Plate Quenching Air Hardening Steels

Leu Custom

Leu Custom

Joined
Jun 2, 2007
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For all of you guys that Quench plate your A2 or whatever Air hardening steel, have you ever ended up with a blade that was warped even a little after being plate quenched?

Does plate quenching completely straighten the blade even if it comes out of the kiln warped in the SS Foil?

Any advice would be very appreciated! Thanks in advance!

Pohan
 
Yes. I've had thin blades warp when plate quenched. I think distal taper keeps the plates from being flat on the blade.

Gene
 
You can still get some minor warping where the blade doesn't contact the plates ( on the grind). But, you can easily removed the warpage with a vise if you do it while the blade is still warm. The steel is still kinda soft at this point. I have some rubber jaws on my vise. If I have some slight warpage I just put it in the vise and tighten it down until I get the warpage out. This is trial and error, but it isn't hard. After you are satisfied then you can cryo or let them cool a little longer and temper as usual. Try it. I was amazed when I tried it. I read it on a thread here some time ago.
-John
 
That one reason why I heat treat before I start hollow grinding my blades out. It help in reducing the possibilities of warping the blade. But that's my method I used. It work for me in the shop. :thumbup::jerkit::D
 
I do that when I make a dagger or some kind of double edged blade. Works great. Just takes a few more belts.
-John
 
so i'm guessing if I generally have plenty of FLAT on both sides of my blades, I won't have to worry about warping during a plate quench?
 
Glad you asked this question!i'm waiting on an oven myself and was wondering the same thing.i also plan to heatreat then grind!
 
Leu its just a timing thing as Barker said you will have plenty to get it straight. I have since switch over to grinding everything after HT, I really do not notice the difference in belts. I like the fact that you grind the blade from start to finish vs grinding then HT (worry about warping ). The steel acts better as well not so grabby like when its annealed.

I place about a 75 pound anvil square on the plates, and I also store my plates in the shop freezer....stuff quench'es fast.

Good luck
Spencer
 
I'm guessing that works well, but lets say you're grinding a blade at 20' degrees chisel grind that is 3/8" thick. That is gonna take you a hundred years! It nearly takes almost 3 hours to grind it being only 6" inches long of a blade. I can't imagine how long it would take if it was hardened! good golly! :D Maybe I grind slow :D
 
Spencer,

When you say "grab" the blade, are you using a jig to grind the blades? Thanks!

Pohan
 
The only problem I've ever had with any warping at all was with 1/16 inch stock. Everything else has come out straight and true with plate quenching.

Rob!
 
A plate mounting trick to help avoid the warp:
Get a pair of plain door hinges ,and a quick clamp. Mount 4"X4" wooden jaws on the clamp. Using one hinge,mount an aluminum quench plate to the clamp with the hinge pin exactly centered in the jaw. This will allow that plate to pivot a little end to end. The other plate should be assembled with a hinge mounted 90 degrees to the first one. This plate will move a little from side to side. When the clamp is tightened, the jaws will align with the taper of the blade in both planes.The jaw/hinge center should be about 1-2" from the center of the plates end to end (at 8-9" on a 20" plate), and centered from side to side.When quenching the blade,place the center of the blade surface (halfway from ricasso to tip) at the center of the jaws, with the tang on the long side. There will still be places not in contact with the plates, but it will make the plates tighter to the blade than having a parallel clamping action. The plates should not be any longer or wider than necessary, but as thick as you want. Test it on the blade prior to putting it in the oven to see where the best place to put the blade will be.It will vary,depending on the size of the blade and the grind. You can mark the blade profile on the plate with a marker to know exactly where to place the blade when quenching ( The mark wipes off with acetone when done).

Once the blade is in the quench plates ,and has dropped below 900F, you can take it out and do any straightening you want until it gets to 400F. You can place it in a vise and twist/bend all you want. I usually just put it on the anvil and tap out any warp and stick it in the vise jaws to remove any twist. It will be like rubber at this point, so go easy,and don't over do it.Until it gets below the martensitic conversion start point at around 400F it won't break.
Stacy
 
Leu Custom said:
Spencer,

When you say "grab" the blade, are you using a jig to grind the blades? Thanks!

Pohan
Click to expand...

No jig I guess what I intend that to mean is when the steel is hard it tends to glide across the wheel ......hope that makes sense.

My kitchen knives are chisel ground, I take the bevels down with a 36grt, really I do all my hogging with a 36 grt take it right to the line then 80,220,etc.

I use to grind my kitchen knives before ht and the very edge would always curl, dang near impossible to get it back to where it need to be.

Spencer
 
Have yet to have a blade edge curl on me, but boy sometimes do they come out WARPED! Some are easy to straighten and then others seems like there's 2-3 different directions the blade is warping!

Some people (like RJ Martin) say to lay blades flat on kiln brick and others say it's bad. Which is it? I have done both flat on the kiln floor and also standing on spine with some ghetto knife holders (which spacers are way too big for 1/8. Works great with 3/8 as it stands up on it's own and i think even 1/4" works well. I think laying them flat on the floor makes them a) not warp at all, or b) if it's really thin material, warp slightly, but you really have to look at it to notice it ...and that drives me nuts too :) Probably doesn't help that my shop is at home and my kiln is somewhere else and that the vise i have there isn't anchored really to anything to straighten blades with :) My does that make it a challenge sometimes to straighten anything :)

Does it really make any difference whether the blade is standing on spine or whether it's laying flat on the brick? Isn't the whole damn thing the same temperature regardless on either position? I keep getting both answers.
 
Leu: Plate quenching does not guarantee a perfectly flat blade, whether the blades are left in the foil or not.

As the Martensite forms, tremendous stresses are being set up in the steel as the structure reorganizes.

A perfectly ground, symmetric blade will warp the least.
A chisel ground blade will warp more. The plates only hold the blade flat. If there is asymettric stress created in the blade during quench, once the pressure from the plates is removed, the blade will "spring" as the result of these forces.

Often blades are loaded with stress from grinding, and they warp as we grind them. Then, we grind out the warpage. The result? the stress is relieved during HT, and the blade appears to have warped IN THE OTHER DIRECTION.

Grind a chisel ground tanto from precision ground stock using a 50 or 60 grit belt and lay the flat side down on a surface plate and tell me it's not warped!

Grind a chisel ground tanto from a bar of hardened precision ground stock and lay the flat side down on a surface plate and tell me it's not warped!
 
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