Thread: Rare earth magnets

Originally Posted by chambezio

While on the subject of rare earth magnets (Slight deviation to original poster, Sorry) For a small hinged box (150mm X 150mm and 50mm deep) I have fitted one magnet 8mm X 3mm and have put a screw head in the lid to "catch" the magnetic activity. It works but marginally.
Would it be best to put two magnets in, one in the bottom and one in the top? I haven't seen any recommendations for fitting them.

Hi,
it may be that the screw head may not provide enough surface area for a good hold, or that it is not meeting the magnet dead square. I would test first with a loose screw and maybe a filed flat nail head and compare the power to that of the fixed screw.
Otherwise fit the second, but i would put something thin between them, like a layer of epoxy to stop them "snapping" i have seen magnets ruin each other through uncontrolled contact. Better get your N/S right too, a floating lid could be amusing!!

Chambezio.
I have used the rare earth magnets quite a few times and have found that a pair of 6mm dia x 2 mm magnets are sufficient to hold a box closed without being too strong to open. I always use a 6mm dia cutter and take it just over 2 mm deep on both the base and the lid. I use a 24 hour Araldite to hold the magnets in place. When closed, the magnets are not quite touching.
Works for me. Try it out on some scrap timber to see the result before committing to the final box.

Often, you'll need to use 2 magnets on one side and one on the other, especially the little 3mm diameter ones.
From the Veneer Inlay website. (Note the use of 3 magnets.): -

Attachment 213422


I made a couple of glasses cases using 3mm magnets and had to do this, otherwise if the case was picked up by the top it could fly open from gravity.
I used 2 sets of 3 magnets to secure the lids firmly, with pairs in the base and singles in the lid.
N.B. These were only 3mm dia x 2mm magnets, though, I should point out.

5mm magnets have more pull.

Originally Posted by Ueee

Better get your N/S right too, a floating lid could be amusing!!

Been there, done that.
Great fun getting a reverse-polarity magnet back out after gluing.

Did that on my major project, day before the exhibition set-up! Luckily, I could drill in from behind and punch the magnet out.

Originally Posted by AlexS

Did that on my major project, day before the exhibition set-up! Luckily, I could drill in from behind and punch the magnet out.

G'day Alex.
Yeah, it's so easily done. Now I always put a spot on the side that's to remain outwards, with a permanent marker, then clean it off with metho and a cotton bud after gluing.
I'll never make that mistake again if I can help it. (Mine was in balsa and I dug it out with a small screwdriver. Messy.)