Motor oil or canola?

E

e.codega

Joined
Sep 16, 2011
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Hey guys! Just about to heat treat my first blade. I used Aldo's 1084. It's a kinda homely lookin thing... But anyway i have couple questions for you guys. I've heard a few times that canola oil will work better than used motor oil, but my mom would probably get mad if i "borrowed" her canola oil, which probably isn't enough anyway, and i have a bunch of used motor oil in my shed, so it's free. So how much performance would i lose using free motor oil vs canola for quenching? And im not too worried at all about getting fantastic edge retention on this blade. Also, how thick should i leave the edge before HT? I think i heard .03" somewhere but not too sure. I plan on heating with a torch, kind of "experimenting" if you will. Thanks a bunch!!
-E
 
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the edge needs to be the thickness of a dime at least. i have used motor oil to quench with but now i use my old canola oil from the deep fryer. it works just fine.

a propane torch will not get hot enough as it is to heat treat a knife. you need more heat like a cutting torch but you can get a blade too hot or burn the blade if you are not careful. i set the torch so the oxygen is turned on just enough to get a blue flame with the flame no longer than 5".

i heat just the edge (back from the edge at least 1/2" and keep the flame from hitting the very tip) until it turns a bright orange. you can also use a magnet to check and see if you have it hot enough. (a magnet will not stick when its hot enough).

i hold the bright orange color for a few minutes before i quench. do this in a dark place without any lights so you can see the true color. hold the flame at least 2" away from the blade and watch out for yellow sparks which means you are getting too hot. a few stray yellow sparks are not bad but a bunch are.
 
Sparks not bad? I disagree, that is serious (many hundreds degrees) over heating. I've forge welded with 'just a few sparks'.
 
If you are getting sparks off the blade you have burned the carbon out from seriously overheating. Do not use motor oil, you will not properly harden the blade, buy yourself a couple of gallons of canola and put it in a metal bucket, heat it to 130 degrees f by plunging heated scrap until it is up to temp.

Please read the stickies especially the ones about heat treating. How old are you?

-Page
 
A gallon of canola oil will be usable for a years worth of blade quenching. Go buy a jug for your own use, and leave mom's alone. Use the whole gallon each time. Let it cool down and store in the jug between uses.

A regular plumbing propane torch won't quite get the blade hot enough. You need a high output torch, like a JTH-7 or a turbo-torch. Using MAPP gas cylinders, and a good torch will usually get the steel hot enough.

If using a torch, set some soft firebricks up so they make a "U" and hold the knife in the "U" while moving the flame up and down the blade. When it gets red, use a magnet to see if it still sticks. When it stops sticking, heat until it is a little redder, about 100 degrees hotter. Quench in the oil, which you should have warmed to about 120F degrees. The oil should be in a metal pan or bucket.
 
OK now Im just confused. can you use propane in a two brick forge or should I stop looking for firebrick?
 
This is very much outside my knowledge base so I was hoping someone could explain to me the purpose of doing this procedure to a knife that already exists? Will this method increase the carbon content of a lower carbon based knife into a harder, higher carbon knife?

Sorry for the stupid question, it's just that I'm not at all familiar with the purpose of of doing this unless you're creating a knife from scratch.

Once again, please forgive my ignorance.
 
Ogien said:
This is very much outside my knowledge base so I was hoping someone could explain to me the purpose of doing this procedure to a knife that already exists? Will this method increase the carbon content of a lower carbon based knife into a harder, higher carbon knife?

Sorry for the stupid question, it's just that I'm not at all familiar with the purpose of of doing this unless you're creating a knife from scratch.

Once again, please forgive my ignorance.
Click to expand...

"Just about to heat treat my first blade. I used Aldo's 1084."


I went back and read all the posts 3 times.

I just can't see what gives you the impression that he is re heating a finished blade.
 
Ogien said:
This is very much outside my knowledge base so I was hoping someone could explain to me the purpose of doing this procedure to a knife that already exists? Will this method increase the carbon content of a lower carbon based knife into a harder, higher carbon knife?
Click to expand...

No. Using motor or (or canola) does not add carbon to the steel. Would that it were doing so... we could eventually forge diamonds. :)
 
12345678910 said:
"Just about to heat treat my first blade. I used Aldo's 1084."


I went back and read all the posts 3 times.

I just can't see what gives you the impression that he is re heating a finished blade.
Click to expand...

Well, Ienvy his knowledge as I am lightyears behind most folks in this section of the forum. Iguess I misunderstood and thought that he was reheating an existing blade.

I'm going to keep an eye on this thread and this section of the forum in hope of learning more.

Please bear with me as I will likely be asking some pretty stupid sounding questions due to my ignorance on the subject of making knives from scratch etc.

tryppyr said:
No. Using motor or (or canola) does not add carbon to the steel. Would that it were doing so... we could eventually forge diamonds. :)
Click to expand...

Don't laugh too hard but I've been under impression that it does for many many years. Why use oil if it doesn't add carbon to the item being quenched?

