DIY Magnetic Folding Shelf Brackets
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
*I am not a painter or paint expert so better materials, methods and results may be possible.
Feel free to leave any advice or suggestions in comments.
Overview
I recommend adding a coating over the magnets to provide impact protection to the magnets and to adjust the friction coefficient. This is not absolutely necessary though, and I have build models without any coatings. Originally I added white electric tape over the magnets to provide some impact protection and to increase friction but now I recommend 4-9 coats of paint/clear coat. Read more on reasons why below. I scuff the magnets with 220 grit and clean thoroughly before spraying and make sure to get all four edges of the magnets as well, not just the face. I apply coats pretty light, hence the need for so many.
Paint, Clear Coatings:
Dupli-Color Premium Automotive Paint: https://amzn.to/3vFYPOU
Rust-Oleum Acrylic Enamel Gloss Clear: https://amzn.to/48D7IHo
Alternative Paints / Coatings:
Rust-Oleum Acrylic Enamel 2x Gloss White: https://amzn.to/3U7FAYH
Rust-Oleum Acrylic Enamel 2x Matte White: https://amzn.to/3Uc5ev9
Rust-Oleum 2x Ultracover Matte Clear: https://amzn.to/3SEKdsd
*Only use Matte if you want more friction.
I do not for portable folding shelves but do in Conex Storage Containers see post.
Optional Coatings (not recommended):
Diamond Strength Nail Polish: https://amzn.to/3tXzz6a
Xtreme Wear Nail Polish: https://amzn.to/3Otlzs3
Paint Marker Milwaukee: https://amzn.to/41XIQYB
U-Mark Inc. 100 P Paint Marker: https://amzn.to/3OtlNzp
Prepare Magnets
In order to help the paint achieve a good bond to the magnets I scuff the magnets with a 220 grit sanding block then thoroughly clean. I use the same process as with the glue side of magnets, vacuum first, use tape &/or putty to remove debris then isopropyl alcohol.
Tape Bracket
If not already taped for the glue process, tape the bracket now for painting. Add additional strips of tape up close to the magnets that we will move out just a little before each new coat so no edge build up (read more below).
Apply Color Paint Coat
I have had good results with several coatings as described below but what I have found to be easy, effective and durable is just 2-3 coats of Automotive Paint followed by 4-7 coats of high gloss clear. I tape up the brackets before spraying but move the tape out just a little before each new coat so no edge build up. I spray just enough coats of color paint to adequate cover that magnetics. We want more coats of clear than color. If any edges I may wet sand with 1000 grit sand paper between coats or after last coat.
(Insert pic)
Apply Gloss Clear Coat
I recommend a minimum of 1 more clear coat than color coat (4-7 coats). The number of coatings will affect magnetic strength as explained below. I tape the bracket up to the edge of magnets for the first coat, then move the tape back with each subsequent coat. The final clear coat will over lap the original white powder coat paint of the bracket ideally with out any paint layer edges or very little. Wet sand edges between coats if needed or desired.
Clear Coat Only
Alternatively you can chose to only apply clear coat which shows off the magnet configuration and actually looks pretty cool. Apply same as described above, apply between 5-9 coats. I have used 7 clear coats on 1/4” model with good results.
(Insert pic, need pic of 1/4 and 1/8 clear coats only)
Further Details and Reasons for Choices
Why so many coats?
I apply coats pretty light, hence the need for so many. A lesser amount of thicker coats may be acceptable or preferable. Again, I am not an experienced painter so better materials and methods may exist.
No Coating or Protection on Magnets
I have made some models with no coating at all just leaving the glue residue wiped down. The problem with this method is potential for magnet damage, the magnets are too strong and the glue residue causes too much friction so brackets wont’t slide down when overloaded as described below.
Benefits of a Coating vs No Coating
Impact resistance to protect magnets.
Vary magnetic strength to desired amount.
Smooth surface to clean debris off easier.
Help lock/glue magnets to bracket better.
Offer slicker surface to slide down when overloaded (depending on model).
Paint and clear coat offers impact resistance on the magnets for repeated mounting of portable magnetic shelfs. Repeated hard impact can possibly shatter the magnets but more likely it can weaken the glue attaching the magnets (this is why we use flexible glue rather than hard glue). Each additional coating layer slightly increased the distance to magnets and weakens the magnetic attraction to the mounting surface. We use this to our advantage two ways. It allows us to control the magnetic strength to our liking and ensures that the magnets are closer to the bracket they are glued to, than they are to the mounting surface which decreases the chances of the magnets breaking free from the bracket.
Previously I wanted rubberized friction so shelf wouldn’t slide. After use and testing of various configurations I now prefer it slides.
Coating Thickness vs Magnetic Strength.
