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O/T quenching oil and keeping a bear on the go

Joe Michaels

Apr 3, 2004
Shandaken, NY, USA
A few years back, I opted to try frying the Thanksgiving turkey. I bought a turkey fryer at Tractor Supply, and my wife bought quite a few gallons of canola oil. I soon discovered the burner was anemic and a strong wind took too much heat away from the pot, aside from the timer on the gas valve being a PITA. After that Thanksgiving, we decided frying turkeys was too expensive and not worth the effort. I poured the used canola oil into the jugs it came in and began using as quenching oil for oil hardening steels. It worked quite well for that purpose. Having decided that using the fryer again was not going to happen, I set it aside. When I built the blacksmith shop, I took the turkey fryer pot and lid and poured all that used canola oil into it. I weighted the lid with some heavy scrap steel. For quite some time I had plenty of canola oil in my quench pot. The oil got black from quenching numerous jobs in it, and from seasoning barbecue forks and other utensils I forged.

Of late, a juvenile black bear began to frequent our property. I named the bear Bruno, since it has brownish fur. Bruno ambled out of our woods onto our lawn a couple of times. A contractor was doing some work on our house, and they had a garbage bag with used paint brushes, empty stain and paint cans, empty calking tubes, rags, and some disposable food takeout containers. Bruno, probably associating black garbage bags with food, tore into that garbage bag. He made quite a mess. I picked up the mess, and decided to check in the blacksmith shop, which, as yet, is awaiting my building a rolling barn door. Sure enough, Bruno had visited the smithy. He had uncovered the quench pot, batting the lid and scrap steel weights neatly aside. He drank better than half of the used canola oil. I have to say Bruno is a very well mannered bear in that he did not tip over the quench pot. I have an old beer keg (one of the old type of tapering 'half kegs' made of stainless steel) that I use for a water tub. This keg had the bottom cut out of it ages ago by a former neighbor who used it to hold winter sand/salt. I salvaged that keg from the woods, and TIG'd cover plates on the side bung openings and plugged the old style bayonet lock for the tapping 'rod'. I kept that keg topped up with water. Bruno apparently was thirsty as the level in the keg is way down as well. Bruno did not tip over the keg, nor the oil quench pot, so I appreciate his 'table manners'.

I haven't seen Bruno these past few days, so wonder if a couple of gallons of burnt, old, used fryer oil plus a few gallons of water sent him running for the woods. All kidding about Bruno aside, used canola does make an excellent quenching oil. I've made knives from 5160 (truck spring steel) and tools from 4140, as well as O-1 and quenched in that used canola oil. Having worked in the old Rheingold Brewery in 1970, while an undergraduate engineering student, I am well familiar with the old style of beer kegs and that type tap. When the neighbors dumped the keg in the woods, I asked about it and they gave it to me. I know most smiths use the modern straight cylindrical kegs, but this old keg does resonate with me. I have a load of hemlock shiplap to make the barn door and window shutters for the smithy, and Bruno has lit a fire under me to get on with that project. Black bears are quite smart and can open doors, so it will be interesting to see if Bruno or his kinfolk know to pull a barn door aside to gain entry.
I have not yet had a bear in my mostly-open shop. I have had goats in there, licking and scattering welding rods because perhaps they taste salty. Goats have bad table manners. I now keep doors closed on any structure with welding rods in

I have a lot of used fryer oil around. A friend had a collection route of local restaurants, and made bio-diesel. When he moved away, another friend with less ambition and less chemical expertise, took the route over, and used some of the proceeds in waste-oil-burning space heaters that he built.

The productivity of the route exceeded his rate of consumption. When his porch started to overflow with oil jugs, he twisted my arm to take the route over, to preserve the supply. I have been using up to 50-50 mixtures of the filtered oil with petroleum Deisel as fuel in a little Yanmar tractor. I have discovered that adding Japan drier to the oil might make it usable as a base for paint. I have sadly discovered that some goats like the taste, and will drink enough of it, from sun-embrittled jugs, to fatally discombobulate their digestive systems. But I think bears, being omnivorous non-ruminants can probably handle it.

A little closer to on-topicness, I have not tried anything but used motor-oil for quenching. But I have used linseed oil successfully for many years as a Loctite substitute, and as impregnant for cardboard gaskets. Although the fryer oil does not dry/polymerize nearly as fast as commercial boiled linseed oil, it seems to work in these applications. I'd love to re-fll Joe M's ravaged quench tank, but that would be geographically impractical.

I have not yet made any of it into soap, but plan to. I have a couple of Caterpillar D-13000 engines that would drink it up, but there are so many projects in line ahead of them that I will drown in it. before they can help. If any reader lives near enough to think it worth a trip to acquire some, let me know. The price will be right.
I've quenched some small (1/2" diameter rod) O1 parts in olive oil. That's certainly not the best choice, even among improvised kitchen quench oils! But it worked, and smells nice, too.

