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Quenching in old motor oil


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Heck, I don't even buy Canola, I get it 5gl. at a time from the local super market deli. They change oil in their fryers weekly and happily fill a 5gl. gerry can if I ask nicely. Make sure it's clean and labeled with your phone number. Be sure to check back quickly you don't want them regretting the favor for tripping over the jug for too long. 

I was hoping for the donut oil but my shop smells like burritos, egg rolls, fish, french fries, etc, when I quench. could be worse.

Heck, a 5gl. jug of Canola isn't that much more than 5gl of cheap  motor oil and it wont poison you.

Frosty The Lucky.

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  • 9 months later...
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Iv used (used)motor oil once from a friends truck and the blade warped in very strange ways, like pretzeling, my assumption would be that the oils were mixed and had some other form of dex cool in there... Or that would be my guess.

Wasnt a good idea to begin with. 

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There's enough sulfur in cheap engine oil(and some expensive ones) that came out of the ground, to make a pretty good sulfuric acid for pickling steel.  Its the sulfur oxidation process from all the engine starts and stops that turns the sulfur into SO2, which in turn breaks down the oil, to grab some of its hydrogen, then more oxygen to make H2SO4, which ionizes with the aid of more acquired water from yet more broken hydrocarbon chains into sulfuric acid.  All that "Cracking" of hydrocarbons in your engine sump, is what turns the fresh oil black.  The metallic wear factor in engine bearings, camshafts, lifters, rockers and cranks in motor cars comes out to be maybe 3 grams, over the whole life of a well-maintained engine.  Dirt?  what dirt, how's it going to get into the engine sump?  Well, there are the situations of poor engine designs that let coolant into the cylinders.  That'll make dirt.

True synthetic motor oils are polymerized out of methane and ethane.  There are a couple of synthetic motor oils that don't have sulfur in them.  That's why they can last up to 50k miles.  Similar synthetic oils were invented by the Germans during WWII to run their aircraft and panzer tanks.

Maybe the best reason for using  some of the vegetable oils is their higher flashpoints.  Automatic Transmission fluids have much higher flashpoints yet, in the range of 600 to 800 degrees F.  In fact, after 10 years of rebuilding tranis, I've never seen the fluid actually combust.  Throw a lit match into it, and it just goes out.  And I've seen some tranis so abused the fluid in them congealed into solid varnish.  Of course there were the cases where the fluid came out stinking and black.  The trani clutch-pack plates in those cases were friction welded together, like a damascus nightmare.

It looks like most of the steel alloys are liquid-quenchable. So, which liquid(s) are best?  None of the motor oils mentioned had associated viscosity or weights attached to them.  Maybe multi-weight oils are better, if they actually increase in viscosity as they become super heated.

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Peanut oil has a substantially higher flash point than canola oil*,  That is one of the reasons that Chinese cooks use it when stir frying food in their woks.

A Chinese restaurant could be a good place to get spent peanut oil.

Vitamin  E  slows down oxidation of the oil..  I put a few capsules into the oil we buy for that reason.

SLAG.

* canola oil's "old" name was rape seed oil.

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Flash point isn't a factor in quenching blade steels all have critical temperatures well above the flash point of any oil I've heard of. Motor oil WILL work but the smoke is pretty toxic, consider it a Darwin Award hopeful quenchant. 

If you're concerned about the actual speed of the quenchant, you buy the oil with the properties you want. They've been listed once here look up the properties. 

Warping blades in the quench is NOT due to some imaginary differences in viscosity because it's used motor oil. It's operator error, you didn't know how to quench the blade. 

Frosty The Lucky.

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4 hours ago, JHCC said:

  if I mess up a blade that badly, I'm going to be hungry!

Mr.  JHCC,

Wrote the above concerning quenched pretzel shaped knives.

The SLAG suggests that all is not lost. Said creation,  ("knife")  could be the start of a wonderful, creative work of art. (sculpture).

Daswulf and Ausfire  do wonders with bits of metal,  for their sculptures 

They are an inspiration,  for such matters.

SLAG.

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  • 6 months later...
On 2/20/2019 at 6:51 PM, eutrophicated1 said:

after 10 years of rebuilding tranis, I've never seen the fluid actually combust

Ahhh...another tranny guy. 

