DIY Magnetic Folding Shelf Brackets
Step 2: Chose, Prepare & Glue Magnets
Page 1: Overview & Step 1
Page 2: Step 2: Prepare & Glue Magnets
Page 3: Step 3: Magnet Coating
Page 4: Read More, FAQ, SN List
Magnet options.
I have built and tested magnetic folding brackets with 3 different magnets sizes (1/2” sq x 1/16”), (1/4” sq x 1/32”), (1/8” sq x 1/32”). For magnetic folding shelf brackets I recommend using 1/4” x 1/4” x 1/32” for a compromise of magnetic strength and build difficulty level but 1/8 x 1/8 x 1/32 is stronger and better overall but more work and more expensive. 1/2” x 1/12’ x 1/16’ is almost too strong for magnetic folding shelfs and I now only use for heavy duty use as in my Conex Containers. See more details and comparisons below at bottom of page.
1/4″x1/4″x1/32″ model video
Magnets are from totalElement Neodymium Magnet Supplier.
Use Coupon Code KTFG for 10% off your purchase at totalElement.com
1/8” x 1/8” x 1/32”: Block Magnets: https://totalElement.com-1/8
1/4” x 1/4” x 1/32”: Block Magnets: https://totalElement.com-1/4
1/2” x 1/2” x 1/16”: Block Magnets: https://totalelement.com-1/2
Layout and Capture Magnets
Layout Magnets
For 1/4” magnets I use 3 columns of 20 for 60 per bracket x 2 (120 total).
For 1/8” magnets I use 7 columns of 40 for 280 per bracket x 2 (560 total).
I have used many application methods successfully. One method is to layout the magnets alternating the poles on a sheet of plastic or paper laying over metal so the magnets will attract to the metal and reduce the chance of balling up. Stack enough paper or plastic so the attraction to metal is somewhat weak though. Draw an outline of the magnets and add magnets until full or keep count. It’s easy to alternate the poles without identifying the poles because the edges of opposing poles will attract and stick to each other. If needed straighten/square up the magnets with an aluminum or any non magnetic straight edge.
Above I layout 7 columns of 40 1/8″ magnets on a paper outline for a total of 280 per bracket. Below I have 3 columns of 20 1/4″ magnets for a total of 60 per bracket. See addition tips & tricks bottom of page.
Capture Magnets
Apply a thick semi-rigid but weaker tape like 15lbs Mounting tape to the magnets to capture and secure the magnets being sure to leave overhang on each end to handle. Plastic layout works better than paper (Read more helpful details below in Tips & Tricks)
Prep Magnet Surface.
Scuff Magnets for Glue Bond
Flip over the 3M tape with magnets and rough the magnet surface with 220 grit sand paper to create a better bonding surface for the mounting glue. Both the hand sanding block with 220 grit sheet applied and 220 grit Emery Cloth role work well. Diablo Hand Block comes with 80, 120 & 220 grit sheets.
Clean Magnets
Clean the magnets thoroughly first by vacuuming then use painters tape or electric tape &/or hand putty to remove fine debris particles from the crevices and finish with isopropyl alcohol. This will be tedious (especially on 1/8” magnets) but it’s important to remove all debris and clean the surface of the magnets.
Keep applying new tape to remove debris until you no longer see any. It will take several strips of tape to remove the debris. Alternatively you can use putty to removes debris or just use the putty after removing the bulk of debris with tape. Be sure to clean with isopropyl alcohol before proceeding.
Glue Magnets
Tape Brackets for Glueing
To reduce glue mess on bracket from handling, I found it helpful to apply painters tape around the bracket before glueing magnets. Tape everything but the top surface where we will glue the magnets. We will keep this tape on for painting as explained on page 3.
Glue Magnets
Once both the bracket and the magnet strip are clean and dry and taped up, we need to apply a strong flexible glue like Gorilla Glue or Loc-tite Silicone Glue. Apply then spread thin a coat of glue on both the bracket and the magnetic strip. Now carefully apply the magnet strip to the back of the bracket. You pretty much have one shot so just slap it on as straight as possible then carefully peal off the 3M Tape trying not to pry off the magnets from the bracket (alternatively you can razor off the 3M after the glue dries). This is why we use a weak 15lbs mounting tape. Anything stronger would just pull the magnets off the metal bracket (read more below). If needed you may be able to straighten magnets up before glue sets but you really have very little time to do so and its difficult so try to get it right while mounting. I have successfully straightened magnets after mount and I have also made worse and should have left well enough alone.
