View Full Version : How I broke my first handmade knife!

Alex Cole
01-20-2003, 09:09 AM
Sorry I don't have any pictures yet of this project but I will be taking some of the results soon!

Well it all started off good. I got my new equipment in and setup in my shop. I have a grizzly 2x72" belt grinder with a 8" and a 10" contact wheel. I have for heat treat a Sugar Creek LKK manual oven.

After getting everything up and making sure all was working correctly I chopped off a 8" section of 1-1/2"x1/8" O-1 steel. I annealed the steel by heating in the ht oven to a temp of 1600 and then buried the piece in wood ashes and let cool slowly for a period of 24hrs. I then drew the outline of the blade that I wanted to end up with and started grinding. I started with a 36 grit belt and profiled the blade and tang of the knife. I then started on the hollow grind. I was using the 8" contact wheel for this knife. Grinding the hollow grind proved a challenge as I figured it would. The problem I was having was that I could do one side much better than the other. I expected this and I know the only thing to make it better is practice. So I worked my way through the belts using 36, 120, 220, 400. After I finished the hollow grind I then started drilling my tang holes and some balancing holes in the tang of the knife. When the drilling was complete it was time to think about heat treat.

I didn't want to use old motor oil cause I figured I would get burnt deposits on the steel that would make for a nasty scale, so I ended up using a mixture of new motor oil and new hydrolic fluid. This seemed to work well and after heating up the steel to temp and letting it sit for about 2min I decided it was time to quench. When I quenched the blade I just droped it into the oil and let it sit there until I was shure that it had cooled to the point of being able to handle the blade without getting burnt. When I took the blade out of the oil I was suprized to see that there was not much in the way of scale on the blade. I wanted to see if the blade had taken the heat treat so I wiped it down with a shop rag and grabbed a file to see if it would bite in. Well the files seemed to half skate across and half bite into the spine of the blade. ???.........I questioned if the blade had been proporly heat treated sence this was my first one and all. So I decided to start cleaning off the scale before temper(this was my mistake, I knew better). I started grinding and didnt really notice the sparks being much different than they were before but didn't pay much mind to it cause I was pretty much positive that the blade would need re-heat treated anyway. I was done cleaning off the scale and did the dumbest thing ever. Before a temper I decided to see(cause I was shure it wasn't hard) if I could bend the blade so in my hand I put one index finger at the tip and the other at the tip of the tang and put both thumbs in the middle of the blade. Then I pushed.................SNAP! I broke it clean in two. In my hands no doubt. Now I was the one that was shure it han't taken the heat treat and breaking it in half was defenatly a result that never crossed my mind, but that is what happened. I spent the next few hours with a look of disbelief on my face and I am just now starting to come to terms with the fact that I just broke my first handmade knife in two with my fingers.

Well I now will say the heck with the scale and right after a heat treat the blade will be washed and then directly to a temper. I have defenatly learned from this one. LOL All I can do is laugh about it now.

Don Cowles
01-20-2003, 09:57 AM
Alex, if you are starting with precision ground O-1, you can skip the annealing step- is already annealed.

Jamey Saunders
01-20-2003, 09:58 AM

I remember when I first started making knives. I knew nothing about tempering steel after hardening. All I had to go by was what it said in the TKS catalog for 440c: "Harden at 1800 degrees and quench." So that's what I did. I had the knife in the vise and was hand sanding it with some sanding boards I had made. I picked up the board to check the finish, and as I lifted up the board, the blade snapped.

You could have knocked me over with a feather. I was releasing the pressure on the blade, and it snapped.

I learned about tempering after breaking two more blades. It is a very important process, and I've never neglected it again.

Ray Rogers
01-20-2003, 10:36 AM
Interesting story Alex. I suppose by now you realize that in fact you had succeeded quite well in hardening your blade.

The next step in your learning curve, after you get the tempering done, is to try once again to break your blades. It's always a good idea to make some blades for destruction any time you are working out a new heat treat process. It really feels great when you get your first blade that stands up to all the horrible things you can think of to do to it. Most blades can be broken if you put a 3 ft pipe on it an just crank it over but that's not what I'm talking about.

I mean cut, chop, and pry with it. Throw it at trees. Dig in the dirt and rocks. Stick it in stumps and twist it out. Split firewood with it by hammering it through the log (use a wood mallet or small log).

Doing these things will let you know exactly how strong your blades will be. The tip is always the most likely to break and this will help you design a tip suitable to the purpose of the knife.

I intentionally have not mentioned edge holding ability. That has to be balanced with the toughness - it's always a compromise whenever the whole blade has the same hardness. Fortunately, O1 can be edge quenched giving a hard edge and a soft back and a whole lot more opportunity for testing ....

mike koller
01-20-2003, 10:53 AM
There is a Tutorial in the How To section written by Terry Primos called "Scale Prevention During Heat Treating". May be something of interest to you.

Alex Cole
01-20-2003, 11:25 AM
I do have a question though. The blade did snap pretty easy, I figure cause of this that the heat treat did work. If this is so how come my files seemed to still dig in? I realize that if they are harder then they will but I would think that the metal would have to have been pretty hard for how easy it broke. Next question is when I annealed the steel I took it to 1600-1650 some where in there and let it soak for about 1 hr. Then I took it out and put it in a pile of ashes from my wood burning stove. The stove was not hot and there was about 4 inches of ash below and 6inches of ash above the blade. I let it set there overnight before I started to work on the steel. Is it possible that I messed up the steel when annealing and burnt out the carbon or did somthing like turn the austenite into perlite when I hardened the blade?? Is there any way I can look at the break in the steel to evaluate wether the ht was good or not?

Thanks for any input

mike koller
01-20-2003, 02:26 PM

Dont know if this will answer any of your questions,but it should help you with getting consistant results.

Find a thermometer to double check your oven...or use a magnetic to check for non-magnetic of the steel.

Pre warm the ashes, and make sure they are dry....0-1 likes to be cooled real slow.

Make sure you have enough quenching medium. I think a gallon should be adequate for one blade at a time. Put the blade in as you would slice a piece of cake or pie and hold for a minute then drop. [U]Do not stir[U] with the blade and be prepared for some flames.

Temper the blade twice. If the edge doesn't pass the brass road test because it is too hard...raise temp 25* and temper again. Continue to raise temp by 25* until it is like you like it.

As far as reading what is going on in the blade with the cyrstal structure. It takes a trained eye and magnify glass, but if you have a university or college nearby by see if the have a way of examinining it for you. The are organizations and individuals out there that offer this service,but I don't know there names.

Hope this isn't just a rant and that you find some useful information here.

Good luck.