Found nothing on this subject.
I removed old ball bearings from one of my hubs and they are CRAZY magnetic. Just received some new ones lableled "Stainless Steel" from Amazon. I thought steel was magnetic... The very barely stick to my magnet. I actually had to place them in the cup by hand...
Anyone have any thoughts on this? Thanks in advance!

Stainless steel is an alloy and depending on the formula may not have magnetic properties

Here is an article that covers the magnetic properties [or lack thereof] of stainless steel

https://www.wisegeek.com/is-stainles...#didyouknowout

And if you found that interesting, here is another that goes a little deeper

https://www.kimballphysics.com/magne...ainless-steels

You probably bought 300-series stainless steel bearing balls which are non to very weakly magnetic. They are extremely good for corrosion resistance but not that good for hardness and wear resistance and are usually specified when corrosion resistance is of primary importance. More common are 400-series stainless balls where corrosion resistance is not as important but hardness is and these are strongly magnetic. Regular chrome steel bearings are magnetic and harder and stronger yet but not as corrosion resistant. For bicycle use chrome steel is the best choice for cost and durability.

The best ball bearing steel is 52100; it is very magnetic, and requires corrosion protection.

440C is a stainless steel, nearly as good a bearing material as 52100, it is magnetic, easy to pick up with a strong magnet. Better at not rusting than 52100, but not very good compared to other stainless steels.

Non-magnetic stainless steels do not make very good bearing balls, avoid.

Good info, clearly explained. Thanks nfmisso.

Grade 25C balls are overkill for our use. had SS in my DA 9sp hub and did not care for them. Replaced them with 25C.

Crazy idea, could they be made de magnetized,
​​​by using the appropriate tool?

Was just an idea. However, I doubt this would have any real life implications.

OK, before I get more confused, when we say a certain ball bearing is "magnetic", don't we mean that said ball bearing is composed of "ferromagnetic" material, for example steel, but may not necessarily be "magnetized"? I used to use a magnet to position new balls into their corresponding cups until I noticed the new balls were becoming magnetized by my doing so and thus sticking to each other. Hopefully only temporarily, but still I know of a great deal of lubricated machinery having a magnet placed inside in a strategic location, usually a drain plug, to attract and hold any ferromagnetic grit or filings so as to keep it all out of the bearings as much as possible. If magnetizing new ball bearings might attract steel grit to them I thought it prudent not to. If just they lose their magnetic fields guickly, maybe no big deal. I still use the magnet to quickly pull out old balls for disposal though.

The balls will loose their temporary magnetism quickly, faster in the neighborhood of other temporarily magnetized balls and when exposed to mechanical force (bearing preload and loads for example).

Thanks. That sets my mind at ease.
I am not an engineer, I just ride on trains.

Ceramic bearing balls are certainly non magnetic, of course.