Step 1: Materials
2. 1/2" pipe flanges (2 since I did 2 stools. I figured I would never use the other crutch otherwise)
3. 1/2" pipe threaded both ends (cut in half for 2)
4. #12 wood screws (I bought 1" but should have got 3/4". I had to cut them down) or carriage bolts.
5. #8 self tap sheet metal screws. Or you can drill through and use a nut and bolt.
6. 3/4" birch plywood. This is the nice stuff used for making cabinets. Any piece of sturdy wood would probably work just fine.
Step 2: Tools
1. Clear polyurethane (or paint or stain or just leave it unfinished) and Brush
2. Sabre saw and Hacksaw
3. Router (or file). Router not shown, I had already put it away and was too lazy to take it back out. You know what they look like anyway.
4. Drill and assorted bits
5. Sand paper
Step 3: Material Prep and Assembly
1. Drill out the rivets in the crutches. This will allow you to remove just the adjustable foot portion. If you need a shorter stool this would be the time to cut down the length of the stool leg (my son is pretty tall and I used kids crutches so no cutting for me).
2. Cut seat plywood into circle. I used 12" across but you could adjust based on your comfort. Note: We have two stools in our household one kids and one adult both use a 12" diameter.
3. Router edge to nice profile or file to smooth edge. For that matter you could upholster it I suppose.
4. Finish the wood. I used clear polyurethane but you could also stain or paint it. I also did some light sanding between coats to get a nice durable finish. I used the satin for a furniture grade appearance.
5. Assemble the pipe and flange. Simple just thread them together. I would suggest very tightly. My sons are capable of taking anything apart, so mine are gorilla tight.
6. Pre-drill and assemble pipe to crutch leg and flange to seat. I used self taping screw on all 4 sides. You could also through drill and put a bolt and nut. I thought the tech screw approach would be plenty strong and a clean look. Note: Make sure you offset the holes or the tips of the screws will interfere inside.
7. Adjust to comfortable height and start using.