Recommendation? Hello and Holy Heat Treat Issues Bat man!

2fishminimum

2fishminimum

Joined
Jun 19, 2018
Messages
25
Hi Everybody!
I am somewhat new to knife making and very new to posting on the forum..
I am putting myself out there on this forum in hopes learning, and hopefully not getting smacked too hard by the experts, :) so please critique me, but please be nice. (in my experience people tend to be harsh on the internet because of anonymity.)

So a brief history of my experience. I have been putting my self through youtube university, and studying lots of posts on the ol interwebs.. Got into this about 2 years ago. Made a couple knives with just files and sand paper, acquired some tools, ruined some knives, built a forge, kept at it, had some successful knives too, got some more tools, pissed off the wife, cut my self a few times:mad:, ruined some more knives, .. you get the idea.

so I made these three recently.
G8askCsl.jpg

zQUS24El.jpg

IngRRadl.jpg

IngRRad.jpg

I really wanted to get into damascus so I bought some and jumped right in.. but i also have the same issues with 1084.

heres what i need help with..

The transition from scales to blade.. my first few knives I was trying to shape the scales after attaching them to the blade.. a greenhorn mistake for sure. as I progressed I figured out that i need to finish the scales as much as possible before attaching.. the Damascus Chefs knife is a good example of my earlier attempts of shaping after attaching.. you can see the transition there sucks.. the smaller knife I took the handle scales to a much more complete state before attaching. but my transition i think could still be better.. any suggestions here would be much appreciated.

saving the best for last.
my concern is that the edge does not seem to last very long.. I sharpen till it shaves my arm hair.. then for example if I cut up a few veggies, and then slice up some meat say for a soup or a sauce for 4 people, the edge will have lost its ability to shave. it will still be sharp enough to slice a tomato with out squashing it mind you.. how long should the edge last?

the steel i got from a well reputed dealers.. as i said the santuko is 1084, and the damascus blades are 5160, 52100, 15n20, and 203E
I suspect my HT method.. and indeed if it is my method, is there a way to fix these knives? because i really really like them..

Prior to HT i take the blade to a 400 grit and get it really close to final bevels and shape.
I heat til non magnetic, then a minute more.. then I quench in mix of coconut and peanut oil (left over from thanksgiving last year). then i file check.. both of these knives the file skated easily across the blades.. i temper for two cycles of one hour in a 375 degree oven on bake (lower element) with the blades on the 2nd to top rack.. the oven back wall at that height measures 360 when i shoot it with my laser thermo meter.. after that i finish the blade being very careful to not over heat, and attach my handles and final sanding and buffing, mostly by hand..

If I had to guess I would say I need a longer soak time in the forge.. maybe im not quite reaching 1525 F? should I change my quenchant? or is my edge performance close to what it should be with this type of steel? should i rethink my temper method? I annealed the steel prior to grinding, but i didnt normalize be for HT.. was that a contributing factor?

Thanks in advance for any helpful info you care to throw my way.
 
Last edited:
How does a known knife behave when sharpened in the same manner?
 
Larrin,
While I have not done a side by side comparison with other knives in my kitchen.. my "muscle memory" of knives that ive used for years tells me their edges last longer..
Ill try a side by side comparison with knives that have similar angles on the edges..
 
I'm new to this myself, so my guess isn't worth the words it's wrote with, but it sounds like you might be dealing with decarb. It should hold up better than that.

You said that you take your blade pretty close to to final dimension before heat treating so you may be leaving a thin layer of decarb on the edge of your knife. If this is the case, you just need to take little off the edge until you get to good steel.

The 1084 should work pretty well with what your doing, I can't speak to the rest, other than 52100 is a pitta to HT without pretty nice equipment, I learned that the hard way. I do normalize my 1084, it's an eyeball method, but the blades end up though, and hold an edge pretty well. I temper at at 400 for two hours twice. I'm quenching in 120-130 degree canola oil.

Other than that, one full minute past non-magnetic in my forge would be to hot. I plunge the blade in and out of the forge to keep the blade temp even, making sure that when I take the blade out I let the tip come all the way back to the same color as the rest of the blade. Basically letting the the hot spots soak into the the rest of the blade. Once it goes non-magnetic, I'm just looking to even out the color, the shadows disappear pretty fast in my forge.

Nice knives!!
 
Last edited:
One other thought, I temper in my oven as well but I keep my blades between two fire bricks, if I don't, they overheat. Radiant heat can be a problem, I use the fire brick to shield the blade from the radiant heat from the element. Contaminates can mess with temper colors but if your blade is really clean, you shouldn't see anything close to blue. 375-400 should just give you a nice straw color as I'm sure you know.
I also preheat for 30 minutes instead of the 6 that the oven does, it keeps the element from kicking on as often because everything in the oven is up to temp. Are you seeing any blue in your temper colors?
 
OK, a couple things:
1) the shape of the handles is too thin. The first photo shows a deep finger groove right up against a pin. This is a broken blade waiting to happen. Make te hanlde larger for both grip and strength. Don't place pins near finger grooves. ( finger grooves are rarely used on kitchen knives, anyway).

2) the edge problem is probably a combination of too soft and too fine an edge.
Hardness - The next HT, try to get it a full shade brghter red before the quench. Your quenchant is also not the best ( and the quantty may not be enough). Try a gallon or two of canola.
Sharpness - Sharpen at about 25 to 30 degrees included (12.5 to 15DPS.
 
nmbarta said:
You said that you take your blade pretty close to to final dimension before heat treating so you may be leaving a thin layer of decarb on the edge of your knife. If this is the case, you just need to take little off the edge until you get to good steel.
Click to expand...

