I wanted to use some NdFeB magnets to hold things on my refrigerator, but I also wanted to be able to grip them for removal (and putting them on without slamming the magnets). I found some 1/2" diameter by 1/4" thick axially polarized disc magnets with a hole countersunk for a #6 machine screw. I ordered the magnets and purchased some stainless steel flathead machine screws and nuts. Please see [Materials and methods](https://www.youmagine.com/designs/push-pin-refrigerator-magnet#bill-of-materials) for details.
I designed this grip (or handle, I am not quite sure what to call it) to resemble a push-pin, as well as to work with the aforementioned hardware. I wanted positive retention of the screw, so I decided to embed the nut in the grip.
There is 1/16" of material below the hex nut to ensure sufficient strength during use. The geometry of the inset for the hex nut has very tight tolerances, particularly regarding the height of the hex nut. These tolerances are due to wanting the first layer above the hex nut to print onto it. There is a relief above the hex nut for the machine screw. This relief has a domed top to allow the print to be completed without support.
I have included the .stl file for the grip, as well as the Sketchup files.
1. Ensure that generating support is disabled in your slicer.
<img src="https://s3-eu-west-1.amazonaws.com/files.youmagine.com/uploads/image/file/169799/01.jpg" alt="Screenshot 1" width="640" height="480">
2. Configure slicer to pause print at the top of the inset for the hex nut. Using a layer height of 0.2mm I obtained the best results by pausing on layer 22.
<img src="https://s3-eu-west-1.amazonaws.com/files.youmagine.com/uploads/image/file/169800/02.jpg" alt="Screenshot 2" width="640" height="480">
3. Prepare the print bed according to your preferences. Prepare the hex nut by applying adhesion promoter to one surface. Thread one of the screws into the nut from the side the adhesion promoter has been applied to until the tip of the screw is even with the opposite side of the nut.
4. Begin the print. I obtained the best results by placing the nut on the heated print bed, the side without adhesion promoter down.
<img src="https://s3-eu-west-1.amazonaws.com/files.youmagine.com/uploads/image/file/169801/03.jpg" alt="Machine Screw and Hex Nut on Print Bed" width="640" height="480">
5. When the print pauses, move the print head out of the way. On my printer this generally occurred about six minutes into the print, but print time may vary based on various factors, including the printer used. Carefully pick up the machine screw (**WARNING:** may be hot) and insert the hex nut into the hexagonal inset in the grip. Be sure to seat the hex nut against the bottom of the inset. This is a relatively snug fit, so some pressure may be needed to seat the hex nut in the inset.
<img src="https://s3-eu-west-1.amazonaws.com/files.youmagine.com/uploads/image/file/169803/05.jpg" alt="Inserting Hex Nut Into Print" width="640" height="480">
Unthread the machine screw and remove it. A number of factors related to his operation will impact the quality of the finished print, but by far the largest is how long it takes to complete this operation. I obtained the best results by doing this as quickly as possible, and found that with very little practice this can be accomplished in a matter of seconds.
6. Resume the print.
7. Once the print has been completed, removed from the print bed, and post-processed as desired assemble the magnet by inserting the flathead machine screw through the magnet and threading into the hex nut captured within the 3D printed grip.
<img src="https://s3-eu-west-1.amazonaws.com/files.youmagine.com/uploads/image/file/169807/09.jpg" alt="Captured Hex Nut" width="640" height="480">
<img src="https://s3-eu-west-1.amazonaws.com/files.youmagine.com/uploads/image/file/169808/10.jpg" alt="Assembly In Progress" width="640" height="480">
8. Tighten the machine screw with a phillips screwdriver while gripping the 3D printed grip. The magnet is now complete.
<img src="https://s3-eu-west-1.amazonaws.com/files.youmagine.com/uploads/image/file/169809/11.jpg" alt="Completed Assembly" width="640" height="480">