David Weaver
...and was thinking about this earlier. My first float is unhardened after the first two inches. It doesn't work great, but it works about 80% as well as it would if it was entirely saw temper - maybe more like 90.

teeth that are unhardened in softwood or that have lost some temper will still work fine.

But I need a good picture to make an attempt at something like this. I know how to incorrectly partially reharden something (as in, underheat and get a partial harden), but haven't experimented with how this affects toughness (that wouldn't be hard to figure out). Plus, you can partially harden thin steel just by doing something like heating it and then blowing on it with a leaf blower.

All kinds of options.