Here's an old project I did way back High School. It's a spiral bound memo pad with steel covers so the notepad doesn't fold up in your hand. You can also scale it up to a full sized 8.5 x 11in spiral bound notebook.

Step 1: What You Need

You just need a small spiral bound notepad (mine's 3 x 5 inch) and a piece of sheet metal. I used steel, but you can use aluminum, tin, even plastic. Keep in mind the thicker your material the less paper you'll be able to fit in the notepad (I used 26 Ga steel)

For tools you'll need (sorry but I forgot to take a picture)
something to cut the metal (I used a grinder with a metal cut off wheel)
A drill with bits equal to the size of the holes in you donor pad
A file
some tape
a marker
and some small black binder clips

Step 2: Disassemble the Notebook

To disassemble the notebook you first want to use the black binder clips to hold the papers together. Leave one of the covers out of the binders because you will need it as a template for fabricating the covers. On the end of the wire spiral binding you will see a tab that is bent to prevent the spiral from unscrewing. Straighten this to match the curve of the spiral and unscrew the spiral binding.

Step 3: Making the Covers

To make the covers you will use the thick paper cover from the donor notepad as a template. Place the paper cover on 1 edge of the sheet metal and trace around it with a marker. Then repeat for the other cover.
Once you've marked your covers cut them out of the sheet metal.
Now place the covers together on a clamp. File the edges to remove any large burrs and to make them uniform in shape and size.
Once they match take them out of the clamp and file some more, making sure to remove and burrs and sharp points. Run your fingers VERY GENTLY along the edge to make sure the edges are smooth. Be VERY CAREFUL doing this because you can very easily cut your self on a burr. Finish off with some sandpaper if you like.

Step 4: Making the Holes

To make the holes you will again use the paper cover as a template.
Tape the 2 pieces of metal and the paper cover together (paper cover on top).
Use a center punch to mark the middle of each hole.
Drill out each hole.
After you've drill all the holes you will need separate the covers and deburr each hole with a file or grinder.
If you want to paint or do some other finish to the metal covers do it now before you reassemble the pad.

Step 5: Reassembly

To reassemble the notebook you just need to put the metal covers on the front and back of the pad and screw in the spiral binding.
You can take off the top 2 binder clips and line up the holes in the cover to the holes on the pad.
Then put the top 2 clips back on the then reposition the bottom clips so they hold the metal covers to the pad.
When screwing the spiral binding back on it will have a tendency to get stuck on the edges of the metal covers. Go slow and don't force it too hard or you will bend up the wire binder and that will make it even harder to get back together.
Don't forget to bend the end of the wire spiral back to prevent it from unscrewing.

Like I said you can scale this up to larger notebooks, but that obviously will involve a lot more drilling and filing. Also, once you've emptied the paper from the notepad you can simple buy a new note pad (make sure it's the same) and replace the paper covers with the ones you've already made.