Magnetism

[tony1941]

I am trying to demagnetise some ball bearings so they won't tend to "clump together". Any ideas? Please see my post in Science for more details

[MichaelZZ]

This might sound daft but it's worth a try.
Depending on how many ball bearings you have find an area with a hard floor (a garage is ideal) and put up pieces of would to stop the bearings rolling everywhere.
Then, a few at a time, drop the bearings from a height of 5 to 6 feet onto the floor. This should remove the magnetism.
As I said, it might sound daft but the technique is known as "mechanical degaussing".
Let me know if it works!

[TonyV]

Hammering as will heating an object in a flame will remove magnetism, but will cause surface damage or discolouration depending on method - which I guess you don't want on your steel balls(pedantic I know, but ball bearing is the name for a complete bearing assembly). 2 things that spring to mind is 1) Untried by myself is to heat a water filled stainless steel pan to boiling point and immerse your steel balls for 15 mins - when removed and returned to room temperature they should be demagnetised - worth a try & 2) Try a local engineering company to see if they could run them through their demag coil

[bert_h]

A problems not mentioned by TonyV is that after demagnetisation by heating, the balls will re-magnetise themselves again in the earth's field as they cool. To avoid this, you would have to keep them rolling about during the cooling process.

However, I think that you have to get way way above boiling water temperature to demagnetise them first, and I don't know what to suggest.

[tony1941]

Hi MichaelZZ. I have tried dropping them down a length of drainpipe vertically onto my kitchen floor quarry tiles - amazing how many bounces you get!! So far, though, I can't detect any reduction infield strength close to the ball. (I should have admitted, I have got a magnetic field strength meter which is sensitive enough to detect the earth's field (face the probe E-W then N-S and see the difference) and that hasn't shown any real reduction yet - perhaps keep trying??

[TonyV]

tony1941 do you have a compass handy - away from magnets will show true North / South - next to magnet will find magnets N /S - not sure how steel balls are polarized though

[TonyV]

sorry tony1941 - if you have some sought of gauss meter that helps

[MichaelZZ]

Hi Tony(1941)!
My suggestion of dropping the balls onto a hard floor was based on practical experience with steel bars. One of my customers, in those far off days when I worked to earn an honest crust, complained that some of the bars in his warehouse were magnetic and demonstrated this by dangling a string of paper clips from the end of one of the bars. I initially suggested that he shouldn't be using magnetic paper clips (nice try!) but he explained that when he was machining the bars the turnings were sticking to the freshly machined surface. There was probably some residual magnetism in the bars from the electromagnets used at some stage in the life of the bars - and although they should have been, they had not been through a demag coil.
I performed my circus trick of saying "Stand back everyone! Mind your feet!" and pulled one of the bars out of the rack and let it bounce around on the workshop floor. I asked the guy to dangle his paper clips again and surprise, surprise, they didn't stick. He said, "Yer a bluddy magician!"
So, Tony, it did work - once!

[TonyV]

bert_h as will all reactions on steel they are time / temperature dependant as I said not something I have tried - but nothing tried nothing gained

[stewey]

Here's a good buy for around 20 pounds. https://www.cousinsuk.com/catalog/equipment/demagnetizers/demagnetizer-swiss-style-platform