My second knife is almost ready for hardening and today I cut my second rasp to be used for knife #3 and #4. 

I only have a two brick furnace for heat treatment. And when fired up I want to aneal the rasps after hardening knife #2. My question is, can I aneal both rasp parts at once? There won't be much space left inside but I think both parts will fit in. 

pack them in there, you will be fine

 

I did it, Steve. I let them cool in the furnace over night and check the result tomorrow. Hardening if knife #2 also went well, tempering will be done tomorrow. This time it won't take a year to finish  I really want to test the much thinner blade compared to knife #1.

it may be too late to bother tempering your blade, it may have cracks already, you need to temper asap after hardening,

Hi Steve,

can you please explain why to do tempering asap after hardening? If you already did, please tell me where to read up.

The knife is the oven right now and there were no visible cracks.  

The blade will have a great amount of stress in it after hardening.  Something as innocuous as setting it down on a cold table top could cause it to fracture.  It is best practice to temper ASAP to relieve those stresses before they relieve it on their own.

I'll do it asap after hardening for the upcoming knifes.

If you're planning to temper in the oven, get it preheated before you start hardening. I'd recommend a good oven thermometer to confirm the temperature and some firebricks or a pizza stone to even out the temperature swings. 

its in the heat treating sticky posts

Thanks guys I'll keep that in mind.

Yesterday I found some time to continue working on knife #2 and #3. Every minute working with my 2x72 is good invested time and a gain of experience. 

But my wishlist is getting longer and longer  a small wheel attachment, a MDF wheel and polishing wheel for my bench grinder and a heat treat oven, some more belts... 

And best of all, it's a very satisfying time.

Knife #2 is ready to use. Compared to #1 it's shorter (because it was the left over part of the rasp of #1), spine thickness is reduced from 4.5 mm / 0.177'' to 1mm / 0.04'', also weight is 50% less. Just did a quick and dirty sharpening on the 2x72 to get it ready to try the thinner blade width. And it cut much easier then #1. I'll sharpen it on my sharpening stones as soon as I find time and patience for it.

Why only one pin in the handle?! Because I forgot to drill the holes before hardening  I did not invest any time in hand sanding because it's a try-out/practice knife. 

#3 will be longer then #1 but as thin as #2. I expect that to become my daily kitchen knife. So I'll go for a decent finish on the next one. 

Since my last post I had to make my own experience to learn for further projects.

I used a big glas jar (for pickling veggies) as a quenching container. It could be sealed and was the right size. For the first knifes I heated the oil with a glowing scrap piece of 1/2'' steel. Then I've read that this method is not ideal for the oil itself. So I tried to put the glas jar behind my two brick furnace while heating up... Dump idea... It took about 5 minutes to pop the glas and 1/2 gal oil was spill on the pavement. What a mess. Instead of knife hardening I spend the time cleaning.

I then found an old aluminium milk can a my grandma's basement and gave it a try. It worked but the bottom of the can is not flat anymore so there is also a high potential of making another mess. So I found an sous vide cooker for 10$ and this will be my new quenching tank. Temperature control included and a solid stand.

Additionaly I made a good deal on a new small wheel attachment for 45$ which others sell for +100$. 

Knife #3 was looking great but again I did grind to thin and this time the blade warped so much that I didn't tried to straighten it.

I hung it on the wall behind my grinder to remind me to keep the edge thicker next times.

Now my last rasp is cut in pieces but I also ordered some 1.2604 (3,2x60x675mm / 0.125x2.36x26.6''). This steel was recommended by a German knife maker and he told me that it can be hardened with simple equipment and that it will have good performance in a larger range of hardening temperatures. Just a good material to learn and continue knife making.

Just as soon as I read "big glass jar" I had a feeling that things were not going to go well.  Live and learn.  Sometimes we can be fortunate enough to learn from the mistakes of others that to have to make them ourselves.

GLASS JAR!?!? I've made mistakes of that scale before just not that one. I'm very happy you didn't burn yourself out. 

If the al milk can doesn't leak you can pop the bottom back in easily enough. Turn it upside down, lay a piece of leather or doubled blanked on the base and using something reasonably heavy but not hard or sharp give it a solid blow, NOT HARD or fast! you want a dead blow. A rubber mallet might work but you do NOT want to try tapping it back, aluminum work hardens ad becomes brittle pretty quickly. One or two good blows and it'll go right back, play pitty pat and it will crack and become a planter.

If that works and holds water, (YES test it) lay a piece or two of sheet plastic or rubber, maybe carpet pile down on the bottom to protect it from dropped sharp pointies. 

I have a piece of expanded steel wit a couple long hanger hook / lift handles in my quench tank. Do NOT use steel or copper alloy in an aluminum container electrolysis could make the tank a strainer instead of container. Just a little condensation moisture could provide the electrolyte and to WILL settle to the bottom. That last precaution may be unnecessary but better safe than sorry. Hmmm?

Frosty The Lucky.

Glass or Plastic are both NOT TO BE USED!  Especially with a flammable oil!  Know a smith with decades of experience who burned his shop down using a plastic bucket to quench blades in.  Bad burn too.

Yes, I've learned my lesson. I do all hardening outside because I don't want to use my little gas furnace inside a wooden shed. Another reason why I want to build a heat treat oven. In my opinion it's safer to operate and more precise than a gas furnace. And I like to design and build stuff 

On 1/16/2023 at 9:36 PM, Frosty said:

Do NOT use steel or copper alloy in an aluminum container electrolysis could make the tank a strainer instead of container.

How electrolysis could happen during quenching? 

My new quenching tank is basically a low temp fryer. The heating element is placed below the container that holds the water/oil. And because I won't do hardening regularly I will strain the oil back to sealed containers after it's cooled down.

That's a Murphy educated speculation on my part. Condensation in oil will settle to the bottom and if there are dissimilar metals in contact with water beads, electrolysis COULD occur. . . Being in an oil bath should keep moisture from direct contact but two things rubbing together or in hard contact might rub enough oil off for moisture to make the circuit. 

Frosty The Lucky.