(Insert pic glue applied)
(Strip set on bracket)
Some excess glue may rise up through the joints of the magnets. Just allow this to dry then razor scrap off. This will create columns of glue at each four corner joint of the magnets which will help reinforce the magnet array. More on magnet prep post glueing on page 3.
Using your finger with a glove or a Sealant Finishing Tool, bevel the excess glue on the edge of the magnet strip. This will make a stronger bond, protect the magnets more and look much better after painting. Wipe away any excess glue past the bevel (on the bracket) with alcohol wipes. Read more below.
Lock Closed Magnet
These Magnets are Important (If used on Portable Folding Shelves)
(pic)
I found that with the folding brackets closed, they can spring open on you with the slightest bump. This happens walking holding the shelf from the handle or when driving if mounted on inside of a service vehicle. This is incredibly annoying so I add one or more lock closed magnets depending on configuration.
(insert pic of 3 Dif mag configs)
I have experimented with several configurations but I recommend just using three 1/4”x1/4”x1/32” magnets alternating the poles. These are so thin that when the bracket is closed, the extra 1/32” is almost unnoticeable. It’s not necessary but I sand or Dremel off the paint for a better bond. I glue the magnets on, then apply a few drops on top of the magnets allowing the glue to settle out and flow over the edges of the magnet. This encapsulates the magnet giving it some impact protection when the bracket get slammed closed.
Glues for lock magnet:
Gorilla Flexible Glue: https://amzn.to/37KJhJw
Gorilla Clear Glue 1.75 (Semi Hard): https://amzn.to/4b8EKAY
(replace with better overflow pic or add pics)
Further Details and Reasons for Choices
Why alternate the magnetic poles? Wouldn’t it be stronger if all poles face the same way?
It’s stronger up close Alternating the poles because it increases the near field but also weakens the far field which is safer and more ideal. We only want to magnet to stick to metal close to it, not attract metal from a distance See illustrations and Read More page 4.
Reasons for Glue Choice & Considerations
To glue the magnets to the bracket, we want a flexible or semi-flexible (non-brittle) glue that is temperature and impact resistant. The repeated impact of the magnets being mounted on metal surfaces can compromise brittle non flexible glues like Super Glue. Most flexible glues better respond to expansion and contraction due to temperature changes as well. The flexible is glue not good to fill holes though.
To Glue Magnets I have used the following flexible glues:
Gorilla Clear Grip Contact Adhesive: https://amzn.to/37KJhJw
Loctite Clear Silicone Waterproof Sealant: https://amzn.to/3HC8nNi
And also a glue that is somewhat hard but not as brittle as superglue:
Gorilla Clear Glue 1.75oz: https://amzn.to/4b8EKAY
I have used the Gorilla Clear 1.75 for both filling holes and glueing the magnets.
See Read More page 4 for notes, lists and results over time.
Why take time to Bevel the Glue
Here is a picture of the second 1/4” model that I made (after 1/4″ prototype). I didn’t bevel the glue and just left as is before spraying with paint (no clear coat, I now recommend CC p3). You can see the clumps of glue on the side of the magnets. It still looks acceptable and works but beveling the glue as shown in the illustration will help reinforce the magnets helping to protect the edges from impact and abuse. It also forms a better glue bond to hold the magnets to the bracket and gives a better base for the paint and clear coat to make a smooth transition from the top of the magnet to the bracket. This somewhat rounds the 90 degree edge of the magnet face and magnet side which helps protect the magnets from abuse.
Reasons why we need a thick semi-rigid but weak Mounting Tape, Tips & Tricks.
If we tried to capture and lift the magnets with a thin tape like painters or electric tape the magnets would just fold onto themselves due to magnetic attraction. We need something rigid or semi-rigid enough to prevent that. While I have used many different methods successfully including custom made jigs, using the 3M is easy and sufficient. I chose 15lbs mounting tape so it’s weak enough to release from magnets once glued on the bracket. I have done this successfully but when mounting magnets that had been in storage on 3M tape for days (rather than glueing same day) I found that the mounting tape bond was much stronger and started to pull freshly glued magnets off the brackets when I tried to remove the 3M tape. I started weakening the 3M by linting it up by applying to my shirt or pant leg and removing several times (a trick I use at work often). I have also applied linted painters tape to the magnets then 3M mounting tape on top of the painters tape to get the weakness of the painters tape but the rigidity of the the 3M mounting tape. The tape only needs to be strong enough to capture, lift and hold the magnetics while we prep and mount. I found found that trimming the mounting tape down the same width of the magnets makes mounting it straight easier.
