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Post by Rockindad on Feb 17, 2019 22:46:18 GMT -5
My sons school holds an arts and crafts fair once a year where the kids can sell their creations. One of the things he would like to do is sell slab magnets. The thinking is using neodymium magnets glued to the backside of the stone. Plan on scuffing up each surface. Looking for recommendations on the best/strongest glue for this application. Cure time is not really a consideration as this is a ways off yet and they can sit on the work bench as long as they need to. I also do not think working time needs to be considered as this should be a pretty easy process.
Even though they are being sold at a kids craft fair he does not want people to have their magnet coming apart on them.
Thanks, Al
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Post by manofglass on Feb 17, 2019 23:01:33 GMT -5
I would use 330 epoxy
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Post by aDave on Feb 17, 2019 23:19:21 GMT -5
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Kai
spending too much on rocks
Member since December 2018
Posts: 331
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Post by Kai on Feb 18, 2019 0:27:22 GMT -5
2-component epoxy resin can work really well, especially if you add a spoon of cotton fibers for endurance.
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Post by gmitch067 on Feb 18, 2019 1:30:11 GMT -5
I made slab magnets for the kids in my Grand Daughter's 3rd grade class in North Dakota ( about 20 kids and faculty). I used 3M foam double sticky side disks to affix the 1/2 inch neodymium magnets to the back of the 30mmX40mm cabs. I used alcohol swipes to clean mating surfaces first...
I have received no complaints so far about the foam and adhesive failing in the winter cold (down to -21 degrees - no wind chill factor)... however... I anticipate that in years to come the foam might crenelate and fail due to sun/heat (they would probably last a long time in the in-house/no sun environment).
Because the larger 1.25 inch neodymium are soooo powerful, they should be used with caution around kids... they could cause a really painful pinch on a toddler's fingers... not good. That is why I used the smaller 1/2 inch magnets for the kid's stones. It held 3 pages of 8/10 inch paper to the side of my refrigerator before the bunch slid down to the floor... So... good enough to proudly display an "A" paper... or a tardy/expulsion slip or three.
For those slab magnets I made for my own kids (adults now) I used the 1.25 inch magnets, and the cabs had to be cut wider to hide the magnet behind it. I used 330 epoxy for those... works great! I don't have to worry that the magnetic pull will separate any foam backing as I grab hold of the stone slab to remove it from the refrigerator... VERY strong... They hold major craft paper art works well.
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Post by gmitch067 on Feb 18, 2019 2:05:09 GMT -5
Additional note of caution...
Be VERY careful when you handle the 1.25 inch neodymium magnets as you work on your slab magnets. I used the N45 ones that came in batches of 6 from Amazon. Of course I had to get four rolls. When I unpacked them, the rolls (6 each with plastic spacers between) quickly became attracted to each other and came together with enough force to cause some severe damage to my hand if it were to be caught between them... I lucked out... I still have two hands... without severe bruising. BEWARE! Not something to subject a toddler's hands to.
As the spacers were removed, and some of the magnets stuck together... getting them apart became a chore of trying to slide the top one off for use. I broke one magnet in half as I slid it half off the stack to lift off. Through trial and error I found a Tupperware plastic (?) pan scraper worked well... forcing the sharp end of the scraper between the magnet segments to lift one off.
Hope this helps.
Glenn
P.S. The larger refrigerator slab magnets are a challenge to pull off the frig... hard to grasp the shiny cab on it's slick sides to get a good pull to remove them. 'Might want to consider roughing up the sides a bit... or something...
One idea is to use 3/8 inch slabs to create the cabs and use a groove grinder to produce a shallow groove around the outer edge to allow something for the fingers to grab.
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Post by Jugglerguy on Feb 18, 2019 5:30:27 GMT -5
I use epoxy. I think my magnets are 3/8 inch. I bought them in packs of 50 or 100 from eBay.
