# First time heat treating approach



## mikaelsan (Nov 22, 2018)

Bare with me if this is kind of nooby or cringy to some, but I really wanted to try the process and see what i could achieve on my own if I just tried.

Hello, kkf, so I decided to try and make a knife, the but a steel bar, cut and grind to shape. I'm working on a dirt cheap belt grinder, with stock that is still a tad too thick, so I got some days to plan for what I intend to do for the heat treat. I know I need to find a magnet, preferably a telescope one, to get an idea of the temperature, and I got a container for the oil that will fit the blade.

I'm working with O2, I'm guessing that's important to know.

I know there are a few skilled craftsmen in here with good controlled equipment for this sort of thing, but how would you go about heat treating it if you had to do so on a budget? 

My first thought was to buy some coal, don't remember the word for it, not the one we normally cook with but the more "woody" kind, and make a fire in the grill. The thing that concerns me about this is placing the steel, moving it around and such, it's a normal size Weber, with the blade being about 30 cm including the gang, it seems impractical.

Second thought was to buy a gas burner and building a 8-10 brick forge, but I don't know how well this works with a cheap gas burner, I would have to get one for the purpose too, I need to get out borrow one for the burn in of the handle anyway. I'm guessing this would be the easiest approach of I am to worry about normalising as well ? 

I have also seen somebody simply use a grill starter chimney, I can't tell if this seems like the easiest or hardest/messiest approach.

Also how far do you grind before heat treating? Should I just leave a mm before create an edge or what do you do?

Any other advice is welcome, im not too concerned about the grinding, sharpening is the main hobby and I have done some tedious thinning Jobs in the past, and I expect what I have to do after the heat treat here is done might be a little worse, and that's fine


----------



## RDalman (Nov 23, 2018)

Yup leave a mm. Get a steel tube to put in the forge and heat the blade in, that will help alot in evening out the heat, but you will still need to move around. Any heat will do, whichever you can make... gauge with the magnet. that is about 770, aim for 820-850c, so a bit more. Quench in canola oil heated to 50-80c. post quench check with a file, it should not be able to cut, steel should be like glass after a succesful quench. you might have a tiny bit of decarb to get through but not deep. if unsuccesful quench, just try again. maybe practice on a few offcuts, when you have succesful quench if offcuts, break them and check grain so you did'nt overheat badly. temper.. have fun!


----------



## milkbaby (Nov 23, 2018)

You will need forced air blower for a charcoal grill to get hot enough, simply lighting a fire is unlikely to get hot enough. If you look up YouTube videos, you can see it can be cheaply done by rigging up a hair dryer to some tubing.

I use a two brick forge for heat treating. Smaller knives you can do okay with a plumbers torch like a Bernzomatic with small propane canister, but the size you're talking about needs a forge chamber probably larger than what that torch can heat. I use a venturi burner from Atlas Forge and Tools company connected to a propane tank used for barbeque grilling. Look up two brick forge on bladeforums shop talk makers subforum.

Edited to add: the firebrick needs to be soft refractory firebrick like what is used in the interior of a pottery kiln. Hard firebrick is just a thermal sink, won't work for a simple two brick forge.

As Robin said, you'll need to move the blade around to keep parts from overheating (the tip is smaller and will heat faster than the heel). On my two brick, the chamber opens all the way through front to back so the tip can pass through the opening in the back to cool and not get overheated. Use similar principle if using charcoal, move it around in the baffle/tube so the knife heats evenly.

Since you need to heat a little bit higher than nonmagnetic, common advice is heat to nonmagnetic, note the color, and then heat to just a half shade higher. It's easiest to judge colors in a darkened area, so I always do my HT at night. Do not judge colors versus any type of chart in a book or online, that's totally useless, always use the magnet.

For a knife that large you probably need a least 2 gallons or 8 liters of canola oil for quenching. Put it straight in, and if you do any agitation to help cooling, only go straight up and down, edge to spine or tip to heel. Avoid side to side agitation, to lessen chances of warping.

As Robin said, you will likely generate a zone of decarb (decarburized material at surface that has lost carbon) which will be soft. If your file bites at first, run it over again a few times to file through the decarb and hit the hopefully hardened steel. Keep an offcut of unhardened steel to compare how the file feels, on hardened steel it will feel and sound different.

Good luck and have fun!


