quenching a thin knife

[Davis]

hi guys,

I need your input here. Forged a filet knife tonight... never mind what it was *supposed* to be...

Began life as a Nicholson so it's what-- either 1095 or W-2?
Blade's 5 1/2", 1/8 to 1/16 spine but the edge is well.... *too* thin.
At the belly-- has a decent, not severe, curvature-- it's 3/4".
About 9 1/2" overall.

I heat treat in the forge, quench in old trans fluid or peanut oil.
Draw in a toaster / broiler oven.
Would like to see a hamon on this; too thin and narrow?

btw, all the files I've been using are old Nicholsons, appropriated from the steel mill 40 yrs + ago.

Advice is good ... I like advice.
thanks,
Trish

[MaxTheKnife]

Definately go for an edge quench Trish. With the blade dimensions you described you may still have problems with warpage. You want some advice? Aaaalllllllrighty then! He he.

Here's what I'd do with it. First preheat your quenching oil by heating a piece of iron or steel and quenching a few times. Get it just hot enough that it's 'almost' uncomfortable to put the tip of your finger in. Of course, you'll need a long shallow quench pan to do the edge quench. Make a nice long bed of coals and get them hot. Oh, are you forging with coal, charcoal or gas? I use coal so that's where this advice is coming from.

Heat the blade slowly (spine down) and evenly up to just non-magnetic (don't try to heat the tip, just let the heat spread from the thicker steel in the blade) and let it cool in still air to below a black heat. Do that three times to normalize and remove the stress from the blade. Then heat it to just above non-magnetic with the spine down in the coals, constantly moving the blade to get a nice even heat and very quickly quench it edge down (at least half of the blade width) and hold it perfectly still until all the glow is gone from the spine and then plunge the whole thing below the surface of the oil for a second or two and move it back and forth. Pull it out and while it's still smoking hot (careful, this is tricky and you can break the blade if it's too cool) you have a few seconds to remove any warpage. You'll need thick gloves for this. Then go directly into your tempering broiler oven. That's what I use too. That file steel should give you a pretty good quench line if you nail that non-magnetic blade temp for the quench. I don't know anything about hamons but maybe someone will chime in here with good instructions about the necessary clay and all that goes with it. Good luck.

Oh, one more thing. Because it's going to be a fillet knife it will need to be drawn at a little higher temp than usual. That will take a little rockwell hardness away but give it the required flexibility and it will be easy to sharpen too. I'd recommend at least 450 for at least an hour. Longer shouldn't be necessary with that thin of a blade. If it doesn't have the desired flexibility after one draw I'd repeat it. Have fun.

[Dana Acker]

Trish, I've quenched boucoups knives that were thin at the cutting edge. Here's some of the things that I do:

Normalize the blade once, and maybe twice before quenching, heating up to non-magnetic, then letting it cool slowly and thoroughly in still, warm (room temp) air.

Everybody has their favorite quenching medium, I like vegetable oil, as it's non-toxic, and makes my shop smell like someone's been cooking in it. But whatever quenching medium you use, pre-heat the oil to 120 degrees F. prior to quenching--less shock to the steel.

With either 1095 or W2, you should get a nice temper line if you edge quench.

Temper immediately following the quench.

I found that by normalizing my blades prior to quenching greatly relaxes the steel, and makes it a lot less susceptable to cracking, especially with a thin edge.

Another way to get a nice temper line, is to coat your blade with refractory paste before the quench. A product call Satanite is some of the best. It comes in a powder and should be available where ever wood stove or furnace supplies are sold. For best results, mix up a thin slurry of the powder with water and just paint the entire blade with a thin coat. Let dry. Then make up a thicker consistancy--a paste, and coat the back or spine of the blade with a thich coat feathering or tapering it down to nothing on the cutting edge but the coat of the slurry. Allow to dry then heat and quench. You can get creative and make designs in the paste with a popsicle stick or something and get a patterned hamon or temper line.

[MaxTheKnife]

This is really just a shop tip but it's very important. Since you use a broiler oven you should really calibrate it with a temp guage. I bought one of those BBQ grill temp guages from a surplus store for $10 and it's easy to install. Just drill a hole level with the rack you put your blades on and mount it with the nut that comes with it. Then set the temp for 400 on the dial and let it warm up for a while. When you can see the heating coils begin to cycle on and off it should be at a stable temp. Check the guage and see if it's off or not. When I checked mine it was off by over 100 degrees on the high side!

