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Alternatives for quenching oil - Hydraulic Oils

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So, after reading this (it appears that globalspec is not commercial website):


And watching Knife Steel Nerds discussing quenching oils:

I've concluded:

1. You should not use Canola

2. Parks AAA and Parks 50 is pretty pricey. Importing it to Belize costs 2x due to shipping

So, to avoid paying almost 500 bucks for Parks 50, have any of you found any article or tests done by anyone or yourself on other quenchants like hydraulic fluid?


Note that this question refers to quenching knives made out of 80CRV2, 1095 and whatever steel leaf spring and farrier rasps are made of (for now) using a gas forge. 


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I have heat treated leaf spring steel with heated canola oil very successfully.  5160 is a deep hardening steel that does not need an extremely fast oil, so heated canola works just fine.  I believe that the others you have listed do need a faster quench.  You could investigate interrupted quenches for those (quick couple of seconds in water then switch to heated canola).  I really haven't done much of that though, so hopefully someone else can advise.

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Ultimately the purpose of quenching is to remove heat from the steel at a rate suitable for that steel.  Depending on the alloy, that could be anything from air cooled to brine. The method of cooling is not as important as cooling at the correct rate for the alloy.

The reason I bring this up is that no quench medium is "best" in all cases.  The guys at Knife Steel Nerds are very knowledgeable, but keep in mind they are attempting to squeeze the absolute best performance out of any alloy they test.   No, canola oil is not the best quench medium.  However, that oil, peanut oil, mineral oil, automatic transmission fluid, etc. may be suitable for your needs if a more suitable quenchant is either not available to you or cost prohibitive.

This is where you may have to get creative.  If you have an alloy you will be working with repeatedly then you can make nearly identical test coupons to quench in different mediums and test to see if they provide the results you are looking for.   This can be a bit tedious, but if you are methodical and take good notes you can figure out what works the best for you overall in your situation.  Of course it gets a bit more involved when you take into account both the quenchant and the tempering temperature.

Although I don't recommend it based on information I learned after starting, I have quenched in used motor oil. I've also used automatic transmission fluid. For alloys needing a medium speed quench those can work out well, but probably not quite as well as a formulation specifically designed as a medium speed quench oil.

Don't let the drive for perfection keep you from doing something that is still quite good.

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any medium will work once you learn and figure out it's character..   

Sloppy mud,  Horse urine, soapy water, Lime water,  brine,  Etc, etc, etc..  

Any new batch of steel as well as any new quenchant should be tested to see if you get the desired results of fine grain, hardness and toughness. 

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On a side note..     I recently read something on the dangers of having 2 slow a quenchant..   We often think that as long as the metal is at the transformation temperature, one can bring down the temp of the metal below the critical temp and this will lock the carbon in and give a good usable product. 

The rates of cooling and times at the different temperatures can be complicated from a home shop ideal vs what is recommended in a heat treaters guide..

I find overheating is much more of a problem than slow cooling times..   

I use Linseed oil in the trailer since it's handy and great for making springs..  So it gets used for nearly all the hardening while in the trailer. 

I don't know if it's a fast oil or slow oil. (I've always assumed a slow oil since it also has bee's wax in it) I always cool off in the oil till I can wipe off the residual oil.. It's still to hot to handle but not so hot I can't grab it with a paper towel for a split second and it burns my fingers. 

I'd say in the 300F range.. 

I've tested for HRc and it's always spot on with 5160 using this method even with hammers that have ample mass to self-temper with slow oil. 

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         I bought a set of the Japanese Hardness Test File Sets, and...

Was impressed in how well they gave me a better idea on what was going on...

After Quenching and Tempering.

Allowed me to vary and or experiment with Quenching and then Tempering for a certain steel.

Admittedly, I only use simple Carbon Steels.

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Keep in mind they only show you the hardness. 


They in no way show what the grain structure is. 

I can take a piece of mild steel over heat it in the carbonizing part of the fire, quench it and get 62Hrc.

Sure it's 62Hrc but the grain growth is useless for anything unless one understands how to utilize the steel and it's character to the best advantage. 

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18 hours ago, jlpservicesinc said:

 I recently read something on the dangers of having 2 slow a quenchant

Yes this is certainly one of the critical parameters.  Great references for this regarding knifemaking can be found on Kevin Cashen's site: https://cashenblades.com/bladesmithing-information/

The TTT diagrams he includes pretty clearly indicate the speed needed in the quench to get "past the nose" to maximize the martensitic transformation that leads to proper high carbon steel hardness.

