Well, I've decided to give blademaking a try, since the good folk at the local John Deere repair shop were good enough to give me a handful of lawnmower blades. (And yes, I know all about the problems with working with mystery steel. Worst case scenario, it'll be some good grinding practice on free steel. Who knows; I might even get a workable blade.)

I've decided to make a Nessmuk knife, as described in George Washington "Nessmuk" Sears's 1884 classic "Woodcraft and Camping". 

The following photo shows (top to bottom) an enlarged scan of Horace Kephart's sketch of the original Nessmuk knife, a cardboard template of that profile, a scaled-up version (Sears was five feet tall; I'm a bit over six), and a modification of the scaled-up version that hews a little more closely to the blade profile of the original and fits my hand a bit better.

You'll notice that the two modified versions have a little belly to the handles. I can't quite tell from the Kephart sketch, but I suspect that the original knife had a stag crown handle. This should make for a more secure grip.

Not shown is the steel I plan to use; that's currently annealing in a container of lime. I'll post a picture of it later.

Good on you Jhcc - if nothing else you'll learn a lot from making it.
For all that people knock them, I've had good successes with lawnmower blade. Heated to critical, canola oil quench, 2 cycles at 180-190 C.
Can cut a sheet of A4 paper in one stroke and has reasonable edge retention.
Known steel is better, but if you have it, play with it!

If they are John Deere factory blades you should be able to find out what alloy they are by xontacting them directly. Brush Hog blades are a proprietary alloy with a high boron content, and thy take a special heat treatment. Do your research before you invest the time.

4 hours ago, BIGGUNDOCTOR said:

If they are John Deere factory blades you should be able to find out what alloy they are by xontacting them directly. Brush Hog blades are a proprietary alloy with a high boron content, and thy take a special heat treatment. Do your research before you invest the time.

That's very interesting. This one is definitely a lawnmower blade, but there are a couple of others that might be brush hog blades -- they're VERY thick and look like they've had some seriously hard use.

Here are the two halves of the lawnmower blade: unmodified on right, flattened and annealed on the left.

And here's the unmodified half with one of the other, thicker blades.

Stamp on the back of the annealed section.

Before I went any further I would contact JD to see what they will tell me, and also take a sample piece and try heat treating it to see how it reacts. That includes a destructive test to look at the grain structure. Mower blades are generally made from alloys to be tough and impact resistant, not hard and brittle.

Google is your friend.

 

http://www.greenpartstore.com/About-John-Deere-Mower-Blades_ep_50-1.html

Sounds like they use are possibly using 5160. 

https://www.deere.com/en_US/parts/parts_by_industry/residential/blades/blades.page

That is some great info, BGD; many thanks!

(Especially since the folks at JD were completely unhelpful when I called.)

Definitely planning to do some hardness tests with the offcuts. In the mean time, I'll be reading up on 5160.

I like the blade shape, looking forward to the finished blade

First cutting session.

(Got a couple of nice offcut bits for hardening tests.)

Second cutting/grinding session.

On 11/28/2015, 8:46:29, JHCC said:

That's very interesting. This one is definitely a lawnmower blade, but there are a couple of others that might be brush hog blades -- they're VERY thick and look like they've had some seriously hard use.

Although I now recollect that brush hog blades are single-ended.

One of the offcuts which I will be using for hardness testing. In the mean time, the 90° bend (one end in the pritchell hole, bent over by hand) seems to demonstrate that the annealing step worked just fine.

Sorry, image didn't upload.

And here's that offcut, hardened:

And with the end snapped off to show the grain. The piece is a hair over 1/8" thick.

On 11/28/2015, 1:45:17, Frozenthunderbolt said:

I've had good successes with lawnmower blade. Heated to critical, canola oil quench, 2 cycles at 180-190 C.

Interestingly, the offcut did NOT harden with a canola oil quench, but it DID when quenched in water. Two cycles at 190°C/375°F tempered it to straw.

2 hours ago, JHCC said:

Interestingly, the offcut did NOT harden with a canola oil quench, but it DID when quenched in water. Two cycles at 190°C/375°F tempered it to straw.

Interesting. What volume of canola did you use and did you pre-heat it? Ambient temperature?
In fairness to you I often tend to do a secondary edge quench in water after an initial oil dip (though I use oil only on leaf spring) that may have affected my results described.

The next lawn blade I do I'll try going straight to water and see if it makes a difference for me :-) I concur with your temper cycles; i'm using a toaster oven (notoriously inaccurate) and 2x 180C gets me a dark straw with occasional patches darkening a little more.

4 hours ago, Frozenthunderbolt said:

Interesting. What volume of canola did you use and did you pre-heat it? Ambient temperature?

About a quart of canola (left over from frying chicken), not preheated. Ambient temperature in the garage (and thus in the slack tub for the water quench) was about 40°F, although I'd had the oil inside the house at about 70°F beforehand.

That volume of oil would obviously be much too small for the knife itself but I figured it would be ok for this smaller test piece (1/8" T x 3/4" W x 6" L). After the quench, the oil and the test piece were hot to the touch, but not so hot as to burn my skin. 

Forgot to mention: After the initial attempt at oil hardening, I could still bend the test piece by hand (thin end in the pritchel hole, pushing down with gloved hand on the other end). It was a lot stiffer than it had been after annealing, but still doable. 

Also, I did a little flattening and re-annealed of the blade blank before I move on to final flat-grinding and filing the bevels. (I also annealed the other half of the original lawnmower blade.) The low air temperature made getting the entire blade evenly to critical temperature rather tricky, but I eventually settled on burying it in the coals, shutting off the blower, and letting it soak for a few minutes. That seemed to work pretty well.

Ground to profile and (most of the) scale ground off. The profile still feels a little bulky, so I may trim that down a bit before I do the final flattening and bevel grinding.

Given the bulky feel of the blank, I've decided to use the other half of the lawnmower blade for the slimmer version from the initial design phase. I'll be making both versions together.

First side (mostly) drawfiled. Learning the importance of keeping the file clean to avoid galling and scratching.

 

 

Working on the first bevel.

Current state of the project (bottom to top; the picture loaded upside down):

Knife #1 beveled and rough sanded, almost ready for heat treatment (I'm trying to eliminate any deep scratches that might act as nucleation sites for cracking). I ended up slimming down the handle substantially, as it felt much too bulky.

Knife #2, rough cut.

Rough blank for a sen, made from another (and much thicker) lawnmower blade. The width and thickness gave me a good starting place, as did the one existing bevel. I will be drawing out the two tangs and mounting wooden handles.

Rivet and lanyard holes drilled, shaping the scales.

And handle is carved and rough sanded. The scales are held on with wooden pins, which will be replaced with brass rivets in the final assembly. Next step: heat treatment.

And so ends my first foray into knifemaking, with a nasty crack right on the edge. I suspect that I thinned it down too much in the filing stage.

Fortunately, I have another blank roughed out and ready to go. Onward!