I can't tell you how much it troubles me to have to say that any more there is no easy answer for this. Just a few years ago I could quickly defeat any argument against not buying a good quench oil based upon availability and price because you could get it and get it cheaper than 5 gallons of any vegetable oil or automotive product. In the last few years a few things have happened- certain quenchant makers decided they didn't want to sell their stuff on the open market anymore and the prices of all oil based things went through the roof, and long with it shipping skyrocketed. So while I know that a well formulated quenchant is the best way to assure consistent quality hardening, I also know that it is not always possible for the regular guy to get anymore.
One of the first things we can do is abandon the fad of fixating on just one oil and expand our searches to a wider number of faster quench oils. I now make it a rule not to even mention Parks #50 without really plugging Houghton international who at least still want to sell us oil, just not always at the prices or quantities we want. Look around out there, internet searches can work for this, and explore the large number of other quench oil makers, just look for something with less than a 9 second quench speed.
Despite what my critics may say, I have never said that if you are using an alternative to quench oil that your product is automatically inferior. I need to lay my cards on the table and explain why I prefer not to even discuss alternative quench mediums if I can avoid it. It is because if ever I have seen a topic that is a true slippery slope that one is it. It seems any time one takes the step to discuss quenchants other than well made quench oils the standards don't just get lowered they get erased entirely and in no time you find yourself discussing things that can only be described as absurd. Many light oils will obtain the speed of a good medium speed quench oil, but quenching effectiveness is not defined solely by speed, if that were the case brine would be the only quenchant we would need. I have found some very light weight automotive fluids that will also do well as a medium speed quenchant, but the health concerns in using them need to be considered.
Viscosity and consistency in thermal extraction rate are critical so thick oils and sludges are just not going to cut it. Canola oil can cool steel, lards and greases cannot, that is kind of common sense. 10W30 is a lubricant not a coolant, it will leave lots of pearlite in your blade, ATF or hydraulic fluid may extract heat better but I don't want it in my lungs or even on my skin.
In short, we are in a bit of a bind these days trying to obtain the best quenching mediums, but that bind does not have to be as bad if we broaden our search between the two extremes of one almost unobtainable quench oil and ineffective or dangerous substitutes. I typed this response because I feel guilty for pushing a product for so many years that now is a problem to easily obtain. In the end all we need to do is make knives on the level we have set for ourselves, be that simply skating a file or killing a specific percentage of pearlite, and then be honest with ourselves and others about it.