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It's interesting to me that "knife steel nerds" has studied the attributes of forging a knife and heat treating at his forge,band his recommendations after all the testing is what I've recommended and explained for the past 30yrs. 

It was great finally seeing someone in the metallurgic field actually do this kind of thing.

If metals had to be processed at a laboratory level to do anything humans would not have survived. 

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Maybe true, but on the other hand some strict scientific protocols for experimentation and rigorous testing might have been able to both shortcut the hundreds (or thousands) of years of trial and error to find effective steel heat treatment formula as well as some of the more egregious misinformation regarding heat treatment (urine of a red headed boy, pointing the quench tank in line with the earth's magnetic field...).

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Thanks everyrone. I found Parks 50 by the gallon very reasonable on Amazon with prime shipping. My shipper and I can then workout the logistics to Belize.


On 8/16/2023 at 2:25 PM, jlpservicesinc said:

I use Linseed oil in the trailer since it's handy and great for making springs..  So it gets used for nearly all the hardening while in the trailer. 

I don't know if it's a fast oil or slow oil....

Depending on the steel you used for the springs, Linseed or Canola would be adequate. Dr. Larrin shows that for 52100 or 5160, a medium quenchant is optimum in his opinion (from Knife Steel Nerds)


However, for the type of steels I intend to use (as a beginner), 80CRV2, 1075 etc, he recommend a fast oil (Parks 50 or even the AAA). And his tests shows to not use Canola (the hardening in Canola is outrageous!!). This is a chart of hardness of 1084 with different quenchants



I've always believed that as a beginner, you should set up for maximum success. When I was learning to weld, I was cleaning all my surfaces and clamping everything square. I'm still mediocre, but after some practice I stopped cleaning and just cook rusty crummy joints with 6011/10, and I start weld slightly out of square to end up close to square after shrinking. So I think I'll just bite the bullet and buy couple gallons of Parks and use Canola for leaf spring and those kind of things after some tests. 


Mod note: typo removed

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1 hour ago, Latticino said:

more egregious misinformation regarding heat treatment (urine of a red headed boy, pointing the quench tank in line with the earth's magnetic field...).

Marketing hype from a time when the blacksmith's craft was a tightly held guild secret and smiths in business had to pay guild dues or loans and so "advertised" THEIR ancient secret methods to draw in the mundanes. You see this all the time from folk who don't actually  know what they're doing but are still trying to start a "business."

What was the name of that short lived discovery channel (I think) series about "mountain" folk forging . . . stuff? I only watched a couple episodes, maybe half the second and every time someone addressed the anvil or quenched a blade they mentioned aligning everything north south. The "interviewer" asked some scripted questions in an amazed tone.  Happily the show wasn't well enough done to last a whole season and I don't think much if any mythInformation made it into the stream.

Frosty The Lucky.

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1 hour ago, ron2k_1 said:

This is a chart of hardness of 1084 with different quenchants at different thicknesses

No.  That is a chart of hardness of 1084 with different quenchants at the same thickness (1/4") and quench temperature.

That was probably the worst showing for canola oil in all of the tests.  Fortunately you've said you'll be able to get some quality quench oil, so that renders the canola oil issue moot. My preference is in the 58 to 61 hardness range (after tempering) for most blades.  You can usually get good edge retention, reasonable toughness, and still be able to sharpen the blades using traditional means in that range.

I like 80CrV2 quite a bit myself.  One word of caution though - it can develop a thicker decarb layer than other simple steels.  Sometimes this might lead you to believe a quench failed to harden the blade if you just do a quick file test.  To check it properly let it cool close to room temperature and grind away a thin layer before testing. 

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Good point.  I think it is worth noting that many bladesmiths (myself included) typically forge and grind down bevels quite a bit further than 1/4" thickness before quenching.  I haven't done specific experimentation like Dr. Thomas,  but strongly suspect that this thinner stock allows even slower oils (like heated canola) to accelerate the quench speed.  Possibly not up to Parks 50 (which I now use for steels that need a fast quench), but to the acceptable levels Buzzkill mentions above.  I believe I recall testing 1084 blades that were quenched in heated canola with hardness chisels and seen Rc at 60, but it was a while ago and I'm not completely sure.  I certainly would feel comfortable using heated canola for 5160 or 6150 or for work where high hardness is not preferred like axes, hammer heads, hawks, chisels...  

