M390 questions

[Natlek]

And cuts 4 times worse

Don t push me I just finished this one , 64 Hrc , 2 mm spine , 0.3mm where red line is and hollow grind It flex like Accordion , I think that will break on half on 10 knots wind
Sorry for off topic guys

 

[Willie71]

Thanks for the info. I think I will start at 62ish and go from there.

i don’t use it a lot. Most of my customers want fine slicers, and s-35vn, vanax, and z-wear/v4e all support finer edges better. I rarely make knives with edges thicker than 0.005”. M390 is a fine steel, but not the best choice for my customers.

 

[shqxk]

I read some article from Roman Landes some time ago.He says that if we compare two edge ,same steel and same hardness . One 0.10mm behind edge and one 0.2mm behind edge knife with 0.2mm behind ege is FOUR time stronger then other one with 0.10mm .

Actually when you double the thickness, the strength and stiffness will be increase by 8 times physically.

 

[REK Knives]

I've run my kitchen knife m390 down to 11dps with 14 dps micro bevel, worked fine until I tried to cut up really hard crusty bread then it chipped out. 61rc on that one. I was pushing it though to see what it could handle and an edge that thin couldn't take the hard bread!

 

[Nathan the Machinist]

I've run my kitchen knife m390 down to 11dps with 14 dps micro bevel, worked fine until I tried to cut up really hard crusty bread then it chipped out. 61rc on that one. I was pushing it though to see what it could handle and an edge that thin couldn't take the hard bread!

But AEBL will handle it fine. I've never been a fan of high carbide steel in the kitchen. How abrasive is food...

 

[DevinT]

It’s the cook that’s abrasive.

Hoss

 

[REK Knives]

But AEBL will handle it fine. I've never been a fan of high carbide steel in the kitchen. How abrasive is food...

Good to know! What hardness levels could aeb-l handle that at do you think?

 

[DeadboxHero]

I like the carbide stuff at high hardness in the kitchen, just not very fun or economic to make. The edges can be very strong and aggressive, lots of ferocity on draw cutting pepper and tomato skin if one uses a proper edge finish to keep all those fancy Carbides poking out rather than smoothing them over.

M390 is highly overrated. I'd rather use something else. While M390 is the most popular "high end" in the community, people don't know what they don't know.

 

[Nathan the Machinist]

Good to know! What hardness levels could aeb-l handle that at do you think?

I made a couple hundred kitchen knives in aebl at 62 with a 15 degree included angle plus micro bevel. They held up well. you wouldn't want to use them on bone or anything like that, but bread would not be a problem.

 

[Stang Bladeworks]

Ok, i have completed the heat treat on 5 blades. On the first one I took multiple readings at every step. The final HRC is an average of all 5 blades. All readings were about +/- 1 HRC from each other. I did verify my tester against a standardized test block to ensure the validity of my numbers. I have not yet tested the knives as they are in progress. They are all spoken for so there won't be any aggressive testing. I do plan to make a fixed blade for testing purposes at a later date. I hope this info helps someone.

1.wrap blades indicidually in high temp foil with johnsons baby powder. I tried other baby powders and they didnt work well. I dont think they all have talc which is what prevents the stick. I coat the blades heavily and pour a bit in the pouch. Double roll all seams.

2.Put in kiln at room temp.

3.Ramp to 1450f AFAP and hold for 25 minutes

4.Ramp to 2140f and hold for 30 minutes. If doing multiple blades add 2 minutes per blade to ensure each is quenched at the correct temp.

5.Quench in aluminum plates while blasting with air from a compressor

6.Remove from foil

7.Place blades in liquid nitrogen for 45 minutes. Wait until blades have cooled to room temp prior to cryo.

8.Flash temper at 250f for 1 hour while waiting for kiln to cool to tempering temp. I do this in a toaster oven. It is done to help relieve internal stresses until the kiln is ready. I flash temper at a lower temp because I dont think the toaster oven is very accurate and I dont want to risk exceeding the actual tempering temp.

9.temper at 365f for two hours twice. Allow blade to cool to room temp between cycles.

Below are my HRC numbers from running this protocol.

After quench 59HRC
After cryo 63HRC
After flash temper 64.25HRC
After temper cycle 1 63.75HRC
After temper cycle 2 62.75HRC average over 5 blades

If anyone has any comments or data of their own Im all ears. Hopefully this is useful to someone.

 

[Robert Erickson]

Thanks for the follow up info.
I'm not sure you want to/need to put the blades in the cold kiln. At least in my kiln that'd be a long time.
Also, I don't think you don't need to do the 1450 step. IIRC that's more for larger, thicker parts.
I've been getting similar final RC with an aus temp similar to yours X 30 min and then plate quench => LN X 1 hr => temper at 350 X 2hr X 2.

 

[Stang Bladeworks]

Thanks for the follow up info.
I'm not sure you want to/need to put the blades in the cold kiln. At least in my kiln that'd be a long time.
Also, I don't think you don't need to do the 1450 step. IIRC that's more for larger, thicker parts.
I've been getting similar final RC with an aus temp similar to yours X 30 min and then plate quench => LN X 1 hr => temper at 350 X 2hr X 2.

Thanks for the info. It would be nice to speed it up a bit. From start to finish it takes 13 hours as is.

 

[Willie71]

Thanks for the follow up info.
I'm not sure you want to/need to put the blades in the cold kiln. At least in my kiln that'd be a long time.
Also, I don't think you don't need to do the 1450 step. IIRC that's more for larger, thicker parts.
I've been getting similar final RC with an aus temp similar to yours X 30 min and then plate quench => LN X 1 hr => temper at 350 X 2hr X 2.

you don’t need the pre heat. It is needed for large or complex parts so the steel structures can equalize. Not needed for knives.