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Quench tanks


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What kind of quench tanks are best for knife making. I thought I remember seeing some made out of 3 tubing which I happen to have. I have probably enough that I could make several small tanks with different quenchants. Or are troughs of some sort or another better? I'm thinking something that I could put a lid on would be nice to keep contaminents out of it.

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Sort of depends on how and what you are quenching. Japanese swords traditionally used horizontal troughs, edge quenched knives often use a baking pan with a rest on the bottom.

My knife quench is vegetable oil and is in the bottom half of a pressurized gas tank that is mounted in a "no tip" wooden frame. I have a coffee can that sits over the top to keep stuff and animals out of it.

Remember the material of the tank needs to be such that it won't burn or melt when in contact with glowing steel and the volume needs to be enough that it doesn't heat up too much if you will be doing multiple quenches close in time.

I know a smith who burned down his shop trying to quench in oil in a 5 gal plastic bucket. He tipped it on it's side because he was low on oil for a long blade and it ignited and burned through the bucket...

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I limit the steels I use to oil quenching only. I am very fussy about oil temp at quench time. I heat the oil up by dunking a warm piece of steel in it and checking the oil temp with a thermometer. If I quench a large knife or more than one small one wehn I recheck the oil temp it has gotten too warm to do another. My tank will fit inside a bucket of water safely and I set it in until the temps come down. Again checked with a thermometer. This works for me. Some folks use really large quench tanks that are not as easy to heat up when in use. I do not have room for that. I would suggest that for anyone new to the spor of knifemaking: keep the steels you use to one or two until you know how to get the most out of them that you can. One steel one quenchant and a log book and a good testing program again with notes will put you farther along in less time than bouncing around with different steels and different quenchants. The lid or cover is a very safe way to handle hot oils. I like mine hinged so I can flip it shut with a pair of tongs when the oil flashes. And lastly make sure it is not tippy. Take pics for the rest of us when you get it figured out.

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Yah i'm starting to think the 3" tubing would probably heat up any quenchant to quickly. I also want to make axes, war hammers, military forks, and other odd shaped items. My interest in knife making is to learn how to forge edged weapons. So maybe I would get more mileage out of a tall rectangular shape? What about something ~12"x12"x48"

Also do your quench tanks sit on an angle to make them easier to quench into? And to keep your hand out of the flames?

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Is something like this a good idea? Is it better to have a larger surface area so you can quench horizontally or is it better to quench more vertically in a more upright tank?


I think you'll see far more vertical tanks simply because of the availability of the material used to make the tank - pipes, gas tanks, etc.
It's just cheaper to find 'junk' than to weld one up or search for the proper sized tank.
I like the entire cutting edge to hit the tank at one time.
When you go in vertically, as the last portion of the blade makes it into the quench fluid, it's passing through oil that has been super-heated by the leading portion of the blade.
So in essence, you are getting irregular cooling of the fine cutting edge due to different oil temps.
Whenever you can, go the extra step to make your processes the best you can.
It pays off in the end.
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Though probably too short for some of the large blade y'all make, I'm using a .50 cal ammo can, and it works quite well for my needs. air/water tight seal on the lid, which can easily be replaced in case of fire. Large enough volume of quenchant to not over heat from ht'ing a couple of blades, but not so large I can't get it preheated by dipping a couple of red hot "lumps" in it.

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The more I look into it i'm thinking something somewhat long, tall and narrow would be best for me and not so much like the squatty looking square tank on the previous page that I posted. How hot do I need to preheat the oil? Is there a table for different temp of oil for different thicknesses? Or is not that exact.

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Mine is an 8" dia SS tube welde to a 10"square baseplate. The tank stands 34" tall.

Metallurgically speaking....

The quantity of quenchant is very important... as well as the spacing between the blade and the walls of the tank. For Bladesmiths, about 5gallons of coolant will sufficiently displace heat evenly, without overheating your medium. You have to consider the vapor barrier that forms around the blade as it rapidly heats the quenchant, too. That precious "1 sec" form critical to 900F is SOOOOOOOO important. (even less time, in some steels) That makes movement a critcal factor. I'm not talking about shaking and swirling the blade around in the tank. I'm talking about CONTROLLED movement of either the workpiece or the quenchant.

Without having to rig up a tank with pumps and heating elements, the next best thing is moving the blade. This can either be accomplished by a narrow, deep tank where you are dipping the piece down into it..... or..... a long, narrow tank where you are dragging or pulling the blade along the length. In either case the tank should accomidate 5gallons.

Don't freak out about the details, though. It all depends on how far you want to go with it. Research your steel and its properties. Find a method that best addresses the BASIC metallurgical needs..... don't kill yourself attempting to make the Holy Grail of knives.... Its supposed to be fun, too!!!


Rick

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.... When you go in vertically, as the last portion of the blade makes it into the quench fluid, it's passing through oil that has been super-heated by the leading portion of the blade.
So in essence, you are getting irregular cooling of the fine cutting edge due to different oil temps.
Whenever you can, go the extra step to make your processes the best you can.
It pays off in the end.


