In the very first post I put up on this build, I talk about the blank I picked up to for the flywheel. To save you the time, the short version is I came across a blank that was half the price of the cast iron or cold rolled steel the plans call for and thought I'd try it. The blank is D2 tool steel, which I'd never even heard of. I started machining it this week while waiting on the ball bearings and a few other things I've ordered. While facing it, I found it was very easily heat treated. A .005" cut turned the chips golden or amber colored. A .010" cut turned them cobalt blue and extremely brittle. Just touching them cracks them. So while it was slow going on my 1HP Seig lathe, I faced it and then cut it to diameter. Now it was time to part off the extra length and get the blank down to the proper size to finish. This is where it got really involved. I started off with a parting tool that was 3/32 wide. I quickly realized that was too wide and didn't seem to be cutting well enough, so I switched to a 1/16 wide tool. That was doing better. Again, I realized that it was bogging down but if held a hacksaw in the cut and let the cutoff blade just trim off the shoulders of that cut, it went pretty quickly. That worked for about the first half inch of the 1-7/8" inch I had to cut. Then I realized the hacksaw wasn't cutting. The teeth were worn away. I switched the blades and made some progress. Then I noticed the cutoff tool was losing its shape; instead of the Tee shaped cutting edge, it was wearing to a point. I turned it end for end and kept going. Let me cut out more details, but say it probably took a good six hours of fighting to cut off the extra half inch thickness. Plus an hour running up to the two local hardware chains (True Value and Home Depot) looking for carbide tipped hacksaw blades. The eventual solution was a carbide tipped blade for my reciprocating saw. https://www.homedepot.com/p/Diablo-...ng-Reciprocating-Saw-Blade-DS0608CF/205426155 It's interesting material to work on. I suspect that forming the flywheel is going to continue to be an adventure. I probably would have been better off paying twice as much for a piece of cast iron. I'm still thinking of doing that.