AEB-L edge thinness before heat treatment.

C

Cornwallis

Joined
Apr 22, 2022
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I’m not set up to profile a blade post heat treat. I’ve got an el cheapo harbor freight 1x30 belt sander and a file jig. My first AEB-L blade warped during cold treatment (dry ice and 91% isopropyl alcohol). I tried to peen the thing straight and it cracked. The good news is when I broke it the grain structure is very fine and I estimate it is 61 Rockwell. At any rate it skated with the 60 file. I made another one with the same heat, cold and temper treatment but the plunge line isn’t as nice so I ain’t showing it here, but otherwise I’m pleased. The thing is scary sharp and I am determined to make knives with this steel. On the warped blade I went down to .02. On the second one I only went down to .040 and had no warping. I clamped the first blade to aluminum stock during cold treatment and laid it flat in the slurry. On the second blade I placed it spine down and did not clamp. So how low can you go on the bevels? Did the first blade warp because of the clamping and possible uneven cooling or was it the thinness of the edge? If I could get it down to .02 before HT I would be super stoked but I don’t want to ruin another blade. A 2x72 grinder is on my list but I’m married and want to keep my nutsack attached to my body.
https://flic.kr/p/2nEBser
 
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You are probably going to have alot of people telling you to use easier steel, staring out.......or..... Send out for professional HT......or..... Grind your bevels After HT.
 
As a general rule folks profile AEB-L (great steel choice) before HT, then do the bevels after HT. It seems that AEB-L grinds about as good post HT as before and it does help with warp. Another very important thing is to clamp to a flat bar during the cold treatment and during temper. With this procedure I've made several knives from .040" AEB-L without warping issues.

Peening is good for removing small warps, and be sure it's done post temper. If you use a full flat grind the dimples created by peening aren't an issue, and no worry about grind lines:)

Once you get $600 or so you can build a GREAT 2X72 variable speed grinder. OR for $1200 or so purchase the Reeder grinder frame and other parts needed.
 
I like to grind a 10dps bevel to a 0.020 inch edge before heat treat. This gets me started on the bevels in soft steel and I find it easier for post heat treat grinding. This also leaves plenty of flat face to be in contact with quench plates.

I also always run a stress releaving step of a slow ramp to 1200F for 2 hours before I heat treat. This step eliminates most of the warp issues I have had.

As to peening straight I like to heat the blank up to close to tempering temperature before I peen, the metal moves a little easier. Started doing this after I tried peening a thin blade straight in a 19F shop, popped a huge chunk that took a nice kitchen knife and made it look like an elfish fantasy knife.
 
Seedy Lot said:
I like to grind a 10dps bevel to a 0.020 inch edge before heat treat. This gets me started on the bevels in soft steel and I find it easier for post heat treat grinding. This also leaves plenty of flat face to be in contact with quench plates.

I also always run a stress releaving step of a slow ramp to 1200F for 2 hours before I heat treat. This step eliminates most of the warp issues I have had.

As to peening straight I like to heat the blank up to close to tempering temperature before I peen, the metal moves a little easier. Started doing this after I tried peening a thin blade straight in a 19F shop, popped a huge chunk that took a nice kitchen knife and made it look like an elfish fantasy knife.
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I think the stress relief cycle might be a good idea in addition to minimizing temperature shock. I rushed the cold treatment on the blades because I didn’t want austenite to stabilize, but according to to what I’ve read the cooling only needs to be continuous. So maybe slow down the transfer from the plates to the dry ice. Maybe all that would allow me to push it a bit more and go down to .03, otherwise I might just stick to 52100 until I get a proper grinder. Or I could just keep going to .04 and convex the thing w/ the ghetto grinder (what I did w/the second AEB-L blade). Either way my arms are going to be buff from the file jig!
 
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I also cracked one peening it but the point of the carbide drill bit was sharp and I went too near to the edge of the blade. Keep away from the edge, use light taps and a lot (100+ for big warps) of them.

I suspect the warping has nothing to do with grinding (unless it was very uneven) but with the nature of AEBL.
 
FredyCro said:
I also cracked one peening it but the point of the carbide drill bit was sharp and I went too near to the edge of the blade. Keep away from the edge, use light taps and a lot (100+ for big warps) of them.

I suspect the warping has nothing to do with grinding (unless it was very uneven) but with the nature of AEBL.
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I tapped pretty hard. It was my first time peening a blade and it actually cracked when I hit near the edge. Thanks for the tips.
 
mooniesdl3 said:
I profile then have my AEB-L blades heat treated, even at 63 HRC it grinds easily.
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Once I get a proper belt grinder that’s the way I’ll do it, but until then I’ll just be more careful about how I grind pre-HT, and also pay attention to heating and cooling rates. It’s really difficult to grind a full flat bevel with a 1x30. I can do some great convexing of the edge with an already full-flat ground blade post-HT so that is what I typically do. I usually take the edge down to .02 and oil quench spine or tip first and have never had warping, but aeb-l is a different animal.
 
