The concept is easy: cut an animal figurine (or almost any solid figurine) in half, drill a few holes, and glue in magnets. The magnets exert enough force to hold the two halves together, and support the weight of thin objects (like photos).
I made this set as a gift for Scoochmaroo, for the Instructables Gift Exchange.
Step 1: Tools and Materials
Well, the requirements are pretty basic.
A bandsaw or scroll saw - I'm not sure that any other saw would work.
A drill press
A 5/16" drill bit (I used a brad point bit, it helps with alignment of the bit)
An X-acto knife
Scrap paper (or tracing paper, if you have it)
Thin double sided tape (optional)
Plastic Animal Figurines (I used genuine Schleich figurines from my local hardware store)
8mm diameter neodymium magnets (I bought a 100-pack, Sku 13518 from DealExtreme)
Two-part epoxy or superglue
Step 2: Cut the Animals in Half
But, we must press on!
For each animal, think carefully about the direction of the cut. Some animals are looking to the left or to the right - you may want to cut on an angle so that the animal and the photo are both facing somewhat in the same direction. Also be very careful not to cut off any feet, tails, or other body parts that aren't firmly attached to the body on both halves! There will be some figurines that you simply can't use for this reason; there just isn't a way to cut it cleanly in two.
You must use either a band saw or a scroll saw to cut the figurine. These saws are capable of giving a perfectly straight cut, with a narrow kerf. This is important because you want to remove as little material as possible (ideally, the thickness of a piece of paper!) Use a thin blade with a high tooth count, to get the smoothest cut possible.
Line up the figurine and start up the saw. Take a deep breath, apologize profusely, and feed it straight through. The plastic is soft and cuts without much issue, but cut quickly - the plastic will melt otherwise.
The cut will be a little rough and there will be a bit of plastic left behind. Trim the excess plastic with an X-acto knife, and lightly sand the cut on a flat surface to remove a bit of the roughness.
Step 3: Mark the Drill Locations
Well, the easy part is over. Marking the drill locations is tricky, because of the precision required on such small, non-square objects.
On all of the animals I made, I was able to fit two pairs of magnets. On some (the jaguar and pig) it was a bit of a squeeze, but others (the elephant) there was lots of room. Ideally, the magnets should be spaced at least a millimeter apart if you can manage it. I'd avoid using a figurine onto which you can only fit one magnet - it's not likely to be able to hold up very much weight. The other benefit of using two magnets is that you can align the poles so that the two halves automatically align.
Take one half of each animal, and trace its outline on a piece of paper. Note which animal the outline is for, and which half the outline was taken from. Now, mark the centers of the magnets onto the outline, staying away from edges if possible. I used my calipers for this - I simply measured the diameter of the magnet, added a millimeter or two, then poked holes into the outline using the points of the caliper. But, freehand is fine too. Once the centers are marked, poke holes through the paper at these points.
Realign the animal half with its outline (be precise!!) and turn it over. You should be able to see the two holes. Stick a pin through each hole, making marks on the figurine. Remove the outline and push the pin in deeper if the marks aren't visible enough.
Next, do the other half. But there's a trick: Since the saw removed some material from between the halves, you may have to offset the outline to compensate. The steeper the angle of the cut, the more you'll have to offset. So, I'll divide this step into two sub-steps:
OK, so the figurine was cut at an angle perpendicular (90 degrees) to its "spine." In this case, hold the figurine against the back of the outline, and use a light to align the two. Again, try to be as precise as possible. Poke the pin through the two holes as before.
If the figurine was cut on an angle, you'll have to offset the outline a bit. Align the second half of the figurine and the outline as with a perpendicular cut. The offset will be about 1mm for a 45 degree cut, and a fraction of a millimeter between 45 and 90 (perpendicular). The direction (whether to shift the outline left or right) will depend on the angle of the cut. If the cut goes from the animal's front right leg to its rear left leg, then the outline will be shifted to the left. If it's cut from the front left to the rear right, then the outline should be shifted right. Got it? Good. Poke two holes with the pin.
Step 4: Drill the Holes
OK, time for some tricky drilling. I wasn't quite sure how to clamp the halves, so I held them (tightly) while I drilled the holes on my drill press. A drill press is pretty much essential, by the way. I can't imagine doing this with a hand drill, without seriously damaging the figurine or my finger!
I recommend using a brad point drill bit. It has a sharp point in the center that is great for aligning the bit to the small pin-hole mark. It also makes a "flatter" hole which is more suitable for gluing magnets into.
So here we go: Hold the half tightly, keeping the cut edge parallel with the drill press table. Slowly drill the hole, a little at a time. Remember, the magnet is only about a millimeter thick! Test the depth of the hole by popping in a magnet. It should sit flush with the cut.
There may be some bits of plastic left behind, trim them off with a knife.
Step 5: Glue in the Magnets
The magnets need to be installed in a particular order, so that everything sticks together happily when the glue dries.
Mix up a small batch of epoxy.
Grab the front half of the animal, and glue one magnet in place with a small dab of epoxy. Direction doesn't matter.
Take the second magnet, and stick it (magnetically) onto the one that was just glued in. This is to determine polarity. Flip that magnet over, and glue it into the adjacent hole on the same half. This way, the half will have a "north" and "south" pole facing out.
Stick the third magnet onto the first one, again to determine polarity. Flip the magnet over, and glue it into the position opposite the first magnet, on the back half of the animal.
Stick the fourth magnet onto the third one, flip it over, and glue it in place. The back half of the animal should now have a "south" and "north" pole facing outward, that mate up with the north and south of the front half of the animal.
And that's it! Wait for the epoxy to fully dry, and the picture holders are ready to use!