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20 hours ago, Buzzkill said:

No.  That is a chart of hardness of 1084 with different quenchants at the same thickness (1/4") and quench temperature.

We're both right. Yes, he quenched a 1/4 inch stock, but to get the chart, he grounded both sides of the stock to test for hardness at different grounded thicknesses. 

Sounds like a plan then. I really still want to test canola and I've heard that hydraulic oils (used for heavy machinery) are good as well, so at least I'll have some sort of slow quenchants for other varieties of steel. 

Thank you all.


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I have revisited that chart several times to try to get my head around it.  It seems to me that it is showing the depth of hardening.  That would have to be measured by grinding away to those depths after hardening the full thickness, not by grinding to size (Depth) before hardening.

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31 minutes ago, ron2k_1 said:

We're both right.

Kind of.   I see what you are getting at, but the thickness of a piece of steel when quenched significantly affects the rate at which it cools.  Therefore, grinding away portions to check the hardness at certain depths does not give you the same information as quenching different thicknesses of steel.   If they had started with 1/8" thick test coupons the results would be nearly identical for some alloys, but most likely significantly different for others.

Usually for knives you can get away with one step slower quench than the manufacturer recommends.  That's because they give their recommendations based on inches of thickness rather than portions of an inch. So, something that normally specifies a water quench can be properly hardened in a fast oil if it's a thin cross section. I've had a couple blades made from O1 air harden. Similarly, you could expect different results than shown for 1/4" thick pieces if you are quenching thinner pieces.

Most of my blades are between 1/8" and 1/4" when quenched, so I would expect slightly different results than shown on the chart you posted earlier.

Like you said though, you can try different quench mediums for yourself and see how they perform.  I highly recommend doing this - and breaking the test pieces to observe the grain structure.  This can really help you figure out what works best for a specific alloy and what quenchants you have available to you.


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Take a look in the knife making sections for its heat treating information.  We have a separate section for blades because of the thickness issues, as well as the unusual steels used in knifemaking,

I also agree that your chart is for 1/4 inch thick (6mm) as it states itself on the graph.  The other numbers at the bottom are depth removed after heat treatment showing how far they are ground down, which is showing the depth of the decarb layer. 

Perhaps this is a language thing causing confusion.  I lived in Germany in 1978 and made many errors due to language myself so I can understand. Also knowing English has many regional differences only adds to confusion.

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You guys are kinda missing the mark..  

Anytime you arbitrarily pull information out of a video, demo, lecture or website there is a lot of information that is lacking. 

This graph says just this and nothing else. 

1084, 1/4" stock, quenched at 1475F..   

Rockwell hardness and of depth of hardness depending on the quench fluid.. 

Speculation one way or the other is spitting in the wind..   "IS" or "IS NOT"..  

So.  Can any of you guys dial into that 1475F exactly? 

Sure with a "heat treating oven"  

Now we can argue..  Salt melts at, or tempil marker.. Blah, blah, blah.. 

What about if the coupons were pulled from 6 different batches of 1084?????   Then what. 

you guys would be better served by doing the same experiments yourself and seeing the results. 


Steve, I don't believe that is the removal of the decarb layer..  The decarb layer at this point should be removed to get a consistent  result.. 

Easy enough to do with a surface grinder.. 

It would have to be speculation that the decarb layer is being measured in this test..  Or more accurately the decarb layer is being removed with each measurement. 


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2 hours ago, LeeJustice said:

The points for the hardness readings don't start until thirty thousandths.  Is that the depth of decarb?  I don't know.  They end at .125, so it is through hardened, for what that is worth.

A hardenss tester needs to have a certain resistance to work properly.   If there is not enough of material or if a layer of decarb is present then it will be wrong. 

There are files..  Which can test across items like damascus but they are not that accurate.. 

A penetrator is needed unless you have $$$$$$$$$$..  

I own 4  types of indention type Hardness testers..  1 set of files, and one bounce or kinetic type tester. 

The files will not work on decarb, the kinetic will not work on decarb.. 

How ever the penetration type will work since the penetractor will go right thru the decarb layer until it hits real material. 

Is it as accurate as removing the decarb.. No.. 

With this said..    You can feel the decarb layer with a regular file and just file or sand off the decarb.. 