----------



## inferno (Nov 24, 2018)

I'm thinking about getting a steel tube, weld it to a stand then weld in a thin long tube where i can put in a thermocouple so it ends up in the middle center kinda. then hook up a thermometer (like a fluke/amprobe), and then simply heat the big tube up with propane or acetylene since this is what we have at work. I have access to big propane burners so heat capacity should be no problem, i think they output 130kw heat or similar. This should be very easy to build, and quite easy to control. and cheap.


----------



## mikaelsan (Nov 24, 2018)

thanks both for the advice, its good stuff. I have done some research ofcourse but i was not aware of the risk of a soft layer on top of the hardend steel. Looking at what i need to put together a small makeshift forge i ended up buying a bag of charcoal, as this will likely be the only knife i make, if i dont make something of the other half of the metal i got.
Hopefully i can get through the pre heat treat grinding soon, so i can get to the heat treat =)


----------



## mikaelsan (Nov 28, 2018)

So I just pulled it out of the oil, fun times but harder then I thought to get a good temperature, I think it's hardned. I did go non magnetic, and I think half a shade brighter

but I don't feel 100 confident. I tried attacking it with the find afterwards and I think there is a difference, but to my untrained eye the difference is not night and day. But I decided to start tempering it.

Do you think I could just create a quick fat af Edge im still in doubt after tempering? And if so would it still be ready to put back in the fire if I failed?


----------



## inferno (Nov 28, 2018)

bodycote in sweden does alot of ht-ing. maybe you could send it there for testing.


----------



## mikaelsan (Nov 28, 2018)

That would have been a real nice gesture of him, and I guess it's not that far away being from Denmark, but if I'm that much in doubt, I should maybe have out sourced the HT in the first place

Anyway, I transferred the principle of the file to my binsui, which is a stone which really can behave differently on different steels and hardnesses. I felt a definite difference from the tang which was not heated as much as the edge, it felt more gritty and grabby on the tang, I take that as a good sign so i can now rest happily


----------



## milkbaby (Nov 28, 2018)

Yes, that sounds good, the file/stone/abrasive should be grabby on soft steel but skate more on hardened steel. You won't necessarily know how hard but it's at least a good start. Once you sharpen, the behavior of the edge can give you more info.

Also, this thread is useless without pics!


----------



## mikaelsan (Nov 29, 2018)

right i guess that's only fair when you come and ask for advice on the project =)
So there is a lot of things that are not perfect and did not turn out exactly how i envisioned it, its sort of a learning - roll with the punches kind of project, but overall i am quite happy. Two things in particular i'm happy with is how evenly the blade was heated before the quench and the profile. Which i quickly gave up on inventing myself, instead i drew an outline of the k-sab, removed some belly towards the tip, and added a little continues curve towards the heel, i also raised the heel when drawing the spine, because the k-sab 20cm is 40 mm at the heel, something i have never come to terms with , this is about 50mm

Also the handle is not finished, its just to show the wood, its way too thick right now, the blade ended up about 154 grams, and will likely be like 10 grams? lighter when i'm done grinding it. i did not mean to remove that much metal from the stock tbh, but the speed of the new power tool i pulled out surprised me

and yes that's a deep fryer in the back, was the best container i could find for the blade 
one flaw my set up had was that the back of the little makeshift forge was open, and hot coal was spilling onto the ground underneath the grill, when i moved the blade around. I am happy i did not attempt this a few months back when the heat was on, with all the wild fires around the world then  that could have been quite a lesson learned back then


----------



## RDalman (Nov 29, 2018)

The way I use file is to really cut with some force. That way (with the file I use for it) I can definately tell if I'm above 65 as quenched. I have confirmed this on blades I sent for hardness testing, I will catch a 64 hrc blade.


----------



## mikaelsan (Nov 29, 2018)

alright that's comforting actually, i think, it is specified to ht to 65 after quench as you imply. My theory is that i hit somewhere slightly below that, hopefully not too far below, there were no flames in the quench, no warping and i decided not to go with too high a temperature for the tempering. apart from it being not completely optimal there should be no real issue with having hit a slightly lower hrc with the quench should there?