Reason for count/layout of magnets
Why 3 columns of 1/4” rather than 4 columns which will fit?
Because the brackets are rounded at the edges 4 columns will cause the magnet edge to just start to get into that rounding causing a slight gap between round and magnet which increases the chance of cracking these thinner magnets. That was less of a factor with the thicker 1/16” magnets and the gap could be filled with glue. 3 columns is plenty strong enough for practical use and I have tested at over 25lbs. Also you don’t have to apply the magnet strip perfectly straight with 3 columns, you have room for error on each side. With 4 columns it must be perfect or you will have magnet overhang. I use 7 rows of 1/8” rather than 8 rows for the same reason (the rounding and margin of error) but you could do 6 or less rows for less work, cost and more room for error mounting.
(make and insert scale illustration)
Why magnets all the way down and not just at top and bottom like previous model.
While it’s only marginally stronger with magnets in the center vs not, it does offer more friction to prevent sliding down (though we want some sliding rather than detach, see page 3 coatings). It has smoother look that’s easier to clean off especially if metal dust or shavings get on it. It’s also easier to prep and mount one full strip of magnets rather than leave a gap in the middle. It’s just overall much better.
(Insert pic of comparison old vs new)
1/4” vs 1/8” Magnet Models
1/4” is the ideal strength for practical use as laptop or medium duty tool/material shelf etc. It’s easier to build and less costly than 1/8”. 1/8” is substantially stronger due to increased pole count and an additional 1/8” column of surface area. It’s more difficult and more costly to build. 1/8” is more ideal for heavy use applications like tools and material shelf. I often work out of a loaded Milwaukee bin resting on my portable shelf. 1/8” has better magnetic field characteristics than 1/4” (and 1/2”) read more below & page 4. The strength of each model can be modified with each addition paint coat as explained page 3.
(Pic of Milwaukee bin with knockouts etc.)
Why I no longer recommend 1/2” x 1/2” x 1/16” Magnets for Portable Magnetic Shelf.
Originally I just used (4 or 6) 1/2” sq x 1/16” Magnetics at the top of the bracket and (2) at the bottom with the middle being open. I found 6 to be almost too strong and 4 to be a little too weak (I will be posting some demo & load test videos soon). I also didn’t like that the back of the bracket wasn’t flat top to bottom. With the smaller paper thin 1/32” thick magnets, I can cover the entire bracket top to bottom with the magnets being practically invisible if painted white yet having great strength due to increased pole count and surface area. The increased surface area equals increased friction as well so no need to add electric tape to magnets to prevent the shelf from sliding down when loaded. More detail on magnet coatings page 3. 1/2” has worse magnetic field characteristics as explained below and page 4.
Magnets are to scale in above image but the magnet fields are just approximations to illustrate the point. If anyone has to ability to create images of real magnetic line simulations, let me know in the comments.
Magnetic Fields & Poles
Larger magnets have a stronger magnetic “Far Field” yet weaker “Near Field” as compared to smaller magnetics making up the same surface area. The stronger “Near Field” and weaker “Far Field” of the smaller magnets is more desirable for my application. Basically the Magnetic Fields of the smaller magnets don’t extent as far away but are stronger up close than the larger magnets. A higher count of smaller magnets equals more poles and more flux destiny per square inch. More on the pull force calculations, science and math (with diagrams) of the magnetic fields in Read More page 4.
Magnetic Size & Configuration Considerations per Application
1/2” x 1/2” x 1/16” Neodymium Magnets buy
I no longer recommend for my portable folding shelf for the reasons listed above but they are the easiest and cheapest option. I do use them on other brackets (folding and non-folding) in my Conex Storage Containers. I glue as many as required for desired strength (can be gauged by testing without glue first). For heaver duty applications I use 1/2” x 1/2” x 1/8” magnets in my conex but i’ll make a separate post on that.
-Recommended for heavier duty use (50lbs+).
-Less expensive per sq inch (8 per bracket / 16 per set).
(+/-0.53 x 8 magnets = $4.24 x 2 brackets = $8.48+/-)
-Easier to install than smaller magnets
-Undesirable stronger Far Field as compared to 1/4” & 1/8”.