We had a suburban in the shop once we were trying to get the job on through a warranty company. My boss said to drop the pan, put it back on, fire up the truck and let it run in reverse till it burnt up. After a bit of running fluid shot out of the dipstick tube hit the wall and burst into flame. 

Seen many a drum chucked in the scrap pile from being welded up. 

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I won't claim to have any idea what I am doing, but, I keep a 45 gallon drum, with a lid, nearly full of used diesel engine oil. I was told that this quench contains more carbon available for absorption. I have never had a problem with flaming. The idea is to completely submerge the part quickly, then rotate it in a circle without turning the part, giving it an equal exposure to the oil moving around it. 

The only flaming is at the contact point while the part is being submerged. The flame goes out once the part is away from the air. The part will boil the oil for a while after submerged. This will emit burnt oil fumes as the bubbles reach the surface. I don't remember the information, but there was a recommended volume of oil related to the size of part, so that the quench was adequate. I remember determining that a 45 gal. drum was large enough to do anything I would ever want.

If you have ever tried lighting engine oils, you will find them hard to start. To ignite them most people mix in a generous amount of diesel oil or you can use a wicking method like placing a paper towel in oil and allowing the flame to transfer from the paper to the oil. I have never been concerned with the ignition of my drum of oil (comprised mostly of 15-40w), though I do keep several extinguishers around the shop. As mentioned, my drum has a good fitting lid, and if there were ever to be a problem my response would be to drop the part and put the lid back on. To  get an idea of the kind of fire fighting conditions you could face try some small controlled experimentation.

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Absorbing carbon during a quench is an Urban Legend.  Carbon migration is a time and temp thing and you will NOT be hot enough long enough to do any good.

Used engine oils usually contain a lot of toxic materials; like worn main bearing metals, benzene, etc.  Why a lot of use vegetable oils to quench in.

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  • 2 months later...
On 10/27/2007 at 7:24 PM, RainsFire said:

what do you guy's think of used veggie oil?  I've quenched a blade in it once or twice.

I use peanut oil on all my blades. Works great and smells good too.  I also use old motor oil to quench all of my non-blade projects.....(hooks, tools..etc....)

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The point of the bulk of this thread is to inform people that used motor oil as a quenchant is NOT a good idea. There's toxins in used motor oil that can be released into the air during a quench. Find something better for your health. You'll be glad you did in 30 years. 

Pnut

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On 2/7/2020 at 2:16 PM, rcull said:

The idea is to completely submerge the part quickly, then rotate it in a circle without turning the part, giving it an equal exposure to the oil moving around it. 

The only flaming is at the contact point while the part is being submerged. The flame goes out once the part is away from the air. The part will boil the oil for a while after submerged. This will emit burnt oil fumes as the bubbles reach the surface.

There are a couple problems with these statements.  If you are quenching thin cross section pieces, such as knife blades, that technique is asking for warps.  Rotating it in a circle will create uneven pressure on one side of the piece compared to the other as the stock is cooling which can cause or exacerbate warping during the quench.  Movement of a thin piece being quenched should only be done inline with the thin cross section - straight up and down or inline with the cutting edge and spine for a knife.

Most oils, including motor oil, do a better job of quenching when they are heated in the 120 to 140 degrees F area.  Your piece will also add heat to the oil.  Used motor oil can reach a temperature during quenching where combustion is self-sustaining and will require extinguishing one way or another. a good fitting lid is probably the best.  However, oil expands quite a bit as it approaches this temperature, so a nearly full quench tank can boil over, spreading flaming oil outside the ability of the lid to snuff.  Some people use a container within a container, each with its own tight fitting lid, to compensate for this issue.

The problem isn't that used motor oil is highly combustible.  The problem is that once it passes the threshold of self-sustaining combustion it is not easy to put out, and it will be putting potentially toxic smoke into the air around you.  Dousing it with water will just spread the problem around.  Between the forging shows on TV, members of this forum who have had shops burn down, and personal experience most of us do not take this issue lightly.

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I've quenched in used motor oil guess it is unhealthy, won’t argue that. But I have also used it as a protective seal on things, if you quench a non-hardening material in a black motor oil it stays really black. Not necessarily pretty.

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