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Post by Rockindad on Feb 18, 2019 8:23:39 GMT -5
Additional note of caution... Be VERY careful when you handle the 1.25 inch neodymium magnets as you work on your slab magnets. I used the N45 ones that came in batches of 6 from Amazon. Of course I had to get four rolls. When I unpacked them, the rolls (6 each with plastic spacers between) quickly became attracted to each other and came together with enough force to cause some severe damage to my hand if it were to be caught between them... I lucked out... I still have two hands... without severe bruising. BEWARE! Not something to subject a toddler's hands to. As the spacers were removed, and some of the magnets stuck together... getting them apart became a chore of trying to slide the top one off for use. I broke one magnet in half as I slid it half off the stack to lift off. Through trial and error I found a Tupperware plastic (?) pan scraper worked well... forcing the sharp end of the scraper between the magnet segments to lift one off. Hope this helps. Glenn P.S. The larger refrigerator slab magnets are a challenge to pull off the frig... hard to grasp the shiny cab on it's slick sides to get a good pull to remove them. 'Might want to consider roughing up the sides a bit... or something... One idea is to use 3/8 inch slabs to create the cabs and use a groove grinder to produce a shallow groove around the outer edge to allow something for the fingers to grab. The strength of magnets and grip are to be considered. The mini slabs are only going in the vibe so they should still have some "texture" on the edges to help with the grip. I have wrestled with larger versions of these magnets before so know they can be a pain, but the holding power makes them worth it. |
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pizzano
Cave Dweller 
Member since February 2018
Posts: 1,390
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Post by pizzano on Feb 18, 2019 15:44:47 GMT -5
Bulletin board, frig magnets are a pastime addition to the many tumbles I give away as gifts.........here's a pic of what I use.
I've found this variety of "ceramic" magnet to be very strong (industrial grade C-8).......not so much that it takes a tool to lift off the surface. The adhesive can be found at most hardware supply and Walmart........been using it for many years, so far it seems to hold-up quite well........just a thought. |
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lookatthat
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Member since May 2017
Posts: 1,360 
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Post by lookatthat on Feb 18, 2019 16:13:49 GMT -5
Also those very powerful magnets shouldn't go to houses with small kids because if they swallow more than one, the magnets will seek eachother and cause awful intestinal damage.
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lookatthat
Cave Dweller
Whatever there is to be found.
Member since May 2017
Posts: 1,360
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Post by lookatthat on Feb 18, 2019 16:14:27 GMT -5
The ceramic magnets are not as strong but are safer.
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pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
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Post by pizzano on Feb 18, 2019 16:24:58 GMT -5
Also those very powerful magnets shouldn't go to houses with small kids because if they swallow more than one, the magnets will seek eachother and cause awful intestinal damage. Properly stored and out of reach of the "little ones" who are still putting anything their in their mouths, shouldn't be an issue. If one is allowing kids of that age to handle "frig magnets" the problem is not with the magnets.......!
I have "little ones".........nothing on the frig or any other location these things are attached, are within climbing distance to their little inquisitive fingers.......lol
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lookatthat
Cave Dweller
Whatever there is to be found.
Member since May 2017
Posts: 1,360
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Post by lookatthat on Feb 19, 2019 10:03:23 GMT -5
I agree, unfortunately many people are unaware of the danger. The kids who are old enough to know better than to put the magnets in their mouths aren't always responsible enough to make sure to keep them out of reach of the little ones. Which was why, when I used these in the school, I was sure to explain this to the kids (and take a count of magnets afterwards.)
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AuroraNan
starting to shine!
Member since December 2018
Posts: 25
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Post by AuroraNan on Feb 21, 2019 2:06:23 GMT -5
I have some thoughts regarding strong magnets and electronics; Magnets can cause unexpected issues with the computers inside the appliance. They can also cause mechanical problems. My husband set a large magnet (that we used on the old refrigerator) on top of the new one. For 2 days, we couldn't figure out why the light quit working. He noticed the light "button thingy" was not releasing when the door opened. He then remembered the magnet, removed it and the light went on! The magnet was keeping the button retracted so it couldn't release the light switch....anyway, strong magnets are not always the right way to stick precious artwork to the best display area in the house. Perhaps encourage using a separate magnetic board on the wall, where magnets are less harmful. It could be the next best art gallery for Nature's rock art and children's masterpieces.
Nancy 
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Post by gmitch067 on Feb 21, 2019 11:02:46 GMT -5
I have some thoughts regarding strong magnets and electronics; Magnets can cause unexpected issues with the computers inside the appliance. They can also cause mechanical problems. My husband set a large magnet (that we used on the old refrigerator) on top of the new one. For 2 days, we couldn't figure out why the light quit working. He noticed the light "button thingy" was not releasing when the door opened. He then remembered the magnet, removed it and the light went on! The magnet was keeping the button retracted so it couldn't release the light switch....anyway, strong magnets are not always the right way to stick precious artwork to the best display area in the house. Perhaps encourage using a separate magnetic board on the wall, where magnets are less harmful. It could be the next best art gallery for Nature's rock art and children's masterpieces.
Nancy 
I appreciate this information Nancy... something new to all to my troubleshooting list. I also like your idea to create a separate magnetic board on the wall (I use a metal cookie sheet to display stuff.  |
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