Plate quenching variations: Anyone try big heat sinks?

J

J. MacDonald

Joined
Jun 8, 2000
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3,140
While I've been flappin my gums about it for a while, I'm really about to order an oven so I can start heat treating stainless blades myself. It seems a lot of guys prefer a pair of aluminum plates to quench air quench steels over plain old air quenching. I was wondering if anyone has tried taking it to a different level by using large finned aluminum heat sinks? It would seem to me that having a faster thermal dissipation might have a positive result on the quenching process. I happen to know where there's a surplus place that I could probably score some reasonably large heat sinks for not a lot of money and am wondering if it's worth pursuing, or if I should just get some 1" thick plate and call it a day. Certainly it would be a little more work to mill off some fins on the ends to allow clamping together, but that's no big deal.

Any thoughts or opinions?
 
Sounds like a good plan to me, especially if you're doing multiple quenches, as it will cool down faster than a massive plate.
 
my 1 inch x 6x18 plates were just about shot after quenching 4 3/32 blades but i pressed on and got 2 more 3/16 blades quenched
i will not be doing that again i had to were gloves to move the plates to the sink to cool them back down for the next round
i have plans on water cooling my plates when i get a full on setup and a shop of my own
 
butcher_block said:
my 1 inch x 6x18 plates were just about shot after quenching 4 3/32 blades but i pressed on and got 2 more 3/16 blades quenched
i will not be doing that again i had to were gloves to move the plates to the sink to cool them back down for the next round
i have plans on water cooling my plates when i get a full on setup and a shop of my own
Click to expand...
butch, what are you saying, you didn't cool the plates inbetween blades?
Scott
 
I use 1" x 3" bars
and always quench with one set at room temp..
(more than one set )
for a heat sink as you mention I would think it would in turn with less mass heat faster, most sinks are for continued use for heats that are much less then 1950F
I'm thinking it will heat to fast if the mass isn't there just my thoughts..

I do like the water cooled plates though..mainly to get it back to cool faster..
 
Razorback - Knives said:
butch, what are you saying, you didn't cool the plates inbetween blades?
Scott
Click to expand...
cooled them between batches i know i pushed it on the last 2 blades but i remember that i could handle all the plates bare handed till the last 2
they were the 2 dress kabars 3/16 thick 12 inch long cpm154
i had them Rc ed cause they seemed to be grinding right (didnt seem hard to me) compared to the ats34 i did at the same time
they came out of temper at 59-60 so i had no problem there
btw the way i saw it was it if you can quench in 800f + salt bath then even if the plates were 300 till they were quenched out it still was plenty fast

i am however planning on water colling my plates and setting them up in a jigfor ease and speed
on the thin stock i bet it took no longer then say 10 sec to be cool to the touch
 
I use 7/8" X 8" X14" plates of 6061 Al and the most I have quenched at one furnace run is 4 blades, 2 at a time. I keep the plates in a chest type freezer until the blades are ready to come out and then just do them all. The plates have never got above being cool to the touch. That is with up to 3/16" S30V stock, coming out at 1975° F.
 
Valimas thread on "plate quenching material" made me think of the same thing. Look for ones with a thick baseplate to get the most thermal mass. Blowing air along the fins ought to cool them off fairly quickly. The mounting surfaces are usually milled by the manufacturer to guarantee flatness. Look for them at metal recyclers or at places that scrap out large electrical equipment. Clean off any white silicone grease with rubbing alcohol or acetone ASAP. Otherwise it tends to get smeared everywhere and is really hard to wash out of your clothes. Most of the ones with really deep fins will be bonded together with epoxy so don't get them too hot or the fins will fall out.

Off to check the scrap bin on my way out of work...

Phil
 
No one has mentioned copper plate quench. The thermal conductivity is higher than Aluminum and AL alloys, but Expensive, huh?
 
If expense is no object, you might as well go with silver.

The Al plates do a fine job. I don't believe you will gain much for your extra $.

Edited to add Just for grins, I figured out the relative volumes of my plates to my blades. The average size hunter I make is about 1/80th of the size of the plates. This is using the pre-grind volume of the steel.

I think the great majority of makers that use plates are happy with the results from just a basic set up.
 
I know, Steve...
I had a chance a while back to buy a plate of 1.2x7x33" copper for cheap, but passed on it...
Sometimes we do pass up a great deal.
At the time, I hadn't thought of using it as a heat-sink, and couldn't cut it, so I passed on it.
Al is the economical way to get good results as you said.
I've got a pair of 2x4x22 plates waiting for me to grind something...
 
My thoughts were that a large thermal mass like a 1" flat aluminum plate would just absorb heat, and probably do a pretty good job, but with a big enough pair of heat sinks, it would seem that they would wick the heat away from the blade even faster as that is what they are designed to do. I figured with the price of 1" plate, I could probably find some good sized surplus heat sinks for the same money at a scrap place wher ethey just sell it by the pound anyway. I hadn't really given much thought to the fins cooling the thermal mass down more quickly than a solid plate, but now that I think about it, that would seem to be an advantage as well.

