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Thread: How to Glue Magnets on Acrylic (Dust Foot)?

  1. #1
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    Default How to Glue Magnets on Acrylic (Dust Foot)?

    So I'm making a new dust foot out of 0.5" cast acrylic. I tried gluing the rare earth magnets to it with some Loctite 2 part epoxy from Home Depot (it said it glues metal to plastics). Well... that didn't work to well because they fell off. Any ideas on a glue that will work? Thanks.

  2. #2
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    if you scuff up the acrylic where you want the magnet to stick, a thick CA (cyanoacrylate) should work. Also, I use a polyurethane based hot melt adhesive marketed by Titebond, which incudes an adhesive which would also work very well for gluing metal to plastic (but of course if you dont have or have access to the system it is not worth it to buy it for one job). Silicone sealant should also work if you take the glossy finish off the acrylic where the magnets are to go.

    AJC

  3. #3
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    WeldOn #40 will work...If you can't find that, you can try polyurethane (Gorilla et al) or epoxy.

    -B
    Last edited by Brady Watson; 02-26-2012 at 08:51 PM. Reason: Cross posted with Andrew
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  4. #4
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    it is a tough glue joint. not too much sticks to plastic well and rare earth magnets even when you sand them don't glue well because the coating is so hard. the silicone adhesive is a good choice because it has flex. but one of the keys is to put the magnet into a snug fitting pocket. if they fit nice and tight a little super glue will do the last bit of holding.
    my last one I used a 1/2" wide 1/2" long magnet I cut sample holes in the acrylic till the hole was really tight. then I drove them in and they stay very well.
    the vibration is the issue so with most glues and the two different materials it is tough.
    not the best pic but I used 1/2" magnets on the bottom part and 1/2" threaded rod on the top as two of the 1/2" magnets were too strong. but with these the holes are snug enough I just pounded them in.

  5. #5
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    Paul

    I experienced the same issues you did, both with my dust foot and with refrigerator magnets. For me the solution for the Dust foot was to redesign the foot so that the magnets were in a pocket and the forces were pulling them into the pocket. With the fridge magnets, I cover the magnet and backside of the part with a self promoting sticker.

    Steve

  6. #6
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    instead of drilling a thru hole couldnt you fit a tight pocket with a very thin bottom so the magnetic properties will hold the magnet in its place? i hope this makes sense.

  7. #7
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    you need magnet touching magnet or metal. otherwise the hold is not enough. using a longer magnet lets you use the magnet as a pin to hold the foot in place both sideways and vertical.
    a very snug fit is the best thing to shoot for and a magnet long enough to get a good grip. then just a drop of super glue and a hammer to pound it in will work well. I got 1/2" magnets and they were too strong. I would have a tug of war to get them off and pinch my fingers when I used them so I used threaded rod and that made life easy since it screwed into the plastic and the magnets fit by pressure.

  8. #8
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    you need magnet touching magnet or metal. otherwise the hold is not enough


    Not necessarily

    It's actually very easy to design how much force will be necessary to separate items. The attached chart from K&J Magnetics is for the N52 .5 X .125 magnets I used. I pocketed them into 1/2" ply leaving .125" on both surfaces... As you can see from the chart, when these magnets are separated by .25" (.125 X 2) I have 1lb. of force attracting them together... Since I embedded 8 magnets into each surface, my brush assembly requires 8 lbs. of force to remove... Very adequate!

    Steve
    Attached Images Attached Images

  9. #9
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    Default Magnets

    They make rare earth magnet cups that are pre drilled. You attach the cup to the plastic with a small bolt then place the magnet in the cup. It also increases the holding power of the magnet. Rockler has them.

    Jerome

  10. #10
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    ditto Gene and Steve G...I used some scrap HDPE for my dust boot, so gluing was out. My magnets are 1/2" X 1/8" and they do not need to be touching each other to create more than enough holding power. The receiving holes don't go all the way through (about .020 shy). The upper holes are drilled from the top, and the lower holes are drilled from the bottom, so the magnets, when pressed in, are sucked into their holes and held in place by the magnetic force. It has worked great for over a year now. It takes a couple of pounds of force to pull the brush part away from the top piece. It has never come off when I didn't want it to.

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