Hardening and tempering saw blade?

[heartlandbowyer]

Hey guys, been messing around with an old two man saw to make knives. The blade is .080 thick right now and I can shape it with a file. I can get the saw blade sharp but I want it to hold its edge longer.

Should I heat the finished blade to red hot (demagnetized) then quench in oil?

Should I bake in my toaster oven at certain temp for a specified time to temper the blade.

Thanks, Cory

[Lin Rhea]

Cory, is this a two man cross cut saw? You are wanting to make knives from that saw?

I'm asking to be clear.

[heartlandbowyer]

Lin, yes it is. I would like to make small knives out of this, neck knives etc. Is making knives out of this a bad idea? I thought it would be a nice add to some of the bows I make for buddies and a guy can never have to many knives.

Thanks Cory

[Lin Rhea]

I cant say for sure Cory, but most likely that steel is good for knives. If it's too soft in it current state, yes you would have to harden it and draw it back slightly harder. A saw was meant to be filed fairly often but the steel was hardened once in the early stages of it's existence.

I would cut out the blade shape, anneal, rough grind, thermocycle, harden, draw back, and finish the blade. In that order.

Each of those steps require your close attention or you'll lose it all. Take pictures and ask questions if you need to.

[heartlandbowyer]

Thanks Lin,
I'll have to do a little research on thermocycle and draw back not sure about those terms.

Im guessing thermocycle is what it suggest, heat blade and let air cool, repeat, repeat.

Next harden, red hot and quench.

Draw back would be the temper? Hold heat for a time till I get kind of a corn stalk brown color?

Thanks again
Cory

[Lin Rhea]

Yes, you have the idea, but it will pay to research anyway. Holler if you need something. Post pictures.

[heartlandbowyer]

Alright finally had a chance to work on my crosscut saw blade knife.
Got marked then cut out with the angle grinder.
 
Shaped blade on the grinder then worked on the bevel with a file. Steel was soft enough to work with a file so I didn't aneal the blade. Used a block on the end of the file so I could keep the angle even across the blade.
Don't have a forge yet so I used MAP gas to normalize the blade. Heated it enough to demagnatize and let cool in the air, repeated 2 more times.

Now for the quench. Is there a special oil that I need to get or will regular oil work?

Thanks
Cory

[Lin Rhea]

Canola will most likely work.

How thin is the edge, btw?

[heartlandbowyer]

Lin I would guess the edge is about like a butter knife now probably .025 thick. Will that screw me up?

[Lin Rhea]

It's pretty thin, but it will work if you can get the edge evenly heated and go into the oil straight, whether it you edge quench or full quench. I think you will have difficulty getting the edge heated evenly with Map gas, but since it thermo cycled it,......well, it's up to you. Just to remind you, if you over heat the blade or any section of the blade from this stage forward, you have enlarged the grain and will have to thermo cycle again. In other words, if the heat is not intense enough, you can't move it fast enough to stay caught up. Maybe if the Map gas is in a small chamber forge.  

Immediately after hardening, test it with a file, If it skates all along the edge, get it in the oven pretty quick @ 350 degrees for at least an hour. Then test with the file again and give us the results. If it don't harden all along the edge, simply re heat and re quench. Do not over heat above critical temperature.

[heartlandbowyer]

Lin, thanks for all the direction, gonna give it a try after after work today.

Thanks, Cory

[heartlandbowyer]

Lin, thanks for all the direction, gonna give it a try after after work today.

Thanks, Cory

[heartlandbowyer]

Getting closer got the blade quenched and drawn back at 350F for 1hr. Ran a file across the edge and it would only remove the charing but no metal. I should have taken a pic before I started  but the color was a deep cornstalk color.  Gonna do a little sanding and glue some scales on.

My lanky stone will put a edge on but how can I test to see how the blade will hold its edge, just normal use?

Thanks
Cory

[heartlandbowyer]

Sorry forgot picture.

[Lin Rhea]

You need to draw it back in the oven again and then test. You test by sharpening it and cutting some wood, rope, etc. I would do that before I put handles scales on. You may have to draw it again if it's too hard. Don't take shortcuts now.

[heartlandbowyer]

Sounds like good Saturday am fun. Got a bow to glue up so I will do draw back during glue up then do a little sharpening and testing.

Thanks
Cory

[heartlandbowyer]

Lin, thanks for all your direction on this build. I don't know how many rope cuts to make but I made 8 cuts on this 3/8 rope and could still shave hair off my arm. I think that's pretty good for my first try and it wasn't hard to put and edge on with three different grits of stone on my lanky sharpener.
Went with Bubinga/bocote I beam scales I had lying around.
 

[heartlandbowyer]

Got her sealed and finished need to make a sheath now.