I was going to make a button yo-yo for the kids last night, but I didn't have any matching buttons that were big enough. I decided to try milk caps instead. We have an abundant supply of milk caps, and they ended up working out pretty well.
I started out by measuring, marking, and punching matching holes in the caps with a nail. I measured out a half a centimeter, from each side of the center, of the caps.
Then, with the flat sides of the caps together, I laced a piece of cotton yarn through the holes, and tied it on the outside of one of the caps, to secure them together.
I pushed a little clay into the outsides of the caps to add some weight. It's important to keep the weight even on each side, which is a little tricky without weighing the clay. I think gluing on a couple of washers might be a better option, but I was looking for something quick and adjustable, for testing the weight, and the clay worked nicely for that.
Finally, I cut a piece of embroidery floss (I also tried cotton yarn, kite string, and polyester thread, but found the embroidery floss worked best), about two feet long. I tied a finger loop in one end, and wrapped the other end a few times around the yarn, between the caps, and then tied it.
It's not exactly perfect, but it's close. A little more fiddling, and a little more practice, and we'll be ready for the "how to yo-yo" book, I put on hold at the library. Or, at least my daughter will be - I still have 3o, or so, other on hold books to go through.
It's great to be a homeschooler.