You will need to hold the red heat for a while depending on its cross section it will also need to cool slowley, if I need to do this sort of thing, I used to throw it in the fire and leave it over night to cool, I now have a heat treatment oven so use this instead ……….

having said that if you hold it at red heat for five mins then cool it slow you might get away with it…….

Shaun

Heat to red heat for 1/2 hour and cool as slowly as you can. Wrap in some thin sheet metal to avoid scaling.

Tony

If it is to reduce the height, you could rough it out with an angle grinder, and then get the local machine shop to finish to size on a surface grinder.

Howard

Here is a tool made from a HSS flat bit, the original drill bit is in my album. Hardend all over, most ly cut with the angle grinder, the bottom ground flat with a cup stone in the vertical mill(well covered). I,v made 2 of them, and have another one that can be done at a later date. Ian S C