I think grinding aebl post ht shouldn't be too big of a deal, even on a 1x30. You will definitely need some decent belts, but I would recommend that anyway.

Edit: I say that because I've done regrind on a 1×30 with k390, and maxamet. Didn't notice any issues, but I was using 36 grit blaze belts for the majority of the work, and continued up the progression afterwards also using blaze until 120.

I've ground 10v on a 2x42 with no issues either, but I guess that's a little different, but still no issues.
 
Blankblank said:
I think grinding aebl post ht shouldn't be too big of a deal, even on a 1x30. You will definitely need some decent belts, but I would recommend that anyway.

Edit: I say that because I've done regrind on a 1×30 with k390, and maxamet. Didn't notice any issues, but I was using 36 grit blaze belts for the majority of the work, and continued up the progression afterwards also using blaze until 120.

I've ground 10v on a 2x42 with no issues either, but I guess that's a little different, but still no issues.
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Guess it's time to get educated on the different types of belts.
 
One of my first completed knives was a Nakiri in AEB-L heat treated to 63 HRC before grinding, I ground it on a 1x30" with ceramic belts, it was very easy to grind compared to something like MagnaCut even though all my MagnaCut knives have been done on my 2x72" also with ceramic belts.
 
mooniesdl3 said:
One of my first completed knives was a Nakiri in AEB-L heat treated to 63 HRC before grinding, I ground it on a 1x30" with ceramic belts, it was very easy to grind compared to something like MagnaCut even though all my MagnaCut knives have been done on my 2x72" also with ceramic belts.
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I'll give the ceramic belts a try. The platen on the harbor freight grinder sucks bigly, though. What I might do is grind to .04 because that worked for me, then finish with a ceramic belt. I am NOT confident in my ability to do a nice, even, full flat grind with a 1x30 on a full thickness blade. I'm just not that good yet.
 
Cornwallis said:
I'll give the ceramic belts a try. The platen on the harbor freight grinder sucks bigly, though. What I might do is grind to .04 because that worked for me, then finish with a ceramic belt. I am NOT confident in my ability to do a nice, even, full flat grind with a 1x30 on a full thickness blade. I'm just not that good yet.
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I so recommend taking the platen off and hammering and sanding it flat. I did that with mine, and it does help a bit. I hammered it most of the way there, then took it the rest of the way with sandpaper on a flat surface.
 
Blankblank said:
I so recommend taking the platen off and hammering and sanding it flat. I did that with mine, and it does help a bit. I hammered it most of the way there, then took it the rest of the way with sandpaper on a flat surface.
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Good idea. Or I could get some 1 inch stock and have my pops weld one for me.
 
Update: I successfully heat treated, cold treated and tempered a profiled and beveled blade today. It had a very minor warp that was fixed with peening. I didn’t go as low on the edge as the first blade, but almost. I put the knife in the dry ice slurry spine and handle first and kept it vertical. It is 1/8 stock and instead of a full flat grind I did a high saber which might have also helped. It has the same slightly recurved profile as the one that broke except for a sharper drop point. Thanks for all of the advice.
 
Cornwallis said:
Update: I successfully heat treated, cold treated and tempered a profiled and beveled blade today. It had a very minor warp that was fixed with peening. I didn’t go as low on the edge as the first blade, but almost. I put the knife in the dry ice slurry spine and handle first and kept it vertical. It is 1/8 stock and instead of a full flat grind I did a high saber which might have also helped. It has the same slightly recurved profile as the one that broke except for a sharper drop point. Thanks for all of the advice.
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Pictures?
 
Cornwallis said:
Update: I successfully heat treated, cold treated and tempered a profiled and beveled blade today. It had a very minor warp that was fixed with peening. I didn’t go as low on the edge as the first blade, but almost. I put the knife in the dry ice slurry spine and handle first and kept it vertical. It is 1/8 stock and instead of a full flat grind I did a high saber which might have also helped. It has the same slightly recurved profile as the one that broke except for a sharper drop point. Thanks for all of the advice.
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If you fix warps like Gary Creely does - that is honestly not smart to do. If science explanation is needed, just ask. At that thin cross section, it IS GOING TO WARP. God himself can't stop it. Even if you angle iron it, it creating massive stress and will essentially pull itself apart as the austenite changes to martensite (a metastable phase).
 
Hubert S. said:
Pictures?
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I just took these. I’ve already thinned and convexed the edge down to .008-.010 and I’m about ready to work on the handle.
Pääru Stash said:
If you fix warps like Gary Creely does - that is honestly not smart to do. If science explanation is needed, just ask. At that thin cross section, it IS GOING TO WARP. God himself can't stop it. Even if you angle iron it, it creating massive stress and will essentially pull itself apart as the austenite changes to martensite (a metastable phase).
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No offense, but I’ve always been a contrarian who thinks 90 percent of what he reads and hears is bovine excrement or exaggerated. I don’t know how he straightens blades, but I had a very minor warp and I took most of it out with light peening after tempering. I took this blade down to .025-.030 before HT and it worked.
 
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