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HT time in oil
- Thread starter Stevemo
- Start date
- Joined
- Oct 17, 2007
- Messages
- 4,300
Until it stops glowing. 
In all seriousness, there will be some "relatively" minor variance between steel type (and size), as well as the specific oil or other medium that you're quenching in, but for the average knife, the oil has typically done it's job of dropping the temperature below the pearlite nose within the first couple of seconds. If your blade remained straight during this process, you can give it a few more seconds in the oil to keep it cooling down. If your blade takes a slight warp, you may wish to pull it out of the oil and straighten it while it's still in the austenite stage. This is more a "temperature" thing than a "time" thing, as, again, different oils and steels (and sizes) will react slightly differently.
For me, I rarely have warps with my 1095 blades, as I do most of my grinding after HT, so I'll normally quench for a couple of seconds or so, pull it out for a double check, and then dunk it back in for a few more seconds until it's at least under 400F. From there, it normally cools to near room temp while I'm doing something else (quenching more blades or putting more in the oven), and it's then moved to tempering.
ETA: you can find your specific cooling curves on your specific steel's TTT diagram (Time Temperature Transformation).
In all seriousness, there will be some "relatively" minor variance between steel type (and size), as well as the specific oil or other medium that you're quenching in, but for the average knife, the oil has typically done it's job of dropping the temperature below the pearlite nose within the first couple of seconds. If your blade remained straight during this process, you can give it a few more seconds in the oil to keep it cooling down. If your blade takes a slight warp, you may wish to pull it out of the oil and straighten it while it's still in the austenite stage. This is more a "temperature" thing than a "time" thing, as, again, different oils and steels (and sizes) will react slightly differently.
For me, I rarely have warps with my 1095 blades, as I do most of my grinding after HT, so I'll normally quench for a couple of seconds or so, pull it out for a double check, and then dunk it back in for a few more seconds until it's at least under 400F. From there, it normally cools to near room temp while I'm doing something else (quenching more blades or putting more in the oven), and it's then moved to tempering.
ETA: you can find your specific cooling curves on your specific steel's TTT diagram (Time Temperature Transformation).
Perfect. Greatly appreciated. I have been using 1084. On my second blade.Until it stops glowing.
In all seriousness, there will be some "relatively" minor variance between steel type (and size), as well as the specific oil or other medium that you're quenching in, but for the average knife, the oil has typically done it's job of dropping the temperature below the pearlite nose within the first couple of seconds. If your blade remained straight during this process, you can give it a few more seconds in the oil to keep it cooling down. If your blade takes a slight warp, you may wish to pull it out of the oil and straighten it while it's still in the austenite stage. This is more a "temperature" thing than a "time" thing, as, again, different oils and steels (and sizes) will react slightly differently.
For me, I rarely have warps with my 1095 blades, as I do most of my grinding after HT, so I'll normally quench for a couple of seconds or so, pull it out for a double check, and then dunk it back in for a few more seconds until it's at least under 400F. From there, it normally cools to near room temp while I'm doing something else (quenching more blades or putting more in the oven), and it's then moved to tempering.
ETA: you can find your specific cooling curves on your specific steel's TTT diagram (Time Temperature Transformation).
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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Knifemaker / Craftsman / Service Provider
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- Aug 20, 2004
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As Stevemo said, all the quench needs to do is drop the blade below 900°F. That happens almost instantly to the edge, and takes a couple seconds for the rest of the blade. Pulling out too soon can allow the thicker and hotter parts to bleed heat down into the edge. This could cause a too soft edge in some cases. It is also the mechanism behind an auto-hamon. Beyond ten seconds, the blade is just sitting in the oil and not doing anything but slow cooling. There are times for this, but usually you pull the blade out after 10 seconds.
I quench, count to five, pull out and inspect for warp .... and immediately straighten with gloved hands, and stick back in for about 8-10 more seconds to let it drop some more in temperature. Lately, I have started sticking the blades in the quench plates after taking out of the oil. This assures that the drop past 400°F and down past 100°F will yield a perfectly straight blade. It only takes 60 seconds in the press to be cool enough to take out the blade with bare fingers.
I quench, count to five, pull out and inspect for warp .... and immediately straighten with gloved hands, and stick back in for about 8-10 more seconds to let it drop some more in temperature. Lately, I have started sticking the blades in the quench plates after taking out of the oil. This assures that the drop past 400°F and down past 100°F will yield a perfectly straight blade. It only takes 60 seconds in the press to be cool enough to take out the blade with bare fingers.
Great info. Press plate? Thanks
- Joined
- Oct 17, 2007
- Messages
- 4,300
Quench plates are little more than some plates of steel or aluminum that will "sink" the heat out of the blade while keeping it pressed straight. They are mainly used for air hardening steels (instead of an oil or water quench to cool the blades rapidly, these plates suck the heat from the blades relatively quickly), but as Stacy mentions, they do have their applications for other steels.
Basically, you just sandwich the blade between two plates that are wider and longer than the blade.
For air hardening blades, aluminum plates are normally used, as aluminum conducts heat much more efficiently than steel, and thus pulls it away from the blade much faster. Typically the thicker the better, and the more surface area the better. Thickness not only gives more material to distribute the heat, but also a little more weight to help keep the blade straight, although most makers will add some weight on top of the plates, or better yet, mount them in something like a wood workers vise to compress the plates against the cooling piece. Sometime makers will also freeze or refrigerate their plates before "quenching" or give them a blast of compressed air while quenching to help cool air hardening blades faster.
For the purpose of finalizing cooling and straightening for oil quenched steels, this isn't really necessary, and steel plates could serve the same purpose as well, although it may take a little longer to cool (probably not much though). I've also seen maker clamp pieces to a workbench, or sandwich them between plywood shortly after initial quench, in order to straighten a slight warp.
Many ways to skin the cat....