EVOO ? How long ago were you quenching parts in olive oil ? We used to buy olive oil for our home kitchen in 1 gallon tins, extra virgin olive oil (EVOO). The price of olive oil has shot way up to the point if we do buy EVOO, it is in smaller tins. I must have at least 50 olive oil tins in my shop and garage. With the tops cut out, they are a handy size for holding bolts, drills, fittings, etc for jobs. When I am strapped for shim stock, I've cut olive oil tins and used the sheet steel (about 0.020") for shim stock. If I need to drain fluids from odd/tight locations on vehicles or equipment, I've cut down olive oil tins to just squeak under the drain plugs. I've stabbed scrap EMT (galvanized thinwall conduit) into the side of one of these cut down olive oil tins & soldered it in. This gives me a drain pan with a spout so I can use a tilted plastic jug to catch used oil, hydraulic fluid, etc. Meanwhile, with EVOO prices up around 45 bucks for 3 liter tins, we use it very sparingly. I look around my shop or garage and when I see an old 1 gallon tin from Filipo Berio or Boticelli EVOO, I know it was consumed by us a good few years back when a gallon of EVOO was around 20 bucks- which we thought was steep at the time.
Joe, I don't recall if it was EVOO or not. It was roughly 20 years ago. I recall buying a large rectangular tin "jug" and then transferring things to a blue plastic jug with a larger fill hole for convenience.
I cook with EVOO frequently, but usually just a few tablespoons at a time. I buy 750ml bottles of the Safeway/Albertsons house brand. It's a blend from multiple sources but I've found it pretty consistent. 20% the size of a 1 gallon tin at 13$ currently.
If I were quenching in cooking oil these days, I'd go to a restaurant supply store and get a 35lb container (standard deep fryer bulk size, 4.6 gallons) of canola for about $35. I was curious how canola compares to "real" quenching oils and found an impressively detailed report on the web. To quote from the conclusions: "The biggest takeaway for me is that canola is not a particularly great quenchant."
Bill D:

I note you are in California. Is the olive oil produced locally vs imported ? Here in the Northeastern USA, olive oil is imported from a variety of countries/continents. It is a costly commodity. I do not recall ever seeing an olive oil store here in the Northeast, and have never seen olive oil sold in bulk as you describe.

Thanks for the link to the technical paper about quenching oils vs steels and hardness. I am not a knifemaker (bladesmith ?). I forge ornamental steel work, tools, utensils, and an occasional knife in my blacksmith shop. My methods are not scientific, just a basic knowledge of the 'iron-carbon phase diagram' and some basic knowledge of heat treatment and a bit of metallurgy. I use a coal/coke fired forge with a hand cranked blower, go by color when pulling steel from the fire for forging, forge welding, or hardening. I also go by temper color when tempering hardened work. A simple file test suffices to tell me if a knife blade or other cutting tool is hardened. I've found that older truck leaf spring steel (presumably 5160) hardens 'file hard' in canola oil. Temper color is based on what the job will be used for.
Recently, I got a load of 'drops' of fairly recent leaf spring steel (recent being steel that was new material within the last 10 years). This is spring steel from an auto and truck spring shop. I got a surprise when I went to forge that steel. I had it at an orange heat, had it in the fire long enough to really soak and get heated through. I went to start drawing a piece of this spring steel down using the horn of my anvil (200 lb Kohlswa anvil, made in Sweden) and a 3 lb hammer. Blows that would have drawn down older spring steel easily were barely moving this newer spring steel. I recalled that within the past 15-20 years, the two auto and truck spring shops I've used had 'gone cold'. That is, they'd stopped hot forming and hot arching leaf springs. They are making the leaf springs by cold forming the eye ends and cold arching them. I had not thought about that until I tried forging some of this newer spring steel. My guess is this newer spring steel is not 5160, but some different alloy steel formulated for cold arching. I lugged home over 100 lbs of the stuff, handily in short drops. It's worth what I paid for it.

In my junior year (1967) at Brooklyn Technical HS, we took a basic metallurgy course. We began with learning about spark testing, and using files and prick punches to get some idea of hardness. We progressed to what amounted to our 'term project' exercise. We were each given a short piece of maybe 5/8" diameter hot rolled 1090 steel bar. We were told to layout a series of cuts on this bar, like slicing almost thru a salami. We did this with hand hacksaws, leaving a web of maybe 1/8" of steel to connect the segments of the bar. We then heated the bar to a red heat, and water quenched the first segment and connecting web and part of the second segment. We held the bar upright in the quench tub. When the bar was fully cooled, we did a Rockwell C-Scale hardness traverse along the bar. After that, we put it in a vise and broke off each segment. We noted whether it snapped cleanly with a light blow or took repeated blows and showed some ductility. We examined each fracture and made note of what we saw. Then, we ground the fractured ends off squarely. These pieces were then mounted in plastic blocks and we polished them on fine abrasive paper followed by loose abrasive and water on rotating felt covered discs. I believe this was metallurgy lab equipment made by Buehler. We acid etched the polished specimens (nitric acid + alcohol) and looked at the grain structure under microscopes. This exercise was a kind of in-depth Jominy test. We had to be able to draw the iron-carbon phase diagram from memory and describe the different types of grain structures and know the differences between things like Martensite, Pearlite, and Ferrite. That course was more practical metallurgy than I learned in my undergraduate studies for my degree as a mechanical engineer. I apply that course to what I do in my own shop as well as on some engineering jobs on steam locomotive boiler work where we get into flanging (forming) of pressure vessel grade steel plate, and into weld procedures. As a half assed blacksmith, I am able to do what I need to get done, and knives made from older 5160, quenched in turkey-fryer oil do hold a very sharp edge. I draw the spine or backs of the knives to a blue temper, and keep the cutting edges at a light straw. Makes a very durable knife.
It's a blend from multiple sources but I've found it pretty consistent. 20% the size of a 1 gallon tin at 13$ currently.
I have heard that almost all EVOO is diluted with non-olive oils. It is done by organized crime. The only way to know is to buy brands that are certified. The brand we use is Cobram Estates.
I have heard that almost all EVOO is diluted with non-olive oils. It is done by organized crime. The only way to know is to buy brands that are certified. The brand we use is Cobram Estates.
if you think about the volume of olives needed to make oil.. its not hard to understand why its expensive.