1. Welcome to the New & Improved BladeForums. New software info here. Please report problems in Tech Support, and read existing threads before posting! - Spark
  2. I've changed the default forum style to Flat Awesome based on feedback. Don't like it? Click here to change how the forums look Feedback on this is welcome here.

Oil Quenching - Potential fire hazard or not?

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by zzyzzogeton, Aug 28, 2013.

  1. zzyzzogeton

    zzyzzogeton Gold Member Gold Member

    Feb 17, 2013
    I have a newbie question about hot steel and oil.

    Not that I have any intention of performing any oil quenches in the near future, but as a rural FF for 23 years, never once did we have a call where the cause of the fire was from an oil quench, and I'm sure that there were more than a few knife making attempts in the area.

    So, when you stick the hot steel in the oil, what keeps the oil from catching fire?

    I've see posts with temps of 900, 1000, 1400, 1800 deg F among others and I'm pretty sure these temps are all way above the flash point of most oils. Obviously something is being done to prevent Class B fires in all the home shops when oil quenching is being accomplished, but what?
  2. Willie71

    Willie71 Hobbyist Knifemaker Knifemaker / Craftsman / Service Provider

    Feb 23, 2013
    If the blade is fully submerged, there isn't enough oxygen to combust.
  3. zzyzzogeton

    zzyzzogeton Gold Member Gold Member

    Feb 17, 2013
    OK, I understand that part, but I have seen statements about "partial tempering" or "edge tempering" or something similar implying that only the edge of the blade or just the blade and not the tang gets quenched? That's where I was thinking that the really hot metal and oil interface right at the surface could cause a flash-over like effect. Am I misinterpreting what is happening in those cases?
  4. 12345678910


    Jul 13, 2009

    Sufficient oil volume to absorb that heat and give only a moderate temp increase in the oil.
  5. Mudbug007


    Nov 29, 2010
    There are times when the oil right around the blade will catch fire, but if your container is large enough, it's usually brief. Edge quenching on the other hand is usually done in a large flat container and the surface can catch fire (sometimes a maker will use a flat pan as a quench tank). If the maker is using a veg oil or motor oil, the chances of a flare up increase. Commercial quench oils aren't prone to flare ups, but it can happen.


    Last edited: Aug 28, 2013
  6. redd1981


    Oct 4, 2011
    This is why there are no knife makers left after they do their first quench. only us beginners wanting to learn from people who never lived long enough to finish the first.

    But really......its okay. Its not that serious.
  7. zzyzzogeton

    zzyzzogeton Gold Member Gold Member

    Feb 17, 2013
    Thanks EB, for the explanations. Now, being dangerously armed with a little knowledge, I realize I STILL don't know enough to even think about doing my own HT yet. First, I have to build or buy a "heater", then....... :D
  8. sunshadow


    Oct 2, 2006
    Edge quenching is a metallurgically stupid idea and causes flare ups because you have hot metal igniting the vaporized oil on the surface, people sometimes multiply this stupidity by using motor oil or transmission fluid. Do a full immersion quench with either manufactured quenching oil or vegetable oil and you will not have problems.

  9. sunshadow


    Oct 2, 2006
    If you feel it necessary to do a differential ht or produce a hamon either fully harden the blade and follow with a spine draw or do a clay coat

  10. Blackfeather


    Mar 3, 2010
    Well, if you're in the right shop, and you have things cleared, if it catches it's no big deal. I've had it happen, and I never had a reason to panic. Granted, I've been the type to learn firebreathing and such weird things.
  11. SteelSlaver


    Feb 17, 2007
    and have a good lid handy for the quench tank. I use Parks and have never had a flare up that didn't go right out. But, if I did I would just place the lid on the tank and smother it. Also have a big enough tank it don't slop it over the sides. I got other stuff that I feel has a lot more fire hazard potential. Just like drill presses, grinders and the like, good hazard management is the key.
  12. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Using a commercial quenchant, which has a flare up retardant in the formula, and having a tight fitting lid will take care of any worries.
  13. Bufford

