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[Ron Locke]

I remember someone talking about using magnets in puzzle boxes. I was in Walmart the other day and came across some fairly strong button magnets. I was wondering if anyone has used them and how thick a piece of wood they would pass through and still be effective.

[Robert Yarger]

I never used the walmart brand, but the ones you can buy online can suck the fillings out of your teeth from across the room.  I can move other magnets on the top of my table by placing magnets below, and my table is 4" thick. 

The only thing is that if you are planning on putting additional magnets in a puzzle, be sure that they don't interfere with eachother adversely. 

Anyway, as far as I know there is very little (if any) resistance to magnets as they go through wood, which is normally an insulator for electricity.  What does effect them is distance.  Eric has the more official numbers on distance vs. effectiveness, but roughly it seems that for each doubled increment of distance between magnets, thier effectiveness is cut in half.  For some of those insanely powerful magnets, you don't want them at full strenght anyway.

As a side note, if you think that you might be insane with a particular puzzle concept, then you are probably right on track.

Also, you can get magnets that have + - poles on the ends, but also get some where the poles are perpendicualr to that.  Your walmart magnets are likely postive on one side of the coin, and negative on the other, but you can also get magnets where the poles are like cross half-sections of a coin put together.  These magnets are used to spin mechanical parts as opposed to attracting or repelling. You can also get magnets are are shaped like washers, but have the negative aspect on the inside ring, and the postitive on the external circumference.  These are interesting and can be used on wooden dowels to do a lot of intersting things.

[Canuck]

can suck the fillings out of your teeth from across the room. 

Dude! did you have to go there, you know Stephen is going to jump all over this one

[Eric Fuller]

Ditto what robert said.  The Wal-Mart magnets are probably ceramic, and they are prone to losing their strength over time.  The Neodymium magnets Robert and I commonly use lost something like 1% of their strength every 10 years, even if they are stressed by opposing ot attracting each other.

The box I'm finishing up now has some retardedly strong magnets in it.  Try 2" square by 1/4" thick!  I'll actually have to put a disclaimer on the sales page!

[Robert Yarger]

Eric, sounds like the mailman will be delivering your puzzle to someone, but has to use a crowbar to pry the package off of the side of the mailtruck.  You should include in your disclaimer that you should not have credit cards in your wallet when you operate this puzzle, as it will wipe the information on the magnetic strip clean.  Does a VCR work in the same room as your puzzle?

I will say that I was working on one box in particular, and making cuts on pieces that I had already glued neodymium magnets into.  The sheer force of the magnets actually pulled the sawblade over 1/64th of an inch and caused miscuts.  In other instances, the magnets I had glued firmly in place were ripped out and became attached to the sawblade.  Some of the magnets we use are just insane.

Stephen!!!! Stephen!!! Wake up.  We are talking about magnets now.

[Kerry Verne]

How much was the repair cost on the watch Eric?

[Eric Fuller]

heh, about $150 IIRC.

A good thing to point out to customers who buy products with magnets:

-Don't cuddle with the puzzle if you have a pacemaker
-Keep your Rolex or any other mechanical watch away from the magnets
-Credit cards (natch)

Actually the 1/4" of wood around the bigass magnets I'm using serves to shield them pretty well.  I think the pull is only 2-3 lbs....OK, maybe 5.

Robert...I was having a heck of a time trying to figure out how to sand this box because of the magnets.  Ended up building a small vaccuum table with a 5" random orbit sander built in.  Works like a champ! 

[Ron Locke]

I was just looking through a Edmond Scientific cat. and found some neodymium iron magnets. They were selling a 1/4" dia. x 1/8" magnet with1.75 lb/pull for 2.98 .Is that a fair price to pay? A 1/2" x1/8" had 5.5 lb/pull and sold for 4.95. Where can I get the best price?

[Carl Morris]

Here are a couple sites to check out:

    http://www.amazingmagnets.com/
    http://www.kjmagnetics.com/

Be careful, they can suck money right out of your wallet...   

    -- Carl

[Eric Fuller]

I was just looking through a Edmond Scientific cat. and found some neodymium iron magnets. They were selling a 1/4" dia. x 1/8" magnet with1.75 lb/pull for 2.98 .Is that a fair price to pay? A 1/2" x1/8" had 5.5 lb/pull and sold for 4.95. Where can I get the best price?

WOW, talk about highway robbery!

Here's 1/4x1/8 for $0.19 each:
http://www.magnet4less.com/product_info.php?cPath=11&products_id=100

Here's 1/2"x3/16" for $0.42
http://www.magnet4less.com/product_info.php?cPath=11&products_id=550

magnet4less is a great vendor...very prompt shipping, excellent customer service, you can talk to the owner on the phone.  K&J has screwed me over a couple times - once VERY delayed shipping, once with misleading product description. If you have a problem with K&J, there is *no* support other than email, and they take several days to bother getting back to you.  I don't like doing business with places that are afraid to take a phone call from their customers.  Not to mention that mag4less prices are 50-70% less than K&J.

[Ron Locke]

Eric,
I went to that site that you sent to me. The prices are dirt cheap. They even have a magnet with a 500 lb pull. I'm going to order a few different sizes and see how I might use them in a puzzle box. Thanks for the info.