Dewar

jdm61

jdm61

itinerant metal pounder
Joined
Aug 12, 2005
Messages
47,357
What size Dewar do you guys use? I am looking at the Taylor-Wharton models and it appears to me that I probably need to be looking at the HC and VHC models with the large neck opening and at least 20-25 if not the 34 or 35 liter in order to be able to cryo big blades like Kitchen knives.
 
I haven't made a large kitchen knife in a while and don't think my dewar will work with them. My dewar is a large stainless steel stanley thermos. I took the rubber seal out of the top so it'd vent, put it down in a 5 gallon bucket with bath towels wrapped around it. It'll last me 2-3 days that way. I know I'll be heat treating stainless and get the liquid nitrogen that morning. Cost 5$ from the welding shop to fill. Cost more in fuel to run up there actually.
 
Will52100 said:
I haven't made a large kitchen knife in a while and don't think my dewar will work with them. My dewar is a large stainless steel stanley thermos. I took the rubber seal out of the top so it'd vent, put it down in a 5 gallon bucket with bath towels wrapped around it. It'll last me 2-3 days that way. I know I'll be heat treating stainless and get the liquid nitrogen that morning. Cost 5$ from the welding shop to fill. Cost more in fuel to run up there actually.
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I'm basicly doing the same thing, first time I broke land speed records trying to get back cause I thought it would evap before I got home. I was surprised at how long it lasted.
 
You can use a couple of coolers to put the LN in. You will use some LN getting the coolers to temperature but then you can place the blades in holders above the LN and let them cool in the cold nitrogen gas flow.
 
i had a 10l with the 2.a hair wide mouth and then it just died one day as a replacement i got the 20l with 3.5 inch mouth and its over killl but i can get anything short of a cleaver into it
i get a bit over a month out of it after filling jsut liek the 10l that big mouth is not good for evapration rate
 
butcher_block said:
i had a 10l with the 2.a hair wide mouth and then it just died one day as a replacement i got the 20l with 3.5 inch mouth and its over killl but i can get anything short of a cleaver into it
i get a bit over a month out of it after filling jsut liek the 10l that big mouth is not good for evapration rate
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Butch, I was reading the manufacturers specs and you are right on. The two things that really impact evaporation are the size of the Dewar (bigger Dewar, LN lasts longer) and the neck size (bigger neck, LN evaporates more quickly.) I know that you can buy one of the 35 liter models that had a cleaver size neck, but the LN doesn't last as long.
 
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