hardened. I'm sure there is much more information out there about your possibilities. You are correct about the austenitic stainless being non-magnetic (ferritic and martensitic are the magnetic types) and the possibility of cold-working it making slight magnetism in it (bearings are cold worked in use, but those do not appear to have been used).

-Crazy Ivan

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Smaller bearings are usually considered to be made out of 52100. It has been mentioned that larger bearings are case hardened lower grade steel. Those are out of a large bearing, so they may just be case hardened. Try grinding into one, and see if they get softer (check with a file) once you get .0625"_.125" in from the surface.

As for stainless, the hardenable grades such as 440c are very magnetic.

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clean it in dish-washing detergent or vinegar and leave it outside in the dirt for a week or two if it rusts its 52100, if it doesn't its high chrome. it looks like a standard well used roller.

 

most bearings are through hardened unless there is a reason not to. case hardened bearings will handle heavy shock loading without cracking right through.

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places I have dealt with in the past that make bearings ( I have ball bearings up to about 4" diameter ) make them from many materials.

in the past I have had bronze and brass, stainless, high and medium carbon steels and some tool steels, also ceramics

 

magnetic indicates a steel

spark test may help

case hardened or through hardened may help.

 

I have used the inner and outer parts of ball races in the past and some of them are even quite hard when hot and still ring when hit at yellow.

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All thanks for your comments.  My research into the engineering literature on bearings is affirmed by the comments here, plus the great practical suggestions you have made to try and narrow down the field.  I note that though the picture I had attached my suggest otherwise, these bearings are very much used, which is why I kept the possibility open they are cold-worked.Thanks very much, I will start playing with the stock and see how it behaves!  I am interested to see how informative the density data is- it strongly suggests a high chromium alloy, so the predicted out come of your experiment yahoo2 is that it should not rust.  I will have to file into one too.. :)

N

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Ok I'm wrong, I looked it up the standard non lab rust test is,

wash in detergent then clean with alcohol, boil a cup of water then stir in as much salt as the water will hold, stand  the bearing in the water for 24 hours.

 

if its brown with rust its soft steel, chrome steel, high speed steel or hard carbon steel. that narrows it down to 52100.

 

why dont you do as I-dwarf suggests and spark test it, if you have some other bearing material around you can do direct comparison, you wont get a long tail with something that hard but you should see a red fringe with 440 and not a lot of side sparks, a lot like grinding high speed steel. chrome steel I think of as a fluffy orange spark.

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I'm a little concerned about your density calcs:  I assume you are using a high grade scale that was calibrated recently and used a micrometer *many* times to get an accurate volume.  However there are a number of differing alloying elements that are lighter than steel---carbon being a very big one and they are often mixed making a density  from composition calculation *very* difficult especially when changing the ration of various alloying elements could possibley keep the same density.

 

As for "cold worked"  this generally refers to a substantial amount of deformation to an item making the dislocation content high enough to provide the "work hardening"   A bearing should never be deformed that much in use as that is pretty much the definition of catastrophic bearing failure.

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Thomas, I am concerned about those readings on the scale too.  I will have access to a much better one tomorrow.  My dimensional measurements were done with a caliper; those were probably close enough.  I will see what a good analytical balance gives for mass..N

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I tried Yahoo2's saturated salt treatment with this bearing, pic attached.  (Cleaned bearing with detergent, alcohol, then soaked 24 hours in saturated table salt) The bearing is obviously darkened where it had soaked.  I know it is possible for ss to corrode, but I do not have a sense of how to interpret the result.

N

post-46507-0-77984600-1392948450_thumb.j

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  • 3 weeks later...

hi nicole, sorry for the delay, my power has been off and on for the last few weeks from lightning strikes, taking my home network down with it.

 

What I was going to say originally is that it is worth looking at this from the perspective of a bearing manufacturer and not a blacksmith. Those guys dont care what is technically possible in regards to choice of metals they are all about practical and cost effective solutions. Most of them tool up to use a very small selection of metals.

By far the largest majority of taper bearings are 52100, they run in oil or grease behind seals (no exposure to water, acids or grit means the wear very slowly, keeping there tolerances) once the bearing becomes loose the shaft it holds starts to move about, this wears the seals and lets in contamination and the bearing rapidly fails. 52100 has about 1.5% chromium this contributes to the hard wearing abilities but it is not nearly enough to stop surface rust forming given the chance. Of the four choices that rust I listed in my previous post only chrome steel (52100 or similar) is a candidate for typical taper bearing rollers.

 

When a manufacturer makes a taper bearing for a environment where the seals are exposed to high levels of acids or bases, steam, high pressure water, organic compounds etc they accept that there will be a higher wear rate and quicker seal failure so to counter this, some of the load rating of the bearing is sacrificed to provide about 15% chromium rust resistant surface, most commonly 440C stainless.

 

Is it possible to find a taper bearing made from something else? yes but it is very rare. Is it likely that this large roller is an exotic material? No

In my mind this narrows your testing to a choice of three, 52100 or similar, 440C or similar , something else.

 

If the blackening is just a light sooty film that can be rubbed off with the finger and there is a clean bright surface underneath it is not rust. My guess is that it is rust, but it has been slowed by some anti rust oil additive that is still clinging to the roller, the stuff I use is almost impossible to remove completely. Just as with the spark test, it helps to directly compare with a known sample.

 

there are ball bearing manufacturers that produce balls for other uses that are made from all sorts of materials and grades of steel but it is the same thing, if you have some Idea what it was used for, that narrows the options to just a few choices.

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Yahoo, no worries on the delay! The bearing discoloration did not rub off. Prior to the test I washed it with dish detergent and then rubbing alcohol. So for now I will stick with it likely being 52100.  Looking it up it is something I can harden up rather nicely it seems.    By the way I found an interesting link on bearing materials here: http://www.precisionballs.com/ball_material_selection.php

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  • 3 months later...

What was the bearing manufacturer?  If Timken then I'd bet 52100 and be confident enough to forge a blade out of it and test, especially if I had enough rollers from the same bearing.  I've got a bunch from a triplex mud pump that are quiet large and test out as 52100.  I don't use it for my higher end knives, but when I'm playing around doing one off's I use them, or any time I want to use 52100 and don't want to use my expensive virgin stock.

 

Before forging I'd spark test with a known sample, if the same then try forging out.  52100 can be a bear to forge without a power hammer or press at forging temp.

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Thanks for the information Will. I've no clue about the manufacturer; no obvious marks I identified on them.  I still have to spark test against a standard.  I do have access to a PH so...I can always draw some out, see how it behaves!

Nicole

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