So this is a new type of key ring that I thought of. It’s supposed to open and close easily so that it’s easier to put keys on and take them off. It should also stay closed pretty well because of magnets in the top ring and the spacer on the bottom ring. You put keys on by first putting them on the top ring and then sliding them onto the bottom ring as it closes. It’s made entirely out of plastic (except for the magnets) so that it can be made with a 3D printer. So here is how to make it.

## Step 1: Bottom Ring Base

Make two circle sketches. One with a radius of 2.5mm and another with a center of 3mm. Make sure that their centers are in the same spot. Next extrude the bigger circle by 0.25mm. Then extrude the smaller circle by 1mm. This new smaller circle should light up red and when you hit enter, it should automatically cut the same shape out of the bigger, shorter cylinder. Now we have the basic ring.

## Step 2: Bottom Ring

We are going to finish the bottom ring in this step so that all we will have to do to make the top ring is subtract a couple a parts and flip it over and position it. : )

Now you need to make this shape. Here are the dimensions:

Lengths (mm) - Side 1: 0.668mm; Side 2: 0.447; Side 3: 0.3; Side 4: 0.358

Angles (degrees) - Angle between side 1 and 2: 129.3; Angle between side 2 and 3: 180; Angle between side 3 and 4: 103.5; Angle between side 4 and 1: 76.2

Once you have this shape extrude it by 0.75mm and uniformly scale it up by 2. Then move it into position like in the picture. Once it’s in position, subtract it from the ring base so that you have the cut ring.

Now filet both the bottom inside and outside edges of the ring by 0.045.

Now to make the spacer for the top ring, you need to a 2D sketch of the cut and it needs to match the shape exactly. I used the polyline and the 3 point curve to make the shape for mine. Once the shape is made, flip it over 180 degrees and move it to the left by -5.46mm to line it up exactly with the other side. Then extrude it by 0.25mm and move it 0.5mm. Then combine it with the ring so that they are on piece. Then filet both the inner and outer edges by 0.045.

Now we need to make the hole in the ring for the pin to fit in. First make a cylinder with a height 1 and a radius of 0.12. Then scale the cylinder up by 1.40 and move it into the position like in the picture. Also make sure that it goes all the way through the Ring. Once it’s in position, subtract it from the ring. Now make another cylinder with a radius 0.15 and a height of 1. Then scale the cylinder up by 1.40 and move into position directly over the hole we just made. Then move it down so that the top edge is in the ring the thickness of the filet, like in the picture.

We have finished the bottom ring! =)

## Step 3: Top Ring

Now we are going to make the top ring. Copy and paste the bottom ring and move it (make sure you move it only to left and write down how far you moved it). Then select a face of the spacer on the new ring (click it till it turns blue) and then hit backspace. Now flip it over 180 degrees and move it up 0.5mm. Now move the top ring to the right (remember how far you moved it to the left at the beginning? Now move the opposite of that number. Ex: moved it -8mm, now move it 8mm)

Top ring is complete and it is its place! : )

## Step 4: The Pin

Now we make The Pin!

This is the 2D sketch of the pin that you need to make. I'll start with the length of the longest length of the sketch and then go clockwise: 0.46; 0.12; 0.045; 0.02; 0.06; 0.02; 0.355; 0.08. Now revolve the sketch a full 360 around the longest length on the left. This is the inner pin. Now for the outer pin:

Make this 2D sketch for the outer pin. Here are the dimensions starting with the length on the left that will be the axis of revolution: 0.0105; 0.08; 0.355; 0.02; 0.415; 0.02; 0.045; 0.12. Now revolve the sketch a full 360 around the longest length on the left.

Now put them together and make them one object.

Now you have to scale the pin by these factors:

Overall scale of 1.40.

Then: x and y of 1.23 and z of 0.6. After these are done scale the z axis by 1.05 again.

Now rotate it 90 degrees and move it into position on the ring.

## Step 5: The Magnets and the Finishes

Almost done!

Now we have to cut a spot for and make the magnets that keep the ring closed.

First make a rectangle that is 0.3 by 0.4mm and another one that is 0.3 by 0.2.

Extruded both of these rectangles by 0.15 and duplicate them so that you have two of each.

Now move one of the bigger into the position shown and hide the bottom ring so that it is easier to see. Then subtract the rectangle from the ring.

Repeat this process with the bottom ring and hide the top ring.

Now position the two smaller rectangles (the magnets) into these new holes and make the part of each ring respectively.

Now a final touch, filet the edges of the cutout space on the bottom ring.

You’re Done! =)

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