Remember, I am just a beginner, and I am sure that the more experienced woodworkers in this site will be able to see all sorts of flaws in my methods.
1. I have access through a friend to a band saw, but it does not have a fence and therefore I made Jig #1 to get a standard width on the wheels. To do this, I butt the dowel against the jig which I have set for 3/8 of an inch from the blade. If your band saw has a fence, you will not have to make this jig.
2. For safety sake, and to make sure that the cuts are straight, I made Jig #2 which runs in the miter slot of the bandsaw. The dowel is placed in the slot, butted against jig #1 for width, and then is advanced into the band saw to cut. Take your time and let the saw do the work.
3. You now want to put a hole in the middle for the axel. Once again, I have a jig (#3). This is made by cutting a shallow round the sizes of the wheels you might want to make using a Forstner bit or a Spade bit. Using a regular bit the size of your axel, enlarge the hole in the center; you can drill it at least partially through your jig wood. On your drill press, clamp the jig so that the drill is centered in the hole. Place the wheel into the jig hole and hold it with a pair of pliers; you really should keep your hands away from it as they will get burned if the wheel catches and turns in your fingers. Now you really have a production line; drill out the axel hole, take out the wheel and then put the next one in. Always a good idea to check now and then that your bit remains centered.
4. You now have a rough cut wheel which needs sanding. I use the jig (#4) which, I believe, either Udie or Doc suggested to me and attaches to the side of my sander. This sands the bottom of the wheel, and the flat sides are sanded on the top of the sander.
5. Now you want to round over the sides of the wheels to make them pretty. I have a router, which I placed into an inexpensive router table and attached a 3/16 inch round over bit. I have two sizes of wheel jigs, both made from scrap materials in my bin (Jig #5). The smallest is made for the small car wheels and is made of 3/4 inch medium density fiberboard. Cut the central area so that you will have lots of room to guide the wheel around the router bit. Make the top strap so that it has a little pedestal and drill a hole slightly larger than the bolt you are going to use which should be slightly less than the size of the axel. I mix metric and imperial here so that I do not have to struggle to get the bolt in and out of the wheel, but the wheel remains centered. Put a small washer on the bottom. Use a wingnut for the top; I use a nut with spikes (name?) that I drove into a reject wheel. Make sure it is tight or the router will grab the wheel and cut out chunks. The jig for the thicker wheels is made just the same, but allows for the increased thickness of the larger wheels. Now take your jig assembly to the router and adjust the bit so that it is set just to round off and not to edge over. Then, turn on the router and advance the wheel jig in the appropriate direction (with the turn of the router bit), circling the router bit. Turn off the router and then take away the jig. Keep your fingers away from the bit by placing them only on the outside of the jig. Flip the wheel over and do the other side.
Seems like a lot of jigs, but remember, you use them over and over again and they will actually save you a LOT of time.