Sometimes I see something that seems so simple to make, I wonder why you would ever buy it from someone else. In this case, it was the Anthropologie "Library Letters" that run about $20 (or Etsy knockoffs that run about $13-15). My boss's daughter is a big reader, and wanted to host her birthday at the library. Being the creative mom she is, she wanted to offer her daughters friends one of these letters, but wanted to see if I could make them instead of buying them online. That way, at least in her daughter's case, she could make sure the book was meaningful to her.
I looked up a few DIY tutorials on this project, and found all of them helpful in their own way, and decided to take a bit from each and (as always) make my own.
Scroll Saw (or Band Saw)
X-acto or Utility Knife
Different sizes paint cans, flower pots, etc.
There are a lot of tutorials that tell you to print out your letters in the font of your choosing and affixing them to the front of your book as a template. With the different sizes and shapes of the books I was doing, it seemed unnecessary to take that step. I know what letters look like, so surely I could create the letters using simple math.
I didn't take any photos except the one above, so bear with me, sorry. It'll all make sense.
When buying your books remember that thinner is easier, and don't use anything thicker than 2". Even 2" was pushing it - I broke a blade my first time through a thick dictionary (shame, it was a cool book). The thicker you have, the harder it is to keep it square as you're cutting. Also, get some extras to start so that you have something to practice on. Especially if you're new to the scroll saw like I was, practice straight cuts, curves, diagonals, and most importantly, inside angles.
For the "M" seen above, I started by measuring the book and finding the center points, marking them lightly with a pencil mark. Then I decided how thick I wanted the legs of the M and drew those. Then I used the Speed Square to create the 45 degree angles that intersect at that center point. In this case, I also wanted to make sure the Mockingjay was intact, so I made sure the top part of the M was thicker than the legs. Plus, the chunkier the letter, the more stable it is, obviously.
Once I'd penciled the letter, I took it over to the scroll saw. I started with the two straight cuts on the bottom. Then I cut the angle on the top. To do the inside angles, I cut into the bottom right side, curving until I met the first angle on the left. Then I did the same thing to the other side. Because you're not working with wood, sanding is not an option afterward, so take it slow and steady.
For letters like "C" and "G", I used a gallon paint can for the top and bottom curves and a quart paint can for the inside curves. For the inside, you don't want to make a circle, so decide how thick you want the letter, and then draw the top curve and bottom curve and connect the two with a straight line down the left side.
For letters with a cutout, like "A" or "B", I've seen some that appear to have used a hole saw to drill it out, but that doesn't look right to me. I would rather (though I didn't have to, luckily) take the time to use an X-acto or Utility Knife to hand-cut the middle piece. For something larger, like a "D", you could drill a hole, disconnect the scroll saw blade, thread it through the hole, and reconnect it to the saw.
To finish, you could also use a brushed glue on the outside of the pages, 3-4 coats, to create a more rigid piece.