Magnets

[ian.mcdougall]

Hi everyone
I have a variable speed control unit for wood lathe that I want to be able to position anywhere on the lathe I had some magnets from a Microwave that have a strong pulling force but when I tried them on the control box they tend to slide sideways easily on the metal parts of the lathe I have a rubber sheild over them to stop scratches and breaking when attaching them. Does anyone know can the force of a magnet be improved by different mounting methods eg mounting a circular plate on the magnet front or back or both. Is there a better type of magnet and where to buy from that would perform better
Regards Ian

[MarkyB]

Microwave magnets are strong but quite big I believe.
Computer hard drives have equally strong magnets but a bit smaller which may make them more usable.
You need maximum surface area contact, if there are letters cast into where you want to put it you won't get that.

I have a suspicion that cast iron is less attractive than steel, but I might have made that up or dreamed it .

[ian.mcdougall]

Hi MarkyB
the unit is about 6" x4" so magnet is OK size wise and magnet on its own seems to be hard to pull off straight but when mounted to back of unit with its weight and slight pressure is easy to move and the surface its going onto is smooth

[MarkyB]

A bit of research, and the look of them suggests that microwave magnets are Ferrous magnets, Hard drive ones are rare earth.
http://en.wikipedia.org/wiki/Rare_earth_magnet
Or about 3 times stronger.

A chat with my bother in law suggest that if you fix a round chunk of iron or steel in the middle of, but not touching, you magnet, then you will create a sort of return path and have to bust a blood vessel to move the control box.

[ian.mcdougall]

Thanks MarkyB
I think I will try the idea of a central core and let you know the outcome