Salt Pot Question

ddavelarsen

ddavelarsen

Joined
Dec 7, 2000
Messages
5,179
How do you mount the thermocouple in your salt pot? Is it inside a nipple welded inside the tank or just suspended in the salt? Or something totally obvious that hasn't occurred to me yet?

And where, exactly, in the salt should it best be located?

Thanks for any ideas.
 
For the most accurate results you want the thermocouple in the salts and as near to the centr as possible. I like to have the tip of the thermocouple touching the blade when it is in the salts. After all, it is the blades temperature that I really care about. you would be surprised at how much temp deviation you can get just a few inches away in the salts.
 
So Kevin, you don't advocate the use of thermowells to house the thermocouple? I know some makers do use them. They go right up the middle of the tank... Would you also allow that this style would work as well, or do you think there would be an extreme difference in accuracy?
 
I had it marked down but can't find it. :confused: :( What salts and where to get it??? I have all the pieces just got to put it together.
 
jhiggins said:
So Kevin, you don't advocate the use of thermowells to house the thermocouple? I know some makers do use them. They go right up the middle of the tank... Would you also allow that this style would work as well, or do you think there would be an extreme difference in accuracy?
Click to expand...

Each man marches to his own beat. All I will say is that after observing (for more than a few years now) the way the salts react and heat, how the controllers adjust them and how the thermocouplers read them, I must have mine in direct contact. For what it is worth, this will eat up more thermocouplers, but my observations tell me it is worth it. Salt baths have the potential to be the most accurate heat treat method yet devised, for me personally, to interfere with that is like owning a formula one race car and blocking the accelerator at 45mph.

I know a guy who used the thermowell and told me his readings were dead on. I asked him "how do you know if all you have ever read is the interior of the thermowell?" He just sort of scratched his head and thought about it. The next time I saw him, he told me how white he had turned when he saw the deviation in temp when he put the probe against the work piece instead. He also noted how long it took for actual equalization of the blade, long after the salts read level, and how this time seemed to deviate a bit with every blade.

IN defense of other guys who do it differently, I may be splitting hairs here, and a good long soak may be enough to over come some of the issues. I play with testing and research applications that require funny deviations and tighter accuracy, so once again - to each his own.
 
Hi Kevin, Good information here from you as usual. One question...since the temperature variations should be fairly consistent/repeatable in a given high temperature salt pot, what do you say about using a thermowell to protect the thermocouple and then doing a calibration with the standard dunk technique to find the offset?

Ok two questions... do you agitate your salts when they're up to temperature in any way? Any elegant ways to do this that you know of?

Well, let's make it three questions...as I.G. asked, I'm interested too in what type of salts you're using (for both high temp and low temp)...I know you've told us before, but I can't seem to find it...

Thanks Kevin, really appreciate you taking the time away from the shop to help answer these questions, I know I appreciate it! BTW, over on CKD (or well, the new Knife Network), there is a new heat treating forum...sure would be nice as that forum gets rolling for you to pop in from time to time there too! :)

:)

-Darren
 
Hey Darren, last I remember Kevin was using Nu-Sal for the high temp salts and Thermo-Quench for the low temp. Both are Heatbath Corp. products. The only reason I know this is I have been researching and printing every last item I can find online about salt pots and their operation and I have it all organized in a nice binder at home.

Here's an alternative to the commecial brands that works well from all accounts, I got it from Mike Starling's website and it's what I'm going to use. For high temp salts you can use a 50/50 mix of sodium chloride and calcium chloride. Seems to work pretty well, Jonathan Loose uses this mix as well in his pot. This mix has the advantage of being effective and very cheap. Fifty lbs. of sodium chloride can be bought for nothing even at the grocery store for use in water softening systems and calcium chloride is a common ice melting product, since I live in FLorida the calcium chloride was a little hard to find but I eventually found a place online and it was still pretty cheap.

Several makers I know use Brownell's bluing salts for the low temp quench which is convenient for bluing operations as well. Ed Caffrey uses this product in a large pan with a simple propane pipe burner underneath it. The low temp salts are a simple blend of nitrates and nitrites that can be bought separately from chemical supply companies very cheaply online but since 9/11 it has been next to impossible to buy them unless you are a business as these are also basic ingredients for explosives.
 
Thanks Guy, that's great information. I have a large pile of parts (Thanks Mike S.!!!) sitting in the cart that will one day (soon hopefully) hold my high and low temp salt pots. I think it's about time that I get off of my behind and assemble this pile of parts into a set of working salt pots. ...I think as soon as I get caught up on forge orders in the very near future, I'll start on this project, in the mean time, I'll be lurking and learning from you guys. Thanks! :)

-Darren
 
I agree...get off yer ass and get to work! :eek: Tell me what it's like so I'll know what to expect if I ever change my mind and want to try again..... :D
 
Darren Ellis said:
well fitzo, you just carry your ass on down here and we'll build you a set too! :D

:)

-Darren
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Darren: He would have to make two trips. He is Bretha Butts brother. :eek: :D :p
 
Darren, would you please explain to this Portagee reprobate that, having seen me, it's the belly that's fat and the ass is like a tackhammer. :eek:

I'm looking forward to seeing you at Bowie's this year, Darren. Have a horizontal forge ready for me, please. Large size. Need more length, but that's the story of my life.... ;) :barf:
 
fitzo said:
Darren, would you please explain to this Portagee reprobate that, having seen me, it's the belly that's fat and the ass is like a tackhammer. :eek:

