Heat Treat question

Bigjohn

Bigjohn

Joined
Sep 30, 2002
Messages
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I'm starting to gather equipment to transition into doing my own heat treating.

Can someone please tell me the best place to buy a Dewar?

Also what is a good liter size, I'm finding them from 3 to 30 liters.

Anything else I'm may not know you can think of please enlighten me.

thank you

Bigjohn
 
I cannot help you with where to buy a dewar as I am in the UK but I found mine on E-bay.

Things you need to think about:

How are you going to get it filled? I have a guy come and fill mine up but I could quite easily put it in the car and take it somewhere to be filled. It is a 30L unit and easily liftable when full.

How much HT are you going to do? Obviously bigger will last longer and do more blades. My 30 L Dewar will stay cold for months.

What sized knives will you be putting in the Dewar? The space inside needs to be long enough for your blades, also the hole in the top needs to be big enough. Some of the dewars designed to hold their charge for long periods have a very small opening in the top. Mine is one of these and max blade width it will take is about 50mm ( 2inches to you guys)

A dewar is a vacuum flask and old ones can loose their vacuum. I dont know if there is any way to check so be careful if buying used.

Get some insulated gloves and goggles and dont put your head above the opening. The Nitrogen can boil quite violently and spit out when you put stuff in. You dont want it in your eyes.

Don't dip your dewar with an old tent pole !!!
 
These questions belong in the knifemakers area, in particular SHop Talk. We will move this there, so you can get answers from other knifemakers. General Knife Discussion is for discussing knives, actually finished production, custom, and semi-custom knives, not how they are made.
 
A 10L off eBay will fit anything up to 2" wide and is plenty tall for a 10" chef's knife.
Any smaller than that and it will start becoming a limitation
As for size that depends on how you plan on organizing your batches of knives. A 30l will hold nitrogen substantially longer than a 10l.
I have a 10L as I generally do a batch of 30-50 all at once, and then take the next month or two to finish all of them off. I only heat treat a couple times a year so a bigger dewar would just be a waste to get filled.
If you plan on doing a blade or two a week, then I'd probably go for a big one
 
It's worth doing the research and getting a good one. Mine holds liquid for a really long time. Last time I filled mine is was January and it still has liquid in it. It's only 20L but has an evaporation rate of .09L per day and the opening is over 2" I'm thinking 2.1875". So look at the specs and don't get one just becaus it's cheep. It costs me around $65 to fill mine but I don't fill it very often I just like having it on hand when ever I need it.
 
So Sorry Red, I did look for Shop talk, I couldn't determine where it was located. I had to use the search panel to get here. Sorry , My bad , thanks
 
Thanks Guys, I was under the impression that a smaller one would tend to be more restrictive, but would reduce the evaporation rate. I have a 10L coming from Ebay, new.

I figured the times I create a Big Bear or any large knife I would use Peters Heat treating as I am currently.

I really appreciate the help

Bigjohn
 
I was talking this over with the guy at the gas and welding supply where I buy dry ice (Roberts Oxygen around here, i'm sure you can search for others). While I'm not at the production level that can justify it (And the only stainless i use is AEB-L which responds well to DI quench) I don't need it, but he said they have used dewars for sale. You may want to check with one of those businesses, especially since they may be a source for the LN as well.
 
I'm sure you'll be happy with that dewar. I've got the Chinese 10L off eBay, and it holds it for a surprisingly long time. For the price they are pretty hard to argue with
 
Thanks guys I'm in for the 20L. Found place nearby that sells the Nitro so im off to the races.

Now I need guidance on a hardness tester. man those things are not cheap
 
awesome, so the reason for choosing one like you purchased is space saving? and mobility. Over the larger more customary ones I see makers use. did I get that right?
 
Bigjohn said:
awesome, so the reason for choosing one like you purchased is space saving? and mobility. Over the larger more customary ones I see makers use. did I get that right?
Click to expand...

Shipping a larger one to Canada would cost $500.00 or more. When I bought my portable one, shipping was included. The smaller ones are rated for the same accuracy as the benchtop models.
 
Willie71 said:
Shipping a larger one to Canada would cost $500.00 or more. When I bought my portable one, shipping was included. The smaller ones are rated for the same accuracy as the benchtop models.
Click to expand...
Oh great point, I didn't consider shipping yet. Thanks
 
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