Best adhesive for magnets?
I need to glue some rare earth magnets to mild steel rods, both .25" diameter. Same design as an eraser on the end of the pencil.
They'll be holders for various small antiques. The magnets allow them to be mounted without mutilating them, and to be removed for inspection with a minimum of fuss.
What's the best adhesive for this? Hardware store superglue hasn't lasted so long, even with careful cleaning of the surfaces. Is there a particular grade of superglue, or a flavor of Loctite that works well for this?
JB weld has worked ok for larger magnets, but it seems a bit sloppy for .25"
I used to do this professionally, but boy, its been a long time.
In the late 70's, I worked in a woofer factory, and we glued magnets to steel all day long.
We used a loctite product, which required a particularly odd smelling oily activator, and the glue itself looked like honey. It dried to a translucent golden color. It was an anerobic, but not a super glue.
Not sure, however, which loctite product that was- I used to order it in 5 gallon pails.
I think JB weld is actually a pretty good solution- just mix it up on a piece of cardboard, and apply with a paper clip.
We make 3/8" thick sliding shims from prehardened steel and bore holes in them to secure some rare earth magnets. We've always used JBweld and have used it for years. We simply leave about .004" clearance (just enough to squeeze the air out) and clean up the excess with alchohol before it cures. It works quite well.
Epoxy labeled for metals should work fine.
You did not state if the rods were the antique, if the magnet is on the display and is used to secure the item, then make pres fit holes in the rods for the magnet to be pressed into.
I would suggest Devcon High Strength 5 minute epoxy. I've had excellent results with this product for years, and have used it in in many professional metal/metal applications where I needed strength, durability with exposure to handling and attractive finish. Fast setup times...nice clear finish, easy to work with. My local hardware sells it fwiw, but they have a variety of packaging choices online. I usually get the (2) 4.5oz bottle pack
Originally Posted by Sea Farmer
Last edited by John Madarasz; 10-16-2010 at 02:02 AM.
Reason: add pdf
Loctite 620 is what we used for magnets to steel. If you glue on aluminum 416 Loctite does alright.
Maybe 35-40 years ago, my snow blower wouldn't start. Found when pulled off the flywheel, the magmets had come "unglued" and re glued them with a regular 2 part epoxy. Good surface prep-clean all surfaces well- they are still firmly attached.
Originally Posted by SND
Thats what we use at work.
Thanks everyone. I have both JB Weld and Loctite 620 on hand, so it'll be one of those. I'll remember the devcon high-strength epoxy too, as I'm getting more of these projects.
Best adhesive for magnets
Simply use a household flexible adhesive. I have a fair number in my workshop which have held or hold alloy rulers and plastic stuff without any bother.
I was looking at a pair of these digital boxes to take cheap digital chinese scales. They are flexible glued to stick onto my lathe- in this instance.
Really, it's as easy as that.
Outboard motors use a glue to hold magnets inside flywheels that routinely handle 6000 RPM! If you can find out what it is. I know it is available because some older motors need to be re-glued because the magnets have shifted.
I'm a little surprised at the recommendation of J.B. Weld for super magnets. My experience was the disappointment for watching the "metal filled" epoxy creep out of position, along the magnetic field lines rather than stay in place. I guess that might be OK if you wanted to embed the magnet in epoxy.
I routinely use Loctite 331 it is a one part contact adhesive, cures fast works good.
We also use an external mix two part epoxy that cures in 30 seconds (cant remember the name)
True magnet bond adhesives cure very fast. Loctite publishes a magnet bonding guide.
I wouldn’t use JB weld or anything with a filler, it will change the magnetic flux.
The best adhesive type is acrylic adhesives as they bond fast, bond metals well and are tougher which translates into impact resistance. The most common is an adhesive from Loctite called "Depend" where an activator is sprayed on one side and adhesive applied to other. Once mated it fixtures (ie only has to be clamped) in under 10 minutes. This is the type of adhesive used at OEM's for electric fan motors.
That beign said if just doing one part many adhesives will work as people who have used 620 and Instant adhesives have commented.
I used Loctite 326, a 2-part adhesive. Works like a charm. I also used it to repair a broken antique cast iron tool handle, worked great for that.
These pieces are subject to mild stress; as much force as a human hand can exert, but not a mechanical force. No temperature extremes. So far, so good, for this adhesive.
The activator is the same Loctite activator I use for threadlockers -- 7649.