I believe this is a phenomenon sometimes seen in the less well made Japanese kitchen knives. The edge needs to be ground down past the decarb layer which is soft. A user sometimes will need to sharpen a few times before getting to the good steel, but it's better that the knifemaker achieve that in my opinion.

I use a two brick forge with passthru in the back so i can pump the blade to try and get even heating without overheating the thin parts like the tip and edge. 1084 is simple, you just need to get the carbon in solution and don't need a long soak. If using a forge HT, the balancing act is getting everything into solution versus overheating which grows the grain. Large grain will be detrimental to edge stability.

I only have a one speed 1x30, so for handles I draw the general shape on the scales and rough grind on the 1x30 only. Then I use hand files for final shaping. It's slower, but slower is better for me because less mistakes.
 
Have you tried the blades in something other than vegetables or fruit? I ask because I have noticed that it is possible when cutting acidic fruits to take the bite of the edge with carbon steel knives. They are great on veggies but cut a pile of lemons and limes and it will no longer shave. Try some known materials with another knife that you have used in the past and see how it works.
 
nmbarta said:
One other thought, I temper in my oven as well but I keep my blades between two fire bricks, if I don't, they overheat. Radiant heat can be a problem, I use the fire brick to shield the blade from the radiant heat from the element. Contaminates can mess with temper colors but if your blade is really clean, you shouldn't see anything close to blue. 375-400 should just give you a nice straw color as I'm sure you know.
I also preheat for 30 minutes instead of the 6 that the oven does, it keeps the element from kicking on as often because everything in the oven is up to temp. Are you seeing any blue in your temper colors?
Click to expand...
Hey thanks for the responses.. No i dont see any blue in the temper.. i like the fire brick idea.. i have some ceramic plates 3/4" thick that i can sandwich them in.. also from your previous post about soak time in the forge.. my forge takes a good 3 or 4 minutes to heat the blade up to temp.. im still concerned that its not getting hot enough.. the next one I do, ill film it and post the vid for reference.. as far as decarb goes.. ill also try to leave them a bit thicker.. currently i leave the edge about as thick as a dime.. is that too thin?
 
Stacy E. Apelt - Bladesmith said:
OK, a couple things:
1) the shape of the handles is too thin. The first photo shows a deep finger groove right up against a pin. This is a broken blade waiting to happen. Make te hanlde larger for both grip and strength. Don't place pins near finger grooves. ( finger grooves are rarely used on kitchen knives, anyway).

2) the edge problem is probably a combination of too soft and too fine an edge.
Hardness - The next HT, try to get it a full shade brghter red before the quench. Your quenchant is also not the best ( and the quantty may not be enough). Try a gallon or two of canola.
Sharpness - Sharpen at about 25 to 30 degrees included (12.5 to 15DPS.
Click to expand...
Stacey thanks so much for the reply. I really appreciate the advice about the pins.. i felt like they were too big, and too close to the edge of the tang.. that one will mostly be used in my kitchen as a paring knife.

im definitely going to try your advice about sharpening and heat treating..
 
milkbaby said:
I believe this is a phenomenon sometimes seen in the less well made Japanese kitchen knives. The edge needs to be ground down past the decarb layer which is soft. A user sometimes will need to sharpen a few times before getting to the good steel, but it's better that the knifemaker achieve that in my opinion.


Im intrigued by this decarb layer thing.. so does it form because the edge of the blade gets too hot in the forge?

i also try to hand sand as much as possible.. less mistakes and smaller ones at that.
Click to expand...
 
skillgannon said:
Have you tried the blades in something other than vegetables or fruit? I ask because I have noticed that it is possible when cutting acidic fruits to take the bite of the edge with carbon steel knives. They are great on veggies but cut a pile of lemons and limes and it will no longer shave. Try some known materials with another knife that you have used in the past and see how it works.
Click to expand...
oh yea, meats and the like.. the other day, I smoked a few racks of St.Louis style ribs :p and when i was cutting them after smoking, I sliced thru a few of the ribs with no trouble.. the edge showed no deflection, or roll overs.. but of course its ability to shave was long gone.. but i think in that case it made sense..

thanks so for your response.
 
2fishminimum said:
Im intrigued by this decarb layer thing.. so does it form because the edge of the blade gets too hot in the forge?
Click to expand...

Decarb can form from heating in an oxidizing environment, same as scale can form. You are probably familiar with scale which is the colored usually blackish oxidized iron left on the surface from heating steel in your forge.

Carbon oxidizes to but to carbon dioxide and carbon monoxide both of which are gases so the only thing left is the decarb zone where the carbon migrated out of. The oxidation is at the surface where oxygen is present which is why scale and decarb occur there. When steel is hot, carbon can move in it faster, especially fast in austenite phase, so as it oxidizes at the surface, more will diffuse towards the surface where it gets oxidized as well. The longer you heat it, the greater the depth of decarb. This is why stainless steel which need a long soak like 30 minutes can't be HT without protection against an oxidizing atmosphere; you'd get a ton of scale and lose the carbon necessary for hard steel.

The edge if ground thin prior to HT can be decarb simply because of its size and shape. Just as an example, if the depth of decarb is 0.005" and your edge is 0.010" then it could be all decarb at the edge.

I'm not sure this is your problem though. If you sharpen enough times, you should eventually grind away all the decarb and have good steel at the edge if it hardened properly.
 
Before I worry too much about the edge life, I would try to figure out how it lasts on veggies only over say 3-4 months of daily use without resharpening, only steeling or stropping at your pref. I would go with the steel. If you can slice cut peppers and tomatoes cleanly after 4 or 6mo, the HT is perfect for a veggie slicer. If the thing is dull at 2 mo or so and you haven't cut any bone or similar with it, your HT or geometry is a problem.
 
You must log in or register to reply here.
Back
Top