If you are not sure about the colour and if you hit the right heat, Just heat it till its not longer magnetic.
How do you check whether the steel is still magnetic ? You check it when it is red hot ?
And, what if the steel is cooled down in the water at a temperature higher than 800 degrees ? It becomes too brittle ?
But something else... how do you center your tip when its just screwed in? Threads are not exact enough to center something...
With some precautions, threads can be accurate enough. For the best concentricity, I first fix a full brass cylinder inside the core of the top, with epoxy resin. When the resin is hardened, I put the whole top on the lathe, precisely center it, and only at this moment I drill the hole to be threaded.
I finish the hole with a boring tool for better centering the hole. Then for threading I use a screw cutting tool, which is more accurate, as for centering, than a tap threader.
Two grub screws are screwed in this hole; the first is a short one, the second, holding the tip, is screwed in tightly against the first one, not only for steadiness, but this set up also helps improving the concentricity of the tip.
Still there can be a few hundredths of millimeter of error in concentricity of the tip, which are enough to make the top to wobble a bit:
I don't correct this by shifting the tip, but by moving the grub screws in the flywheel.
Doing so, I shift the center of mass of the top exactly above the tip, and the top doesn't wobble anymore.
In my older tops I didn't use the grub screws in the flywheel and I corrected the unbalance in them by shifting the contact point of the tip, filing on side of the tip, which is an effective but a somewhat rough technique; the grub screws in the flywheel are easier to use and permit a more accurate balance.
Someone in this forum (Aerobie) made a top with three screws for fine tuning the position of the tip, which is another way to solve the problem.
I think that a balancing system integrated in the top is useful in heavy tops, which suffer wear of the tip, because each time a tip is replaced or resharpened, the top needs to be balanced again.
Some time ago I made this video, about how to balance a spinning top, (by simple methods, not high tech):
https://www.youtube.com/watch?v=fpRlsWLgeQ0