I had also only been thinking of a passive approach, but after all this discussion, I'm starting to envision a contraption with a fan, or perhaps fans moving air actoss the fins for a more active solution. I happen to have a nice box full of 5" pancake fans that would probably be just right for a job like this.

Hmmmm. time to start scroungin.....
 
John, the fins cool convectively, which is a lot slower than the conductive transfer of heat by the metallic thermal mass. It serves to cool the Al OK, but will not make an appreciable difference in the conductive cooling. If the plates were so small that they didn't have enough thermal mass to cool the blade, the fins might help, but would not be anywhere near as good as larger plates.

Howie, The 6061 I got came as a single 14" X 16" plate. I had to cut it with a 4" offset grinder. It took 5 4" metal cutting disks to make two plates out of it- one 14" cut. I would hate to try copper that way.
 
Steve,

Thanks for clarifying. What if the heat sink had significant thermal mass, like a 1" thick base? Would there be any advantage in cooling the plates for a subsequent quench?

If I find a big chunk that needs to be parted down, I'll be really glad I have a bandsaw :)
 
Think of the Al as a large area with a crowd (of electrons) rushing through as it cools away from the heatt source. The surface of the AL, whether it be flat, or fins, or whatever acts as a gate and impedes the flow because the heat can only transfer as fast as the surrounding gas or fluid can take it away. The heat has to radiate out of the metal and then flow away in the air or whatever. In the meantime, the heat builds up in the metallic mass evenly (more or less) at the speed at which the particular kind of metal conducts it. Metals are the best conductors of both heat and electricity-at normal temperatures-and conduct much faster than they radiate through their surface. Al, Cu and Ag are among the best conducting metals. Steel also conducts well and I have talked to several makers that press quench with steel plates.

I guess the point I want to make is that the shape of the plates on the sides away from the blades doesn't matter, as long as you have enough mass. The fins are irrelevant because their process is so much slower.
 
Steve Hayden said:
The fins are irrelevant because their process is so much slower.
Click to expand...
thanks Steve
I mite add
the fins, would help in the way of helping get the plates ready (cooled) for use again faster then with-out the fins..

butch I only mentioned that for consistence sakes

these are some of the reasons why I'd go with water cooled
if I didn't have enough plates to do each quench..
it may make no difference, but for consistencece sakes.:)
 
Dan Gray said:
butch I only mentioned that for consistence sakes

these are some of the reasons why I'd go with water cooled
if I didn't have enough plates to do each quench..
it may make no difference, but for consistencece sakes.:)
Click to expand...
ooo and just what do you think you know about anything:) :D
just to make sure everyone knows im just having a little fun
so far my bro inlaw and i are working on vert and horizontal plans depending on just how i think it will be faster to get a blade out and snap the plates closed speed for me will be the key
thinking that holding with tongs as they would be comming out the kiln i could get away with maybe an inch gap(think toaster) instead of like 4 inch (think shop press) to make easing the blank between the plates
i ll try to have something posted when i figger it out
butch
 
butcher_block said:
ooo and just what do you think you know about anything:) :D
just to make sure everyone knows im just having a little fun
so far my bro inlaw and i are working on vert and horizontal plans depending on just how i think it will be faster to get a blade out and snap the plates closed speed for me will be the key
thinking that holding with tongs as they would be comming out the kiln i could get away with maybe an inch gap(think toaster) instead of like 4 inch (think shop press) to make easing the blank between the plates
i ll try to have something posted when i figger it out
butch
Click to expand...

well I do know ... rrrr .. no that's not it .. ahhh maybe I know.. rrr. no I was told that this morning,, how about this hmmmm rrr. no not that either,, you're right butch
I know nothing...just ask anyone :D don't ask IG, no one believes him..:D

my thoughts would be
horizontal ...
two plates hinged
with the hinges spring loaded and adjustable (preloaded) to any pressure you want
in a fashion that when you close the contraption the mechanism
will cause the plates to level on the blade under pressure so it will work on any thickness of blade..kind of like a George Forman waffle iron on steroids..:D and long handles;)
 
Dan Gray said:
well I do know ... rrrr .. no that's not it .. ahhh maybe I know.. rrr. no I was told that this morning,, how about this hmmmm rrr. no not that either,, you're right butch
I know nothing...just ask anyone :D don't ask IG, no one believes him..:D

my thoughts would be
horizontal ...
two plates hinged
with the hinges spring loaded and adjustable (preloaded) to any pressure you want
in a fashion that when you close the contraption the mechanism
will cause the plates to level on the blade under pressure so it will work on any thickness of blade..kind of like a George Forman waffle iron on steroids..:D and long handles;)
Click to expand...
hahahahahah thats the one now i got to get 10 made and sell them do i need to send you your cut now or can you wait :D
 
butcher_block said:
hahahahahah thats the one now i got to get 10 made and sell them do i need to send you your cut now or can you wait :D
Click to expand...
what's so funny :confused:

50% of the gross profits ;)
:D
 
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