Hello Dennis, I like to try to let other people give as much input as they can, because I am certain people can grow tired of my droning on, but I got a heads up and am incapable of refusing to help with a request for information.

Coming up with an exact volume for quenchants for our applications can be difficult and that is often why people don’t really have exact answers to your question. Since heat extraction is what quenching is all about, the accumulation of heat is the antithesis of what we want, there are several considerations in this. Volume of quenchant is a major factor, also rate of agitation is important, and finally if the use is heavy as it is in industry special operations and cooling equipment for the oil comes into play.

If one has all the considerations above and has a serious industrial commitment to heat treating on a large scale there are actually formulas to give exact answers to the question:

Vm = H / Wm Sm (T4 - T3)

Vm: Volume of quench medium

H: Maximum heat load in BTU’s/hour

Wm: Weight of quench medium

Sm: Specific heat of meadium

T4: Temperature of medium leaving tank

T3: Temperature of medium entering tank

So obviously industry has one way of approaching this question and we have another, with the above example being just so much gibberish for our applications. We need to make educated guesses based on our individual needs.

The first thing to remember is that quenchant volume is like anvils or computer ram and hard drive space, you can have too little but you can’t have too much. Always err on the high side.

Since most knifemakers will be using a static quench tank agitation by moving the blade it will become much more important, so often the space to keep the blade moving in fresh cooling liquid will often exceed the mere consideration of quenchant volume in doing it one blade at a time.

For vertical quenching blades up to bowie size I don’t like to go much less than an 8” diameter tube 30” in depth. This allows me to plunge both up and down and edge to spine for maximum cooling. Vertical quenching is a must for double edged blades and will work for most single edged blades of appreciable width. With flat ground single edged blades of a narrower width, and certainly of longer lengths, nasty reverse curvatures can result in simple alloys that can be exacerbated by a vertical quench.

Horizontally I like to work with a tank of at least 8-10” wide, at least 7.5” deep and as much length as I can handle but anything less than 18” gets a bit tight. The longer the horizontal tank the more continuous your tip to tang stroke agitation in the quench can be.

I also do swords so obviously my personal quench tanks are much larger.

If you are just doing 1-3 blades at a time then the agitation room is your significant consideration, but if you are batching your process and will have a dozen knives to do at a time, you will need to increase the volume of quenchant to handle the heat load. Remember most oils work best from 100F to 150F, above that you will begin to loose quenching effectiveness.

As for quenchant volumes, since most makers buy quench oil in 5 gallon increments I normally consider that the volume to go with, since using less can more quickly reach the limits and buying two 5 gallon buckets is often beyond what they budgeted.

I think your 5” steel pipe would be a little too constrictive for me, not allowing me to move the blade properly and also holding over heated oil too close to the blade without room to convect fresh quenchant to replace it.

Parks #50 is perfect for the 1084 (congratulations on obtaining one of the best quenchants ever made for that steel), it is a bit fast for the 5160 but if you are careful it should still work well. The only concern you could have is with cracking, and 5160 has so little carbon that I don’t think the danger will be too high, temper ASAP and you should be all right.

Since I know that you didn’t easily or cheaply come by that Parks #50 allow me to give you some tips about keeping it in the best working order for many years to come (if my opinion matters but I can only think of one other bladesmith that has been working with that oil longer than I have). Keep it covered when not in use so that it always maintains that clear light amber color, dirt and especially moisture are very bad. Periodically clean all the scale and deposits out of the bottom of your quench tank, if you clay quench clean much more often and be careful to give more agitation and time to cool. Never flash (allow it to ignite and burn) the oil, or significantly overheat, this will shorten its life dramatically, get all hot steel completely below the surface to cool, a proper quench in #50 shouldn’t produce hardly any smoke at all (watch the tongs, hot tongs holding the blade are the most common source of ignition or heavy smoke). This would also mean that if you want to play with edge quenching burn up some vegetable oil or motor oil, and save you Parks #50 for the full quench. Don’t worry too much about the preheat, #50 can actually be used at a warm room temperature, and if you are going to preheat, a gentle heater mechanism is easier on the oil than a large overheated bar of steel.

Thanks Kevin. Sounds like I need to double my tank size. I will try a 10 to 12" vertical with at least five gallons of Parks.

Hi Kevin and Dennis,

What is your take on the edge quench tank as far as regulator blocks go? My question is this: If the regulator block only allows the blade edge to enter the quenchant, then does that same regulator block also restrict convection of fresh quenchant to the blade edge and hamper proper hardening? How can I ensure that the quenchant can flow properly around the blade edge and still control the depth of the quench?

Hi Ed, in the ABS there are far too many toes involved in edge quenching for me to succesfully avoid stepping on any of them by discussing in detail why I personally don't ever edge quench. But you have scratched the surface on one of the more obvious reasons. Perhaps not a solid platform but a rigid mesh would work better for you. If I really need to differentially harden a blade I myself clay it up and do a full quench where I can get all the agitation, conduction and convection benefits, not to mention that added ability to shape the hamon to whatever tickles my fancy. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />

However due to the investment value of a good quench oil I will take this opportunity to reiterate that edge quenching greatly raises the risks of factors that will be very detrimental to the usable life of a good quenching oil (overheating, oxidation, flare ups, smoking etc...), and thus I recommend one of the many alternative quenchants many use for edge quenching.

Thanks for the advice. I was thinking some kind of mesh would be the way to go... I have never edge quenched or differentially hardened using clay, and I am looking forward to trying both methods and testing the blades. When you clay quench, do you use some "special" formula clay, or can you just use a refractory cement? Everything I have read to date indicates a special mixture with different types of additives, but it seems to me the key is the refractory cement. Does one really need the other "stuff"?

