Heat Treat- 2 Simple Questions, 1 Theory Question

[Dominick Maone]

Hope you all are doing well. I have two general heat treat questions and a more theoretical question. These are all AEB-L from .08 to .1. Any tips would be appreciated.

1. Do I need to make sure the blades are perfectly straight before sending to a professional heat treater? I know they will straighten, but will they straighten even if not straight when they receive? See pics, this is the worst bent one from this batch, probably close to .5" (12.75mm). Sorry it is so hard to see in pics.

2. Is this finish acceptable to send to heat treat? Last time I surface ground all of the blades before sending. But my platten is no longer flat so would have to get a new one or flatten by hand. But very little of the existing metal will be visible (or even there) on the finished knife, so seems like it might be a waste of time.

3. (Edit- see post 6, I do not believe it is a heat treating issue) I know this question gets asked repeatedly but I am going to ask again. What hardness should these knives be? It is close to 50 knives I will be sending and probably 45 are kitchen knives. My last batch was professionally heat treated to 61-62. I made one of the knives for my mom and after a month it was in the condition below. I said Sue, "what did you do to this knife? The tip is missing and it's chipped" Once I convinced her it WAS chipped and the tip WAS missing, her response was, "I've had knives my whole life and never had one chip or the tip break. There must be something wrong with it."

I am confounded what to do. I think the problem is that when sent for heat treating, the HRC is hit, but is it the toughest it could be for that HRC? Probably not. I would like to make them around 64 to maximize the steel, but if it is chippy for a non knife nut at 61-62, it might be really bad at 64. I may consider selling some of them and I think knife enthusiasts would prefer the higher HRC, especially for the Japanese style blades I am making. I think the solution is to heat treat them myself, but that would require running 220 to my garage, buying oven, buying foil, buying liquid nitrogen or dry ice, buying aluminum plates, straightening myself, buying hardness tester, and probably some other things I am forgetting. My girl will not be happy if I spend 2k more on knife stuff. Thoughts?

 

[Lee Hester]

Dominick, if it were me I would:
Only profile the blade and drill the holes before heat treat, don't even bother grinding the flats before heat treat.
Do your best to correct any big warps before sending it out for heat treat. In my experience the steel will take a bend and keep it much more easily before heat treat than after, where it will spring back.
Send to a reputable heat treater like Jarod Todd who knows how to deal with AEB-L and will correct any warps from heat treat.
If you want an oven, get an oven, but in batches as large as what you're doing, sending them out to a pro can make a lot of sense. Also, if they can correct the warps for you and let you focus on the parts of knifemaking that you like doing, even better .

As far as hardness goes, I've been trying to get mine in the 60-61 range according to the heat treat schedule I use, but I don't have a rockwell hardness tester, so I don't know if that's what I'm hitting. I haven't had any AEB-L blades chip yet.

 

[Britt_Askew]

A- if I was sending aeb-l out for HT ,I would send it to JT.
or
B- buy all the stuff you need to do HT yourself and tell your girl it cost 417.00

Try to straighten the blades best as you can before HT

 

[Willie71]

You should have no trouble with AEB-l at Rc61/62, for a kitchen knife. I suspect a heat treat issue.

 

[samuraistuart]

My wife uses a 62-63HRC AEBL santoku I made her almost every day for the last 3 years or so. It has never chipped.

 

[Dominick Maone]

Dominick, if it were me I would:
Only profile the blade and drill the holes before heat treat, don't even bother grinding the flats before heat treat.
Do your best to correct any big warps before sending it out for heat treat. In my experience the steel will take a bend and keep it much more easily before heat treat than after, where it will spring back.
Send to a reputable heat treater like Jarod Todd who knows how to deal with AEB-L and will correct any warps from heat treat.
If you want an oven, get an oven, but in batches as large as what you're doing, sending them out to a pro can make a lot of sense. Also, if they can correct the warps for you and let you focus on the parts of knifemaking that you like doing, even better .

As far as hardness goes, I've been trying to get mine in the 60-61 range according to the heat treat schedule I use, but I don't have a rockwell hardness tester, so I don't know if that's what I'm hitting. I haven't had any AEB-L blades chip yet.

I might keep this batch in the same range then.

A- if I was sending aeb-l out for HT ,I would send it to JT.
or
B- buy all the stuff you need to do HT yourself and tell your girl it cost 417.00

Try to straighten the blades best as you can before HT

This was the only blade that was this bad. I will try to straighten it better before sending.

You should have no trouble with AEB-l at Rc61/62, for a kitchen knife. I suspect a heat treat issue.

I think I will keep them in that range. It was professionally heat treated by a very very very very reputable heat treater, I do not want anyone reading this to think I think it is a heat treating issue. I have two knives from this batch and this heat treater that I use regularly with no issues.

My wife uses a 62-63HRC AEBL santoku I made her almost every day for the last 3 years or so. It has never chipped.

Thanks for all the responses. I am convinced it is a user issue. I have two kitchen knives heat treated from this batch that I have used a decent amount with no issues. I made a cleaver in this batch and my friend uses it four or five times a week. I even cut up a bunch of chicken and helped prepare Thanksgiving side dishes with my mom's knife before sending to her. I do not believe it is a heat treating issue. I guess my point was more along the lines of in her opinion, this knife is too hard. I imagine she cut on her granite countertops and cut through bone with this knife, that is why it is in this condition. Similarly, I made a 1075 kitchen knife for my girlfriend's friend. I basically said if you leave this knife wet overnight you will just have a handle when you wake up. So what does she do? She doesn't use the knife at all. So to me, I want a knife at 64+ HRC to experience what the steel is capable of. But if I send this batch out to be 64 HRC, there will be some knives that do not turn out to the users liking. And I realize you can not please everyone, but I think 61-62 leaves some qualities of the steel unused.

 

[HSC ///]

I would say user as well based on what you wrote. Some are not cut out for hand made performance knives


This is an AEBL knife that just got tipped. The wife is a cyclone in the kitchen. Ground thin, of course it will get tipped.

This is a 26c3 thin slicer a year old. Customer lent it to a friend. Came back with a crack. I reground the blade.