Quenching tank

Hey guys,
I've got a quick question about quenching and tank size. What size tank do you all use? Mine is small, and I have to take breaks between quenchs to allow the oil to cool. But if I go to a larger volume of oil, would I have to do a lot of preheating the oil before quenching?

Josh Blount
www.blountknives.com

Hey Josh
I use to have the same problem until I went with a larger tank. The tank I built has a pump to keep the oil moving and it also keeps the temp within safe limits. I can do 12 to 15 blades and the oil is still around the same temp that I started with. Of course you still have to preheat the oil first. Just heat up a big hunk of steel and stick it in the oil.

The old double-edged sword thing.Yes a smaller tank is good for makers HT a blade or two,but if you go to a larger tank it will take proportionally as long to preheat your oil.My tank is homemade and about 15" long ,4" wide and about 8" deep.It holds about a gallon and a half, good for about three or four small knives or one big one.I don't HT in large batches though.Dave

The above is right on the money! Both of my quench tanks are about 24" long X 4" wide X 6" deep. Each will hold about 1 1/2 gal of oil. There are times when I also have to wait for the oil to cool down, but that's only when doing several large blades.
When I was out at Bill Cottrell's place before the Eugene show, he had installed a small water heater element in his tank to pre-heat the oil.........AND MAN did it work! That tank was at quenching temp within a couple of mins!
Eventually I plan to make larger tanks, but just haven't gotten around to it yet. I also think I'll incorporate the heating element and a circulating pump too.

Ed,

Any info available on the kind of heating element that was used?

I am very tired of quenching bars of steel to get my tanks up to temp.

As a side note- my brine tank is about 16" wide by 28" deep for vertical quenching. I had poor luck with smaller containers and I theorize it is due to not enough circulation of the quench media. I think this is more of an issue for water quench steels. However.... I was at the Ashokan Bladesmithing Conference a few years back and Phillip Baldwin was going to heat treat a blade in a charcoal pit and a 6" x 48" or so tube filled with vegetable oil. The blade would not harden and Tim Zowada said it was due to not enough mass / circulation of the oil. Adjusting my tanks upward in scale solved many of the problems I get with my own finicky damascus... but I hate spending an hour heating the dang tank by quenching!!!!

J.....

The element in Bill's tank was a typical water heater element. Not sure if it was 110 or 220V. It's only about 4" long. The way he had it installed was by welding a internally threaded fittng into a hole in the tank, and then screwed the element into that. It's a very simple (but really neat) idea/setup. I'd like to spend a week inside Bill's head just to harvest some of the knowledge and wisdom that man has!

Mine has the water heater element controlled by a electric oven control switch. This allows you to vary the oil temp. Be sure to put a safety plate over the element. When a damascus bowie tip penetrates the element things get interesting for a moment. my tank is a piece of pipe stood on end. The convection of the heating oil moves the oil nicely. mike

For full quench, mine essentially is a hotwater heater mounted on a dolly to make it easy for me to roll right up to the heat treat oven/furnace. You electronically minded boys will have to help here. The control is the same used on a kitchen oven. I think that's called a rheostat -- right?



This makes it so nice -- just set the temp and forget about it. It heats up quick, and the quenchant circulates the whole time the thing is running.

That pan you see on the bench behind my full quench tank is a large steam tray. These are the things used in a cafeteria to keep food warm. That's one of the things I use for edge quenching. If I have just one small hunter sized blade to edge quench, my third quench tank is a stainless steel dry wall bucket. That's the little pans you use to hold the gypsum mud when doing dry wall taping and floating.

Anyway, here's a shot of my full quench tank from the top.



Notice that the quenchant is a few inches below the top of the tank. That's done for two reasons. One is so I can tilt the tank back and roll it away when I'm finished. The other reason is that you have to allow room for the quenchant to expand when hot.

Now before anyone starts emailing me for plans, I didn't build it. A knifemaker friend over in East Texas wanted to buy one of my hunters but was a little strapped for cash at the time. He built this little jewel and saw me drooling over it. He offered me the quench tank plus $25 for one of my knives. I can tell you he didn't have to offer twice. To this day he say's that he got the better end of deal, but I say "no way". I love this thing.

Terry's Website

If you Guys lived in S.W. AZ. like I do you would not need to heat up the quench oil for a half year. My quench tank is a 40mm ammo can with a tight fitting lid holds a little over 6 gallon works great. Gib

The 40mm ammo can is what I'm useing but I installed a pump to circulate the oil. No more moveing the blade around to keep it in cooler oil. I heat up a piece of steel 6"X4"X2" to preheat the oil. I usually work large batches of blades at a time, sometimes 15 to 20 and since installing the pump I never have the problem with the oil getting too hot.

Before when the oil would over heat I would put a large piece of brass (Probably weighed around 8 pounds) in the oil to act as a heat sink. It would cool the oil a little but took too much time.

Well Then...

Thanks all for the inspiration... I guess I'll be building something to get the quench up to temp without all this fussing about with thermocouples and quenching bars of steel...

Primos, thanks for posting the pics- they answer about a thousand questions with... you know... one picture and all.

I've been thinking about building something akin to my salt tank set-up for heating quenching media and actually tried it at one point... but the resulting mess was... well... a learning experience. However... I can see plainly where your quench tank is going, Primos...

After Blade... Yeah... that's when I'll build it...

My tank uses a water heater element, it is a 220v but I hooked it 110v and just plug it in until it is at quench temp. (no thermostat) . I just cut the fitting out of the old heater and welded it in the new quench tank.

It's inexpensive but cheap!

Hey Folks! You can go to any Resturant Supply house, in the nearest large town, your from. They'll usually let you look through the used equipment. I bought a deep fryed (french fryer) that only cost me $75.00! It holds eight gallons of oil, and is 10" x 20" and 12" deep. Make sure the plate is in the bottom of it, covering the element. It's full of holes. You can take that plate, use four long bolts and some washer and nuts, and BOOM you have a limiter plate for edge quenching!!! The whole thing is Stainless, has a temperature gauge that you can set and forget! I set mine to say 125-135 Degrees, push the button and it's ready when I'm ready It will maintain any temperature you set it at. Having the temperature gauge built in, really helps to keep an eye on the temps. I usually quench 10 knives in succession, and the oil temp. never varies more than 10 degrees. After you've let the knife quench for a couple of minutes, swirl the knife around and it helps to dissipate the hot spot you created. I got mine so cheap, because it won't heat up to frying temperature, anymore. but it'll go up to 170 degrees, which in more heat than we ever need for quenching. Good luck!

How fast should the oil be moving? I have the tank and the heater element but what about the pump? I have a pump for running water in a motor home but it may be too fast. Any suggestions on the speed of the pump? How many GPM?

You don't need a lot of pressure, just enough to move the oil around.