Never used Mineral oil. I whole quench and draw back; olive oil, canola and I just got some Parks 50. I have read that mineral oil works.

I used "vet grade" mineral oil on 1080/1084 for probably two years. Made some "good" knives. I was tempering at 425 to get to RC 59/60 on small hunters. Then I got some 10 second commercial quench oil. The same 1084 edge chipped at a 425 temper, telling me that the faster oil was getting better martensite conversion. A 450 temper brought me back into spec.

The key piece of missing information from your post... what steel are we talking about? 1084, yes. 5160 or O1, likely. 1095, not likely.

Generally speaking mineral oil isn't the best. That is not to say you won't be able to harden a blade in it, but you probably won't be able to get the most out of the steel. In the long run you will want to get a quenching oil. These come in different speeds, and you will want to match the speed of the quench with the type of steel you are using.

The question of whether to differentially harden or draw the temper is largely one of personal preference and I think there are advantages to each. Which will ultimately work best, will largely depend on your choice of steel.

I started out much the same way, I was forging any piece of steel I found that had enough carbon to harden and quenching in used canola oil from work. I got some halfway decent blades, but it really wasn't till I started using a known steel with known temperatures and matched my heat treat techniques to the steel that my work saw any consistency.

What type of steel are you using?

James, one consideration in your question is how you are quenching. If you are edge quenching just about any low viscosity oil will work. The dynamics of an edge quench will fight total martensite conversion regardless of what oil you use, but more importantly the same circumstances will almost invariable result in overheating, or flashing, the surface of the quenchant which would only destroy the investment you made in a good quench oil. If you plan in edge quenching simply get a volume of canola oil and replace it when needed. Mineral oil may, or may not, be a suitable quenchant. That, as has been mentioned, would depend on your steel choice, but also on the fact that mineral oils can come in any number of viscosities. Some have made the error of reading that quench oils use “mineral oil” in their manufacture and assuming that they be simply replaced with mineral oil. All that means on an MSDS sheet or ingredient list is that the quench oil was not made from vegetable based oils. There is a whole lot of other chemistry going on to make the quench oil behave optimally in hardening steel, even if the other ingredients make up a small percentage; the steel you are quenching is probably at least 97-98% iron and yet just .5% to .8% of one ingredient makes that unusably soft iron into a fine steel blade.

As to the question of who does edge quenching vs. full quenching, obviously the guys preparing for the Journeyman or Mastersmith test are either doing edge quenching or drawing the spine back. I was just asked a question yesterday that involved this topic and, after thinking about it, I do believe the last blade I put a soft back on, for any functional concerns, was my mastersmith test blade almost 20 years ago; that was the last blade that I wanted to easily bend. If you are preparing or practicing for a test blade I would suggest a full quench with a spine draw for 5160 and an edge quench for any 10XX series steels. But if you are using a quenching oil, canola oil probably has the best cooling curve as well has the least health concerns. If you are using an alloyed steel like 5160 the mineral oil should meet the cooling demands as well.

thanks guys at this time i am using 1095 and 5160 .I want to try other steels in the future

just trying to get a handle on quenching . I am aware of the many different variables that

come with the many different steels .From the sound of things I will be better off going with

parks or something like it .

I'm new to this, but Parks or something like it seems to be the way go go for the faster steels. I haven't been able to find anything like Parks where I am (Ecuador), but using Canola has been just fine on the blades but terrible on the wallet. It just doesn't last, even though we have a pretty mild climate here in Quito (0 degrees latitude, but almost 10,000 feet elevation). Canola gets very funky very quick, and I'm sure that its performance suffers dramatically after a few quenches, which means I switch it out frequently. It's added up, in the past three years, to more than a five gallon bucket of Parks.

So, IMO, even financially speaking, something intended for quenching is the way to go simply because it lasts longest--I think most people buy their Parks out of Seattle or Texas, so shipping shouldn't be that much of an issue for you in NM, either. They might even give you a deal on shipping if you order a bucket of medium speed oil for the 5160 at the same time...not sure.

(We're moving back to Alaska this coming summer, and one of the things I'm looking forward to is cheap and easy shipping...which just goes to show that everything is relative.)

Two points about the Parks #50, one that Steve touched on is that it is rather fast for an alloyed steel like 5160 and I would expect to see greater amounts of stress related issues such as distortion or possible cracking, although the latter would be less likely with 5160. The other, I touched on but bears repeating, is I cannot advise people strongly enough against edge quenching in Parks #50. Parks #50 has very good vapor suppression but its flash point is much lower than other oils. If all hot steel is below the surface of the oil I have never had it flash, but if hot surfaces are above its surface a flame up is almost unavoidable. Not only do I abhor this situation for the obvious safety reasons, but this will absolutely trash the oil, turning it into an oxidized, black liquid lacking the consistent and predictable qualities that you spent all that money to have. This would be a similar situation that Steve described with the expense of replacing canola, but at the cost of Parks #50.

I would certainly consider the Parks #50 for the 1095 as that is the only oil I have found that can consistently through harden that steel in an entire blade of typical dimensions, but I would reserve it for full quenches with steels such as 1095, 1075, 1084, W1 or W2. If full quenching 5160, any medium speed quench oil(Parks #50 is a fast oil, not medium) will work well, but if edge quenching I would go with any of the low cost alternatives suggested for the reasons I have previously mentioned.

Another option for differentially hardening without edge quenching would be to clay the blade.

Also if you are going to be doing edge quenching (or any oil quenching really) make sure you have a lid that you can put on the quench tank in case it does flare up.

I have never used mineral oil, but sure it would work for 5160, though not 1095, unless razor thin. I used diesel fuel for quenchant for years with 5160. Works great. Easily replaceable.

I prefer to lower the austinizing temp(all steels), and soak the blade at that temp longer. This reduces flash dramatically (and cracking/warping. Dan