I don't recommend using this method to calibrate the tips. It's better to measure at the 3 set points and write down the info. Then go through the calibration setting just punching in the numbers. Then test it out. I almost always have to add a little more offset, especially at the 450° setting. Keep all this written info just in case the iron settings get erased or you buy a second soldering unit (which I am). You can then quickly put all the info back in.
