Hey Eide, nice to hear you are into the thick of it. It sounds most likely that you are quenching at too low a heat. If the metal comes out of the quench and you can still cut it with a file this is certainly the case. If you overheat and quench, several things might occur, none of them good. Slightly overheated steel (50?-100?f) usually comes out of the quench with an "orange peel" surface texture. Sometimes you can still get a workable tool in this scenario. When overheated much more than 100? most likely the steel will crack or split. Just say "sh-- Da--", and start over. O-1 seems especially susceptible to cracking when overheated. Another problem with overheated steel is warpage. This can be severe enough to make a tool unsharpenable. Trust me, if the blade is severely warped it is a waste of time to try and compensate by grinding. Often the tool design,(shape and cross section) is the cause of warpage and not overheating. This should NOT be a problem with a simple plane blade shape. O.K. those are the problems. So how do we get it right? Without special gear you need to train your eye to discern subtle changes in the heat glow of steel. The magnet trick is certainly helpful, but the point at which the steel appreciably hardens is really a bit higher,50? or so. I think the best place to start might be to get some 1/2" O-1 drill rod and do some testing. This material is inexpensive compared to the flat stock. First cut several 6" lengths of rod for samples. If you do not have a pyrometer then use your magnet to indicate an "almost there" temperature. One sample at a time, progressively raise the quenching heat, (note the heat color) until the sample comes out file hard. Don't stop there! Keep doing samples until the steel comes out cracked or split. Hell, burn the shit out of it and see what happens! If you do this enough times your brain WILL remember the right color and you should be able to get consistent results with out a lot of expensive gear. In dim, indirect natural light the spectrum of incandescent colors produced when heating steel is quite broad and directly corresponds to temperature. Avoid florescent lighting as it limits the spectrum. Also avoid bright direct sunlight. I can't tell you how many things i have ruined by being fooled by ambient light. Eide, you seem determined to do this. This heat treating thing on simple shapes is NOT rocket science. Judging heat and color is an intuitive skill and it just takes paying attention to get it right. So get on it and let me know how it turns out.