You could probably get by a season without hardening the shaft, but since we have not tested doing so I could not tell you what the results would be.
Here are the measurements I got from the gears; I do not have the shaft measurements for between each gear.
Third Gear:
1.014''
Second Gear:
1.001''
First Gear:
1.001''
Being that we used second gear the most it had the least amount of wear because it was not able to "freewheel'' on the shaft.
Overall the shaft was at 1.008'' in diameter, I am not sure of what it was when it was after being machined.