----------



## RDalman (Nov 29, 2018)

mikaelsan said:


> alright that's comforting actually, i think, it is specified to ht to 65 after quench as you imply. My theory is that i hit somewhere slightly below that, hopefully not too far below, there were no flames in the quench, no warping and i decided not to go with too high a temperature for the tempering. apart from it being not completely optimal there should be no real issue with having hit a slightly lower hrc with the quench should there?


Yea, what matters at the end is if the knife works as you like. If you next time felt like it should have been better heat treated, trial-quench a few offcut pieces and see if you can dial in your temp/color to which really gets glass hard, also break the samples to have a look at grain. I would guess your austenitizing temp might have been slightly low. Worth to keep in mind also is importance of agitating/keep moving with oil quench.


----------



## milkbaby (Nov 29, 2018)

Nice job! I like it a lot... :thumbsup:


----------



## mikaelsan (Nov 29, 2018)

Thanks!

Two further questions, if I did manage to get it propper hard and I realise the knife is too hard for my liking can I simply put it back in the oven at a higher temperature of will the same temperature soften it further?

And how far would it be safe to thin on the belt grinder? Can you thin all the way to the apex? It's not a crazy aggressive machine, but it's not exactly slow running either I am at between .3 and .5 mm at the apex so far


----------



## milkbaby (Nov 29, 2018)

Robin will chime in with more experience, but I like to post. 

Some people like to "walk their temper up". That means choosing a temperature a little lower than what they are aiming for and then testing. When you don't have the greatest temperature control in HT, this allows wiggle room for less than optimal hardening. If you only got 95% expected hardening, then tempering at the temperature you wanted too initially will lead to lower hardness than you want in the finished blade. Starting lower and walking up the temperature lets you adapt for that possiblity.

Edited to add: Yes, if too hard, then on the next round of tempering increase the temperature.

Everybody is different on grinding the final bevel. Some people like to leave some meat off the grinder then move to stones or sanding with a hard backer for most even bevel. If you go all the way to zero on the grinder, then you'll lose height off the blade when you try to even out your bevels with stone/hand sanding. The benefit of working by hand is also being slow which makes for less possiblity of quick mistake. I personally like to go to zero on the grinder for general purpose chefs/gyuto because I don't feel 100% even bevel grind is a necessity nor even the best geometry depending on how the knife is used.


----------



## mikaelsan (Nov 29, 2018)

thanks, thats exactly what i hoped you would say, i would love to just finish the grinding on the belt grinder, i will just go slow then, dunk in water excessively and check for my progress, having tried putting it on my shapton pro 120, im happy i dont have to change to handsharpening yet.
and i feel the same way about even grinding, i am much more about cutting performance then looks these days, and the grinder will do a nice job of keeping things looking somewhat nice and uniform. And as it gives a little bit of slack it will also give me a little more convexity then i would have done by hand which is nice to me


----------



## samuraistuart (Nov 30, 2018)

I'm not sure how much work you do, but you might look into buying (or building as in my case) a mister system for your post heat treat wet grinding. I'm not sure where you live, but there is a company called Arizona Mister (or Phoenix Misters???). They make little brass nozzles that shoot a mist of water. You can build a system using PVC and those misters. I have 2 of them spraying on the belt/blade while grinding post heat treat, and they do an "excellent" job of mitigating heat. I will go to almost "zero" on the grinder, but I don't go past 220 grit on the grinder. So when I switch to hand sanding, I am at 220 grit, and will take the edge to "zero" by hand, lubricated as well. Depending on how tall the blade is, a perfect full flat grind on a kitchen knife is not always desirable, like milkbaby mentioned. A slight convexity an inch or so above the edge helps to reduce food sticking! (As far as food sticking goes...if you haven't already, do a little research on the "S" grind"). It is convex near the edge, and hollow as you move up toward the spine.


----------



## mikaelsan (Nov 30, 2018)

Well had I read your post when you had posted it I might had stopped where I was [emoji4]
I blew out a few tiny spots, when I hit zero. Grinded a new to to get rid og that part but the other is by the heel.
It's funny you mention the s grind, that's exactly what I attempted the hollow ended up a little less pronounced and further up the blade then I ment for it, but hey it's my first blade I'm just happy is present at all. 
As for the grinding I'm switching over to sandpapir freehand, and I'm going to try and minimise the damage, finish the thinning and call it a day


----------



## mikaelsan (Dec 3, 2018)

handle is still wip, but its burned in and sharpned


----------

