Constructing a Magnetic Knife Holder is a popular project using our neodymium magnets. Here we've built our own using simple construction methods and include what magnet sizes can work best! The construction really is pretty simple, but the choice of magnets is where it can be more difficult to decide what will work best.
Materials include: wood of your choice, magnets, glue/adhesive and screws.
Tools: Table saw, router, and drill.
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Step 1: Cut Out Desired Size
Cut out a block of flat wood to size. Ours is 2" tall and 16" wide, from 3/4" thick cherry. In hindsight, 18" might be nicer. We have heard from some folks who want to make a fancy design, say the letter K for kitchen. Whatever your design is, the process is still the same.
Step 2: Create a Fixture for the Groove
We created a fixture for cutting the groove in a nice, straight line with a handheld router. At this point, you should decide which face of the wood is nicer, so you can cut the groove on the opposite side. You may have a different way to do this, or other tools that can be used. With the tools we have here, this was the best option for us.
This simple fixture is made from some MDF board and is sized to our router. We used a table saw to cut out the hole in the MDF board, but a Jigsaw or Bandsaw might work better (and be safer!).
Step 3: Cut the Groove
Using the fixture and router, we cut the groove in the back of the knife holder. Make sure to set the depth properly to leave the desired thickness of wood. We left 1/16" thickness of remaining wood.
This is where some technical information about magnets comes into play, but it is simple. The less material left, the smaller (and cheaper) magnets you can use. The more material, the stronger the magnets will need to be to effectively hold the knives. We think 1/16" of material left is a good thickness. This means we set the router depth to 11/16".
Step 4: Route the Other Edges and Sand
After cutting the groove, we wanted to have a nice fillet on the other edges, so we used the router for this. Again, your design might be different, ours is pretty simple. We then sanded the groove and piece smooth. At this point, all major cuts on the block are finished, so you can sand to finish as well.
Step 5: Insert Magnets!
This next step is our favorite part, inserting the magnets! We placed the block on a steel cookie sheet, to help hold the magnets in place while putting them into the groove. We put paper in between to protect our finishing sand. Our groove is 1/2" wide and we used 1/2" x 3/16" magnets (our product number D83). Thinner D82 magnets could also work if there is 1/16" of material left.
The orientation of the magnets is important. They should be placed in alternating polarities. If you look at the magnets, the poles will be North, South, North, South, etc. The edges attract in this orientation, so you will know if they are being put in right. If you try to place them side by side and the magnets repel, simply flip one of the magnets so it attracts.
Note: Neodymium magnets are very hard and brittle. If they are allowed to slam together, they could potentially break. This process should be done carefully. The steel cookie sheet really helps hold the magnets down so that they don't slam to each other.
Step 6: Adhere the Magnets in Place
In this last step, we adhere the magnets in place while still on the steel sheet. While many different types of adhesives will work well, we used a silicone adhesive. Make sure to cover all of the magnets along the whole groove. Don't be afraid to be generous with the adhesive!
After the adhesive dries, you can finish the block with whatever finish you choose (oil, stain, wax, etc).
Step 7: Install the Block
Once the adhesive is dry and your block is finished, its time to install the block! We fastened it to the wall using screws for a quick, easy install.
Make sure you drill a pilot hole before screwing! It would be terrible to get all this way and then crack the wood with a screw. Once your block is fastened to the wall (or wherever you place it), place your knifes to the block and enjoy!
Step 8: Warning: Techincal Magnet Info
Here is a chart we've come up with that shows the relation between wood thickness and magnet diameter. As previously stated, the thickness of material between the magnets and knives is important. The thicker the material, the bigger the magnets will need to be!
Again, the thinner the material left, the smaller, cheaper magnets you
can use! We think the extra work of routing the groove in the back is economically beneficial for this project.
For each increment of material thickness, there are different choices of the magnet size. A magnet's strength involves both its diameter and thickness.
The right magnet size depends on a number of factors, including:
The number of magnets used, the size, shape and weight of the knives to be held (here we plan for typical kitchen knives) ,the thickness of the material between the magnets and the knife -- this is the most important factor! Use this chart if you plan on using a different sized groove or plan on leaving more than 1/16" of material.
Of course, comment or contact us if you have questions on which size magnets you should use! Thanks for reading!
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