Choosing magnets for magnetic tool rack?

[victorhooi]

Hi,

I'm hoping to construct a magnetic rack to kitchen utensils and pots/pans - similar to here:

http://audzipandesign.blogspot.com.au/2011/03/diy-magnetic-knife-rack-tutorial.html

I'm currently trying to find suitable magnets - how should I compare magnets from different vendors?

For example, this site:

http://aussiemagnets.com.au/product/100-x--12.7-x--12.7mm-Block-(Rare-Earth).html

lists a magnet with a "pull strength" of 34 Kg and a surface Gauss reading of 6092 G, grade N42.

Another site:

http://www.frenergy.com.au/products/Block-30x10x46-mm-N40.html

lists a magnet with a "pull strength" of 25.21 kg and a surface Gauss reading of 6311 G, grade N40.

My question is - how comparable are these numbers from site to site? And which of these should I be focussing on for this application (holding up heavy metal implements)? From the name, I'd say the "pull strength", but is that actually correct? Are the other specifications not important here?

Basically, I want to be able to hold the heaviest implements safely and securely.

Cheers,
Victor

 

[EdStainless]

The best way to get holding force is to use magnets and pole pieces.
Say ferrite magnets that are rectangular, 1/4" x 1" x 2" with the N-S through the 1" length.
Or you could use Alnico pin magnets, or blocks.
Then you use two strips of magnetic metal, such as a 400 series stainless steel.
It will need to be about 1/4" x 3/8", so that it it stands up from the surface of the magnets.
This will not rust and it will carry the field.
Do not wrap the ends, just tun it along the N side and S side.
All of the magnets should be aligned the same polarity. You may need to glue them to a non-magnetic back piece to hold it all together because the magnets will want to repel from each other. But you don't need them touching each other. You won't need that much strength.
If you built one with NdFe you might not be able to pull the knives off.

You would end up with one of these

http://www.frenergy.com.au/categories/Magnetic-Tool-Holders/

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Plymouth Tube

 

[MagBen]

To make magnets comparable, the dimension need to be similar.

NdFeB could be too strong for your applications, also, its corrosion resistance and mechanical are inferior to AlNiCo or ferrite.

using pole pics on both sides of magnets is to form a close magnetic circuit when utensils are lied on rack, so that the useful flux density is high (as close to remanence as possible), and so a higher holding force.