Recommendation? Quench Plate thickness

E.Carlson

E.Carlson

Joined
Mar 28, 2016
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Do you guys think I could get away with 1" thick aluminum plates, or should I keep digging for something thicker? Looking at a pair that is 1"x4"x16" for 45 bucks shipped.
 
That will work fine ! Set it up so you can move it quickly from heat to plates .A vice or your standing weight is all you need to insure straightness.
 
mete said:
That will work fine ! Set it up so you can move it quickly from heat to plates .A vice or your standing weight is all you need to insure straightness.
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How long between the plates are we talking about? 5 to 20 seconds. I know there are plenty of variables but what's a rough idea?
 
I use plates with a thickness of 1.5 ", with thick blades of up to 0.2" in about 1.3 minute, the blade temperature is such that you can take the pack using gloves.
 
The quench should be near the furnace and the plates setup so there is little time spent adjusting the plates .
 
Yes, copper has a higher thermal conductivity, but at four times the cost it isn't a practical choice. Both are more than sufficient as a heat sink, so cost becomes the main factor.
In BTUs, copper has a thermal conductivity rating of 223, and aluminum at 118. Steel is 17.

FWIW, diamond has the best thermal conductivity at 1000 .... diamond quench plates, yeah, that's the future.
 
Diamond quench plates.....that will be so cool :eek: Stacy , what about say half inch thick cooper / or quarter inch /on one inch Al plate , if the cooling rate matters ?
 
mine aren1x6x18 if i was to buy again i might go 1.5x24 i do have 6 inch wide .25 copper that i thought about
"bolt cladding" to my al plates but my quench speed seems plenty fast for the steels i use
 
When quenching several large blades, one after the other the plates can be dunked in water to cool down between quenches. You can also mist some water over the plates for a faster quench, but can't tell it's really needed. Remember, all that's required is to get below 1100ºF in less than 2 minutes.
 
I have a few sets of aluminum plates, and use all of them. One is 1 1/4 x 4 x18, and I use it for most of my regular knives (hunting knives, Skinners, small kitchen knives, ect)
The next set is 7/8x4x24 and I use it for things too long for the other plates, mostly long roast carving knives. I'll also use it once the other plate starts getting too hot.

The last one is a pair of 12x12 squares of 3/8 plate which I only use for head knives for leather work. It works on a flat piece of 1/16 stock, but I wouldn't recommend them for anything else. I've found a BBQ spatula to actually work better for taking the head knives out of the kiln than tongs. Plus it's somewhat entertaining having people ask why there is a spatula on my tong rack
 
I considered putting copper faces on the plates, but then thought, "Why???" It does not need it.
In the new shop, maybe I'll do it just for the high-tech look.

IIRC, my plates ar 2" to 3" thick and around 4" by 24". Way more than needed, but were dirt cheap at the salvage yard. I use a pipe vise that flips open and latches when closed to do the clamping. The lower plate is affixed to the bench and centered on the vise. The upper pale is loose and set on the lower plate by hand. The vise is set so it is about 1/4" more open than the two plates. I open the vise, set the foil HT packet on the lower plate, set on the upper plate, flip the vise close, and give the handle a turn to lock it all down tight. Because the assembly clamps only from one point, the blade taper is accommodated by the plates being able to be non-parallel. Probably by the time it is tight, the blade has dropped close to Ms. If doing multiple blades, I leave it clamped and check the oven to see how much it dropped in the short time I opened the door to remove the packet. It usually takes about a minute to rebound. When the temp is back up, I open the vise, remove the last packet from the plates, and then am ready for the next blade packet.

People worry far too much about quench speed with plate quenching. Most of the blades we plate quench work fine with an air quench, so, the plates will be ten times faster than air even it very warm to the touch. As long as they are below 400F, they are going to do just fine to bring the blade down to Ms.

One very neglected use for quench plates is to stick a long or wide blade in them right out of an oil quench. It will help a lot to prevent warp and twist. The plates actually do this better if warmed up a good bit. This slows the drop between Ms and Mf a tad. I heat a 2" by 12" bar of 1/4" thick steel red hot and put it between the plates. This will warm them to about 150F.

As far as how long to leave them in, just pull the blade out when the next blade is ready to go in .... or leave it in overnight ... it won't make any difference. After 60 seconds in the plates, it is done as far as quenching goes.
 
I have a set of 1" x 4" x 18". I keep a 5 gallon bucket of ice water next to my setup to cool them every 2 blades or so. I also use compressed air to blow between them. i weight the top plate with a 12" piece of RR track. I also use the plates to clamp blades when I put them in the DI bath. Or, if i am doing a batch of unground blades (like chef's knives) I just clamp the stack (usually 4 or more identical blanks) together with some small c clamps and forgo the plates in the DI. It has worked well for me thus far.
 
here is where i need to chime in about quench speed and clamp weight. plates tha are 400f will still pull the first 1000f out of the blade (and thats the key part) getting under 1000f in under 3 min for most air quench steels (or something like that point is anything you due to speed up the quench of air quench steels is better then air and the key temp is 1000f) the temp exchange between high and low (hot blade and "cold plate") never changes. tho thermal mass and total heat soak due build up the temp can auto temper. coefficient of heat transfer on solids is for the most part unchanged. now since i harped on getting that blade under the magic 1000f guess what boys and girls... thats not the Mf point nor is room temp on most any air quench steel so less you plan on continue a at the least a sub zero quench you are missing a bunch in HT. as if it never ends a foot of rail track is not goin gto have the force needed to clamp and hold most blade stock to make sure full compression and contact even on 3/32 stock. guys using a vice are miles ahead in PSI and in my cast i use a 12 ton press to clamp my plates. when you read stories of makers standing on plates and still having problems anything less then 400lb is iffy for clamping force
 
I'm not sure I follow. I am talking about unground blades, so I'm getting full contact. I thought the clamping was just to reduce warp, which my in my experience with .091 AEB-L, my method does.why would higher clamping pressure be required?
 
What Butcher Block said it's not wrong.
Even with flat ground and parallel blades, from a machinist point of view, you'll have at best 3 point of contact between mating surfaces....assuming rigidity. Those are the high points.
With enough pressure you'll squeeze, flexing the metal, and ensuring way better actual contact....and heat transmission
 
My thought process has been that since the directions for heat treat of AEB-L (what I'm using, so that's my example) is to quench in still air. So the only real reason for plates is to prevent warp. A secondary benefit being reduced time to get down to Sub zero quench time. If my blades aren't warping, and I'm hitting my hardness target, is what I'm doing an issue?
 
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