52100 is a different sort of animal, in that you have to do everything right to get a good knife. It dosen't like to move very well under the hammer at it's recommended forging temp and if you over heat it you end up with crap. now then if you really want to prove you are macho/masachistic then you will forge it at no more than 1650 degrees and no less than 1450 and then finish it at 1250 to 1450 at these temps it is almost like forging cold mild steel. but it also seems to be what it takes to make a great knife. it is just very labor intensive in that it is in and out of the fire maybee a hundred times and you really have to beat the heck out of to get it to move. But for mee it is all worth while because I feel that I am making the best knife that I can make. I Have tried all the things that other makers say work great looking for ways to make thing progress faster and easier. Some work most didn't. I will not sacrifice quality or performance to make knives faster/easier.
I start by taking a 2 1/2 to 3 inch square by fiveish inch long piece of 52100 and give it a normalizing treatment in my paragon. Then start forging this chunk of steel into a billet under my little giant power hammer. when breaking this down I heat it to 1850 or so. After I have a billet i then start working the end into the blade shap that I want. the closer I get to the finished blade the lower the heat I use and the more I hammer by hand. When the blade is finish forged I the heat it in the forge to just over nonmagnetic (checked with a magnet) and then quench in room temp texquench a oil. I do this three times and the blade is in the oil for only about 45 seconds so it never really has a chance to fully convert to martinsite but this does really seem to help with grain size reduction. I then heat the blade to non magnetic aagain check with a magnet then hold it in a darkened area and watch the phase transformation that occors as the blade passes from nonmagnetic to magnetic. This is an allotrophic phase change and can be identified by watching the steel go from red to nearly black and the it will actually go back to red again. this happens because the phase change creats creates energy wich manifests itsself in heat which causes the blade to gain color. this change can also be seen in the opposite when heating a blade but it very difficult hard on the eyes because you have to stare into the forge to see it happen. anyway I do this three times and then reheat the blade and let it cool to room temp. I then put the blade into the freezer over night. the next day I take the blade out of the freezer and let it warm to room temp then put it in a cold heat treating oven and heat slowly to 1250 degrees and hold that temp for two hours, then let slow cool back to room temp. the next day I repeat but heat to only 1150 and repeatthe next day but heat to only 1050. I then grind the blade and finish it to a 220 grit finish before hardening. I then harden three times by heating the edge to just over non magnetic and qeuench it in 165 degree texaco type a quenching oil. this is repeated twice more with the blade resting in the freezer between quenches. I then temper to the desired hardness three times again letting the blade rest in the freezer over night between tempering cycles. After all this (it has taken me nine to ten days so far) I then grind the blade to my finished dimensions and work my way upp in grit to a x30 norax belt (1200 grit) At this point the knife is pretty sharp and it it time for some testing. the first thing that I do is to flex the edge full length over a brass rod. the edge must flex over the rod and return to its' original position without chipping and it cannot stay bent. in a thin edge as found in a kitchen knife 52100 will do this at a hardness of 63 hrc if I got the grain reduced to where it should be. After this test it is time to cut stuff. I sharpen the blade on a norton fine india stone. thi stone is fairly coarse about 320 grit but will put a fine enough edge on a knife that it will easily shave hair with no pulling. My favorite test medium is hemp rope. I buy it from a rigging supply house in six hundred foot rolls and I cut up about one roll per year. I take a peace of 1 inch rope about a foot long and separate the three twists ond then start making slicing cut using about 101/2 to 2 inches of the blade and take about 1/8 inch of rope per slice. I count the number of cuts and when the blade slides and will not make a full cut in one slice call it quits. and check for sharpness by feeling the edge and checking to see if the blade will still shave hair. if it does i then try the rope again and continue the count until it slides and no longer feels sharp and will not shave hair. I then compare the number of cuts to what my other knives in the same style did and determine if I want to finish the knife and put on a handle or test further until the blade is destroyed. if the blade is good I the regrind the blade starting at an x30 and finishing with an x5 (3000 grit) thenpolish and hand sand back to 2500 grit the slightly buff. at this point the blade is a freaking razor and I am very caful while I put on the handle and fittings. the last thing I do is to sharpen and sign the knife. I am not going to put my name on anything that I am not 100% happy with.
some of these steps are done one knife at a time and some are done to sereral blades at once. I end up taking most of a month to do one knife from start to finish with from forty to sixty hours spent on each knife. I can make a knife in about five hours but have never done one that I was proud of when trying to hurry so I just don't hurry.