Glueing Magnets??

Re: Glueing Magnets??

johnv

or silicon glue.

Re: Glueing Magnets?? *LINK*

Bill Howatt

I buy the metal cups the round magnets fit in and screw the cup to one side of the door or cabinet. The cups hold the magnet well and have the bonus of increasing the strength of the magnetic field.

Here is an example: https://www.leevalley.com/en-us/shop/hardware/rare-earth-magnets/accessories/cups/32066-steel-cups-for-rare-earth-magnets

You can usually remove a smaller magnet from the cup if necessary by applying a larger and stronger magnet over top of it.

Bill


Magnet Cups

Epoxy's fine, and

Bill Houghton, Sebastopol, CA

If you're using magnets in door and jamb, make sure you've got the orientation right before you glue them in.

You can probably imagine how I know that.

Re: Glueing Magnets??

John in NM

Maybe epoxy would hold. I've used it often but I've had some failures of it, usually after a couple or three years. Could be wood shrinking (its dry here) and the epoxy bonds to the wood better than the magnet and is flexible enough to go with the wood and pull away from the magnet.

I don't like those cups either -- good idea, but when I used them I often had the magnet stick to the disk on the door and pull out of the cup. Still works, but it can be annoying because the door may not close right with the magnet having to re-align to the cup.

I really liked the solution in Svante Nilsson cabinet posted about 3 weeks ago - put the magnets behind wood plugs. Problem solved, the plug is wood to wood, magnet need not stay firmly attached to whatever adhesive is used. May be too much fuss for your needs in this case however.

I've noticed that nothing much likes to bond to those magnets. I bet the silicon caulking JohnV suggested would hold well if you can stand to use the stuff. I've never tried that but next time I might.

Good way to keep track of the magnet polarity is to put a sharpie dot on one side of a magnet, then mark all your others to match that. Dot comes off easily with alcohol once installed.

Re: Epoxy's fine, and

Johanna Johanson

Thanks for a good laugh this morning!

Epoxy

John K Jordan

I have had success and no failures using epoxy on super magnets. I scratch the magnet with a file first to give the epoxy something to grab and clean well with alcohol before gluing.

I've also used medium CA glue for fastening magnets to metals for indoor use.

I often epoxy disk magnets to the lathe, bandsaw, etc. for holding tools and such when the magnets would otherwise sometimes slip or stick to the tool.

I agree with marking to align the polarity before mounting. I write N and S with a fine sharpie where I need pairs.

I've been using rectangular magnets for such things, about 2 x 6 x 20mm.

Note that two magnets, one on the door and one on the cabinet, might actually be too strong. On some recent small doors on a small enclosure I tested and found two attracting magnets were WAY too strong for that application. Instead of a pair of magnets on each door I used a piece of thin steel and a single magnet.

One interesting experience about gluing super magnets with epoxy, specifically the JB Weld type which contains iron particles. I mounted a small cylindrical magnet in a hole in a fence staple holder, meant to hold the staple while hammering. Problem was the staple would sometimes fall out but the magnet works well to hold it. But when gluing it in place I put JB in the hole and put extra around the outside to make a fillet for the longish magnet. While I watched, the JB Weld mixture started to rise up from the surface and form a glob above the magnet! I pushed it back into place repeatedly until the epoxy started setting up. (The result was perfect - hammered hundreds of staples with it since!)

JKJ

Don't know what to tell you...

John in NM

I've had epoxy fail. As I said, could well be the dryness here, could maybe have been a bad mix of epoxy, I sure don't know. Just the regulation 5 minute epoxy from Home Depot.

I believe I pushed the magnets back in and ran some thin CA around the edge and they've held since then. Perhaps a new application of epoxy would have worked too, but with such tight clearances I didn't want to try.

Re: Don't know what to tell you...

John K Jordan

>>>I've had epoxy fail. As I said, could well be the dryness here, could maybe have been a bad mix of epoxy, I sure don't know. Just the regulation 5 minute epoxy from Home Depot.

I believe I pushed the magnets back in and ran some thin CA around the edge and they've held since then. Perhaps a new application of epoxy would have worked too, but with such tight clearances I didn't want to try.

Don't know, but two things. I use high quality 30min epoxy, haven't tried the HD version but most should be fine.

I do leave a little clearance when I use epoxy, maybe that makes a difference.

JKJ

Re: Don't know what to tell you...

Bill Howatt

I also have had epoxy failures but I likely didn't do your procedure of roughing the surface first. I notice that on my Lee Valley magnets, and perhaps others, there is a thin metal plating on the surface and maybe what is under it bonds better. I probably also used 5 minute epoxy but it would have been from LV.

I only use 1 magnet in the cup and a piece of metal on the other surface thus my magnets never dislodge.

Bill

Plating failures...

John in NM

Those are common. Some magnets never seem to have the problem, others do. I have yet to see it in a glued in magnet however, just on loose ones.

At a very wild guess maybe too much difference in CTE between the plating and the magnet material, seems like some of the magnet stays with the failed plating - not surprising as the magnets themselves are very brittle.

Just a guess though, the temperature swings in my shop are no longer as huge as when I lived in Arizona - now maybe 30F winter low to summer high (uncooled shop, woodstove for heat). Doesn't seem like that would be a problem for anything.

Re: Glueing Magnets?? Speedtape

John in NM

Not a bad idea at all!

Goes in the recess with magnet on top I'm assuming? Gonna try that, might even try the cups again with a little punched out round of double sided tape at the bottom of the cup.

Re: Glueing Magnets??

William Duffield

To deal with magnet releases, you need a more flexible adhesive, for example Alumilite epoxy resin (often used for filling Nakashima style and river tables), or E6000.

Lee Valley's rare earth magnets are pre-marked for polarity with a small red spot, but you might remove it if you clean the magnet with acetone to help it adhere to the glue.

Re: Glueing Magnets??

Pete in Holland MI

All glue bonds will work better when they are gripping to a rough or porus surface, as you get more of a mechanical bond rather than a chemical bond.

Cleaning the surfaces to get rid of any dust or oils (especially finger oils) will help all adhesives to bond to the parent piece, not the oils & dirt in between.

A well designed adhesive joint relies on shear of the joint to fail. A straight tension pull or a prying pull is very weak.

Coarse grind the edges of your magnet. Slightly undercut the hole in the wood with a Dremel tool.

Oh.....and........silicon is the stuff electronic chips are made of. Silicone is the caulk/adhesive stuff. Watch your e's.

I've also had epoxy fail

GolfSteve in Calgary

After about 10 years of service the magnets (both of them) came loose. I used 5 minute epoxy. I re-glued with more epoxy and hope to get 10 more years of service. These were small 3/8" magnets directly epoxied into thin wood (maybe 1/4" thick) so metal cups could not be used.

If the wood thickness allows for it, I prefer to use the metal cups that are screwed into the wood. There will be no failure with those.