I marked a little more than 1" of shaft because too long is better than too short. If you cut the shaft too long, it can be shortened. If you cut the shaft too short, you'll need a new one.

You will need a circular saw with a metal cutting/carbide blade. A sawzall will NOT work. I used a 4.5" hand grinder. When using a grinder, make sure you cut slowly and no more than 30-60 seconds at a time. This will prevent the shaft from getting overheated and warping.

If the shaft isn't square at the end, grind it down to make it square.