Captive Ring Puzzle

I love puzzles. Not jigsaw puzzles where you assemble a box of oddly shaped pieces, but objects that make you think. Objects that make you look at everything from a different perspective, that make you understand the world isn't always as it seems. These are the puzzles I love.

I first saw this puzzle posted by pocket83 and knew I needed to make my own.

This simple puzzle is made of metal, brass, and wood. The ends are not removable, the ring doesn't come apart, there is no optical illusion present, nor is the image changed to deceive.

With a handful of tools and some scrap wood, you can make this simple puzzle to amaze your friends and family.

There are a few things you will need to make this puzzle.

Tools:

• Saw
• Drill Press - preferred (a hand held drill could also be used)
• 1/4 inch drill bit
• Compass
• Awl
• Disk Sander, Palm Sander, or Sanding Blocks
• Hacksaw or Angle Grinder

Material:

• Scrap Wood
• 1/4 inch Metal Rod (purchased from a local big box store)
• 6mm Neodymium Magnet
• 1 1/4 inch Brass Ring
• Epoxy
• Spray Lacquer

Cut two wooden squares that measure 2 3/4 x 2 3/4 inches (and about a half inch thick). I used a crosscut sled on the table saw. Using an awl or nail, mark the center of each block and draw a circle with radius 1 5/16 inches using a compass. Using a band saw or similar saw, cut out the circle just bigger than the mark made by the compass. Make the discs perfectly round by removing the excess material with a disk or belt sander.

Using the compass, draw a new circle with radius 1 1/32 inches and divide that circle up evenly with the compass. This can be done by keeping the compass at the same radius as the circle, select a point on the circle and mark the radius away from that point. Transferring the "center" of the compass to these new marks and marking the radius again will result in the circle being divided into roughly six sections. Select and mark three of these divisions.

Drill out the holes as deep as possible without drilling completely through the wood.

I wanted the grain of the two discs to go in the same direction, so I took special care to mark the points of the second disk so this would happen.

Take a 10 inch section of rod and insert it into a drill. Starting with 220 grit and ending with 600 grit sand paper, sand the rod till it's as shiny as you'd like. You can even use buffing compound if it's available to make the rod really shine.

Using a hacksaw or angle grinder, cut the rod so you have three pieces 2 inches long, and one 1 3/4 inches (this center rod will be too long and will need to be cut to final length later on). Using a bench grinder or disc sander, remove the burs caused by cutting the rod.

The center holes are the core of this puzzle. Drill one hole deep enough to recess the magnet about 1/16 of an inch. This will be what holds the center post in place making it appear solid. Drill the other center hole as deep as possible without drilling completely through the wood. Then take a 1/4 inch straight router bit to flatten out the bottom of this hole. This will allow the center rod to slide as far as possible, and give clearance for the brass ring.

Test fit everything. Make sure everything fits together and that the center rod gives enough clearance for the brass ring to be replaced. If there isn't enough clearance, carefully trim the center rod shorter until there is enough space for the ring to slide in and out.

Using a router, add a small chamfer to the edges of each disc. You could place any edging you like on the disk to suit your personal taste.

Using a palm sander or sanding blocks, remove all rough edges and markings from the design layout process.

Insert nails through some scrap cardboard to support the pieces to be finished. Using fine sandpaper to clean up irregularities in the finish between coats, apply four or five coats of lacquer.

Using a hacksaw or thin disk angle grinder, cut notches for the epoxy to hold onto the rods in the next step.

Using quick set epoxy, embed the magnet into its corresponding hole. Allow this to dry for a few hours to ensure the movable center rod will not pull it out of place when finishing the assembly (speaking from experience, trying to reattach the magnet after it has fallen out is nearly impossible to do without ruining the rest of the puzzle). Apply epoxy to each of the posts and ensure everything is square. Let sit for 24 hours.

If you haven't figured out how it works by now, it's deceptively simple. The center post slides down when pulled from the magnet. This allows the ring to slip over the top of the post.

If you happen to make one or something similar, please leave a comment showing your favorite puzzles.