Or better yet..  Since this is a real shop with real testing equipment..  Just put it on the surface grinder and remove a measured amount of material.. 

On thru hardening steels it amazing just how thick is thoroughly hardened vs a surface hardening steel like plain carbon steels..  

Plain carbon steels  1000 series (1010, 1020, 1030, 1040, etc, etc 1095) are surface hardening.  Meaning that for a given cross section, once the material get to a certain thickness, it's only a layer on the outside that is hard. 

5160 is thru hardening..  This means for a very thick section I have found about 1/2" X 2X3 or even 1/2"X3X3 will be thru hardened with very little unhardened material if heated and cooled appropriately. 

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  • 3 weeks later...

Just to add a little bit to the discussion of the chart and how those values were measured:

A common tool in a metallurgical lab is a micro hardness tester. This instrument allows you to test the hardness of all sorts of very small features within the microstructure of materials by first locating the feature using a microscope then, without moving the specimen, an indenter is positioned over the area of interest and a hardness meusurement is made. One of the advantages of this type of instrument is that the platform that holds that specimen can be positioned using a micrometer type adjustment. This lets you precisely move the specimen a desired distance in fractions of an inch or fractions of a millimeter from some reference location and then make another measurement. In the case of 1/4 thick steel bar, the way I would have tested this would have been to conduct the quench, then cut a small bit using a water cooled abrasive saw. This could be mounted in epoxy to create a round disc about 1.25" in diameter with the steel in the center. The steel is position so that the thickness (1/4") dimension is visible when looking at the face of the disc. This is then ground and polished to a very fine finish, usually 1/2 micron grit size. Basically it is a super mirror finish. This is then placed under the microscope and the edge of the steel is located in the view finder. The edge becomes your zero position. The specimen can be moved precisely a few thousandths a time. A hardness measurement can be made at regular intervals. This allows for an assessment of change in hardness through the thickness of the specimen without having to grind a little, check, grind a little check etc. I dont' know if this is the method that Dr. Thomas used but I'm sure he is aware of the technique and if you have access this equipment it is probably the best way to asses change in hardness versus location from the as quenched surface.


What Dr. Thomas is showing in his graph is that a 1/4 inch thick piece of 1084 heated to 1475 and quenched in canola oil will not get as hard as when it is quenched in the other fluids shown. If the conditions are changed, such as if the section size is thinner (as in the case of most blades at the time of quench), the choice of austenitizing temperature, which might be differenet depending on your preferred temperature, the grain size and the level of agitation in the bath, the as-quenched hardness of a 1084 blade quenched in canola oil likely will be different, and possible quite a bit harder, than shown in his experiment. In fact, by looking at the graph, we can see that when quenched in water, the hardness is in the upper 60s HRc. Water has a faster cooling rate than the various oils shown. If we increase the cooling rate by reducing thickness, as in the case of a knife forged or ground to shape before quench, rather than by swithing away from canola oil, we will in fact get higher hardnesses than shown on the graph. Will they be as high as those obtained with water? I don't know. Possibly. Once you have cooled the steel fast enough for it to reach its maximum hardness, further increases in the cooling rate will note result in any further increases in hardness.

There is no doubt that all sorts of fluids have been used to quench for thousands of years. Keep in mind, though that up until the mid 1850s the only alloys available were iron/carbon combinations. These alloys can only harden to extremely shallow depths, so water quenching was common and necessary. Various oils were used for parts with small thicknesses. After about 1882, alloy development really took off. New alloys would harden to much greater depths and maximum hardness could be achieved with slower cooling rates. At about the same time E. F. Houghton developed the first synthetic oil quench. This had the distinct advantages of giving manufacturers a quench fluid that was consistent from batch to batch and maintained a level of consistency of performance that was unparrelled at the time. Oils like canola and other animal or vegiitable based products degrade over time, especially when regularly heating and cooling large masses of steel. In industrial practice, various synthetic oils are still widely used, but now water soluable polymers have replaced them in many applications becuase of the reduced risk of fire, smoke and in some cases, cracking.

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Patrick, very interesting.  It strikes me that in testing the hardness of a sample that it could be etched lightly to define the grains and then hardness could be measured by grain and area within a grain, e.g. is a grain harder at its margin than at its center? Or, how much does grain size effect overall hardness.

It would also be interesting to test after tempering.

I recall reading about quenching in molten lead which sounds like more fun than I'd want to have.

"By hammer and hand all arts do stand."

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