The more coatings we apply, the larger the gap between the magnets and the surface we will mount or magnetic bracket too. Magnetic attraction is inversely proportional the the square of the distance which basically means the the magnetic force is made much weaker by only moving a little distance away. We can use this to our benefit by modifying the magnet strength to our liking by just adding more layers of clear coat. Wait, why weaken it any, why not just keep as strong as possible? Well that depends on what you’re using the the magnetic brackets for. This magnetic configuration is much stronger than needed for simple repeated light/medium duty tasks such as a laptop shelf. If that’s all its going to be used for you don’t need it unnecessarily harder to remove than needed especially if repeatedly moving it. It’s no harm to have it too strong it’s just basically for ease of use and convenience to tune the magnetic strength to your needs.
Grippy magnet coatings vs slick coatings explained with Pros & Cons of each.
Originally I thought I needed a grippy surface so the shelf wouldn’t just slide down when loaded. I have come to find that I prefer a semi-slick to slick surface though so that the shelf will slide down when overloaded rather than detach and fall. With electric tape (and some flat paints, flat clear coats) the shelf with hold more weight but will fall once overloaded or pushed down hard on. This friction coefficient varies of course depending on the surface you attach the shelf to but on a painted metal surface like an elevator controller I found a gloss paint or clear coat gives a good combination of weight capacity and overload protection. As the surface gets roughed up over time it may need a wet sanding with1000 grit or conversely if you find it too slick you can rough the surface up slightly with some 220 grit sand paper.
Grippy Surface Coating
– Pros: Higher weight capacity, won’t move as easily if bumped or pressed on.
– Cons: Detaches and crashes when overloaded rather than slide down.
Slick Surface Coating
– Pros: Slides down when overloaded rather than detach and fall.
– Cons: Lower weight capacity.
Friction Coefficient – Higher Weight Capacity vs Safer
Originally I added electric tape to my 1/2” magnet models because I thought I wanted extra friction to stop the folding shelf from sliding down so it would increase its’ weight carrying capacity. The 1/2” magnet models had less surface area making contact because I only used magnets at the top and bottom vs down the entire bracket like with 1/4” & 1/8” models. However I found that I much prefer the shelf sliding down when overloaded rather than detaching and crashing at a higher weight capacity. So even with the 1/2” magnet models I stopped using electric tape and started painting, then later painting and clear coating with high gloss. Keep in mind that as a shelf begins to slide down when overloaded it may tilt to a side while doing so, dropping the contents off the side. In practice though you notice the sliding when loading, have time to react and it’s still preferable to instantly detaching and crashing.
*Note, the 1/2 magnets are slick and smooth unpainted so you can choose to leave unpainted if not concerned about impact damage but the smaller magnets, especially the 1/8” collectively aren’t as smooth because there are so many of them and the thicknesses vary slightly. They really need a paint coating to smooth and flatten out the surface to be slick enough to slide down if overloaded.
(Pics of fully load then slid down yellow)
(Video of yellow severely overload with books and pipe wrenches before sliding down)
Why I no longer use Electric Tape as a Magnet Coating.
The electric tape was never ideal, it was just quick and easy while I experimented with other options. The electric tape does provide impact protection for the magnets but it has too much friction (see above) and also wrinkles up over time and eventually needs to be replaced. In heavier weight use applications (such as bracket in my Conex Storage Containers) I found that the magnets would slide down the electric tape. The electric tape adhesive was the weak link with very heavy loads on heavy duty brackets. Keep in mind, extreme heat was likely a factor. A matte paint and/or clear coat more idea for that scenario (see Conex post).
Methods & materials I did not have great success with or too time consuming:
Again, I am not a painter so results could be user error, improper method/environmental conditions. Rust-Oleum Automotive Self Etching Primer: seamed to eat into the glue somewhat and wrinkle. (Bracket #002) It still worked and I use the bracket but I don’t recommend.
(pic)
Behr Paint+Primer Gloss White 52: Orange pealed. (Bracket #005) I wet sanded wrinkles down. It still works fine and may have just been user error.
(PIC)
Paint Markers (Milwaukee & U Mark). Way too tedious to apply and uneven. (Bracket #008) I wet sanded smooth before clear coat but a little too much sanding and due to magnet thickness varying slightly some magnets protrude thorough the white maker but it almost looks kind of cool.
(PIC)
Nail Polish: Very strong but tedious to apply and uneven. (Bracket 001) I wet sanded then clear coated. Can be used without a clear coat and left uneven. I have done so on a 1/2” magnet model with good success (see video and pic below) but too time consuming vs spraying on full magnet models.
Plasti-Dip: Early models when I thought I wanted friction, I tried Plasti-Dip. It would eventually peal off and I no longer desire friction.
(inset pic of pealing)
Diamond Strength Nail Polish: https://amzn.to/3tXzz6a
Xtreme Wear Nail Polish: https://amzn.to/3Otlzs3
Paint Marker Milwaukee: https://amzn.to/41XIQYB
U-Mark Inc. 100 P Paint Marker: https://amzn.to/3OtlNzp
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.