Bad And Good Magnets?

[+Thot]

A while back I read in these forums that Radio Shack ceramic magnets like these are poor quality and do not have the holding power of ordinary ceramic magnets. Is this true? I ask because it’s the only place locally I know of that I can buy small quantities of ceramic magnets.

Edited April 28, 2005 by Thot

[+DaveA]

A while back I read in these forums that Radio Shack ceramic magnets like these are poor quality and do not have the holding power of ordinary ceramic magnets.  Is this true?  I ask because it’s the only place locally I know of that I can buy small quantities of ceramic magnets.

dunno anything about the radio shack magnets, but if you want the strongest magnet for it's size you should consider rare earth magnets rather than ceramic.

 

Looking at the price radio shack wants for theirs you will likely save money even with shipping if you buy from here and you can buy in lots of any size including just 1.

[JohnX]

I can't speak to the quality of the magnets at Radio Shack. I have purchased dozens of round ceramic magnets at local craft shops and have good luck finding them there.

 

I take it you are looking to make magnetic mounted micro containers. You could try this source for magnets if you can deal with internet mail order.

 

If you have access to discarded hard drives you can take them apart and remove odd shaped magnets that are much stronger than ceramic magnets. It's a bit of a fiddly job if you don't have the property tools.

 

I edited this post to add a shameless plug for a web site I created on how to make your own motor with those magnets you have left over from your micro containers. As soon as I get more magnet wire I will be making a cache where the only swag is motor kits.

Edited April 28, 2005 by JohnX

[+Sputnik 57]

There are several sources for neodymium magnets in the linked thread. When I want to search for them, I can never remember how to spell "neodymium"

 

Edit: With neodymium magnets, you aren't limited to micros. You can hold an ammo box onto a metal post with the DC6B. 25+ pounds of pull force in a 3/4" x 3/8" cylindar! Just don't get two of them stuck together.

Edited April 28, 2005 by Sputnik 57

[+horsegeeks]

If you don't care what the magnet looks like and need something VERY powerful use the the magnets out of old hard drives.. They are a pain to get out but worth it for a strong magnet. There are two in each HD

[+Eswau]

I had good luck with the ones I bought on eBay.

[bogleman]

I will agree the magnets in computers are great. Just go around on garbage night and look for a tower or hit some dumpsters near a computer store. The hard drives are tough to open and the magnet mounting brackets are held on with epoxy, just soak them in acetone overnight in a sealed container. There is a regular cache in my town that is held onto an electric service box with the hard drive magnets, they really work well. The cache container weighs about 4-5 pounds and looks like an electrical/phone service box.

Ian

[+DaveA]

I will agree the magnets in computers are great.

The magnets in old hard drives are the rare earth/neodymium magnets. You can buy such a magnet in a less goofy shape for a buck, less in quantity.

 

Just wanted to point that out in case some aren't interested in scrounging hard drives and dismantling them.

[+nfa]

reading this thread inspired me to buy some magnets from http://www.kjmagnetics.com/...

 

nfa-jamie

[+DaveA]

reading this thread inspired me to buy some magnets from http://www.kjmagnetics.com/...

 

nfa-jamie

be careful, I started out that way too. Soon I found myself wanting more sizes/shapes and now I have literally hundreds of magnets stuck to my garage service door.

 

I have so many that I now leave a stack as a trade item in caches.

 

If I put them all together I could probably lift my car with them...lol. Beware the addictive magnets.

[+Yamahammer]

Hi! My name is Mark! ... (Crowd says, "Hi Mark!") ... And I'm addicted to (gulp) ... magnets. (Crowd gasps!) "Oh no Mark! Not that!!!"

 

Ya'll have a great day!

[+CompuCash]

Thot -

 

I have use some of the RS magnets for non-gc purposes - they suck!

 

they were all I needed at the time but they are pretty sad and if you wnat them to hold a chace it ought to be pretty light.

 

get some good rare earth mags

[+Thot]

Thanks for all the replies. Now another question.

 

What size do I need to hold up an object that weighs a little over a half pound?

[bogleman]

assuming that there is a good solid flat base to attach the cache to and the size and makeup of the cache container is small at least two one inch squares/circles (R/E magnets) set in epoxy INSIDE the container should be fine. Test prior to placement to make sure it will hold up over the long run. The more the better and if the magnets are inside completely covered they will still hold if the glue fails.

[Mvillian]

Just go to your local Hardware store,all in my area carry an assortment of great magnets at great prices

[+planetrobert]

reading this thread inspired me to buy some magnets from http://www.kjmagnetics.com/...

 

nfa-jamie

hmm....this could be a bad site to have introduced me to....

[+Night Stalker]

I was able to buy some really good small magnets at Hobby Lobby.

[+DaveA]

Thanks for all the replies.  Now another question.

 

What size do I need to hold up an object that weighs a little over a half pound?

Well if you go to the kjmagnetics pull force page they list the pull force of each magnet they sell.

 

The listed pull force is under ideal circumstances (they describe what that means on their site).

 

My recomendation is to buy a magnet that is rated 5-10x stronger than the weight you need to bear because you will likely not place the magnet in an 'ideal' circumstance and if you are using this for a cache you have no guarantee those who return the cache to it's place will place it as 'ideally' as you do.

 

Also, stick with the circular or square magnets rather than the rods for best results. I have a bunch of magnets in varying shapes/sizes and the bottom line is the more surface area the part of the magnet that 'sticks' has the better it holds.

 

To give you an idea of the strength of the magnets I use 1/4" round magnets with a 1/8" thickness to replace all my refrigerator magnets. These magnets are capable of holding a clip with several papers very securely to the fridge. I have a 1/4"x1/4" magnet holding a stethescope to the fridge. This is not mounting the magnet in an 'ideal' fashion because the weight of the stuff the magnet supports pulls across it's pull force rather than directly against it since the magnet is stuck to a vertical rather than horizontal surface.

 

If I were to place a micro sized cache and wanted to be certain it was securely in place regardless of how it was positioned I would use a 1/2" circular magnet that was 1/8" thick. It has a 5.8lb pull force rating and I would figure the micro to weigh less than 1lb.

[+Thot]

If you don't care what the magnet looks like and need something VERY powerful use the the magnets out of old hard drives.. They are a pain to get out but worth it for a strong magnet.  There are two in each HD

I just discovered that a surplus electronics store in our area carries these magnets salvaged from hard drives.