Plate quench question

T

Taximanny

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Jul 27, 2015
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Because I do my grinds before HT will this effect the plate quench ?
I'll be using CPM 154
So the full flat grind will actually float between the plates.
Am I asking for warpage.
With doing small folder blades 3/32"
Is air cool a option?

I'm leary of grinding post HT because I use a 2x42 craftsman.
I'm getting better with the grinder at not getting the metal hot dipping after every pass.

Thanks for any info
 
With the blade clamped between the quench plates the cooling will take place rapid enough the bevels that are not touching will still be cooled sufficient to HT the blade. Wait, let me think about that statement a minute - that statement is based on the idea of a blade having a full tang, and perhaps some flat above the bevel. You said folder blades that are full flat grind. That would mean you would only have the small amount of flat in contact with the quench plate - the part for pivot hole, and very little of the actual blade because it will be a sort of taper from a full flat grind as it approaches the point. That might induce warping also since most of the blade would be floating free between the quench plates.

If you wish to do some bevel grinding pre-HT, a better choice might be to do a partial bevel leaving some flat on the blade all the way from stem to stern so the blade would be in full lenght contact with quench plates.

Ken H>
 
With an air cooling steel in knife blade thickness, a plate quench will adequately cool and prevent most warp. The less contact with the blade surfaces the more possibility of some twist or minor warp, but it will cool plenty fast enough. Immediately after removing from the plates, finish the quench in dry-ice slurry or LN. A snap temper for 20 minutes at 200F is OK if you worry, but I have heard no one who had problems with going directly from room temp to -100F.

I want to reiterate that last point- the quench is from 1950F to -100F. If you stop at room temp, it will not completely harden. The more continuous and immediate the drop, the better the hardening.
 
The above is also what I do. If you have some warp or bow then you need to straighten it right out of the plate quench. It will be very soft for 5-10 mins and you can do it by hand. I haven't been able to straighten after they are fully hardened or tempered.
 
So am I better off trying to grind after HT
To avoid problems ???
Do many people grind before HT ?
 
I think what they are saying is leave as much flat steel as you can. Maybe do a 3/4 height grind? If it's 1/8" or less I think I'd do it after.

I tried a neck knife that was a taper tang and a full flat grind. Didn't turn out like I wanted!😱
 
I've always did grinding pre-heat treat on blades over .100" and below .100" I've started grinding post HT - especially on .070" stuff - just works better once I did a few to get the feel for it.

Ken H>
 
Many people grinds after the ht, but i advise against it unless you don't have a wet belt running.
It just takes a spray bottle to sprinkle the belt before a couple of passes and you won't ruin your temper. It is not necessary a dripping belt, just wet.
Another tip: train yourself in straightening warped blades; just make a sacrificial testing one by quenching it sideways in oil and improve your straighening techniques as you get the feel of how much the blade can take... you'll be surprised.
My favourite is post full tempering, raise the blade's temp to 380 °F and straightening while in temperature...i use an heat gun aimed at the spine to keep the temp during the procedure, and clamp with wood jaws, since the metal will suck the heat quickly. Then a 3 rods setup or just prying always do the trick, but if the blade cools it will snap!!
 
Thank you for the write up Stezann...
I'm sure the same applies to CPM 154 which will be plate quenched.

I was thinking that exactly... A sacrificial blade just to see how it reacts or what I can do to fix it.
Not for sure what a three rod set up is but will do a search.

I'm just gonna have to dive in this new metal for me... And figure it out.
Hopefully a small learning curve.
 
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I intended the usual 3 point setup in a vise. You have 2 rods on one jaw and one in the opposite jaw: when you squeeze the blade in between you compensate the bend.
You can use shims and a flat bar with a clamp or any way to gradually overbend the blade to straighten it, but always when the blade is in temperature (370-400 °F) since the yeld point is way lower at those temps and the blade will be more willing to take the new set with less over bending.
 
Another thing to consider is to leave an extra strip of steel on the spine of your knife.

This will help heat transfer and help hold the blade straight.

You can then carefully grind it off after HT with little risk of overheating the edge.

I will add that I have never done this myself as I grind after heat treatment.
 
I plate quench cpm154 exclusively, and grind pre and post HT. However, I have a couple of variable speed grinders and my blades have large flats on them. I've had no warpage problems to date, even with pre HT edges down to 20 thousandths or less in some cases (to my surprise).

Smaller folder blades with very little flat surface area might be an issue. Grinding post HT with your grinder could be as well. Even with good synthetic belts and slower speeds, burning is easy to do if you loose concentration or hold it too long while trying to clean up near the tip. And this is on blades that have more mass than a small folder blade.

Be sure to wrap the blades with three layers of foil and crimp the edges closed well. If done properly, this will leave a multi color patina that can be removed with scotch brite by hand and reduce or negate any clean up grinding so you won't have to worry about burning on the grinder after HT.

I'm not sure what belts are available for the craftsman, but the Norton Norax engineered AO and ceramic both cut pretty cool and only when pressure is applied. This might allow you to leave a flat for quenching that can be ground out afterwards. Carefully...

The quench in LN really helps as well. It adds a point of hardness and evens out the blade so that it reads consistently from tip to end on my hardness tester. I didn't see this so much with the dry ice/alcohol bath. I believe the bath helps, the results just weren't as apparent as with LN.

If you can get this process down, it will leave you with a blade that will hold a working edge for a very long time.

There are pics of the patina that forms after HT on cpm154 on my FB page. It's really quite beautiful and I'm going to try to leave it on the next knife or two.

Justin
Black Raven Arms
https://www.facebook.com/Black-Raven-Arms-947029985371467/
 
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Straightening -- I prefer to do it at 400F or higher . You could go as high as the original tempering temperature
 
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