Posts Tagged ‘magnets’


In:In the Shop

Comments Off on Making a Magnetic Bottle Cap Opener

Let’s start with the easy stuff, sourcing the wood and cap opener.  If you’re reading this you’re likely a woodworker and if you’re a woodworker you likely have some scrap wood lying around so your wood may be free for this project.  Something around 3″-4″ wide by 8″-10″ tall should work fine, 3/4″ thickness or more is recommended.  For the opener itself thousands exist.  A quick search on the internet for “wall mounted bottle opener” will give you more options than you can shake a stick at.

Lots of choices…

Now for the magnets.  I’ve made a few of these openers now and I’m pretty comfortable saying you’ll want to use 1/2″ diameter rare earth disc magnets.  They should be 1/8″ – 1/4″ thick depending how many you use, but I’ve found 4-6 total does the trick.  With all that out of the way, here’s the process I’ve used.

Begin by sizing and shaping your board as you see fit.  This can take 5 minutes or 55 minutes depending what kind of detail you want to go into, but in short make your board flat on two faces, dress up the edges, and move on.

This opener was for a client. He ordered the opener, I selected the cherry with a live edge.

I cleaned up the live edge with a spokeshave. This leaves some of the surface variation intact. I could have used a hand plane, but that would have made the edge perfectly uniform, something I wanted to avoid on this particular edge.

After cleaning up the board, I decided to mimic the live edge detail on the other side.

I removed the bulk of the material with heavy cuts from my jack plane, then finished with a block plane.

The top and bottom edges received a simple 1/4″ chamfer…

…and were cleaned up with a block plane.

Once the board is brought to size and shape the various holes to be drilled can be laid out.  I start by positioning the opener where I want it and mark the screw holes.  I also mark what portion of the board will be covered by the opener when it’s mounted.  Pre-drill the screw holes for the opener, then look at the available space in the “will be covered” portion of the board.  Drill and countersink/counterbore a hole in the area large enough for a screw that can be used to mount the board.  Since it will never be seen I used a basic drywall screw.

With the opener in position, mark the location of the mounting holes.

On the back of the board, layout your magnet array.  I’d go with two rows of three magnets or a triangle layout with three magnets at the bottom, then two above that, then one above that.  You can test various configurations on scrap wood until you’re satisfied, then break the scrap wood apart to retrieve the magnets.  The drilling process is crucial for these boards since the strength of the magnets decreases exponentially as the distance from the magnets to the bottle cap increases.  To get the magnet as close to the surface as possible, two bits will be used as described below.  You can also read more about magnet selection and installation from this Rare Earth Magnet Article.

First use a standard brad point bit to drill a hole the same diameter as the magnets you are using.  Set the depth stop on your drill press so the tip of the bit stops about 1/16″ from the front face of the board.  I use shim stock to locate the bit.  Drill all your holes, then replace the brad point bit with a sacrificial bit that has had its tip ground flat.  This can be a twist bit or forstner bit, but it must be ground flat.  Set the depth of this flat bit to the same 1/16″ depth and re-drill the holes.  This will clean out the bottom of the original hole and leave a flat base.  Now drop the magnets into the holes and plug the back of the hole with a dowel.  Be careful not to pound the dowel in.  You left 1/16″ or less of material in front of the magnet and driving the dowel home will split the wood and force the magnet through the surface of the board.

Drill all the holes with the brad point bit, then reset the depth and re-drill the holes with the flat bit.

The board is just about ready for mounting at this point, all that remains is adding a nail to the back of the board to prevent it from rotating around the mounting screw (which is hidden behind the metal opener).  I just pick anywhere towards the bottom of the board between the magnets, and pre-drill a small hole.  Before tapping in the nail, apply your finish of choice.  I typically use some whipe-on poly to build a thin finish and provide a little scratch protection from the bottle caps.  Once the finish is dry, tap in a nail then cut the head off and file it to a point.

Anti-rotation nail installed, head cut off, shank filed to a point.

The board is now complete, but there is a bit of an installation process to follow.  The opener must be removed and the mounting screw taken out.  Figure out where the nail should go, drill a small hole and press the nail in.  Align the board and mark where the mounting screw will go.  Take the board off, pre-drill the hole for the screw, then put the board back again.  Install the mounting screw, then the opener.  I use a screwdriver here, not a drill, to avoid slipping off the screw head and damaging the board.

Pre-drill a hole for the nail. Install the board. Mark where the mounting screw goes. Remove the board. Pre-drill for the mounting screw. Install the board. Add the mounting screw. Add the opener with a screwdriver, not a drill. Done.

There are lots of ways the board could be mounted, I use this method so the end result looks as clean and simple as possible.  Anyway, have fun with it and when you’re done you can enjoy a frosty beverage as a reward for you efforts (which will taste better when drank out of this).

Board up…

…and ready…

for action.