Generally speaking, that is true... but you must also consider the speed of the whole event... At less than a second from 1500F to 900F, the benefit of dispersing that vapour blanket through movement dwarfs any other issues that arise with the process. The motion of the blade through the oil, coupled with the rapid heating, creates A LOT of flow in a vertical tank. Tested blades have shown no difference in RC hardness readings from tip to heel. If that is still a concern, you can make a long deep tank and plunge edge first.

I have NEVER had a flash since adopting this practice. Even after HT'g several pieces in one sitting. That says a lot for its effectiveness.

Rick
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Mine is an 8" dia SS tube welde to a 10"square baseplate. The tank stands 34" tall.

Metallurgically speaking....

The quantity of quenchant is very important... as well as the spacing between the blade and the walls of the tank. For Bladesmiths, about 5gallons of coolant will sufficiently displace heat evenly, without overheating your medium. You have to consider the vapor barrier that forms around the blade as it rapidly heats the quenchant, too. That precious "1 sec" form critical to 900F is SOOOOOOOO important. (even less time, in some steels) That makes movement a critcal factor. I'm not talking about shaking and swirling the blade around in the tank. I'm talking about CONTROLLED movement of either the workpiece or the quenchant.

Without having to rig up a tank with pumps and heating elements, the next best thing is moving the blade. This can either be accomplished by a narrow, deep tank where you are dipping the piece down into it..... or..... a long, narrow tank where you are dragging or pulling the blade along the length. In either case the tank should accomidate 5gallons.

Don't freak out about the details, though. It all depends on how far you want to go with it. Research your steel and its properties. Find a method that best addresses the BASIC metallurgical needs..... don't kill yourself attempting to make the Holy Grail of knives.... Its supposed to be fun, too!!!


Rick


Rick is your SS tank straight vertical? Why SS? just to prevent rust? Do you have to heat it?

".. a long, narrow tank where you are dragging or pulling the blade along the length. In either case the tank should accomidate 5gallons."

I think i'm going to weld this tank. Like a narrow tall tank as you can literally quench most any blade shape in it. Should I weld this out of aluminum? Stainless? or is mild steel fine? Do I need to heat it?

sorry 4 my typing my wrist is in a cast
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Generally speaking, that is true... but you must also consider the speed of the whole event... At less than a second from 1500F to 900F, the benefit of dispersing that vapour blanket through movement dwarfs any other issues that arise with the process. The motion of the blade through the oil, coupled with the rapid heating, creates A LOT of flow in a vertical tank. Tested blades have shown no difference in RC hardness readings from tip to heel. If that is still a concern, you can make a long deep tank and plunge edge first.

I have NEVER had a flash since adopting this practice. Even after HT'g several pieces in one sitting. That says a lot for its effectiveness.

Rick


Is it more likely to flash in a vertical tank or horizontal tank and how dangerous is the flash? and do you just extinguish it by placing a cover over it.
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Flashing happens when the oil temperature is so high that it ignites. Most of the time it only flashes for a few seconds. Unless the entire tank heats up... then the fire on top perpetuates itself and the oil keep burning. That's when you need to cut the oxygen off. Flashes aren't usually dangerous unless they spill over and catch everything on fire.

If your tank is too small the oil will over heat. If you don't have motion, the oil superheats rises to the top and flashes. Once the piece is completely in the oil, ANY flashing is a bad sign. (as you put it in, the surface will flash a bit, but should go out quickly)

The tank doesn't need to be stainless...... any metal will do.... avoid plastic or anything that will melt if the hot blade touches it.

You need to be able to heat your oil to 120F-140F in most cases. (Some quenchants work at different temperature, though) I quench bars of heated mild steel to get my tank up to temp. It really sucks if you go over. If you don;t have room to add cooler oil, you'll have to wait it out.

The tank dimensions are up to you.... just remember....

CONTROL

VOLUME + PREHEAT + MOTION/FLOW = GOOD QUENCH


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So do you use a small pump and a dip tube to move fluid, or is your plumbing welded in? Is moving the fluid going to improve quench versus just moving the object for smaller objects (knife, punch, chisel, hammer head, etc.)?

Do you use a basket on the bottom in case you drop something?

Phil

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Phil... having fluid flow would be the best way but it takes alot to fit a quenchtank with pumps and heaters. I chose the next best thing... which is blade movement.

I have a spigot about 8" up from the bottom of my tank to lower the level enough to get something out. I would like to make a basket at some point... it would be much easier.



Rick

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Yah I will probably get myself some of these Caswell Inc. - Heaters & Thermostats tank heaters.. 2-3 should do it and they do the job quite well for 5gallons of fluid. Much easier and more precise temperature then quenching hot iron to raise/control the temp. There is also a cheap "filter" through caswell that works also as an agitator. The filter I found to be rather useless when I was plating, but the fact that it circulated the solution turned out to be very beneficial to my nickel plating. So i'd proly just buy one again to move the oil around quickly.

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Actually, I can have my tank to temp within 5degs in less than 5mins.

You also need to have symetrical flow if you choose to agitate your tank. The flow must be the same on either side of the blade. You are better to have no agitation at all then have inconsistant irregular flow.

Rick

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