I'm looking forward to seeing you at Bowie's this year, Darren. Have a horizontal forge ready for me, please. Large size. Need more length, but that's the story of my life.... ;) :barf:
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Sorry Fitzo, I refuse to make any comments about your ass...ex-military homophobic thing you know...(and no wise cracks about me being ex-Navy!!!) :) Your tool rest looks fine though. :D

By the hammer in this Fall I'm hoping to be so far ahead that I have stock sitting on the shelf ready to go! :) If you need an extra long forge, just let me know, I'll make you whatever you want! :D

:)

-Darren
 
Thanks, Darren. I'll call you soon to discuss it. Need to pick the electronics part of yer brain, too. Got an anodizer I need to cut down the current flow on.
 
fitzo said:
Darren, would you please explain to this Portagee reprobate that, having seen me, it's the belly that's fat and the ass is like a tackhammer. :eek:

I'm looking forward to seeing you at Bowie's this year, Darren. Have a horizontal forge ready for me, please. Large size. Need more length, but that's the story of my life.... ;) :barf:
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FINE!! You X Scooter Trash. You can go to Darren's Hammer-In and you can't come to mine. :mad: :grumpy: :p ;)
 
If you guys are looking for Calcium chloride in 50 pound bags or so check out a pool supply place. Comercial pools use Calcium Chloride to raise the calcium hardness of the water... You can usually get it quite cheap there compared to buying ice melt... especially in summer... it sometimes goes under the name "Calcium Flake".

Hope it helps...

Alan Folts

alanfolts@hotmail.com
 
Then way that I understand it for the best results, you would need two pots. One to bring the blade up to non-magnetic and the other set at 400 DEG. for quenching.
 
Hey Kevin Cashen, thanks for once again expertly justifying to me the nature of things. A thermocouple is a fair price to pay for better accuracy. I'll be doing the dunk method when I build mine. :)
 
Darren Ellis said:
Hi Kevin, Good information here from you as usual. One question...since the temperature variations should be fairly consistent/repeatable in a given high temperature salt pot, what do you say about using a thermowell to protect the thermocouple and then doing a calibration with the standard dunk technique to find the offset?

Ok two questions... do you agitate your salts when they're up to temperature in any way? Any elegant ways to do this that you know of?

Well, let's make it three questions...as I.G. asked, I'm interested too in what type of salts you're using (for both high temp and low temp)...I know you've told us before, but I can't seem to find it...

Thanks Kevin, really appreciate you taking the time away from the shop to help answer these questions, I know I appreciate it! BTW, over on CKD (or well, the new Knife Network), there is a new heat treating forum...sure would be nice as that forum gets rolling for you to pop in from time to time there too! :)

:)

-Darren
Click to expand...

I wholeheartedly encourage testing of all sorts, as opposed to following the words of others on faith. Dunk testing while calibrating for a well may yeild good information. I have found the lag and lead times with rebound to vary on almost every heat treat job, however, so you would still be working off the assumtion that Mr. Murphy and his laws can't touch you. Either way attempting your calibration couldn't hurt, if nothing else, it would show you how much accuracy can be gained or lost with either method, and it would only be about 10 minutes of lost time.

An elegant way to agititate 1500F. salts, hmmmm, you got me on this one Darren ;) I give them occasional stir and let convection handle the majority. Mixing up the salts is more important with gas (due to the hot spot) than with electric. I have a couple different lengths of thermocouples and check for temp variation at differnent depths. All of my cross checking is made easier by a switch that I made out of a motor reversal drum switch. I have one lead comming out of the controller and into the switch with two leads comming out to thermocouples. One thermocouple head is labled "I" the other is "II" and the positions on the switch correspond to this. This way I can switch thermocouple readings in an instant with a flick of a lever.

Agitation is of much greater benefit in the low temp salts and I used to have a propeller driven circulator that went to the bottom of the tube and move then salts quite well. But, being the brain that I am :rolleyes: , I mounted the motor directly on the shaft and the heat transfred up and burned it out eventually. I have design that offsets the motor and protects it better but it would take time to make and I have been too busy to get to it, so for some time now I have benn regularly stirring my low temp as well. Of course I have the quenched piece in constant rapid motion when it goes into the salts.

As has been already discussed I use the Nusal and the Thermoquench. I am rather neurotic about having my stuff made by the guys that really know how, as opposed to me getting creative. But then I have the luxury od being able to drive to Detroit and get a 400 pound drum in 2 hours, when I need to.
Once again I encourage experimentation with the homemade mixes, but I also strongly encourage testing. One test that should be essential is to etch the blades as they come out of heat treatment (clean off the low temp first, as this stuff strongly interferes with etching). The only real damage that bad salts can do is either pit the steel (I only had this once, I don;t know what made them do it, but it was BAD), or decarburization. If your etched blade has little silver polka dots all over it, looking like somebody sprayed WD-40 near your blade right before going into the etch, then your salts are not neutral and you are losing carbon. Heatbath goes through a lot of trouble to make the salts neutral before I have to mess with them, and they also offer a graphite powder (and other specail addatives) to keep them that way.

I did not know there was heat treatment forum at the new CKD, is this new or was it there before and I didn't see it?

I am literally spending time away for the shop as I type this. This month I offically broke groudn on my addition that will be my metallurgical testing a research facility. It will be much cleaner to house all the testing equipment, microsopes and electronics. My back is killling me since I have spent the last wekk doing concrete work and laying blocks :(
 
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