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I use a few pipe clamps in my shop. A few years ago I read, in Wood Magazine a tip. It said you could easily made wood pads for pipe clamps and hold them in place with rare earth magnets. So I made them for my clamps. I glued the magnets into place with two part Loctite Epoxy. Three of the glue joints have failed, the magnets, coming out of the socket.


What did I do wrong?
 

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make the hole for the magnet tight fitting...
make it a fuzz deeper than the magnet is thicker...
film the pocket w/ thin viscosity epoxy to seal the wood... you are sizing the hole...
use thickened/full body epoxy to glue in the magnet..
make it a combination of glue up and press fit...

good chance the wood grain absorbed your epoxy some and then it could not bridge any gaps...
basically your glue up ''broke''
 

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Sink a screw under the magnet into the wood. It will have about as much attraction to the screw as it does the clamp. Then the glue shouldn`t have to hold that well.
 

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Small is Better

How about adding a thin face of hardwood and glue in a really strong/big magnet?
Tom; like Berry, I use the same pad system. Mine are plywood.
The issue is for the pads to slip around while you're trying to get the clamps into position; large magnets are not only unnecessary, they're potentially a p.i.t.a.
The big issue is the one Berry's having, where the magnet wants to pull out of its hole.
The other thing is the difficulty in swinging the pads around on the pipe. All you really want is for the pads to stay put until you get some pressure on them.
I don't have magnets on mine, but I'll fix that oversight asap with small R.E. magnets, held in with epoxy putty...cleaning the magnet with alcohol first.
 

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to reduce the holding strength of the magnet..
put a piece of tape over it....
recess it into the hole by a schosh...
 

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I think Dan is right about cleaning. Did you use alcohol to clean off the magnets? I have some with a very thin coat of something - mineral oil I'd guess. I'd expect that to reduce the holding power of epoxy.
 

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Actually, If the epoxy isn't holding the magnet you need to make some changes.

The magnets are plated and most of the suppliers recommend that you "rough up" the part in contact with the epoxy. You have to provide some "tooth" for the epoxy to stick to the magnet. I have done this for years and have never had a magnet come loose from the epoxy glue. I generally use 100 or 120 grit sandpaper. Sand the epoxy side of the magnet in a cross hatch pattern. In addition, I cut a small relief in the side of the hole for any air to escape, making sure that there isn't an air pocket preventing contact with the epoxy.
 

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Screw a bolt in from the side and tighten it a little.
 

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Discussion Starter #12
I think Dan is right about cleaning. Did you use alcohol to clean off the magnets? I have some with a very thin coat of something - mineral oil I'd guess. I'd expect that to reduce the holding power of epoxy.
I did not clean them in any way. I've been wondering if that isn't the cause.....
 

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I drilled a hole in each clamp, close to the web, and put a screw in from the back. These fixtures are only used on wood though. I haven't had one crack, but it was a concern. You can also get cups for the RE magnets. Same idea as putting a screw under it.
 

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Or you can glue a washer in the hole for the magnet to grab, or hold the washer in with a small flathead screw. And get away from that messy old epoxy

Herb
 

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And question your mixing technique. Two part epoxy always needs more.
 

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If no one mentioned it yet consider drilling a 2 part hole, run a forstner bit the size of the magnet from the wrong side and leave a strong 1/16" of wood od the right side. Then drill an 1/8" smaller diam. hole from the correct side, maybe temp plug the hole prior to drilling the smaller diam for support. then plug and glue the wrong side if required.
 
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