Sorry for the stupid question.
 
Propane will get the blade hot enough if you use heat-reflecting surfaces to contain and concentrate the heat. This is how the one and two brick forges work.
 
Thank you so much guys. I've done LOTS of reading on this forum, but have mostly kept to myself. I plan on changing that and letting you guys know how this works out for me. I cant figure out how to post pictures though... I guess ill try to make a 2 brick forge. And I had no idea the canola would last so long, although looking back I dont know why I thought it wouldnt. Does the canola just have better convection properties than motor oil? Thanks again guys!
 
Ogien said:
Well, Ienvy his knowledge as I am lightyears behind most folks in this section of the forum. Iguess I misunderstood and thought that he was reheating an existing blade.

I'm going to keep an eye on this thread and this section of the forum in hope of learning more.

Please bear with me as I will likely be asking some pretty stupid sounding questions due to my ignorance on the subject of making knives from scratch etc.



Don't laugh too hard but I've been under impression that it does for many many years. Why use oil if it doesn't add carbon to the item being quenched?

Sorry for the stupid question.
Click to expand...

Very simple explanation.
Steel must have a certain amount of carbon to harden. 1084 has around .84% when you heat the blade to 1475 degrees the carbon spaces itself equally. If allowed to cool slowly, the steel forms pearlite and will be soft. If it's dropped below 900 degrees quickly, then the steel forms martensite. Martensite is hard and brittle. You then temper the blade making tempered martensite.
The oil, or water is the quenchant for carbon steels. It's used as a cooling medium.
 
Ogien said:
Well, Ienvy his knowledge as I am lightyears behind most folks in this section of the forum. Iguess I misunderstood and thought that he was reheating an existing blade.

I'm going to keep an eye on this thread and this section of the forum in hope of learning more.

Please bear with me as I will likely be asking some pretty stupid sounding questions due to my ignorance on the subject of making knives from scratch etc.



Don't laugh too hard but I've been under impression that it does for many many years. Why use oil if it doesn't add carbon to the item being quenched?

Sorry for the stupid question.
Click to expand...

And that is the reason why we have a section of stickies labeled something like "Newbies Good Info Here"

Unlike many forums, the stickies pinned at the top of the Shop Talk subforum are a wealth if useful information for everyone from beginner to somewhat advanced

-Page
 
stevomiller said:
Sparks not bad? I disagree, that is serious (many hundreds degrees) over heating. I've forge welded with 'just a few sparks'.
Click to expand...
i have had sparks (from carbon buildup on the torch head) come off but only 3-4 individual sparks. the blade was not hurt. its when you actually see sparks coming off the steel is when you have the blade too hot.
 
richard j said:
i have had sparks (from carbon buildup on the torch head) come off but only 3-4 individual sparks. the blade was not hurt. its when you actually see sparks coming off the steel is when you have the blade too hot.
Click to expand...

So you use a slightly reducing flame on your torch? It wasn't clear to me from your previous post.
 
e.codega said:
Thank you so much guys. I've done LOTS of reading on this forum, but have mostly kept to myself. I plan on changing that and letting you guys know how this works out for me. I cant figure out how to post pictures though... I guess ill try to make a 2 brick forge. And I had no idea the canola would last so long, although looking back I dont know why I thought it wouldnt. Does the canola just have better convection properties than motor oil? Thanks again guys!
Click to expand...
The canola oil has several advantages over motor oil. It's not toxic, cheap, available everywhere. As far as performance, motor oil can't usually get the steel below the pearlite nose fast enough. you'll likely struggle to get full hardness from the blade. As it pertains to a quenching medium for steel.

#1. Low price
#2. Great availability
#3. High flash point
#4. High smoke point
#5. No vapor jacket or vapor stage
#6. High speed at the onset of the quench
#7. Finishes slow
#8. High stability compared to other common vegetable oils
#9. Less sensitive to temperature variation than are the parrafinic oils
#10. Non toxic and relatively safe to use

Can you think of any others?

Quote:
“Overall, the cooling properties of the vegetable oils were comparable to each other and it is notable that only convective cooling was obtained with no extended vapor blanket cooling (film-boiling). This cooling profile shows that vegetable oils would not require a cooling rate accelerator and would be acceptable even for difficult to harden, crack-sensitive carbon steels.” VEGETABLE OIL QUENCHANTS: CALCULATION AND COMPARISON OF THE COOLING PROPERTIES OF A SERIES
OF VEGETABLE OILS

That's from this thread if it helps. :-)
http://www.bladeforums.com/forums/s...anola-oil-advantages?highlight=Canola+oil+tai
 
Ogien....

Different steels harden at different temperatures ranging from about 1500 degrees F to 2300 degrees F. The rate of cooling is important when quenching the steel also. Some steel is designed to be quenched in water, some in air and some in oil. The density of the oil makes a difference in how fast the steel cools. It is a combination of the hardening temperature, the quenching medium and subsequent tempering temperatures that determine how hard the steel hardens. Generally, the more carbon in the steel, the harder it will get.
 
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