Re: Magnetic solution X
I received my eBay order (40 cents each) for some neodymium magnets and put them to the test this weekend. They are N50, fairly strong, but not the strongest grade you can get. If you can find higher N numbers of the same size they will be stronger, but usually they cost more. They have a countersunk hole in the middle which makes for easy attachment to the back of a cradled panel or stretched canvas. I got larger diameter magnets than what I used previously because the hole in the middle reduces the surface area of the magnet, making them weaker than the same diameter magnet without a hole in it. Make sure the screws you select fit flush below the top of the magnet. You can also use pre-made boards with the magnets already on them and attach the boards to the cradled panel. (Great idea Dcam!)
Dimensions: 20mm wide x 3mm thick with a countersunk 5mm hole in the middle.
I drilled a pilot hole in the basswood cradles and set my power drill to the lowest torque setting to screw them down to the boards using a countersunk style flat head wood screw. Even that low setting was too much. The magnet instantly cracked into several pieces when the screw was torqued down. On the next one I hand tightened the screw until the magnet was still free to rotate around the screw head but didn't rattle. No breakages.
Four of them will hold a 9x12 cradled birch panel on a piece of steel that is 0.035" thick. Thinner steel has less magnetic attraction, thicker would have more. A non glossy finish on the metal also helps with the grip. Eight of them spaced around the edges will keep a 30" x 40" 2" cradled birch panel in place, weighing just shy of 9 pounds. Pull away resistance isn't really a problem. The main issue is having it slide down under its own weight. The magnets are nickel plated and very slippery. You can almost double the amount of sliding resistance by smearing a paper thin layer of hot glue or silicone caulk over the surface of the magnet, or using tape as shown by Dcam. . Let the glue dry fully before mounting it on the metal panel or you will have a very hard time removing it!
For un-cradled panels I will be attaching two strips of 1x2 pine at the top and bottom edges of the panel and screwing the needed number of magnets onto those boards. I will leave them on the painting until it is completely done and ready to sell. The magnets come off quickly with an electric screw driver and the boards used on the bare ACM and Hardboard panels will stay on the piece so it will be ready to mount into a regular rabbet style frame or a floater. I wish I could come up with a light weight metal panel to use for plein air but thin metal doesn't give enough magnetic hold and thicker metal is too heavy for me - not to mention the bulk, so I will stick with my mast setup for outdoor work. Thanks again Dcam for telling us about the magnet system! I am hooked or rather stuck!
Last edited by contumacious : 04-14-2019 at 05:11 PM.