Aluminum quench plate question

Joseph Bandeko

Joseph Bandeko

Knifemaker / Craftsman / Service Provider
Joined
Dec 9, 2021
Messages
1,352
Hello,

I tried using the search engine for this but wasn't able to find anything.

As some of you know I've finally acquired a heat treating oven. And though I usually just use high carbon steel, I also use a fair bit of high alloy steels.
Anyway, enough rambling, I need some quench plates and I'm wondering what's the thinnest aluminum stock that I could safely get away with?
Most quench plates I've seen are an 1" thick, but is that really necessary? I mean it's not like I'm gonna use it on a bunch of blades at once, and even if I am heat treating several blades at a time I don't mind dunking them in water before each blade.
Any thoughts on this are much appreciated!
 
I had that very same question last year, but being honest with myself I was just trying to be cheap, because there really is no other reason to use thinner material. So I searched on Ebay and ended up ordering a pair of 1" thick plates, I think they measured 5.5 inches by 18 inches. I can't recall how much I paid, they weren't cheap, but they work great! I bought an Irwin carpenters wood vise at Lowes for about 20 bucks, then drilled and tapped the plates and mounted them to the vice. Mounted the entire assembly horizontally to my workbench next to my oven. A 1900 or so blade cools down to where you can handle it with bare hands in well under a minute. Thinner plates might work fine, but I know for a fact that mine work very well.
 
You could always use steel plates they can suck up more heat, if you're only using them for one blade, you can probably go thinner, thus cheaper.

After all, the steels that we are using for knives are air hardening, any metal in direct contact will speed up the cooling rate, and keep your knife straight.
 
Yeah I guess it’s probably worth it to just buy it once and be done with it, instead of trying to save a buck.
With that said I think I’ll start by asking around and going to junk yards, or perhaps someone here has some laying around that they don’t use they’d be willing to sell me?
 
Mass is important. Thinner and wider is an option. Thinner and too small will kinda work. But thin has a drawback. Al stretches when heated and when it's too thin good contact can be disturbed due to warping. Thicker will remain straight.
 
you're not just quenching with the plates, you are also clamping your blades flat. If the aluminum is too thin the plates won't be flat for long. I'd say that 1" is the minimum thickness that I'd want to use, but I'd go up another 1/2" from that.
I also have a little air compressor tucked away which I use to blow between the plates while quenching. Seems slightly more useful for large blades than small ones
 
I use these 50x60x500 mm aluminium blocks standing and free floating against the blade/blank, with speed clamps. A lot of mass, no need to worry about an unaligned vice, and quick to cool when needed.

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my plates are 1x6x18 but i have got a new kiln so i need longer plates. when i batch HT blades i need to keep a bucket of ice water handy to get the plates cooled every 6 blades or so (3/32 thick kitchen knives) quenching more mass means more quench plate mass needed before cooling them off my next set will likely be 1.5x6x24
 
What about getting thinner aluminum plates and bolting them together?
 
There is always a temptation to make something cheaper, but it usually results in a cheaper product that works not as good.

Bolting quench plates together could bring all sorts of issues with thermal expansion.

A pound of aluminum is a pound of aluminum. It doesn't matter if it is four 1/4-pound sheets or 1 one-pound block. Shop around on eBay and check with some larger machine shops that do a lot of aluminum work. You might get some for basically scarp price.
 
Bunker Hill Blades said:
What about getting thinner aluminum plates and bolting them together?
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To achieve same thermal draw, one needs thermal paste between them. It's not cheap. Another thing to consider is individual thermal expansion which can bring a thermal break. The cheapest solution is to go thick. Mine are 30mm and I keep a bucket of water to cool them after 5-6 blades (6mm).
Some things are just made to do them right from the start.
I have a question. How much does Al go for over there? In EU Al 5xxx series is not expensive. It can be bought for 60ish US money for a pair of plates.
 
Be interesting to have a real world test of the coolant plates V's solid plates.

Both are 25.4mm at the start and removing around 30% from one would have to effect the rigidity, along with bolts and gaskets as posiable failure points.

Coolant for batching is certanly more elegant than dunking the plates in water but at what cost to rigidity?

A bean counter could run the cost benifit analysis of the 2 methods.
 
Stacy E. Apelt - Bladesmith said:
There is always a temptation to make something cheaper, but it usually results in a cheaper product that works not as good.

Bolting quench plates together could bring all sorts of issues with thermal expansion.
Click to expand...

JoeBusic said:
To achieve same thermal draw, one needs thermal paste between them. It's not cheap. Another thing to consider is individual thermal expansion which can bring a thermal break.
Click to expand...
Yeah that’s what I figured, but hey there’s no such thing as a stupid question so figured it was worth an ask.

I went ahead and ordered some 1”x4”x16” plates from USAknifemaker.
At this point I’ve got enough demand that it’s more worth my time to just buy the right thing instead of searching all over hell’s half acre for it.

Thank you to everyone that took the time to answer my questions!
 
Ive heard some people say you can get away with 3/4 inch. But 1 inch is a much safer bet.

I see got some decently sized plates on the way.

I ended up doing the plate quench vise setup, and i really like it. The only thing i would change, is eventually ill buy a quick release vise for it, instead of the normal woodworking vise i use. Dont get me wrong, it works fine, and im able to still get knives into it quickly. But with a quick release i could have it wide open and quickly drop it down to make it even easier.

Instead i check how far i need it open to fit the knife in without issue before putting the blade in the oven. Either way, i like having the vise for it a lot.
 
My quench vise is an old pipe vise I got at a yard sale. It applies the pressure in one spot, so the plates align with the blade taper as needed. The plates are around 2" and 1.5" thick and 4" wide.
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Blankblank said:
I ended up doing the plate quench vise setup, and i really like it. The only thing i would change, is eventually ill buy a quick release vise for it, instead of the normal woodworking vise i use. Dont get me wrong, it works fine, and im able to still get knives into it quickly. But with a quick release i could have it wide open and quickly drop it down to make it even easier.
Click to expand...
What's the rush? It's air hardening. There is time for a coffee break to. :)
But, if it's done fast, O2 can be plate quenched. Maybe not a bad idea anyways. :)
 
J. Hoffman said:
Look at 1" copper plated for quenching, and then you will realize that the 1" aluminum plates are a steal of a deal. Don't try to make it any cheaper 😁
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Well if we’re gonna go that route let’s just use bronze!
$$$$ 🚽
 
J. Hoffman said:
Look at 1" copper plated for quenching, and then you will realize that the 1" aluminum plates are a steal of a deal. Don't try to make it any cheaper 😁
Click to expand...
And if 1" cooper plate look to expensive , look at 1" 24 carat gold plate . I hear it conduct heat very, very fast and AEB-L can reach 70 HRC ;)
When time comes I will use mild steel plates for stainless steel HT , anyway its purpose is only to keep steel straight
 
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