1/4” x 1/4” x 1/32” Neodymium Magnets buy
I recommend for best compromise of strength, cost and build difficulty.
-Recommended for medium weight use, laptops etc (25lbs+).
-Relatively cost effective (60 per bracket / 120 per set).
(+/-0.09 x 60 magnets = $5.40 x 2 brackets = $10.80+/-).
-Relatively easy to install with proper technique and material.
-Good balance of Near Field and Far Field strength.
1/4″x1/4″x1/32″ model video
1/8” x 1/8” x 1/32” Neodymium Magnets buy
While this is my personal preference, I don’t recommend for others because of the build difficultly due to the skill and experience required.
-Recommended for heaver use (40lbs+).
-More expensive (240 per bracket / 480 per set)
(+/- 0.04 x 280 magnets = $11.20 x 2 brackets = $22.40+/-)
-Difficult to install unless experienced and skilled.
-Best magnetic field characteristics for the use.
Magnet Price Comparisons
1/2” (40 pack) $21 (53 cents each) (53 x 8 magnets = $4.24 x 2 brackets = $8.48)
1/4” (200 pack) $18 (9 cents each) (9 x 60 magnets = $5.40 x 2 brackets = $10.80)
1/8” (500 pack) $20 (4 cents each) (4 x 280 magnets = $11.20 x 2 brackets = $22.40)
These are prices at date of post. Keep in mind you get significant price reduction by buying larger quantities (qty 5 is 15% off) plus you get and additional 10% off using my coupon code KTFG at checkout. *note 1/2” listed is 1/16” thick vs 1/32” for 1/4” & 1/8”
Example:
1/4” (200 pack) qty 5 brings the price down to $15.29 per (200 pack)
Buy more than you think you need, you will use them on many projects.
Magnetic Folding Shelf Model_023 (1/4″x1/4″x1/32″)
First Load Test video
Next Page for full details on Step 3: Apply Magnet Coating
Page 1: Overview & Step 1
Page 2: Step 2: Prepare & Glue Magnets
Page 3: Step 3: Magnet Coating
Page 4: Read More, FAQ, SN List
If any questions regarding a project or tutorial, ask in the Comment Section of the web post or YouTube video, not by email. That way the answer can help many people with the same question.
Hi Kevin,
I’ve been looking for a way to add some more surface area to my camping set up and came across your folding magnetic tray and I knew that was the set up for me. Love the idea and love the detailed breakdown even more.
I’m planning on mounting the shelf to the side of my car on one of the passenger doors, however, the car has a slight contour at the height that I want the shelf to be at and the folding brackets would not be able to site completely flat. In order to avoid that I’m thinking of taking a contour gauge and using it to map the contour and then 3D print a mount that would be flat on one side and contoured on the other. I would basically glue/mount the 3D part between the bracket and the magnets.
Do you foresee any issue with this in terms of strength and/or adhesion of the glue on the magnets? I’m using PLA filament to print with which is pretty solid in terms of strength but I don’t know what the result will be relative to the gluing.
I’ll likely place some threaded holes into the 3D part so I can attach it to the bracket with some screws in order to avoid filling the holes on the bracket with glue. I’m also think of recessing the surface where the magnets sit so that it will be flush with the 3D piece and also make placement easier.
I’m not too worried about it being low profile as it will just be sitting in my car as opposed to me having to carry it around. Let me know what you think, any feedback is welcome. Alternatively, if you know of another method that would solve the contouring issue, I’m all ears.
Thanks!
Sorry for the delay, I just now saw this question.
I do think it would be difficult for magnet to stay glued to the 3d print. To overcome the contour you can just add magnets to the top and bottom of the bracket, leaving the middle empty. Since you don’t need it low profile you could use cup magnets, which you can mount tilted. But if not cup magnets I recommend 1/4″x1/4″ by 1/16″ or maybe even an 1/8″ thick if that’s enough to get over contour (rather than 1/2″x1/2 by 1/16 thick).
Let me know what you decide and how it works out.
If you like I can post of picture of it on the web post citing your work.
Man if you were to sell these I swear they’d sell like hotcakes
Thanks, I have sold many to co-workers and elevator mechanics in the area but they expense it to the company as a specialty company tool. Most people decide to build there own rather than pay out of packet the $150 minimum I charge. People generally underestimate the amount of time and effort it takesto complete a task or project.
Judging from the sales of brackets I estimate over 100 people have built folding shelves from these instructions or from my YouTube videos.