If yours if off like mine was just adjust it until you find your normal tempering temp and make a mark on the dial so you can always be sure it's right. I almost always temper at 400 degrees because I use plain old carbon steel. But I went ahead and calibrated it to 350, 400 and 450 just in case. Hope this helps.

Thin pieces of steel act different than thick pieces, large pieces act different than small. Thin pieces cool more rapidly, and tend to "through harden". If the edge is very thin, it will chill before it hits the quenching medium. In this case, my theory is that the thin edge is actually "air hardened" before it enters the quenching medium.

[MongoForge]

Do stock removal blades
need to be normalized before
heat treated..
In this case it was Precision ground 1095...
And its a thin booger to

If it got hot or bent during the grinding, it may need to be normalized.

[MaxTheKnife]

It depends alot on your grinding habits Mongo. If you ever get the blade hot enough to turn colors then yes, I'd normalize it. Back when I was doing stock removal I did that to myself several times and finally figured out what was happening. The heat generated from a 'less than fresh' grinding belt will be on one side of the blade only. That will sometimes cause it to pull a warp on the quench. At least in my experience.

[MongoForge]

Thanks Max and Tai..

I was going to have this one
treated in an oven.
But i decided to do it
myself, and if i mess
it up Oh well!...
Everybody needs a fancy crooked
letter opener dont they?

If it gets red hot during grinding, there may be some air hardening in the blade, depending on the geometry and type of steel.

[Phillip Jones]

Mongo,
I'd normalize it anyway, just to be on the safe side.

I would definitely quench that thin fillet blade pointing at magnetic north to help keep the thin edge from warping and looking wavey.

[Fox Creek]

As an alternate to the edge quench strategy, standard shop practice for avoiding warping, etc in irregularly shaped objects, or objects with significant changes in thickness (such as a knife blade) is to put the thickest edge/part into the oil first. For a knife blade this means a spine first immersion. This, plus slowing down just a hair on the quench by taking 3/4 of a second or so to ease the blade in, plus pre=heating the oil as Max describes (very important i think) should take care of most problems. With 1095 you will have a short time to get it cooled down enough to harden, so all this needs to flow smoothly. You may well end up with a blade that is less than absolutely 100% fully hardened, but you would never know. Also harden from the lowest heat that will result in hardening. (and in my experience this is a bit lower than you think.) Over heating will contribute to warping.

[Davis]

Wow, thanks fellas... really thanks.

I normalize everything 3 times. Just in case. Anneal everything too. Besides, running the forge gets the shop nice and warm.

Will use peanut oil at 150F (hot plate) to quench.... and then get it into the broiler oven--450 for 1 hr, got that-- *real quick*

If I get a hamon, then I do; if not, and I tend to agree with Tai on this (also cause I've done it before), then it's going to be thorough hardened.

Temps are determined by a candy thermometer. Hey it works. Usually.

I have used refractory and it does work but is, in the vernacular, a bitch to get off. A buddy suggested exhaust cement, as I have some, I might try that ... will let you know.

I have some Satanite here, not as much as I'd like. Has anyone heard that RHI Refractories might not be selling the stuff much longer? I called their Pittsburgh warehouse (412/562-6570) and got one more bag 2 weeks ago... an FYI thing....

Off to clean it up now, thanks again, all.
I will let you know what happens..

Oh-- one more thing-- how do I go about posting a picture? Could I just scan the knife in or do the web hosting thing?

Ohhhh, nuthin like an adventure in non-commercial heat treat.
Due North you say .... I will try that too.

Thanks,
Trish

Trish, if you want, just e-mail me the pic and I'll post it. If you have a scanner it will probably work, or you can scan a photo print.

I use vegetable oil to quench with too. It's the way to go.
taigoo@msn.com

[Dana Acker]

Trish, here's a link to the CKD forum's helps on posting images on any of its forums, including this one.



The above post is from the main CKD Forums page link at the top left of the posting page. Under the heading Open Channel Discussions, click on Computer Center, and on that forum there is a lot of info on how to do it your self, and a lot of knowledgeable people who can give you tips and techniques. Of course, we're all here to help too if you get stuck.