    Bufford Gold Member Gold Member

    Mar 13, 2006
    Never gave it much thought. Many times when I plunge the blade into the oil there is a brief flame in the oil around the hot blank but it goes out by putting the lid on the bucket. I'm more concerned about getting rid of the oily fumes before they can circulate around the shop and out into the house.
  14. Spalted

    Spalted My name is Britt Askew I like making knives Knifemaker / Craftsman / Service Provider

    Dec 9, 2010
    I remember a while back somebody was thinking about using the plastic 5 gallon bucket the oil came in to quench, if he was to try this and he let the blade slip your beeper will probably go off.
  15. Karl B. Andersen

    Karl B. Andersen

    Jul 27, 2003
    Ya' think? :rolleyes:
    (And I completely agree with your previous statement as well.)

  16. NickWheeler


    Dec 3, 1999
    One of the dumbest things I've done in the shop involved a flash up like this. :eek: :foot:

    I was doing an interrupted quench on a very large W2 blade (11-1/2" L x 2-5/16" W x 0.350" ricasso!). I pulled the blade from the digitally monitored forge, plunged it tip first into a tall, vertical 8 gallon tank of Park50, in for a few seconds, and pulled back out for 2.... None of this so far is anything new to me, I had done it a hundred times.

    The difference, was I normally do it with the blade hanging from a wire. I had this blade held by a pair of tongs and I completely forgot to put my welding gloves on. :eek: :thumbdn: With a pair of gauntlet style welding gloves this wouldn't have been an issue. But, I didn't have 'em on, and I got a big flare-up that wrapped itself around my hands/forearms, I dropped the tongs+blade right into the tank, warped the blade like a frigg'n banana, and didn't have any hair on my forearms for a few weeks. Luckily, the burns were only bad enough to blister my hands.

    One of those things where I got busy trying to do 5 things at once, and made a stupid mistake.

    I've never had anything happen while oil quenching that would cause fear of starting a shop fire though.
  17. Nathan the Machinist

    Nathan the Machinist KnifeMaker / Machinist / Evil Genius Moderator Knifemaker / Craftsman / Service Provider

    Feb 13, 2007
    I singed some eyebrows and probably modified my hairline a bit a few years back oil quenching a bunch of 4 pound hammers. There's enough thermal mass there that even 15 seconds after submersion they're still hot enough to ignite the fumes if they break the surface while agitating. The fire ball was large enough that if I had been doing it in an unwise location it could conceivably have started a fire. There was an impressive amount of heat generated. You wouldn't want something like that around a bunch of WD-40 soaked belts and wood dust for sure.

    I was using a commercial quenchant. I wonder if something like canola oil, which doesn't really create much oil vapor, would have made a smaller flame?
  18. mitsaru


    May 15, 2013
    I am new to knife making and do not have and "real" quenching oil yet so I use canola oil for my 1075 steel. I was using a 1 gallon metal paint can and dipped my knife tip first and went as far down as I could, for some reason I lifted the knife and had a flare up. I stayed calm as the flame burned all my hand hairs and the flame went out as fast as it flared. It was the second largest fireball I have ever created. As my skills progress with grinding I will start upgrading my equipment including a more proper quench oil and quench tank.
  19. Carcara


    Dec 13, 2005
    Since every tool we use is borrowed from industry; in big commercial settings heat treating tanks have been fitted with lids
    held open by fuseable links. The links are much like what is found in a sprinkler head, so when there is a flare up the links melt and the lid falls down by it self.
  20. ANeat


    Aug 7, 2013
    You can sure get a flare up, just be prepared.

    Here is a video, Its a "promotional" video so excuse the music, its where I work, go to right about 56 seconds. They were filming different things at the plant, the guy was using a radio controlled helicopter and got pretty close LOL

    This was a large piece, probably 4140, being quenched. The tank is about 25 feet deep, you can see the open oven in the background, fun to watch, even in person


Share This Page