Help! Quench Question.

Are you sure you want less than 5 gallons? I'm asking because if you are making some, I'd assume it would continue and the stuff is hard enough to get perhaps you can simply hold on to the excess for a while? I know you need to change it periodically, but I'm new and have NO idea of when (or how long unused oil would last). I'd basically given up on smaller amounts and was going to bite the bullet and try to track down 5 gallons of either Parks or Houghton if I can. That is a BIG if though.
 
i like smaller amounts so that i can try out different ones, so i can learn which ones work best for me and my needs seeing that i am a nube myself. buying 5 gallons at over 100 delivered is to costly to just do the old pig and a poke and hope the one you picked is the right pick for you. it of course would be different if i was a pro pushing out volumes of knives but i am not. just a hobbyist obsessed with knives lol.
 
You want the quench that is right for the steel, not right for you. 1084 is a good choice of steel for your needs, and is not terribly picky about the quench. As long as it is a fast oil. Parks #50 would be a top choice, but not the only. Any of the oils nearing the speed of the Parks would do fine. Canola oil may be an answer for your needs. It is fast enough for 1084, and you can buy just the amount you want. Tai Goo uses it for 1095 with apparent good results, and 1084 is much less demanding than 1095 is.
 
Speed isn’t the only thing to consider and choosing a quenching medium based strictly on steel type is a bit misleading. Blade geometry or part design and the intended end use also play major roles.

It isn’t difficult to get the thin edge section of a blade to harden, just about any oil will do. Where it can get tricky is to try and get full hardness along the spine without over stressing the edge. Hardening knife blades, (especially the most important part, the edge) isn’t as much of a problem as warping/distortion, excessive micro fracturing and quench cracking.

The petroleum based fluids exhibit 3 cooling mechanisms with different heat transfer rates, vapor phase (slow), boiling phase (fast) and convection, in that order. The vegetable oils exhibit one, convection, with virtually no vapor or boiling phases. With the petroleum based fluids what happens is you get different cooling mechanisms, with different heat transfer rates, working on different areas of the blade at the same time. This compounds the stresses associated with the inherent thermal gradients of knife blades. In other words, the thin edge section gets to the fast boiling phase while the spine is still in the slow vapor phase, just the opposite of what would be ideal. This isn’t a problem with vegetable oil, you just have the inherent thermal gradients themselves to contend with. The petroleum based fluids are a bumpier more stressful ride for the steel. Vegetable oils are fast enough, with less stress to the steel. The vegetable oils are fast during the high speed initial part of the quench because there is no slow vapor jacket phase and the difference in temperature between the blade and quenching medium is at it's highest.

During the low temperature transformational part of the quench, or slow part of the quench, the speed is regulated strictly through viscosity and at this point both types of mediums exhibit the same cooling mechanism, convection. So, which ever fluid has the lowest viscosity will cool faster and which ever has the highest viscosity will cool the slowest. Some of the super thin fast accelerated petroleum based oils like Parks #50 actually have a lower viscosity than the vegetable oils, which means that they would also be more stressful during this part of the quench.

The best things about the petroleum based fluids are that you can buy them in different speeds, (not significantly so with the common vegetable oils), and they can save you money in the long run. The worst thing about the vegetable oils is that they aren’t as stable as the petroleum based fluids and need to be changed out more frequently.

This is all just theoretic nit picking and it doesn’t mean that you can’t get good results with either type of quenching medium. Depending on a number of possible variables, in some cases the accelerated petroleum based fluids may be a slightly better choice and in others the vegetable oils. However, aside from the metallurgical advantages of the vegetable oils they are also safer to use, biodegradable, and easy to acquire in small quantities at a local grocery store.
 
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...Some of the super thin fast accelerated petroleum based oils like Parks #50 actually have a lower viscosity than the vegetable oils, which means that they would also be more stressful during this part of the quench....

Oops, typo. Tai must have mistyped this, as quite the opposite is true, as is even described in the Totten study that I know Tai is very familiar with. It is vegetable based oils which display a notably faster cooling rate in the later part of the curve where martensite would form. I can confirm through plenty of first-hand experience that both Parks #50 and Parks AAA have been well engineered to produce a noticeably slower cooling rate in the 600F and below range.
 
I may not have interpreted that part right, but haven't seen any side by side cooling curve comparisons between Parks #50, AAA and canola. They used different oils in the study. It's is closer to AAA than Parks #50 in that area though, judging by the viscosity values, 45 for #50, for 78 canola and 85 for AAA, according to the specs I'm going by. I'm not sure if the scales are exactly the same, but just judging by appearance it seems about right... AAA a bit slower than canola and #50 a bit faster. Of course the temperature of the oil will have an effect on viscosity, so I guess it's really hard to say for sure. All three should be somewhat comparable and generally acceptable for 1084.

... All told, canola seems a closer comparison to AAA than to #50, but somewhere between the two in terms of speed.
 
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For whatever it's worth,... I just checked on it and the viscosity value of, 78.2 for canola, was at 68 degrees F, and the Parks both at 100 degrees F, which means that at 120-130 degrees F, (which is often recommended), canola might be closer to the #50 than the AAA in terms of viscosity.
 
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Thank you all for the responses. It really helps a lot to hear the comments from those who know. I have now added another quinch tank and will have both canola and parks 50. I think it will be fun to use both and compare. for anyone looking for parks 50 The best price by far was maxim 134 delivered to mn for 5 gallon bucket.
 
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