Hugh,
The author expressed little concern for his WonderMill’s tendency to heat the flour it milled, on the grounds that the flour was about to go into an oven anyway. This logic certainly makes sense; however, heated flour can be a problem in some cases. We once had a mill, whose brand I’ve forgotten, that heated its flour quite a bit. We make a fair bit of sourdough, and our starter quite noticeably failed to thrive when fed flour from this mill. Of course we let the flour cool before feeding, so latent heat wouldn’t kill the starter outright, but still the starter failed to grow well. Our hand mill, a Country Living model we’ve been quite happy with, as well as a couple other slower- and coarser-grinding electric models we’ve had occasion to use, didn’t have that problem.
As an aside, sourdough is a skill any bread-making prepper ought to learn. It means not running out of bread when the commercial dry yeast supply runs thin. – EJW
HJL Adds: We have also been very happy with our Country Living Grain Mill, but it was not a cheap option. The mill was one of the most expensive, and the addition of the electric kit made it even more so. In the first four months, the mill had the “newness” of a toy so it was no problem finding someone to turn the crank, but after that, it was either electrify it, or turn the crank myself for an hour every other day. The mill does not heat up appreciably, even on large batches of flour.