After messing with all of it I think all the "eye of newt and toe of frog" that gets added to make clays is mostly for the dramatic effect to keep up mystique and appearances. After trying many things throughout my career good old Furnace cement is the best. There are a lot of guys who do the occasional hamon, but I spend a fair amount of time with guys who do it all the time professionally, and the guys doing the best Japanese stuff, outside of Japan, tend to use something as simple as furnace cement. Control and good adhesion are by far the biggest concerns over other qualities and a good furnace cement rated for 2400F or above does the trick beautifully. The best I ever used was made by the Worchester Brush Co. and was black and rated to 3000F but it is no longer available, as far as I can tell, so most now use Rutland black. You can buy it in a tub or a tube at any place that sells wood stove supplies. I recently used the gray, since it was all that was available for my demo on Troy OH, and while it had lunky large grains in it, the adhesion was so outrageous that I had to grind it off.

Many folks swear by Satanite, but years ago Dr. Lucie and I did an experiment at his shop (well Doc basically indulged my tinkering during one of our forging sessions). We used both the furnace cement and Satanite to blades, side by side, and the furnace cement gave a much more defined hamon line with controlled ashi (the clay hash lines that shape the hardening line) and with excellent adhesion. After seeing a very noticeable difference I considered that Satanite had to be special ordered but the furnace cement was available at any hardware, and that settled it for me.

If you give it a try, be careful to prepare the blade surface. Leave around a 220X finish or less and scrub it very clean of any possible oils. A strong base cleans it very well and I have watched Japanese smiths use ashes or the burned ends of straw brushes to scour the blade before application. Mix the furnace cement with water to make a consistency of thin cake frosting and apply it with a palette knife or a small wooden spatula/knife you can make yourself. I have watched guys who are really good drop on the ashi by letting the cement string off from the applicator and drop in a line in the blade. Drawing from my oil painting hobby years ago, I like to cut into the cement and make a bead in the leading edge of the spatula and then cut it onto the knife surface. You want your ashi to be around 1/8” thick, too thin and they will not shape the hamon, too thick and they will interfere too much with cooling. Coat the side areas you don’t want hardened with a thin layer of clay but scrap the very spine clean. Also don’t cover the very edge with a thin painting of slurry like the Japanese do- they are quenching Tamahagane in water, you are quenching modern alloy steel in oil, these are two entirely different worlds.

Of course the previous paragraph was for shaped hamons, on your first time out you will probably be happy with suguha, a plain straight hamon like you would get from edge quenching, which will be much easier; just apply the clay in a straight edged solid sheet except where you want hardening. If you have an oil as fast as Dennis (#50 is really good stuff) you can pretty much apply the clay where you want your lines, but if you use other oils you will need to bring it back a little bit to compensate for the oil speed. And of course all of this applies to simple steels like W1, W2, 1075, 1080, 1084, or 1095 any alloying will send your hardening right up under the clay and defeat the process. I have done hamon with 5160 but it was always a clumsy and awkward affair compared to the simpler steels.

WOW! Kevin, Thank You so much for the great info. You have de-mystified the process enough that I am going to try it on my next knife from 1084 (I'm currently working on my first integral from 5160...so not this one;) ). I can't imagine how much of the "learning curve", time, and research you have eliminated for me. While I am still working on the basics (metallurgy, grain size, etc.), it is fun to try new techniques. Thansk again!

Thought I might toss in a visual for some ideas you may be able to use.

Pardon the disarray of the shop right here - this was a few years ago.

Note that both tanks - one for Parks and one for Texaco A - both hold a full five gallons, as was Kevin's suggestion, and leave room at the top.

Handles welded on the ends for grasping.

Note the two lids off to the side to keep the contents clean.

See the nearest one is on a small four wheel cart, upon which is a double burner to warm up the oil in the colder months.

This length allows for point-to-tang agitation of the blade once quenched - I almost said "quinced!"<img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' />

Being horizontal, it also allows for easy cleaning of clay debris.

Spend a few bucks and have one welded up or buy the steel and do it yourelf like I did.

Either way, these tanks will outlast me.

Thanks for the photos Karl, I can see how it would be much easier to keep the horizontal tank clean. I'll start working on a new tank tomorrow.

Karl,

The photos help a lot. Could you estimate the dimensions of those tanks for me? Also, is that just an regular electric burner you use to heat the tank? Thanks!

Hi Guys,

Good discussion. I made iron quench tanks that are nearly identical to Karls.

For guys that may not have the resources to make their own, Brownells sells a variety of rectangular tanks in both black iron and stainless.

They also sell the covers to fit whatever tank you choose. Here's a link to a few they have available.

http://www.brownells.com/.aspx/cid=11488/k=/t=P/Products/Black-Iron-Tanks

A little browsing through their pages will turn up even more choices along with their appropriate covers. Cost, IMHO, is quite reasonable.

Ed,clicking on the posted Brownells link and then a chosen tank will find tank dimensions along with their capacity which might be helpful to your tank build.

A little more browsing will find burners they have available for heating bluing and browning solutions.

I think the burners would work well for warming quench oils too if properly set-up and/or monitored.

<img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//cool.gi f' class='bbc_emoticon' alt='B)' />

Thanks David,

I'll check out the link:)

I have been salt bath heat treating and quenching low temp salt some of the time and oil some time. The salt is much easier to work with and clean up, is there any difference in the hardening results between the two methods? I use 52100 and 5160 high temp 1550F low temp 400F. I do one or two knives at a time when oil quenching and keep a thermometer in the oil so I can keep the temp. about 150F. I have tex quench in my tank.

Dennis