Two questions: optimum steel, and leaf spring oil harden?

Chujybear

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Hello.
I'm sure my first question has been covered adnausium, but I haven't found the particular answer in the archives. But please forgive me.

1• I would like to solicit opinions on the best carbon steel for a knife ( in this case I would be making a kitchen knife) that results in a very nice useable knife, but doesn't suffer any in the carveability department?

2• (unrelated to the first question). Is leaf spring steel (from a truck) a standard quality/alloy of steel? I have been making wood tools out of leaf spring forever, and always quenched in oil to harden.. But as I was looking for the right piece of metal for kitchen knife I discovered that some steels were oil hardening , and others were water hardening. Which lead me to wondering, and the true question I have in this thread- is leaf spring steel going to be oil hardening? Or could it be water hardening?
Thank you
Gwaai
 

tim halloran

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Chujybear: Most if not all leaf spring steel is usually 5160H 0r 5160HR depending on alloy content. It is quenchable in oil or a quench ant made of a mixture of Bees wax, used ATF, And bacon grease. This GOO works really well, and if you edge quench, it provides a hard cutting edge with a flexible back-spine. You heat to non magnetic, approximately 1560 degrees, then quench. As quenched hardness is around 63 on the Rockwell C scale. It can then be drawn back, preferably in an atmosphere controlled oven, or it can be done with a torch.
 

highveldt

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As to the truck spring steel. It is unlikely that any spring steel used from a truck is going to be water hardening. Water is too harsh a cooling agent for most spring steel. Even oil if its temperature is too low is too harsh. When I use spring steel I pre-heat the oil to about 125 degrees F.

Quench a piece of oil hardening steel in water and when it is cool, polish it and lay it aside. In an hour or so examine it and you will see cracks on the surface of the steel.

Better steel for wood tools IMO, is to be made from truck axle shafts. Years ago I had a blacksmith shop and I used truck axles to make hammer heads and other tools that needed to be tough. I made wood workers froes from truck axles that worked very well, also made chisels and so forth. The truck axles that I used were form 18 wheeler trucks and I used my power hammer to reduce their size. Unless you have a blacksmith friend you will want to start with smaller diameter axles from a pick-up truck than the 2-3 inch diameter ones I used.

Regards;
Steve
 

Glenn

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There are high quality stainless steels made for blade steel. I think a carbon steel, even good tool steel, is going to rust eventually. With the amount of time it takes to make a quality knife, starting with proper material makes sense. These steels can be engraved easily before heat treating.
 

Red Green

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Even stainless steel oxidizes and corrodes in time, it is care that makes tools last the test of time.

Bob
 
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Chujy,

5160 is a pretty forgiving steel. Definitely an oil quench steel. Before you spend money buying an expensive knife steel try the 5160. You will likely want to make another knife after you make this one.

Yes, it will rust. Just clean it after use and oil with vegetable oil when you put it back in the drawer. 5160 will sharpen well and will hold an edge better than some of the cheaper stainless steels.

It is well suited for beginning knife makers.

There are good reasons that most professional knife makers choose other steels. Like engravers they have a customer that they are making promises to. They have to guaruntee a certain level of performance from the knives they make.

The heat treat instructions above are pretty good.

I would add a few suggestions.

A little trick on heat treating high carbon steel is to heat it below what you think the hardening temperature is. Make a note of the color and remember it. That color is your reference hardening temperature.

Quench it edge first, straight down into new vegetable oil. Don't use used motor oil. If it flares up and makes flames shove it deeper into the quench oil. Move it around, don't stop moving it until it's cooled off.

Test the hardness by trying to file it with an old file. Don't use your good files for this.

If the file just 'skates' over the blade you have it hard enough. If the files bites into the steel you didn't get it hot enough.

Heat it up again and this time go just a little brighter on the color to higher hardening temperature. Quench it again. Repeat until the file won't cut and remember the color of the steel when you quench it. That's your reference.

Clean the oil off the blade. Don't bother any finishing at this point. This is just a sample to get your heat treat process down.

Find an old toaster oven and put a standard oven thermometer inside. The dial is not accurate enough. You want the temp be about 450 degrees to start. Put the sample blade in the oven, let it stay there at 450 degrees for an hour. Turn the oven off and come back a few hours later after it cools. Take the blade out and try your file again. If the file just 'barely' tries to cut the blade you have the heat treat process reasonably close for a home shop.
If the file won't cut the sample at all, repeat at 500 degrees. Repeat until the file just barely bites. Now you have your tempering temperature for that steel.

Now go make your knife blade. Use the same process except this time you know what temperature to heat it to for hardening and the temperature for tempering.

When you make your knife, don't sharpen it all the way to a sharp edge before you heat treat. Leave it a tiny bit dull.

Heat the blade to your hardening temperature. Bury it in wood ashes while it's red hot. Come back the next day.

This will anneal the steel, and allow some of the stress to dissipate. Regrind the blade to your finished condition. Drill any holes you want in the tang.

Reheat the blade to your hardening color and this time quench in the oil. Now it's at full hardness.

Temper it immediately. Don't let it lay around in the fully hard condition. It might crack.

After you temper it in the oven, clean and polish it with abrasive paper, get it to your final size and finish. Put your handle on, the very last step is to sharpen it to a razor edge.

That last bit is important. If you sharpen the blade then try to finish it you will cut yourself multiple times while finishing with your abrasive paper.

There are loads of knife making forums out there with more info.

This should get you started.

Have Fun!

Regards,

Matt
 

Chujybear

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Thank you for the replies.
Thorough and thoughtful.
I am not intending to use the spring steel for the kitchen knife. For that I will order a piece close to my final gage..
The leaf spring I use for dazed and skews.. Partially because I don't have to draw it out that much. But I will try an axel when I get a free day.
Thanks for the tips.
Perhaps I will go stainless for the kitchen knife. Tho I am not unfamiliar with taking care of knives. And all my favorite knives in the kitchen now are not stainless.
 

Tim Wells

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There are readily available blade steels formulated for different uses both carbon and stainless. By the time a fellow hacks one out of a spring he could have bought several blanks for the labor alone.

Personally because of the inconsistencies of auto leaf springs and the unknown metallurgy, the best use I've had for them was making a froe to split shakes with and a spring cut in half for grunting worms to go fish in' with.

For those who don't know what grunting is; drive a good sized wooden stake into the ground about 3 feet long. Rub the end of it with a leaf spring as though you were filing it. The vibration caused by this will make worms dang near jump out of the ground; especially if the ground is a bit wet.
 

Chujybear

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I do intend to buy a piece of sheet for the knife.
I may have muddled things by asking about quenching leaf. I use leaf spring for adzes.. I do draw it out a bit. But not too much. The curve is ready made for adze:)
 
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